KULLIYYAH OF ENGINEERING

DEPARTMENT OF ELECTRICAL & COMPUTER

ENGINEERING

ANTENNA AND WAVE PROPAGATION

LABORATORY

(ECE 4103)

EXPERIMENT NO 5

“CHARACTERISTIC ANALYSIS OF MICROSTRIP

PATCH ANTENNA & ARRAY ANTENNA”

INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

KULIYYAH OF ENGINEERING

ECE 4103

NAME OF EXPERIMENT: _____________________________

Student Name : __________________________

Matric Number : __________________________

Submission date : __________________________

Mark obtained : __________________________

INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

KULIYYAH OF ENGINEERING

ECE 4103 ANTENNA LAB

EXPERIMENT NO: __

NAME OF EXPERIMENT: _____________________________

__________________________

: __________________________

: __________________________

: __________________________

INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

NAME OF EXPERIMENT: _____________________________

1

EXP NO: 5

CHARACTERISTIC ANALYSIS OF MICROSTRIP PATCH

ANTENNA & ARRAY ANTENNA

OBJECTIVE

• To become familiar with the microstrip antenna.

• To investigate the characteristic of single microstrip patch antenna and array of microstrip

patch antenna.

• To investigate the effect of array factor to the microstrip array antenna.

MATERIAL

• 1 Rotating antenna platform 737 400

• 1 Gunn power supply with SWR meter 737 021

• 1 Gunn oscillator 737 01

• 1 Isolator 737 06

• 1 Pin Modulator 737 05

• 1 Large Horn Antenna 737 21

• 2 RF cable, L = 1 m 501 02

• 2 Supports for waveguide components 737 15

• 2 Stand base MF 301 21

• 1 Set of microwave absorbers 737 390

• 1 Set of 10 thumb screws M4 737 399

• 1 Remote control for rotating antenna platform 737 401

• 1 Microstrip antenna

BRIEF THEORY

Microstrip or patch antennas are becoming increasingly useful because they can be printed directly

onto a circuit board. Microstrip antennas are becoming very widespread within the mobile phone

market.

However microstrip antennas also have some limitations compared to conventional microwave

antennas and these disadvantages can be dwscribed as the following [4][5] :

• Narrow bandwidth.

• Somewhat lower gain (~ 6dB).

• Low power-handling capability (~100W).

Patch width, W and length, L

The shape of the patch is its main parameter and naturally affects most of the antenna

characteristics. However, the patch width has a minor effect on the resonant frequency and radiation

pattern of the antenna. So a larger patch width increases the power radiated and thus gives decreased

resonant resistance, increased bandwidth, and increased radiation efficiency. A constraint against a

larger patch width is the generation of grating lobes in antenna arrays. The patch width should be

selected to obtain good radiation efficiency if real state requirements or grating lobe are not overriding

factors. It has been suggested that 1 < W/L < 2.

The patch length determines the resonant frequency, and it is critical parameter in the design,

however the patch length L for TM10 mode is given by:

(1)

Where; fr is the resonant frequency.

= for ............................................ (2)

= for ........ (3)

The following equation is used to calculate the width, W:

………………...……………………..……… (4)

To determine the length, L, of the patch, the following equation is used:

– 2 …………….……... (5)

Normalized extension of the length is :

.................................................. (6)

Antenna Array

Antenna arrays are several antennas connected and arranged in a regular structure to form a single

antenna. Antenna arrays are able to produce radiation patterns that combined, have characteristics that

a single antenna would not.

The antenna elements can be arranged to form a 1 or 2 dimensional antenna array. Antennas

exhibit a specific radiation pattern. The overall radiation pattern changes when several antenna

elements are combined in an array. This is due to the so called array factor: this factor quantifies the

effect of combining radiating elements in an array without the element specific radiation pattern taken

into account. The overall radiation pattern of an array is determined by this array factor combined

with the radiation pattern of the antenna element. The overall radiation pattern results in a certain

directivity and thus gain linked through the efficiency with the directivity. Directivity and gain are

equal if the efficiency is 100%.

(a) (b)

Figure (a) Example of Array Antenna; (b) Assembly of the waveguide microstrip antenna for the

measurement of the vertical directional diagram

Arrays can be designed to radiate in either broadside i.e. radiation perpendicular to array orientation

(the zaxis in figure 1) or end fire i.e. radiation in the same direction as the array orientation (the yaxis

in figure 1).

