Chapter4 About Antenna & Feeder Cable

Wireless Network Planning Table of Contents

Table of Contents

Chapter 4 About Antenna Feeder..............................................................................................1-14.1 Basics of Antenna............................................................................................................1-1

4.1.1 Antenna gain.........................................................................................................1-1

4.1.2 Directional Diagram...............................................................................................1-2

4.1.3 Polarization............................................................................................................1-3

4.1.4 Other technical indicators of antenna....................................................................1-4

4.1.5 Antenna diversity...................................................................................................1-6

4.1.6 Three-sector base station antenna selection derivation........................................1-94.2 Antenna new technology................................................................................................1-11

4.2.1 Shaped beam technology....................................................................................1-11

4.2.2 Intelligent Antenna...............................................................................................1-134.3 Antenna Dip AngleDowntilt Planning.............................................................................1-20

4.3.1 Antenna Dip AngleDowntilt Design......................................................................1-20

4.3.2 Practical Application............................................................................................1-234.4 Antenna Selection..........................................................................................................1-25

4.4.1 Current Problems of Using Antenna....................................................................1-25

4.4.2 Application Principle for Base Station Antenna in Urban Areas...........................1-25

4.4.3 Application Principle for Suburb Base Station Antenna.......................................1-26

4.4.4 Application principle for base station antennas in rural areas..............................1-26

4.4.5 Application principle for antennas to cover highroads.........................................1-27

4.4.6 Other factors in antenna application....................................................................1-28

4.4.7 Notes on special antennas..................................................................................1-28

4.4.8 Reference for antenna selection..........................................................................1-304.5 Combining and distribution unit......................................................................................1-31

4.5.1 Principle for combining and distribution unit........................................................1-31

4.5.2 Combining and distribution unit configuration......................................................1-334.6 Outdoor antenna feeder system.....................................................................................1-35

4.6.1 Tower amplifier....................................................................................................1-35

4.6.2 Feeder lineFeeder cable......................................................................................1-364.7 Distributed antenna system............................................................................................1-38

4.7.1 Principle for composition of distributed antenna system......................................1-38

4.7.2 Types of distributed antenna system...................................................................1-39

4.7.3 Indexes for component key technologies............................................................1-40

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Wireless Network Planning Chapter 4 About Antenna Feeder

Chapter 1 About Antenna & Feeder cable

1.1 Basics of Antenna

In a wireless communiction system, the antenna system serves as an interface with the exterior media. Antenna radiation and receive radio wave: in transmission, the antenna works to convert high frequency current into electromagnetic wave; while receiving, it converts electromagnetic wave into high frequency current. Antenna can be divided into the following types in light of their work frequency band: untra-long wave, long wave, medium wave, short wave, ultrashort wave and mircowave; it is divided into the following types in terms of direction: omni-antenna and directional antena; it is divided into the following types in terms of its structual features: linear antenna and dish antenna. The model, gain, directoinal diagram, driving antenna power, simple or complicated antenna configuration and atenna polarization etc will affect system performance.

1.1.1 Antenna gain

Gain is one of the most important parameters for the antenna system. The definition of antenna gain is related to ominidirectional antenna or half-wave dipole antenna. The ominidirectional radiator is one that assumes radiating equal power in all the directions. The antenna gain in a direction amounts tois the ratio of the fluxpower density to that of ideal point source or half-wave dipole in the maxium radiation direction (dB refers to the difference). See Figure 4-1 for the diagram.

dBd

dBi

Ideal isolated wave source

Theoretical half wave dipole

directional antenna

Figure 4-1 Gain Comparison

dBi indicates that antenna gain is the reference value of directional antenna relative to the ominidirectional radiator, while dBd is the reference value relative to half-wave dipole antenna. The relation between these two is expressed as follows: dB i dBd 2.15.

1.1.2 Directional Diagram

The directional diagram describes the dirstribution of antenna radiation electromagenetic field according to angular coordinate within a fixed range. The

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directional diagram expressed in radiation filed strength is called field strength directional diagram; expressed in power indensity, it is called phase directional directional diagram.

The antenna directional diagram is a space solid figure. But the one in common application is a directional diagram inside two principal planes perpendicular to each other, known as plane directional diagram. For linear antenna, as the ground has great effect, it adopts vertical plane and horizontal plane as its principal plan. The plan antenna adopts E plane and H plane as the two principal planes. The maxium of normalization direction diagram is 1.

The radiation lobe required in the maximum radiation direction in the directional diagram is called antenna major lobe, also known as antenna beam. The lobes other than the major lobe are called secondary lobe or side lobe or parasite lobe. The side lobe in the direction opposite to the major lobe is called back lobe as shown in Figure 4-2(a): diagram of omni-antenna horizontal lobe and vertical lobe, where the antenna is in the shape of a column; 4-2(b): diagram of horizontal lobe and vertical lobe for directional antenna, where its antenna in the shape of a board.

Figure 4-2(a) Diagram of omni-antenna lobe

Figure 4-2(b) Diagram of directoinal antenna lobe

The parameters commonly used for antenna diectional diagram include the following:

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Zero power lobe width refers to the included angle between the two zero radiation directions on both sides of maximum major lobe;

Half power point lobe width refers to the included angle after the maximum electric field falls by 0.707 (the gain falls by 3dB);

Secondary lobe level refers to the ratio of maximum secondary lobe to the maximum major lobe;

Front-to-back ratio;

Electric angle of declinationdowntilt.

1.1.3 Polarization

Polarization is one radiation feature describing the space direction of electromagnetic wave field strength vector. The electromagnetic wave with the space direction of electric field vector unchanged at any time is called straight line polarized wave. Normally, antenna polarization refers to the polarization of electric wave radiated by the antenna in the maximum radiation direction (for transmitting antenna) or the polarization of incident plane wave (for receiving antenna) in the maximum receiving power (polarization match) direction. Take transmitting antenna for example, if the electric filed direction of the antenna radiation wave is within the radiation plane (made up of incident ray and the normal line of reflection plane), as the incident plane is aways perpendicular to the tangent plane of the reflection plane, this is known as vertical polarization; when the electric direction of antenna radiation wave is perpendicular to the incident plane (made up of incident ray and the normal line of reflection plane), it is parallel to the tangent plane of the reflection plane, thus it is called horizontal polarization, as shown in Figure 4-3:

vertical polarizationincidental plane

incidental wave

reflection plane

incidental wave

incidental planehorizontal plane

incidental plane

Figure 4-3 Polarization Diagram

As the horizontal polarized wave is perpendicular to the incident plane, this is also known as quadrature polarized wave; as the electric field vector of vertical polarized wave is parallel to the incident plane, it is called horizontal polarized wave. The electric field vector forms a plane together with the transmitting direction, known as polarized plane.

The space dirction of electric field vector is not aways the same. The locus of electric field vector end points is a circle, known as circular polarized wave; if the locus is a

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ellipse, it is called ellipse polarized wave. Both the circular polarized wave and ellipse polarized wave feature rotating phase.

Both circular polarized wave or ellipse polarized wave is composed of two linear polarized waves perpendicualr to each other. If the two waves are of the same size, they will make up circluar polarized wave; if not, they will form ellipse polarized wave. Antenna may possibly radiate energy it does not need via polarization not preset. The energy of this kind is called cross polarized radiation component. For linear ploarized antenna, the cross polarization and preset polarization is perpendicular in direction. For circular polarization antenna, the cross polarization and the preset polarization are opposite in rotating direction, so cross polarization is called quadrature polarization.

1.1.4 Other technical indicators of antenna

I. Voltage standing wave ratio (VSWR)

For VSWR in the base station antenna of mobile communication cellular system, its maximum value should be less than or equal to 1.5:1. If ZA indicates the antenna input impedance and Z0 is the antenna’s standard characteristic impedance, then the reflection coefficient is:

｜Г ｜｜ZA Z0｜

｜ZAZ0｜,VSWR

1｜Г ｜

1 ｜Г ｜ , where Z0 is 50 ohm. The return loss may also be

used to indicate the match characteristic of the port, R.L.dB 20 lglg｜Г ｜, if VSWR=1.5:1, R.L.=13.98dB.

When antenna input impedance is not consistent with its characteristic impedance, the reflection wave and incident wave will overlap on the feeder linefeeder cable to form standing wave. The ratio of maximum and minimum value of their neighboring voltages is the voltage standing wave ratio. If this ratio is too high, it will shorten the communication distance, and the reflection power will return to the power amplifier of the transmitter, so that the power tube will get damaged easily, thus affecting the normal work of communication system.

II. Front-to-back ratio (F/B)

The difference between antenna maximum beam secondary level and back 180~_30° side lobe maximum beam within back 180~_30° , in positive value. Normally, the antenna front-to-back ratio ranges between 18～45dB. For populous downtown area, the antenna with greater front-to-back ratio shall be used, such as 40dB, so as to reduce the indoor disturbance of the back lobe against high-rise buildings.

III. Port isolation

For a multi-port antenna, such as bipolarization antenna and dual-band bipolarizatin antenna, the isolation between the ports used for both receiving and transmitting shall be more than 30dB.

IV. Power capacity

It refers to average power capacity. Antenna contains other coupling equipment such as match, balance and phase ship, so the power it can bear is limited. In consideration of the actaul maximum input power of the base station antenna (single carrier wave power is 20W), if one atenna port is input a maximum of six carrier

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waves, then the input power of antenna is 120W. As a result, the antenna shall have a single port power capacity of more than 200W (when the environmental temmperature is 65℃).

