k band pass filter

8/7/2019 k band pass filter

1/12

LOVELY PROFESSIONAL UNIVERSITY

CONSTANT K BAND PASS FILTER

TERM PAPER

2008

SUBMITTED BY

ASHISH KUMAR

B.TECH (E.C.E.) 4YRS.

SECTION B G1


2/12

CONSTANT K BAND PASS FILTER

ASHISH KUMAR

B.TECH (E.C.E.) B

ELECTRONICS & COMMUNICATION DEPARTMENT

LOVELY PROFESSIONAL UNIVERSITY

PHAGWARA, PUNJAB.

Abstract:

A Band Pass filter is filter that passes

frequencies in a desired range and attenuates

frequencies below and above Real-world

signals contain both wanted and unwanted

information. Therefore, some kind of

electronic signal filtering technique must

separate the two before processing and

analysis can begin. Every electronic design

project produces signals that require

electronic signal filtering, processing, or

amplification, from simple gain to the most

complex digital-signal processing (DSP).

Designers base their electronic signal filter

implementation selections on the desired

bandwidth and accuracy of the target system.

These parameters, along with hardware

costs, determine the system's speed (sample

rate), resolution (number of bits), type of A/D

converter (sigma-delta, successive-

approximation, flash), and anti-alias filter

technology. The amplitude response of a

band pass filter is flat from the center

frequency down and up to points where it

begins to roll off. The standard reference

Points for these roll-offs are the points where

the amplitude has decreased by 3 dB, to

70.7% of its original amplitude. This is the

passband of the filter. The regions above the

passband to infinity, and below the passband

to zero (or near zero) are the stop band of

the filter circuit.

HISTORY:

In a certain time we used rectifiers, but by the

certain reasons we are getting use of filters.

A rectifier is an electrical device that

converts alternating current (AC) to direct

current (DC), a process known as

rectification. Rectifiers have many uses

including as components of power supplies

and as detectors of radio signals. Rectifiers

may be made of solid state diodes, vacuum

tube diodes, mercury arc valves, and other

components. A device which performs the

opposite function (converting DC to AC) is

known as an inverter.

When only one diode is used to rectify AC

(by blocking the negative or positive portion

of the waveform), the difference between the

term diode and the term rectifier is merely

one of usage, i.e., the term rectifier describes


3/12

a diode that is being used to convert AC to

DC. Almost all rectifiers comprise a number

of diodes in a specific arrangement for more

efficiently converting AC to DC than is

possible with only one diode. Before the

development of silicon semiconductor

rectifiers, vacuum tube diodes and copper (I)

oxide or selenium rectifier stacks were used.

Fig 1 Rectifiers

Fig 2 Rectifiers

Fig 3. Bunch of rectifiers

Early radio receivers, called crystal radios,

used a "cat's whisker" of fine wire pressing

on a crystal of galena (lead sulfide) to serve

as a point-contact rectifier or "crystaldetector". In gas heating systems flame

rectification can be used to detect a flame.

Two metal electrodes in the outer layer of the

flame provide a current path and rectification

of an applied alternating voltage, but only

while the flame is present.

Actually the rectifiers could not rectify

totally ac signal properly, some ripples are

then ever present there.Hence the filters are

being used it filters properly.

Fig 4 Rectifiers

Fig 5. Filter

INTRODUCTION:

A Band Pass filter is a filter that passes

frequencies in a desired range and attenuates

frequencies below and above. A closely

related Knowledgebase item discusses the

concept of the Q of a filter. The

Knowledgebase makes a distinction between

high Q band pass filters and low Q bandpass

filters.


4/12

Fig 6 Filter chip

While there are separate terms for the

opposite of a bandpass filter - the notch and

band reject - there are no corresponding

terms to differentiate between a high Q

bandpass filter - covered by this item - and a

low Q bandpass filter. This knowledgebase

item is geared towards the single tone,

narrowband RF, and IF type of filters. The

audio, speech, and broadband

communications type of filter are covered in

the low Q bandpass filter item.