For broadside arrays only radiation in the z direction is considered. This allows for easy

transformation to 2 dimensional planar arrays with the elements in the xy plane. For linear arrays the

radiation patterns given below are a cross section in the yz plane

Antenna arrays are characterized by their array factor which is given by the formula

AF =

)2

sin(

)2

sin(

ϕ

ϕN

……(7)

Where: ϕ = βθ +coskd ………..…(8)

N the number of elements making the array, k = 2∏ /λ,

θ is the polar angle and β is the difference of phase between any two successive elements forming the

array.

Influence of the element spacing on the array factor

� The array directivity increases with the number of elements.

� The presence of side lobes next to the main lobes: this is typical for arrays.

� The number of side lobes and the side lobe level increase with the number of elements

Planar array provides additional variables to control the array pattern in 3D space. Planar array are

more versatile and provide more symmetrical patterns with lower side lobes. It can be used to scan the

main beam of the antenna toward any point in the space. It is applied in the field of radar, remote

sensing, communication and many others.

Figure: Far field Geometry for MxN element planar array

Array factor for x-axis;

Where:

wm = excitation coefficient of each element

dx= spacing along x –axis

βx=progressive phase shift along x-axis

Array Factor for y-axis

where :

wn = excitation coefficient of each element

dy= spacing along y –axis

βy=progressive phase shift along y-axis

The array factor is found to the product of

both vertical and horizontal array factor

1

)cossin)(1( …= ∑=

+−M

m

kdmj

mxxewAF

βφθ

∑=

+− …=N

n

kdnj

nxxewAF

1

)sinsin)(1( βφθ

)sinsin)(1(

1

1

)cossin)(1(

(53)

yy

xx

kdnjN

n

nyn

M

m

kdmj

mxm

ynxm

ewAF

ewAF

where

AFAFAF

βφθ

βφθ

+−

=

=

+−

∑

∑

=

=

…………=

6

PROCEDURES

Initial Setting (Based on Experiment 1)

1. The antenna measurement system is set-up according to Figure 2.

2. Switch on the rotating antenna platform.

3. Switch on the computer and run the antenna measurement software.

Figure 2

Microstrip Antenna Configurations

A. HORIZONTAL DIRECTIONAL DIAGRAM, E-Plane. (Rotation Of The Test Antenna Is

Carried Out In The H-Plane Of The Feeding Source Antenna).

1. Carefully insert the microstrip antenna (Cat. No. 737427), Screw a 245 mm long stand rod into

the microstrip antenna so that the resonators and the feed lines are aligned horizontally. Mount the

coax detector and connect this to the BNC socket on the rotating antenna platform base using a

coaxial cable.

2. Set the range switch v/dB of the SWR meter to 20 dB.

3. Switch on the rotating antenna platform.

4. Set the bias current to setting 3 using the remote control. An incoming signal should now appear

on the scale of the SWR meter.

5. Now bring the rotating antenna platform slowly (“SPEED” on setting 2 or 3) into motion by

activating the toggle lever “─ ← → + “ on the remote control.

6. Observe the scale of the SWR meter. Stop the rotating base when the maximum incoming signal

in reached. Calibrate the ‘GAIN ZERO” display of the SWR meter to “0 dB”.

r=170cm

7

7. 13. Now try to turn the rotating base of the platform in the desired direction by activating to

toggle lever “─ ← → + “ on the remote control. (“SPEED” set to setting 1). The angular position

of the antenna fastened to the rotating platform is indicated on the display of the remote control.

Observe the power scale of the SWR meter for a possible correction of the gain setting.

8. Now carry out an additional test to see whether the bias current setting at setting 3 (7.5 μA)

provides us with the highest sensitivity of the antenna detector.

9. Try to find a more optimal setting in order to measure with. It may be necessary to calibrate the

SWR meter display to “0 dB” again.

10. Now position the test antenna in a desired angular position, e.g. + 10º by activating the toggle

lever “─ ← → + “. Measure the incoming signal of the test antenna. The magnitude of the

incoming signal can be read directly on the SWR meter. There is a logarithmic scale in dB and

also a linear scale in % available.

11. Use the polar graph to draw a line through the measured points in order to obtain a complete

directional diagram for the test antenn17.

12. Determine the 3 dB width of the two lobes of the parabolic dish.

B. VERTICAL DIRECTIONAL DIAGRAM, H-Plane. (Rotation Of The Test Antenna Is

Carried Out In The E-Plane Of The Exciting Source Antenna).

1. Repeat Part A by vertically polarized H-field of the source antenna.

2. Use the polar graph to draw a line through the measured points in order to obtain a complete

directional diagram for the test antenna.