V. Zero point filling

Base station antenna is designed as shaped beam. In order to make the ratiation level within the service area more even, the first zero point of the lower secondary lobe needs to be filled without nay obvious zero depth. Normally, when the zero depth is greater than -20dB relative to the main beam, it indicates that the antenna is filled with zero point. The base station in parent zone has no such requirement in this respect. In particular, high gain antenna requires zero point filling technology to improve the nearby coverage and avoid signal fluctuation arising from unequal coverage in an effective way.

VI. Upper secondary lobe suppressioin

For cellular system, in order to improve the capacity of frequency multiplexing and reduce co-channel interference against its neighboring area, in shaping beams, the base station antenna should reduce the secondary lobes aimed at the interference area so as to raise D/U value. In this case, the first upper secondary lobe should be less than -18dB. There is no such requirement for parent zone base station antenna.

VII. Antenna input interface

In order to improve the reliability of passive intermodulation and RF connection, the input interface for antenna adopts 7/16DIN-Female. Before used, the antenna port should have a cover so as not to generate oxide or keep from foreign substance.

VIII. Passive intermodulation (PIM)

In order to improve non-linear interference noise, PIM of the antenna should be less than -103dBm (2x10W).

IX. Antenna size and weight

In order for the storage, transport and safety of antenna, besides meeting various electric indicators, the antenna should be as small as possible in size and as light as possible in weight.

X. Wind loading

Base station antenna is normally installed on top of high buildings and iron towers, especially in coastal areas, where the wind is very strong all year round, thus it is requested that antenna be able to work properly against the wind at a speed of 36m/s, and get undamaged when the wind blows at a speed of 55m/s.

XI. Work temperature and humidity

Base station antenna should work properly within the environmental temperature range of -40℃ ～ +65℃. Base station antenna should work properly within the environmental relative humidity ranging between 0～100%.

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XII. Lightning protection

all the RF input ports of a base station antenna are required to be directlly grounded via DC.

XIII. “Three proof” capacity

The base station antenna must possess the capacity of “three proof”, that is, proof against moisture, proof against salt atmosphere and proof against mildew. The omni-antenna in a base station must permit of reverse installation and meet the above three proof requirements at the same time.

1.1.5 Antenna diversity

I. Diversity characteristic

Signal fading in mobile radio environment will give rise to serious problems. With the movement of mobile station, rayleigh fading will vary rapidly with the signal instantaneous value, while the logarithm normal fading varies with the signal average (median value). These two values are the major factors attributed to unstable receiving signal in mobile communication, which make the receiving signal deteriorate greatly. Although this situation can be improved by increasing signal transmitting power, antenna size and height etc, such methods cost much in modile communication, and sometimes are obviously far from realistic; however, using the diversity method, that is, receive the signals hardly related to each other which carry the same message in serveral tributaries, then output the signals from various tributaries after consolidation; in this way will the probability of heavy fading at the receive terminal be reduced to a large extent. Normally, diversity technology is used at the receiving station address in that the receiving equipment is passive, which will produce no interference. The diversity is of two types: one is obivious diversity and the other is implied diversity. By implied diversity, it is meant to imply the diversity function in the signal to be transmitted using signal design technologies, such as RAKE receiving technology, channel interweaving, antifading error correction coding technology. Only obvious diversity is discussed hereunder. This diversity may be divided into two types: base station obvious diversity and general obvious diversity.

In the base station obvious diversity, several base stations separated by space fully or partly cover the same area. As there are multiple signals available, the effect of fading is reduced by a large degree. Due to different transmitting paths of electric wave and different shadow effects of land forms and ground objects, the multiple slow fading signals transmitted via independent fading paths are unrelated to one another. It is unlikely that the signals undergo heavy fading at the same time; therefore, if using diversity combination and selecting tributary with the best SNR from the signals of various tributaries, that is, choose the best base station and mobile station to establish communication so as to eliminate the shadow effects and other geographic effects. Therefore, base station obvoius diversity is also called multiple base station diversity.

General obvious diversity is used for suppressing rayleigh fading. The traditional ways for this purpose are space diversity, frequency diversity, ploarization diversity, angle diversitym, time diversity and field component diversity etc.

It can be seen that the above diversity only improves the quality of uplink signals, while the limit of mobile station in terms of volume, price and battery capacity etc makes it possible to implement speace diversity of multiple antenna. To improve the transmitting quality of downlink signals, whether it is possible to use the principle of reciprocity for linear system to implement the diversity technology for receiving end of

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mobile station larged limited in volumn shifted equally to the transmitting end. And this is so-called transmitting diversity technology. Such technology is with a problem: principle of reciprocity can not be applied unless the mobile communication channels are simplified into an approximate linear time variation system. Moreover, the implementation of principle of reciprocity for receiving and transmitting of this system also requires that the transmitting and receiving are done within the same frequency band with the same fading characteristics. But in fact, most mobile communication systems resort to FDD work mode, where the interval between receiving and transmitting is far greater than the related bandwidth. To reduce the effect of deterioration on transmitting diversity out of FDD work mode, we usually adopt closed loop control to send diversity. The transmitting diversity technology is applied widely in 3G.

II. Diversity and synthesis

The diversity characteristics depend on the relevant coefficients between the quantity of diversity tributary and the receiving diversity.If each coefficient relevant to each tributary is identical, then various diversity plans are able to implement the same related persformances.We must also consider how to synthesize the multiple signals received by the diversity, because proper synthetic technique will bring forth desirable

performance.For example, use Q multiple diversity with Q signals as S1(t), S2(t), ...Sq(t) before synthesis. Considering that the synthesis can be performed between each diversity antenna and the receiver, at the frequency output terminal and at the fundamental frequency output terminal after demodulation, S i(t) here should be understood as high frequency signal, medium frequency signal or fundamental signal in general form. The so-called synthesis is nothing but how to sum up S i(t). The signals after synthetized can be expressed as follows:

S(t) k1S1(t) k2S2(t) ... kqSq(t)

where k1, k2, ..., kq refers to weight coefficient. To select different weight coefficients will produce different synthesis method. There are four synthetic techniques in common use: maximum ratio compound (MRC), equal gain compound (EGC), selective compound (SEC) and switch compound (SWC).These compound techniques are an important part of antenna technology. As it goes beyond this textbook, its details will not be mentioned herein. Mobile communication usually adopts space diversity and polarization diversity with the diversity gain of around , 5dB. These two methods are discussed as follows.

III. Space diversity

Space diversity is performed using the random change of field indensity with the space changes.In mobile communication, any slight space change may result in great change in filed indensity. The longer the space interval, the greater difference the muli-path transmission will have and the less relativity of the filed indensity received. In this situation, as it is very unlikely that heavy fading occurs at the same time, the diversity will reduce the fading effect to its minimum.For this purpose, it is required to determine necessary space intervals. Normally, the diversity antenna is designed in

accordance with the parameter . The relation between and the actual antenna

height h and antenna interval D is: hD . For antenna placed in horizontal interval,

is normally 10.For example, the antenna is 30 meters in height, the antenna interval of 3 meters will get better diversity gain. In addition, the vertical antenna interval is greater than the horizontal antenna interval.Up to date, the space diversity antenna commonly seen in the project is made up of two sets (receive/transmit, receive) or three sets (receive, transmita and receive).

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IV. Polarization diversity

The polarization of electromagnetic wave is described hereinbefore. Currently, more and more projects have applied dual polarization antenna. Antenna is poluarized in two manners: horizontal poloarization and vertical polarization, while one frequency carries signals of the said different polarization manners. In theory, as coupling effect is not used for medium, mutual interference will not occur. But coupling effect will occur in mobile communication environment. This means that after the signals are transmitted via mobile radio medium, the energy of vertical polarized wave will leak to the horizontal polarized wave and vice versa.Fortunately, compared with the main enery flow, the enery leakage only involves a very small amount. Favorable diversity gains can be obtained through ploarization diversity.The greatest advantage of polarization diversity antenna only requires the installation of one set of antenna, thus reducing the installation cost.

V. Comparison between space diversity and polarization

The greatest advantage of polarization diversity is to save antenna installation space. The space diversity requires two pieces of receiving antenna at certain intervals, while polarization requires only one such antenna. This antenna contains two different types of polarization dipole. General space diversity is able to obtain a link gain of 3.5dB. As the path loss of horizontal polarizaton antenna is greater than that of vertical polarization antenna (the horizontal polarized wave has more chance of deploarization than the vertical polarized wave), for one dual poluaration antenna, its gain improvement degree is 1.5 dB less than the space diversity. However, dual polarization diversity is able to provide low relativity indoors or in a car compared with the space diversity. As a result, it will gain 1.5 dB in improvement more than the space diversity. In comparison, the advantage of dual polarization receiving antenna is saving space for antenna installation. As transmitting antenna, if the base station shares it for transmitting and receiving antenna in the way of dual polarization, the dual polarization antenna using vertical and horizontal quadrature polarized dipole compared with the dual polarization antenna using ±45°quadrature polarized dipole (suppose the other conditions are the same), in an ideal free space (a mobile phone receiving antenna is vertically polarized), the signals received by the mobile phone from the antenna is 3dB more than that of the latter. But in practical application environment, as multi-path transmission exits, when various multi-path signals at the receiving points are averaged, the above difference will basically disappear. The accuracy of this conclusion is verified in various tests. However, the said difference may possibly exist in a vast plain, but how much difference remains to be proved in test. There might be a difference of 1～2dB. To sum up, there is no much difference between the said two polarization methods in practical application. ±45°quadraturequadrate polarization antenna is commonly seen on the present market.

1.1.6 Three-sector base station antenna selection derivation

First of all, let’s make clear a concept concering the cell base station radius as shown in Figure 4-4.

This is a standaard three-sector celluar layout. From the diagram, we can see that the interval between the two three-sector base stations is R+r, while R=2r. However, we usually use R to estimate the cell coverage radius, for this direction is that of the major lobe of directional antenna; but r is often used to indicate the cell radius in cellluar layout. In a celluar cell, for the area whose included angle with the major lobe direction of the cell antenna, this cell is requried to cover a range of r=R/2. If calcualted from path loss, it will be around 10dB less than that in the direction of

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major lobe (deduction is as follows), that is, the effective radiated power in this direction as required may be about 10dB less than that in the direction of major lobe.

Figure 4-4 Three-sector Celluar Layout

According to this feature, this layout may adopt directional antenna with a horizontal lobe (Azimuth beamwidth) of 60～65 degrees, because their diagram of horizontal lobe gain has this feature, too.

If R indicates the cell radius, then the cell area is S=0.6495×R×R. However, people sometimes call r as the cell radius. At this point the cell area is S=2.5981×r×r. Therefore, while discussing a problem of this kind, we need to make clear what to be used as the cell radius.

Figure 4-5 Presentation of R and r

Let’s deduce the theoretic basis for the difference of 10dB between R direction and r direction in terms of path loss. As shown in Figure 4-5, in this standard cell of 120 degrees, the distance covered in r direction is half that in R direction, i.e. r=R/2. To keep balanced coverage, the field intensity on the edge of this cell should be basically equal, that is, RxlvelB=RxlevelC. Suppose

EIRP transmitted from Cell A is EIRPR in R direction and is EIRPr in r direction.

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We choose urban HATA model for the path loss and the path loss from Point A to Point B is expressed in Equation (1):

EIRPR-RXLEVB=69.55+21.66lgf-13.82lgh1+(44.9-6.55lgh1)lgR (1)

The path loss from Point A to Point C is expressed in Equation (2):

EIRPr-RXLEVc=69.55+21.66lgf-13.82lgh1+(44.9-6.55lgh1)lgr (2)

The two equations subtract each other and the following equation will appear after coordination:

EIRPR-EIRPr=(44.9-6.55lgh1)×(lgR-lgr)=(44.9-6.55lgh1) ×lg(R/r)

Put R=2r in the result and you will get the following:

EIRPR-EIRPr=0.3×(44.9-6.55lgh1)

Through computer simulation, as the height h1of base station increases from 5m to 100m, and (EIRPR-EIRPr) decreases from 12 to 9.5, it may be roughly treated as 10dB as shown in Figure 4-6.

◆ Series 1◆ Series 1

Figure 4-6 Diagram of relation between the height of base station and value of EIRPR-EIRPr

1.2 Antenna new technology

1.2.1 Shaped beam technology

In the cellular mobile system, it is always a complicated problem to reduce interference of the same channel. Shaped beam technology has improved the reuse of spatial frequency spectrum.There are two types of shaped beam. One is the radial direction diagram on the shaped plane, i.e. shaped plane; the other is radial direction diagram on the shaped vertical plane. In the cellular system, while replacing the omnidirectional beam with the fan-shaped beam, the cellular interference distance will increase, so that base station antenn will radiate level as low as possible to another cell using the same frequency, while the base station antenna will radiate level as high as possible to its service area radiation.

When the antenna at a fixed height illuminates a limited horizontal plane, the antenna vertical directional diagram indicates that the existance of side lobe zero point may possibly lead to blind zone within the area to be covered. Using the cosecant square shaped beam power directional diagram of the vertical plane may eliminate the zero

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points below the major lobe, so that the area to be covered has equal receiving signal level. This is also known as zero point filling technology.

In addition, the global celluar system around is basically using a processing technology known as beam declination downtilt.The said technology mainly aims to decline the major beam so as to compress the FR level towards the directio and increase the carrier-to-interference ratio.In this case, although the carrier wave level on the edge of area falls, the interference level drops more than the carrier level, so the total carrier-to-interference ratio increases. Strictly speaking, beam declinationdowntilt is not really the shaped beam technology, but they are for the same purpose.To date, there are two ways to decline the beam.One is electric adjustment declinationdowntilt to adjust the beam declinationdowntilt by changing the excitation coefficient of antenna array; and the other is mechanical adjustment to change the declinationdowntilt angle of the antennal.

Corresponding to different methods for beam declinationdowntilt, antenna is divided into electric adjustment antenna and mechanical antenna. After electric adjustment antenna adopts the methods combining mechanic and electronics to decline by 15°, the directional diagram of the antenna will not change greatly with the coverage distance shortened obviously in the direction of major lobe. The overall antenna directional diagram is within the local base station sector. To increase the declinationdowntilt degree will reduce the sector coverage, but will not produce interference. We simply need such a directional diagram. Electric adjustment antenna is of two types: one is the preset fixed electric declinationdowntilt angle antenna, and the other is antenna to make adjustment of electric declinationdowntilt angle one the site according to practical needs. The latter is described as follows. When the mechanical antenna declines by 15°, the form of antenna directional diagram changes greatly from the shape of juicy pear (grown in Hebei Province) to the shape of spindle. Although the coverage distance in the major lobe direction is obviously shortened, the overall antenna directional diagram is not within the sector of base station and the sector in the neighboring base station will also receive the signals from the said base station, thus resulting in interference. This is attributed to the following reasons: the electric antenna is installed perpendicular to the ground (mechanical declinationdowntilt of 0°～5°is optional). Once the antenna is installed, in the course of adjusting antenna declinationdowntilt angel, the antenna itself will not move. Through electric signal the antenna dipole phase is adjusted, thus changing the breadth of horizontal and vertical component as well as the component field intensity, so as to change antenna coverage distance. At the same time the filed intensity in each direction of the antenna increases or decreases, so as to ensure the antenna directional diagram will not change greatly after the change of declinationdowntilt angle. After the mechanical antenna is installed perpendicular to the ground, while adjusting the declinationdowntilt angel of antenna, the antenna itself will move too. It is necessary to change the antenna declinationdowntilt angle by adjusting the position of the rear rack of antenna, and changing the declinationdowntilt angle. Although the coverage distance in the major lobe direction of the antenna undergoes no obvious change, the vertical component and horizontal component of the antenna will remain unchanged in terms of breadth. Therefore, the antenna directional diagram will be transformed seriously. As a result, the advantage of electric antenna is: in the event of great declinationdowntilt angle, the coverage distance is obviously shorten in the major lobe direction with antenna directional diagram changing not so much, so as to bring down the call loss and reduce the interference. In addition, in the event of network optimization, management and maintenance, to adjust the antenna declinationdowntilt angle, you do not have to shut down while using electric antenna. In this way, you may use special test equipment for mobile communication to monitor the adjustment of antenna declinationdowntilt angle, so as to ensure the antenna declinationdowntilt angle is at its best value.

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The step degree of declinationdowntilt angle for electric antenna is 0.1°, while the step degree for mechanical antenna is 1°. Therefore, electric antenna is highly precise and yields good result. When electric antenna is installed, while adjusting antenna declinationdowntilt angle, the maintenance personnel do not have to clime to the place where the antenna is installed but adjust the declinationdowntilt angle on the ground. They may also perform remote monitoring adjustment on the base station antenna on top of high mountains and in remote areas. While adjusting the declinationdowntilt angle of mechanical antenna, it is required to shut down the entire system. And monitoring cannot be conducted when the antenna declinationdowntilt angle is being adjusted. The declinationdowntilt angle of mechanical antenna is a theoretical value through calculation by computer simulation analysis software, and it will differ form the actual best declinationdowntilt angle to some extent. Besides, it takes much trouble to adjust the declinationdowntilt angle for mechanical antenna. Normally, the maintenance personnel shall have to clime to the place where the antenna is installed at night before making adjustment. Furthermore, it is rather difficult to adjust some antennas after they have been installed, such as mountaintop or special buildings.

In addition, the index for Level 3 normal intermodulation of electric antenna is -150dBc, while such index for mechanical antenna is -120dBc. Thus, the difference of the two is 30dBc. However, the Level 3 intermodulation index is very important to eliminate adjacent frequency interference and scattering interference. In particular, in the area of high traffic intensity with small distance between base stations but much carrier frequency, it is requested that the index for Level 3 intermodulation should reach around -150dBc. Otherwise, large interference will occur.

Currently, China Mobile Communication Network is suffering much call loss and large interference in the areas with high traffic intensity. One of the important reasons is that the declinationdowntilt degree of mechanical antenna is too large, so antenna directional diagram gets distorted seriously. To solve the problem of insufficient capacity in areas with much traffic, it is necessary to shorten the station distance and increase the antenna declinationdowntilt angle. But while using mechanical antenna, when the declinationdowntilt angle is more than 10°, the antenna directional diagram will be distorted quite seriously. Therefore, it is very different to solve the problem of high call loss and large interference in areas with high user intensity through mechanical antenna. It is recommended that the mechanical antenna be replaced by electric antenna in traffic-intensive areas. The replaced antennas may be installed in the rural areas and suburbs where the traffic intensity is relatively low.