3. Determine the 3 dB width of the two lobes of the parabolic dish.

C. Single Microstrip Patch Antenna

1. Repeat Part A for single microstrip patch antenna

2. Use the polar graph to draw a line through the measured points in order to obtain a complete

directional diagram for the test antenna.

3. Determine the 3 dB width of the two lobes of the parabolic dish.

4. Compare all, and observe the changes. Explanation should included the discussions

8

RESULTS

1. Manual Procedures for Plotting Radiation Pattern

(A) HORIZONTAL DIRECTION

Table 1: Directional Diagram

Types of Test Antenna: Polarization:

Type of Source Antenna: Polarization:

Distance Between Source &

Test Antenna:

cm

Detector Bias Current: µA

WR Meter Range: dB Frequency:

Angle [º] SWR Meter Level [dB] Angle [º] SWR Meter Level [dB]

0 0

-10 10

-20 20

-30 30

-40 40

-50 50

-60 60

-70 70

-80 80

-90 90

-100 100

-110 110

-120 120

-130 130

-140 140

-150 150

-160 160

-170 170

-180 180

9

(B) VERTICAL DIRECTION

Table 1: Directional Diagram

Types of Test Antenna: Polarization:

Type of Source Antenna: Polarization:

Distance Between Source &

Test Antenna:

cm

Detector Bias Current: µA

WR Meter Range: dB Frequency:

Angle [º] SWR Meter Level [dB] Angle [º] SWR Meter Level [dB]

0 0

-10 10

-20 20

-30 30

-40 40

-50 50

-60 60

-70 70

-80 80

-90 90

-100 100

-110 110

-120 120

-130 130

-140 140

-150 150

-160 160

-170 170

-180 180

10

(C) Single Microstrip Patch Antenna

Table 1: Directional Diagram

Types of Test Antenna: Polarization:

Type of Source Antenna: Polarization:

Distance Between Source &

Test Antenna:

cm

Detector Bias Current: µA

WR Meter Range: dB Frequency:

Angle [º] SWR Meter Level [dB] Angle [º] SWR Meter Level [dB]

0 0

-10 10

-20 20

-30 30

-40 40

-50 50

-60 60

-70 70

-80 80

-90 90

-100 100

-110 110

-120 120

-130 130

-140 140

-150 150

-160 160

-170 170

-180 180

2. After plot manually, then change the device in order plot by computer. Attach the output from

the computer generated result(s).

a (θ ) – Diagram

a / dB

Directional Diagram in Polar Coordinates: R-Axis – Relative Amplitude (Log)

a (θ ) – Diagram

a / dB

Directional Diagram in Polar Coordinates: R-Axis – Relative Amplitude (Log)

a (θ ) – Diagram

a / dB

Directional Diagram in Polar Coordinates: R-Axis – Relative Amplitude (Log)

14

QUESTIONS

1. Calculate array factor 2x2 and 4x4 for planar antenna. Compare both answer

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

2. Which radiation resistance RR is needed in order to assemble an antenna containing 16

elements for 9.40 GHYz with the following technical data:

Microwave substrate: Duroid 5828 with h=1.57mm + 0.05 mm

Relative permittivity εr = 2.20 + 0.02

4 rows with 4 individual radiators each

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

3. What dimensions are required for the radiator patches and the stripline segments of this

antenna? Measure the microstrip and compare them.

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

4. Compare both direction of microstrip antenna. Comment on it characteristics

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

15

DISCUSSION & CONCLUSION

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------

APPENDIX / GLOSSARY

ATTENTION!!

Microwave Radiation

The power of the microwave generated here is only slight (≈ 20 mW). But in view of normal

professional working conditions with sources of higher power, we recommend that the student be

trained certain points of safety when dealing with this material. When carrying out changes in the

experiment set-up. Switch the modulation of the PIN modulator to “EXT”. This reduces the power of

the radiated microwaves by approx. 10 dB. Nevertheless, avoid looking into the radiating aperture. If

this cannot be avoided, then there is no other alternative but to briefly switch the Gunn oscillator off.

This, however, results in corresponding temperature effects (TC approx. 0.3 MHz/K).

The theoretical fundamental of microstrips have been known for some time. However,

practical applications have only become feasible in recent years due to the special demands placed on

the microwave laminates at high frequencies. The construction of a microstrip is depicted in Fig. 4.

Figure 5: Construction of microstrip and field distribution

1. Signal conductor of the width w

2. Metallic ground plane

3. Dielectric with a thickness h