1.2.2 Intelligent Antenna

With the rapid development of global telecommunication services, the wireless mobile communicaiton technology as the major means of individual communication in the future attracts much attention among the general public. It has become major factors for people to consider how to eliminate co-channel interference (CCI), multi-address interference (MAI) and multi-pathm fading in improving the performance of wireless mobile communication system. The intelligent antenna uses digital signal processing technology and adopts advanced switched beam technology as well as adaptive spatial digital processing technology, to produce space directional beam so that the antenna major beam is aimed at the direction where the user signals arrive with its side lobes aimed at the direction where the interference signal will arrive, so as to attain the objective of making most of mobile user signals and of deleting or suppressing the interference signals. Compared with other deepening and maturing technologies for eliminating interferences, the applied research on intelligent antenna technology is just in the ascendant and reveals huge potentials.

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The greatest disadvantages of system wireless base station is it wastes radio signal energy. Normally, only a small amount of signal energy can reach the destination. In addition, when the base station is receiving signals, it receives not only useful signals but also interference noice from other signals. It is not the case with intelligent antenna. It is able to receive the signals from a specified user and transfer the signal enegy to the said user in a more effective way. Different from traditional TDMA, FDMA or CDMA, intelligent antenna introduces the fourth dimension multiple access: SDMA. With the same time slot, frequency or address code, the user is still able to differentiate them in light of the space transmitting paths of the signals. Intelligent antenna is equal to a time space filter, which works to notably reduce the interference of user signals with each other under the control of parellel antenna beams directed to different users. To be specific, intelligent antenna will improve the performance of future mobile communication system in the following aspects:

(1) Enlarge system coverage;

(2) Reduce interference and raise system capacity;

(3) Improve utilization rate of high frequency spectrum;

(4) Raise the sensitivity of base station;

(5) Reduce transmitting power of base station, so as to lower system cost and reduce interference between signals and environmental pollution of electromagnetism.

Intelligent antenna is of two major types: multi-beam intelligent antenna and adaptive array antenna, known as multi-beam antenna and adaptive antenna; the latter is the main type of intelligent antenna.

Multi-antenna uses multiple parallel beams to cover the entire user area with each beam pointing to a fixed place. The beamwidth varies with the number of array elements. With the users moving in the cell, the base station will choose different beams accordingly, so as to make the signals received the strongest. As user signals are not necessarily at the center of fixed beams, when the user is at the edge of beam with the interference signal at the heart of beam, the receiving effect will be the worst. Therefore, multi-beam antenna cannot achieve best reception of signals. It is generally used as receiving antenna. However, compared with adaptive array antenna, multi-beam antenna has such advantages as simple structure and no need for judging the direction where the user signal reaches.

Normally, adaptive antenna adopts an array element structure of 6～16 antennas with a interval of 1/2 wavelength between array elements. If such interval is too large, the correlativity of received signals to each other will be reduced; if such interval is too small, there will arise unnecessary grid slobes. Thus, the interval is generally half wave length.

Adaptive array antenna system adopts digital signal processing technology to identify the direction where the user signals reach and then form major beam of the antenna in this direction. Adaptive array antenna provides different space channels tantamount to the cables for wire transmission in light of different user signals, so as to ward off the effect of interference on the system. The general structure of intelligent antenna is shown in Figure 4-7(a):

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Figure 4-7(a) Structure of Intelligent Antenna

(b) Diagram of TDD Wireless Base Station with Intelligent Antenna

Antenna array may take such shapes as straight line, circle or two-dimention plane. The core of antenna system is the digital signal processing unit, which enables antenna array to produce directional beams pointing to the mobile subscribers according to certain standards and automatically adjust the weight coefficient so as to achieve space filtering as required. Intelligent antenna is required to solve the following two key problems: identify the signal direction and achieve digital shaping (matrix). The representative algorithm for signal direction AOA (Angle of Arrival) is Music, ESPRIT, and maximum likelihood algorithms etc. The aim of adaptive beam shaping is to obtain best weight coefficient through adaptive algorithm. What algorith to take requires considering adaptive rules, the most common of which are SINR, MMSE, minimum mean square and maximum likelihood etc. It has been proved that the best weight coefficients using the above four rules will result in equal steady state solution, or Wiener-Kolmogorov solution. Adaptive algorithms in common use include the following: (1) Direct sampling covariance matrix inversion algorithm (DMI); (2) various minimum mean square algorithms (LMS); recursion least square algorithm (RLS); (4) constant model algorithm (CMA) etc. These adaptive algorithm has their own advantages and disadvantages. Proper algorithm should be selected in practical application in light of practical conditions.

Hereunder is the detailed description of matrix expression of shaped beams.

As shown in Firgure 4-7(b), it describes a block diagram of CDMA base station with intelligent antenna, working in TDD mode. From the figure, we can see that compared with the traditional base station without intelligent antenna, it has FR part composed of an antenna array and a group of receive-and-transmit units on its hardware, while the hardware for baseband signal processing is basically the same. What should be pointed out is that this group of wireless receive-and-transmit units will use the same local vibration source, so as to ensure this group is working in a corelative way.

As shown in Figure 4-7(b), each FR receive-and-sent unit has ADC and DAC, which convert the baseband analog signals received into digital signals, and convert the digital signals to be transmitted into analog baseband signals, so as to perform the conversion between analog signals and digital signals. All the signals received and

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transmitted are connected by a group of high-speed digital buses and baseband digital signal processor.

From Figure 4-7(b), let’s first study the signals from multiple user terminals. These upsteam signals have such effects as multi-address interference, fading, multi-path transmission and doppler frequency shift, and have other interferences and noises. Use Si(n) for the output of Receiver i as shown in the figure at n time point. Through deamplification and the corresponding digital siganl processing, you may get the data received from each code channel. If we use Xji(∫) to indicate the array elements of Symbol ∫of Code channel j received at Antenna i , then after beam shaping (composition) on the baseband, the total data received from the intelligent antenna should be:

W refers to uplink beam shaping matrix, whose matrix element is Wij(∫).

Next, the intelligent antenna will shape its downlink beams. Use Yj(∫) to indicate Symbol∫tranmitted to this user from code channel j. The signals transmitted from antenna array element i via the downlink beam shaping of intelligent antenna (adjust the amplitude and phase of the signals transmitted from each transmitter in the base station) can be expressed as:

where U is downsteam beam shaping matrix for element uji(∫).

Obviously, to get the best receiption, we must find out a good algorithm for uplink beam shaping, or a method for obtaining W matrix; in order for the user to get the best signals, it is necessary to find out a good algorithm for downlink beam shaping, or a method for obtaining U matrix. It must be pointed out that the only thing already known is the geometric structure and the signals received by various receivers of the antenna array in finding this beam shaping matrix. In this respect, the researchers have done a lot of work, and there are several algorithms available, mainly limited to the processing capacity of baseband processor and the requirements on real-time work.

Intelligent antenna technology will bring much good to wireless communicaiton, especially in improving CDMA system performance and reducing its cost. However, consideration must be given to the problems arising from the application of intelligent antenna to CDMA system. At the same time, the following problems should be solved in respect of standard, produce and network design:

I. Ominidirectional beam and shaped beam

Intelligent antenna’s major functions are performed through adaptive transmission and shaping the received beam. Furthermore, the shaping of beams received and

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transmitted is done on the basis of geometric structure, system requirements and the user signals received with respect to the base station antenna. Under mobile communication system, the intelligent antenna uses shaped beams on the uplink signal of each user, which serves to improve the system performance directly. However, when the user is not transmitting but only receiving signals and moving within the area covered by the base station (idle status), it is impossible fo the base station to know exactly where the user is. In this case, the base station will use omnidirectional beams for transmission (such physical channels in the system as Pilot, synchronization, broadcast and paging). For the base station with omnidirectional coverage as shown in Figure 4-8, different beams are transmitted from different code channels. That is to say, the base station must provide omnidirectional and directional shaped beams. In this sense, an omnidirectional channel requirs much higher transmitting power (the maximum power possible is 101gN dB higher than the dedicated channel,where N is the quantity of antenna array elements. This must be taken into account in system design.

Figure 4-8 Diagram of Coverage Requirements on Different Channels

II. Shared downlink channel and discontinuous transmission

The mobile communication system providing IP data services is designed with uplink and downlink channels shared by multiple users and discontinuous transmission technology is used in the base station and at the user terminal. In a base station using intelligent antenna, as the users move, it is impossible for the base station to locate the useres; therefore, in general, only omnidirectional downlink beam should be used. In addition, one more access process may be added to transmit signals to each user in a fixed direction. These two methods each have their advantages and may be possibly used.

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III. Alignment of intelligent antenna

While using intelligent antenna, it is required to provide technology of automatic and real time alignm of intelligent antenna. While using intelligent antenna in TDD system, use the uplink beam shaping coefficient directly to shape downlink beam in accordance with the principle of reciprocity in electromagnetic field theory; but for actual wireless base station, it is impossible that the radio transceiver on each channel is totally the same; moreover, its performance may vary with such factors as period, work level and environmental conditions. Without real-time automatic alignment, the downlink beam shaping will be affected seriously. It will not only fail to gain the advantages of intelligent antenna but also cannot even communicate at all.

IV. Frame structure and relevant physical layer technology

There is no special requirement on physical layer technology for a mobile communication system in using intelligent antenna. Moreover, basic technologies for the physical layer as modulation demodulation, spread spectrum, channel coding, error correction and data multiple connection, will definitely be totally the same. However, to use intelligent antenna may allow you to design the physical layer in a more effective way. For example, in the TD-SCDMA-recommended system, synchronous CDMA technology is used to simplify the tranceiver; specified uplink and downlink Pilot time slots are used in the design of time slots at the physical layer, so as to reduce the interference arising from cell search and random access etc., thus the functions of intelligent antenna are brought into full play.

V. Combination of antenna with other anti-interference technologies

Presently, there must be a comprise between the algorithm complication and real time implementation of the intelligent antenna. Thus, the practical intelligent antenna algorithm still can neither solve the problem of multi-path interference arising from time delay over the width of one code nor overcome channel deterioration as a result of doppler effect out of high-speed movements. Under the serious environment of multi-path high-speed movements, it is required to combine the intelligent antenna with other anti-interference digital signal processing technologies, so as to achieve the best results.These digital signal processing technologies include joint detection, interference cancellation and Rake receiption etc. Currently, the combination of intelligent antenna with joint detection or interference cancellation already has practical algorithm, while the algorithm for its combination with Rake receiver is still under research.

VI. Problem of beam shaping speed

It must be noted that due to the mobility of user terminal, mobile communication is a time variant channel. Intelligetn antenna uses received signals to shape the uplink and downlink beams, so it is requested that TDD cycle should not be too long. For example, when the user terminal moves at a speed of 100km/h, its doppler frequency shif approaches 200Hz and the change of user terminal location within 10ms will reach 28cm. At 2GHz frequency band, it already exceeds one wavelength, resulting in huge error in shaping downlink beams. Therefore, TDD cycle is expected to be reduced at least by half, so that the interval between transmitting and receiving is within the range of 2-3ms in order to ensure the intelligent antenna works in a proper way. If this system terminal is required to mover faster, TDD uplink and downlink conversion cycle should be shortened further.

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VII. Consideration of equipment complication

Apparently, the performances of intelligent antenna will increase with the increase in the number of antenna array elements. However, to increase the number of antenna array elements will add to the complication of the system. Such complication will ascend by geometrical progression in respect of the quantity of baseband digital signals to be processed. Nowadays, CDMA system trends towards broad band and the code rate already stands quite high, so the complication of baseband processing requires more and more in respect of microelectronic technique. In this way, this determines it impossible to have a large number of antenna elements.According to the current level, the number of elements should range between 6 and 16.

In addition, as the mobile communication environment is particular, other new problems occur to intelligent antenna: serious multi-path problem and message sources generally outnumber antenna array elements. The characteristic of multiple sources and paths requires the research and development of intelligent antenna to gain momentus in the following aspects: have a full understanding of the mobile communication environment, especially the space dimension characteristic, which requires not only new models created for mobile communication environment but more test results. On the basis of understanding the particularity of mobile communication environment, develop new algorithms in seamless connection with the mobile communication system and other wireless technologies; research on the interworking of intelligent antenna with other technologies, such as power control, multipl user detection, synchronous technologies and RAKE receiption with the objective of eliminating, balancing and utilizing interference in a better way so as to improve system performance.

Currently, intelligent antenna technology is considered internationally as a major development trend of mobile communication technology later than the third generation. It has become possible to apply intelligent antenna to WCDMA TDD system. As a matter of fact, intelligent antenna is one of the key technologies for TD-SCDMA system.

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1.3 Antenna Dip AngleDowntilt Planning

In cellular communication, coverage theory, frequency multiplexing theory and BSS functional algorithm are all based on the same precondtion, i.e. regular cellular layout. The factors affecting cellular layout in wireless network planning are mainly reflected through the design of project parameters, ranging from the macro layout of multiple base stations in wireless network to the location of a single base station, antenna height, lobe width, direction, dip angledowntilt and EIRP etc, thus forming a specific celluar network. Normally, the performance indexes of the antenna itself are selected according to the characteristics of wireless network such as the intensity of base stations and macro coverage goal; once the location of base station is determined in combination of networking requirements and external ojective conditions, it seldom changes thereafter; while the antenna height, direction, dip angledowntilt and coverage goal should be finalized in accordance with the parameters specified previously and the specific coverage goal of a single cell.

Hereunder is the analysis of the relationship between such elements of the anntenna as its height, direction, dip angledowntilt and coverage goal (cell radius is R), and the recommended value of the antenna dip angledowntilt under certain condition will be given.As radio signals are transmitted closed related to the environment (such as loss in the area with dense high buildings, the reflection of mountains, water surface or huge glass walls, which will have effect on the transmission of electric waves), it is not necessarily adaptable to all the transmission environments. However, if careful consideration is given to the regularity of cellular structure as well as the range to be covered by the cell and coverage goal, it may help lay a solid foundation for the quality of wireless network.

1.3.1 Antenna Dip AngleDowntilt Design

In designing antenna dip angledowntilts, consideration must given to the following factors: antenna height, azimuth angle, gains, vertical half power angle and the cell range expected to be covered.

As is known all, when the antenna gain is determined, the horizontal half power angle of the antenna is in inverse ratio against its vertical half power angle with their relationship expressed as follows:

Ga=32600/( )

Where Ga is antenna gain (a multiplying factor, which should be converted into dB

value), is vertical half power angle and is horizontal half power angle. It must be noted that this formula only yields a theoretical value. As a result of such reasons as manufacturing technique, the actual antenna index will be different, especially the width of vertical lobe. Therefore, before specific application, it is prefered to look up antenna technical manual.

From the above formula, we know thaqt when antenna gain is relatively small, the vertical half power angle and the horizontal half power angle of antenna are normally large, and vice versa. In order to better control trans-regional coverage, it is appropriate to select the antenna with higher gains in network planning within a region of intensive base stations, but antenna with high gains will easily result in unfavorable coverage in the vicinity. In serious cases, zero point filling technology must taken into account.

For the base stations distributed in downtown areas, when the antenna has no dip angledowntilt or the angle is very small, the service range of each cell is subject to the

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height, azimuth angle, gain, transmitting power and land forms and ground objects with regard to the antenna. In this case, the coverage radius may be calculated through Okumura-Hata or COST231 formula; when the antenna dip angledowntilt is relatively large, as the above formula fails to consider the dip angledowntilt, thus it is impossible to work out the coverage radius (if there is an accurate transmission model and digital map, ASSET may be figured out). At this point, direction estimation can be done in accordance with the size of vertical half power angle and the dip angledowntilt of the antenna on the basis of triangle geomety formula as follows:

Suppose the radius to be covered is D(m) with antenna height as H(m), dip

angledowntilt as and the vertical half power angle as , then the relation between the antenna major lobe beams and the ground as shown in Figure 4-9.

Figure 4-9 Relation between Antenna Major Lobe Beams and the Ground

It can be seen that when antenna dip angledowntilt is 0 degree, antenna beam major

lobes or major energy radiate horizontally; when antenna declines by

degrees, the extension line in the direction of major lobes will ultimately intersect a point on the ground (Point A). As antenna is of certain beam width vertically, much energy will be radiated in the direction from Point A to Point B. According to technical performance of the antenna, within the scope of half power angle, antenna gain will come down slowly; beyond the half power angle, antenna gain (especially the upper lobe) will fall sharply. Therefore, while considering the size of antenna dip angledowntilt, the scope ranging from the extension line of the half power angle to the intersection point on the ground (Point B) may be regarded as the actual coverage area of this antenna.

According to the above analysis and the theories for triangle geometry, it can be deduced that the relationship between antenna height, dip angledowntilt, and

coverage distance is as follows: arctanarctanarctanarctanarctanarctan(H/D)+ /2

The above formula may be used to estimate the coverage distance after the dip angledowntilt has been adjusted. The actual result of practical application on the optimism site reveals that this formula is of great guiding significance. However, the application of this formula is limited by the following conditions: the dip angledowntilt must be greater than half of the half power angle; the distance D must be less than the distance worked out according to the formula in absence of a dip angledowntilt. For vertical beam width in the above formula, pleaes refer to the specific antenna technical index or work out the rough value.

In a situation where the vertical beam width is 17 degrees and the base station antenna is 40 meters high, the relationship between the coverage distance and antenna dip angledowntilt is shown in Figure 4-10. When the vertical beam width is 6.5 degrees and the base station antenna is 40 meters high, the relationship the coverage distance and antenna dip angledowntilt is shown in Figure 4-11.

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coverage distance-declination angle

dist

ance

(m

eter

)

declination angle (degree)

Figure 4-10 Relation between Coverage Distance and Dip AngleDowntilt (vertical beam width as 17 degrees, and antenna height as 40 meters)

coverage distance-declination angle

dist

ance

(m

ete r

)

declination angle (degree)

Figure 4-11 Relation between Coverage Distance and Dip AngleDowntilt (vertical beam width as 65 degrees, and antenna height as 40 meters)

Seen from the above two figures, when the antenna height and dip angledowntilt are specified, the relation between the coverage distance and the vertical beam width of the antenna is as follows: The smaller the vertical beam width, the coverage distance will be shorter. As a result, to control trans-regional coverage in a better way, we should choose an antenna of small vertical beam width with zero point filling function while selecting antennas in the planning stage. In this way, it will prevent trans-regional interference and improve the coverage in the vicinity and indoor coverage. However, when the vertical beam width grows smaller, the horizontal lobe or gain will get larger, thus causing new trans-regional interference or excessive cross coverage between neighboring cells. As a result, antennas of medium gain are usually chosen

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in urban areas. For example, GSM900 selects antenna of 65 degrees and 15dBi. At this time, the width of vertical lobe ranges between 11-15 degrees. It must be noted that the adjustment of dip angledowntilt may serve to control the coverage area in addition to improve the indoors coverage in the vicinity of the base station, but the coverage far from the base station will get worse.

1.3.2 Practical Application

In order for practical application considering the necessary overlap of some areas between adjacent cells. The distance D from the base station in downtown area to the coverage desitination may be simplified as the designed cell radius (diameter as R); the antenna height H refers to the relative height of the base station and the coverage designation, and this article only treats of the areas similar to plains.Antenna declinationdowntilt is divided into mechanical declinationdowntilt and electric declinationdowntilt, both of which have equal effect on the coverage. As electric declinationdowntilt is more expensive and requires customization, we usually adopts mechanical desclination. It is generally believed that it is a scientific approach to keep the mechanical declinationdowntilt of the antenna below 10 degrees; in the event of more than 10 degrees, the lobes are easily distorted, thus causing unexpected interference against other cells; another conclusion is that the dip angledowntilt of mechanical declinationdowntilt should not exceed the half power beam width within the vertical plane of the said antenna. Otherwise, coverage is distorted.

Therefore, in terms of the goal of maximum rationaliztion, we wish to adopt electric antenna in populous downtown areas for networking. As the anntenna capable of onsite adjustment of electric declinationdowntilt angle is rather expensive, we normally use antenna with preset factory 6～7 degrees of electric declinationdowntilt (or the average declinationdowntilt angle within the coverage area). Combine mechanical declinationdowntilt in network capacity enlargement and optimization, so as to set large declinationdowntilt angle of 15～20 degrees.

According to what is discussed above and in combination with A anntenna in most common use and the commonly seen antenna height antenna (25～50 meters), the value recommended for antenna declinationdowntilt angle under the cell radius of 250, 500, 800 and 1000 meters. The same is true of other circumstances.

Antenna modelVertical half

power angle of antenna

Cell radius R(m) Antenna height DeclinationDowntilt angle

65 degrees, a gain of 15 dBi 12 200 50 2065 degrees, a gain of 15 dBi 12 250 50 1765 degrees, a gain of 15 dBi 12 250 40 1565 degrees, a gain of 15 dBi 12 250 30 1365 degrees, a gain of 15 dBi 12 250 25 1265 degrees, a gain of 15 dBi 12 500 50 1265 degrees, a gain of 15 dBi 12 500 40 1165 degrees, a gain of 15 dBi 12 500 30 1065 degrees, a gain of 15 dBi 12 500 25 965 degrees, a gain of 15 dBi 12 800 30 865 degrees, a gain of 15 dBi 12 1000 30 2

From this we can see that when the cell radius is too small, antenna mechanical declinationdowntilt cannot ensure control of coverage area. At this time, we cannot but reduce the antenna height; if it is difficult to reduce the height, it is necessary to adopt the combination of electric declinationdowntilt and mechanical declinationdowntilt. In application, for a base station with its antenna of 40-50 meters in height, the minimum cell radius is 250 meters. Normally, the ideal height for macro cellular antenna in downtown areas is 25～30 meters and the antenna in suburbs or directed to the suburbs is 40～50 meters in height.

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The above method for calculating declinationdowntilt angle is mainly applicable to the dense base station networking with an interval of less than 1200 meters (i.e. R=800m) between stations.

When the base station is over 800 meters away from the coverage destination, the most concern is still the coverage of a large area. It is not necessary to consider the effect of vertical half power angle in working out the antenna declinationdowntilt angle. At this time, the angle of declinationdowntilt is normally 1～4 degrees; under special circumstances, for example, if the base station has been installed in a higher position, its angle of declinationdowntilt may also be large.

However, the surroundings around the base station are quite complex. The declinationdowntilt angle must also take the reflection from the neighboring mountains, water surface and tall glass walls into consideration in that such reflection will easily cause unexpected adjacent frequency interference with other base stations and even its own time dispersion effect; consideration should also be given to shadow effect caused by the buidling roof, dense architectural complex and slope on electric waves.。However, in practical networking, the surrounding geographical environment around the base station will be combined to use the obstruction of tall building or mountain to control the coverage area. It is required to consider the declinationdowntilt angle at this time.

Networking in populous downtown area should also consider the street effect and unexpected trans-regional coverage arising from the antenna major lobe right directed to the street. In general, the major lobe should avoid being directed to a straight street.

When a cell needs to cover an area higher than the antenna, it is possible to adopt inverse directional antenna or negative angle of declinationdowntilt. The antenna is required to proof against water.

If the base station is placed too high and thus necessitating the coverage of valleys far lower than the base station ( more than 50～60 meters or depression angle more than 5 degrees) and only omni-antenna can be used, it is necessary to consider using omni-antenna characterized by electric declinationdowntilt angle (3 degrees or 5 degrees etc.), wide vertical lobe (low gain), zero point filling or improvement on the gain of lower secondary lobe in order to improve the coverage near the base station and avoid possible signal fluctuation caused by “blind under tower” and unequal coverage.

We must also give consideration to the direction after the antenna back lobe declines on the major lobe of the antenna, because the front-to-back ratio for general antenna nowadays only stands at 20dB. The back lobes with strong signals will easily cause much interference against high buildings. Therefore, it is recommended to adopt electric declinationdowntilt while selecting antenna in populous urban areas, and take note of the effect of upper secondary lobes.

Normally, the vertical power angle of omni-antenna is symetric vertically along the plane, and thus the inverse and upright installation will have equal effect; in practial project, the vertical directional diagram of specific omni-antenna should still be taken into consideration to check if the electric declinationdowntilt angle is already available. In this case, careful consideration should be given to inverse installation.

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1.4 Antenna Selection

In mobile communication network, it is a very important part to select an antenna. We should make a choice in light of practical conditions such as the requirement on coverage, traffic, interference and network service quality of the network. A proper antenna will enlarge the coverage, reduce interference and improve service quality. As the selection of antenna is closely related to coverage requirement, the environment for using antennas can be divided into 4 types in light of the land form or the distribution of traffic: urban area, suburb, rual area and highroad.

1.4.1 Current Problems of Using Antenna

Little consideration is given to the relation between the actual land form and the antenna directional diagram with antenna selected simply in consideration of the distribution of covered traffic. For example, in selecting omni-antenna, the entire network uses a single type of omni-antenna, which leads to “blind under tower” as a result of narrow vertical plane beam when the antenna is placed high.

Oblivious to the limit on the use of antenna, many places decline the antenna in a very large angle in order to reduce interference without regard to antenna directional diagram, thus distorting the directional diagram and causing problems with coverage. Actually, simulation indicates there should be different limits on declinationdowntilt angle in light of antennas with different gains.

Too much attention is focused on the high gain performance of the antenna without regard to the disadvantages of such performance. As a result, almost the gains of all the antennas used in the entire network stand quite high. The weak points of high-gain antenna are as follows: large size, heavy, high secondary lobe, deep zero lobe and narrow vertical beams.

Without regard to the difference between dual polarization antenna and vertical polarization antenna in terms of use, consideration is only given to selecting dual polarization antenna from the angle of engineering installation.

1.4.2 Application Principle for Base Station Antenna in Urban Areas

In urban areas, as the base stations are densely distributes, it is requested that a single base station covers a small area in hopes of reducing trans-regional coverage, reducing the itnerference between base stations and improving frequency multiplexing rate. In principle, the antenna should meet the following requirements:

I. Selection of antenna plane horizonal half power beam width

As there are a large number of base stations distributed in urban areas, overlapping coverage and frequency interference will arise as a serious problem. To reduce the overlapping area of adjacent sectors, and reduce the interference between base stations, the beam width of antenna planehorizonal half power should be small. Normally, we select an antenna whose plane horizontal half power beam width is 65 °. Normally, those antennas with beam width over 90° will not be chosen._

II. Selection of antenna gain

As the base station in urban areas normally requies no large coverage distance, it is recommended to select the antennas with medium gains. Thus, the vertical plane

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beam of antenna can be made wider, so as to enhance the coverage effect within the area to be covered. At the same time, the size and weight of antenna can become smaller instrumental to the installation and reducing cost. According to the current antenna models, it is recommended to select a gain of 15dBi (900MHz) or 15-18dBi (1800MHz) for antennas in urban areas.

For a base station on the outskirt of a city, if the coverage distance is required to be long, antenns with higher gains such as 17dBi、18dBi can be selected.

In principle, while designing base station coverage in urban areas, we should select an antenna with fixed electric declinationdowntilt angle, whose size is subject to practical conditions (6-9°preferred).

Inside a city, in order to raise the frequency multiplexing rate, reduce trans-regional interference and improve D/U value (the ratio of useful signal level to useless signal level), it is allowed to select an antenna with its first upper secondary lobe suppressed and the first lower zero point filled (shaping technology). However, the antenna of this kind usually has no fixed angle of declinationdowntilt.

As it is different to select a site for an urban base station, the installation space for antenna is limited. Generally, it is recommended to select dual poluarization antenna. Under indentical or similar electric indicators, it is better to select an antenna of small size.

1.4.3 Application Principle for Suburb Base Station Antenna

In the suburbs, things are largely different. We may estimate what type of antenn is required according to the coverage area as required. Generally, we may comply with the following basic principles:

We may select an antenna with its plane horizontal half power beam width as 65° or 90°in light of practical conditions. When there are few base stations around, it is imperative to give priority to the antenna with its plane horizontal half power beam width of 90°.

If a lot of base stations are around, refer to the selection antennas in urban areas for the the principle for antenna selection.

With a view to smooth upgrading in the furture, in general, it is not recommended to adopt an omni-antenna in this case.

Whether to adopt an angle of declination downtilt is subject to practical conditions. Even if a declination downtilt angle is used, it is generally very small.

1.4.4 Application principle for base station antennas in rural areas

As rural areas require small amount of traffic but large coverage, the application of antennas should follow the principles hereunder.

If the base station is required to cover its neighboring areas without obvious directions, and the traffic around the base station is scattered, it is recommended in this case to adopt the omnidirectional coverage of base station. It should be noted that the large coverage herein does not mean long coverage distance but large coverage area without apprarent directions.At the same time, we should also pay attention to the following fact: as omni-directional base station has small gains, the coverage distance is not as long as the directional base station.

If the equipment buyer requires farther base station coverage distance, it is required to use three directional antennas to attain this objective. Normally, we should use a

25


directional antenna with plane horizontal half beam width of either 90°or 120°. Another thing requiring attention is that vertical polarization antenna has more diversity effect and stronger capacity against slow fading than dual polarization antenna. As required for large coverage in rural areas, if conditions permit, we may substitute two pieces of vertical polarization antenna for dual polarization antenna.

For high stations in mountaineous areas (the relative height of antenna is over 50 metres), we should generally select antennas with zero point filling function to solve the problem with “blind under tower” in short range. While solving this problem via an angle of declination downtilt, we should note the reduction of coverage area.

1.4.5 Application principle for antennas to cover highroads

To cover highroad areas, the principle for selecting antenna is as follows:

For a base station designed to cover the areas along railways and highroads, narrow beam directional antenna can be used to this effect.

To cover highroads and scattered villages around them, we may consider using an omni-antenna.

To cover expressways, 8-shaped antenna may be used for this purpose.In this way, the number of base stations may fall, so as to achieve the coverage of expressways.

To cover an expressway and the towns along the highroad, the antenna with plane horizontal half power beam width of 210° may be used. It is recommended to give priority to 8-shaped antenna and 210° antenna to cover highroads. The directional diagram of the said two antennas is shown as follows.

210¡ ã directional diagram

highroad

base station

mountain

town

Figure 4-12 (a) 210-degree Antenna

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8-shaped directional diagram

HighroadBase station

Mountain

Figure 4-12 (b) 8-shaped antennas

1.4.6 Other factors in antenna application

The basic principles for selecting antennas in different places are described as above. In fact, capacity expansion in the future and basic performances should also be taken into consideration in selecting antennas.

Here is a simple example:

If 210°antenna is selected for an expressway, the quantity of carrier frequency should increase to meet the demand on capacity expansion provided that the said area sees a traffic rise in the future. Due to different CF configurations of base station, with the increase of carrier frequency, insertion loss will increase. In this case, capacity expansion will inevitably lead to the drop in coverage distance. Unless cavity combiner is used, these problems should be anticipated when antenna type is selected.

In addition, in selecting antennas, consideration should be given to the distribution of traffic and surrounding station types, especially in rural areas, where few types of stations exist, this must be considered more carefully. In rural areas, if the traffic is distributed equally around the base station, we may consider using omni-antenna. At the same time, we should take into account of an omni-antenna with zero point filling. If the traffic is only distributed on one side of the base station, and there is almost no traffic on the other side, we may consider 210° antenna. If traffic exists only on a narrow and long highroad, we may consider directional antenna of narrow beams or 8-shaped antenna.

In addition, as the azimuth angle of antenna requires regular adjustment during the network optimization period, it is recommended to select an antenna with its azimuth adjusted electrically after the antenna with electrically adjustable azimuth is mature upon argumentation.

1.4.7 Notes on special antennas

Zero point filled antenna serve to solve the problem of “blind under tower” without any effect in other respects. It is recommended that antennas with zero point filling are used for all the omni-antennas so as to avoid the problem of “blind under tower”.

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With regard to 8-shaped and 210° antennas, it is recommended to give top priority to them in respect of expressway coverage.

If a base station installed on top of a mountain is required to cover the areas at the foot of the mountain, it is recommended to select an antenna with wide vertical plane half power beam for the coverage, such as omni-antenna with a gain of 8.5dBi or a directional antenna of 14dBi with vertical plane beam width of around 20°.

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1.4.8 Reference for antenna selection

Land form Statoin type Recommendation for antenna selection Remark

Urban area Directional station

Normally, select antennas with low or medium gains and fixed electric angle of declinationdowntilt, subject to the density

of base stations; if an antenna with electrically adjustable azimuth is

available, it should also be selected.

While installing an antenna, make sure that

the mechanical declinationdowntilt angle

is no more than 10 degrees.

Suburb Directional station

Normally, select antennas with high gains, permitting of electrically adjustable

azimuth or mechanical declinationdowntilt angle.In addition, if some areas are not

well covered in some directions, antennas with its planehorizonal half power beam width of 90 degrees may be selected.

If mechanical declinationdowntilt angle

is to be installed, the angle should not be too large.

Plains & rural areas

Directional station

Generally, select an antenna of 90 degrees or of 120 degrees. It is perferred

to use vertical single polarization antenna.

Generally no declinationdowntilt angle

is added.

Omnidirectional station

First there must be zero point filled antenna without regard to angle of

declinationdowntilt.


is added.

Exressways Directional station

First consider 8-shaped antenna and then consider 0.5/0.5 configuration using

power splitter; it is preferred to have zero point filling.


is added.

Directional station +

omnidirectional station

First consider 210-degree antenna, then consider the combination of directional

antenna+ omni-antenna


is added.

Mountainous areas

Omnidirectional station

First consider antenna with zero point filling function, then consider antenna of

lower gain before adding a declinationdowntilt angle.


is added.

Directional station

First consider antenna with low gain and vertical plane beam width before adding a

declinationdowntilt angle.


is added.

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1.5 Combining and distribution unit

The combining and distribution unit is mainly to achieve transceiver duplexing, transmitting signal combiner, filtering and receiving signal filtering, low noise amplification and distribution, and provide tower amplification with feeding circuit, and share the same antenna unit with multiple signals transmitted and received.

1.5.1 Principle for combining and distribution unit

The combining and distribution unit has the following functions of detection and alarm:

(1) Standing wave dection: to monitor the status of antenna feeder; When it detects that the standing wave exceeds the preset threshold (1.5:1 or 2.5:1), it will give corresponding alarm signals and indication.

(2) Low noise amplifier fault alarm: as the fault signal is taken from the feeding current of low noise amplifier, when the current exceeds a certain range or there is no current, alarm signal will occur.

(3) Tower amplification alarm: when tower amplification works with the fault signals taken from its feeding current, when the current exceeds a certain range or there is no current, alarm signal will occur.

(4) Control function: to exercise the control of the power attenuation over the master and slave receiving channel (dynamic state 15dB, step 1dB); perform function of switching on and off feeding current; select different tower amplification feeding current at the same time.

Take Huawei equipment for example, it has three kinds of modules that can provide combining and distribution unit: CDU, SCU and EDU.

Schematic diagram of CDU is shown in Figure 4-13.

Figure 4-13 CDU Schematic Diagram

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SCU schematic diagram is shown in Figure 4-14.

TX1

TX2

TX3

TX4

TX-DUP

Com

binerC

ombiner

Com

biner

Figure 4-14 SCU Schematic Diagram

EDU schematic diagram is shown in Figure 4-15.

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Figure 4-15 EDU Schematic Diagram

Different combining and distribution units have different losses, which are configured and used in light of different station types. The following indexes are specified: for each combination (two combined into one), in theory, insertion loss is 3dB and duplexer insertion loss is 1dB or so.

1.5.2 Combining and distribution unit configuration

This section takes Huawei equipment to explain the configuration of various combining and distribution units:

FC number for each cell Regular configuration plan

Large coverage configuration plan Remark

7～8TRX 2CDU＋2SCU

Large station is mostly located in the urban area, which is basically applicable to large coverage.

5～6TRX CDU+CDU+SCU CDU+CDU+SCU

In applying large coverage configuration plans, it is necessary to combine Huawei’s concentric circle technology

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3～4TRX CDU+SCU Dual CDU

1～2TRX CDU EDU or dual CDU

EDU is only applicable to the situation where each sector has no less than 2 CF. Changes are required in capacity expansion.

What should be noted is that large coverage plan as mentioned above is a recommendation on the precondition of not increasing antennas and feeders in each cell. In practical network application, we may flexibly select different configurations (antennal feeder + amplifier {40W 、 60W 、 80W etc})in light of the coverage and capacity demands for different stations if the conditions for uplink and downlink balance are met; and in combination with Huawei Company’s BSC software algorithm (such as concentric circle control technology applicable to when each CF coverage is not the same in the same cell), so as to attain the best coverage effects.

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1.6 Outdoor antenna feeder system

Outdoor antenna feeder system includes antenna, tower amplifier, feeder linefeeder cable, jumper and lightning arrester, as shown in Figure 4-16. Antenna has been described above and the following is devoted to tower amplifier and feeder linefeeder cable.

Figure 4-16 Composition of outdoor antenna feeder system

1.6.1 Tower amplifier

In terms of technial principle, tower amplifier is to reduce the noise coefficient of the base station receiving system, so as to improve the sensitivity of base station receiving system. Tower amplifier makes different contributions to uplink, distinguished from each other in light of the performance of low noise amplifier of the tower amplifier itself, but it is not the right way only to focus on its gains. Generally, the uplink and downlink balance with tower amplification increased should be modified and calculated in accordance with the method for testing its actual sensitivity. Tower amplifiers of sub band or all band should be seleted in light of different frequency bands.

The principle for triplex tower amplifier is shown in Figure 4-17. This tower amplifier shares signal transmission and reception (only one feeder tube is required) and has bypass functioons (automatic bypass in the event of fault, when it receives a gain of about.

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Figure 4-17 Digram of Duplex Tower Amplifier

1.6.2 Feeder lineFeeder cable

It is very important to select feeder linefeeder cables in the overall system design. As the line is exposed outdoors, the cable needs to stand up to the water wash. Foam is pressed into the cable as isloation medium and air can be also taken as isolation medium.When bent, the air-insulative cable can easily result in short circuit; therefore, it is seldom adopted.

I. Use of feeder linefeeder cable

There are two types feeder linefeeder cable in common use, that is, 7/8" feeder linefeeder cable and 5/4" feeder linefeeder cable. They are used as follows:

(1) GSM900 feeder linefeeder cable:

7/8" feeder linefeeder cable is used for a length of less than 80m, while 5/4" feeder linefeeder cable for a length of more than 80m.

(2) GSM1800 feeder linefeeder cable：

7/8" feeder linefeeder cable is used for a length of less than 50m; while 5/4" feeder linefeeder cable for a length of more than 50m.

II. Technical indexes for the insertion loss of several feeder linefeeder cables

Feeder lineFeeder cable type 100 meter attenuation (dB)Standing wave (Any length)

890MHz1,000M

Hz1,700M

Hz2,000MHz

SYFY-50-22(7/8 inch) 4.03 5.87 6.46 1.15LDF5-50A (7/8 inch) 4.03 4.3 5.87 6.46 1.15LDF6-50 (5/4 inch) 2.98 3.17 4.31 4.77 1.15M1474A (7/8 inch) 4.3 6.6 1.15

HFC22D-A (7/8 inch) 4.47 6.7 1.15FSJ4-50B(1/2 inch) 11.2 11.9 16.1 17.7 1.15

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III. Installtin of feeder linefeeder cable

The feeder linefeeder cable used for installation should be the shortest of all and easy for installation and maintenance. The curvature of feeder linefeeder cable should comply with the requiremetn of manufacturers on feeder linefeeder cable.Whether the antenna is installed on the tower, roof and any other place, the external conductor of its feeder linefeeder cable should be grounded well before it goes into the equipment room.

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1.7 Distributed antenna system

With the development of mobile communication, the subscribers have higher and higher demand on service quality. People expect to communicate anywhere at any time. However, as some places (complicated areas with multiple blocks such as inside a large building, tunnel and metro) are not reachable if only covered by outdoor base station antenna and there will arise some blind spots unreachable by signals, thus causing communication interruption. In some areas, as the signals from different base stations are all quite strong, the mobile station has to switch frequently, thus causing communication interruption. Someone calls this pingpong effect. To resolve the above problems, distributed antenna system comes into existence. Besides, we may also transfer the capacity of a cell with excessive communication capacity to another area, so as to solve the problem with the distribution of system capacity.

1.7.1 Principle for composition of distributed antenna system

Figure 4-18 is the schematic diagram of the composition of a distributed antenna system. In terms of function, it is equal to one single poluarization antenna connected to a base station.

Figure 4-18 Diagram of the Composition of a Distributed Antenna System

The downlink signals from the base station go to the distributed antenna system via the interface. These signals form multiple tributaries via the power splitter, each of which can be divided into smaller tributaries via the power splitter. The end of each tributary is connected with a small antenna. Each small antenna covers a certain area. When the signal is not strong enough, it will be amplified by bi-directional amplifier with certain gains; on the contrary, the uplink signals in each tributary area, via small antenna, power splitter and bi-directional amplifier, will reach the base station through interface.

In the above system, the transmission and distributiojn of signlas can be performed through coaxial cable and FR power splitter or through optical link. In addition, it can also be a mixture of coaxial cable, power splitter and raditation antenna: disclosure cable.

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1.7.2 Types of distributed antenna system

I. Coaxial feeding distributed antenna system

Figure 4-19 Coaxial Feeding Distributed Antenna System

II. Disclosure cable

In some narrow and long coverage areas, it is a better way of coverage in using disclosure cable. A terminal load is required at cable terminal.

Figure 4-20 Disclosure cable

Compared with coaxial feeding, the cost for the equipment and fees for installation for disclosure cable are quite expensive.

III. 3. Fiber feeding distributed antenna system

For applications with large coverage and long transmission distance,

optical fiber can be used to replace coaxial feeding.

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Figure 4-21 Fiber distributed antenna system

Figure 4-21 is the diagram of fiber distributed antenna system. The manufactures may differ from each other in practice.Compared with coaxial feeding, fiber feeding for short haul system is more expensive but the feeding loss is small. Its disadvantage is that it requires local power and automatic detection equipment.

IV. Summary

Distributed antenna type Advantages Disadvantages

Coaxial feedingFlexible design

Low costHigh reliability

Large loss

Disclosure cable Flexible design High cost

Fiber feeding Low lossEasy for installation

High costPoor design flexibility

The equipment at overage terminal requires power

1.7.3 Indexes for component key technologies

I. Two-in-one combiner (mixed conducting bridge of 3dB)

The technical indexes of combiner are shown in the following table:

GSM900 GSM1800Work frequency band 890～960MHz 1710～1880MHz

Port imbalance 0.25dB

Insertion loss 3.6dBPort standing wave 1.5dB

Power capacity 300W

II. Equal power divider

Equal power divider works to distribute the energy of base station equally into several tributaries, thus forming common components for coverage distribution. To simply the project design, the system only adopts two types of equal power dividers, whose indexes are as follows:

Description 1 to 2 1 to 4Work frequency band 800～2000MHz

Power distribution ratio 1:1 1:1:1:1

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Insertion loss 3.5dB 6.5dBPort standing wave 1.5dB

Connector type N_Female

The insertion loss as defined in the above table includes the distribution loss.

III. Power coupler

The coupler here is bi-directional coupler, also known as unequal power divider. In project design, couplers with different coupling degrees can be selected in light of practical needs, to distribute the signals of the base station equally to each antenna in order to ensure equal coverage and avoid waste of energy. With a view to reducing the types of system components so as to bring down the cost, this system only selects the following three types of couplers with different coupling degrees:

Description 7dB coupler 10dB coupler 15dB couplerWork frequency band 800～2000MHz

Coupling degree 7dB 10dB 15dBInsertion loss 1.2dB 0.5dB 0.3dB

Port standign wave 1.5Connector type N_Female

As we stipulate that this system is a small-sized one for simple indoor coverage, the above three types of couplers can basically meet the requirement for project design. In the system design of distributed antenna, we should try to avoid the existence of more than two power dividion components (or coupler) along the path from the base station to each antenna, so as to ensure power balance of uplink signals.

IV. Indoor antenna

In general, the distributed antenna system uses antenna of small gains and does not specifically require the half power width of beams. This is attributed to the characteristics of indoor coverage. The following three kinds of antenna is nice to the look and enjoys desirable performance, which basically meets the requirement for indoor coverage. For places with a small area to be covered by a single antenna, it is recommended to use dual frequency omnidirectional antenna. If a long and narrow area is to be covered, it is however recommended to adopt a directional antenna.

Dual frequency band omni-antenna

900M directional antenna

1800M directional antenna

Work frequency band 890～960, 1710～1880MHz 890～960MHz 1710～1880MHz

Gain (2dBi) 2 7 8Horizontal beam width 360 90 90Form of polarization Vertical

Power capacity 300WStanding wave <2 <1.5 <1.5Connector type N_Female

V. Coaxial connector

As the length of the feeder linefeeder cable for indoor distribution system is not specified, it is necessary to specify the length in light of practical needs and make connectors. The system selects two types of coaxial connectors.

Type N type N typeDescription Coaxial connector-N type

connector-50Ω/right angle/male-nut installation-configured with SYV-50-

Coaxial connector -N type connector -

50Ω/straight/female-

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7-1 configured with 7/8"LDF5-50A cable

Type of calbe configured SYV-50-7-1 7/8"Impedance 50Ω

Standing wave 1.2

VI. Disclosure cable

In such narrow and long coverage areas as tunnel and metro, it is a better way to use disclosure cable. Disclosure cable is common cable with holes in its shell, so that the electromagnetic wave may leak from the holes to cover a certain area. In this case, each hole is equal to a small antenna.

DescriptionCharacteristic impedance 50Ω

Attenuation constant 900MHz：0.051dB/m；1800MHz：0.076dB/m

Coupling loss 900MHz：72dB；1800MHz：84dB; ( the loss 2 meters away from the coupling hole with an error of ±10dB)

Cable structure specification 7/8"Type of supporting connetor 14040121

Fire-proof performance Able to prevent flaming and proof against ultraviolet

VII. Ordinary feeder linefeeder cable

In the project design of antenna system, feeder linefeeder cable should be used to connect all the components. Two types of feeder linefeeder cable in the list are selected. One is SYV cable easy to be bent with a large loss but low cost; the other is 7/8 inch feeder tube with little loss but high cost, which does not get bent easily. The former is applicable to the tributary connection from the power divider to antenna, and the latter is applicable to trunk connectioon from one power divider to another power divider.

SYV-50-7-1 LDF5-50A-7/8"Performance impedance 50Ω 50Ω

Attenuation constant 900MHz: 0.22dB/m1800MHz: 0.31dB/m

1000MHz: 0.0446dB/m2000MHz: 0.0659dB/m

Type of N connection configured 14040184 14040121

Bending properties Good Poor

VIII. Load

While using disclosure cable, its end may either use a small antenna as load or use the load directly for match. The load index as defined in the list is:

Work frequency band 0～2GHzCharacteristic impedance 50ΩPort standing wave ratio <1.15Connector type N_MalePower capacity 300W

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Documents

Chapter4 About Antenna & Feeder Cable