Fig 7. Bandpass filter

Fig 8 filters

The amplitude response of a band pass filter

is flat from the center frequency down and up

to points where it begins to roll off. The

standard reference points for these roll-offs

are the points where the amplitude has

decreased by 3 dB, to 70.7% of its original

amplitude. This is the passband of the filter.

The regions above the passband to infinity,

and below the passband to zero (or near zero)

are the stop bands of the filter.

The -3 dB points and -20 dB amplitude

points of the filter are determined by the size

of the passband in relation to the center

frequency, in other words the Q of the filter.

The Q knowledgebase item will have

additional information, but it is hard to talk

about the roll-off points of a bandpass filter

without defining the Q, which is the center

frequency divided by the bandwidth. In the

case of the figure below:

The -3 dB points are at about 1 kHz and 100

kHz for a Q of 0.1 and a center frequency of

10 kHz. The low and high frequency roll offs

look exactly like what would be expected

from a single pole high pass and single pole

low pass. At one tenth the frequency of the

lower -3 dB point and ten times the

frequency of the upper 3 dB point, the

response is down 20 dB from the center

frequency. This means that the two pole filter

bandpass filter is effectively putting a single

pole on the low frequency end and a single

pole on the high frequency end of the

passband. This is not always desirable, as

cascading subsequent stages to get more

rejection in the stop bands will merely add

more single poles on each end. An alternative

technique that provides much better

performance will be described in the low Q

bandpass filter knowledgebase item.


5/12

Fig 9. Input characteristics

The -3 dB points are at about 600 Hz and 1.6

kHz for a Q of 1 and a center frequency of 10

kHz. The -20 dB points, however, are now at

about 1 kHz and 100 kHz, which are NOT at

one tenth and 10 times the lower and upper -

3 dB frequency, respectively. The shape of

the curve is also different, looking like a

rounded 90 degree angle more than a single

pole characteristic. The single pole

performance has been lost in the region

between the -20 dB points, or within ten

times the bandwidth. Outside of this region,

however, the single pole response of the

bandpass filters returns. Therefore, for Q

values between 0.1 and 1, the response of a

bandpass circuit will change to whatever is

required to satisfy the requirements of the - 3

dB points, as determined by the Q and an

ultimate slope of - 20 dB per decade for the

region between 10 and 100 times the

bandwidth. This is a final value of slope, and

will be maintained at higher multiples of the

bandwidth.The response of the bandpass filter with a Q

of ten dramatically illustrates this effect.

Between the -20 dB points, the shape of the

response is completely opposite what it was

for a Q of 10. The initial -3 dB points are so

close to the center frequency that they have

not been highlighted, but the -20 dB points

are the same as -3 dB points for a Q of 1. In

the region between 10 and 100 times the

bandwidth, the slope continues to change to

its final value of -20 dB per decade at 100

times the bandwidth.

Fig10.Response

The phase response of a band pass filter

shows the greatest rate of change at the

center frequency. The rate of change

becomes more rapid as the Q of the filter

increases.

TYPES:

Filters are categorized by their characteristics

& working

Low pass filter

High pass filter

Band pass filter

Stop band filter

Band reject filter

LOW PASS FILTERS:

A low-pass filter is a filter that passes low-

frequency signals but attenuates (reduces the

amplitude of) signals with frequencies higher

than the cutoff frequency. The actual amount

of attenuation for each frequency varies from

filter to filter. It is sometimes called a high-


6/12

cut filter, or treble cut filter when used in

audio applications.

Fig 11.low pass filter

Fig 12. Low pass

Fig 13 signal

The concept of a low-pass filter exists in

many different forms, including electronic

circuits (like a hiss filter used in audio),

digital algorithms for smoothing sets of data,

acoustic barriers, blurring of images, and so

on. Low-pass filters play the same role in

signal processing that moving averages do in

some other fields.

Fig 14. Output signal

Such as finance; both tools provide a

Smoother form of a signal which removes the

short-term oscillations, leaving only the long-

term trend.

HIGH PASS FILTER:

A high-pass filter is a filter that passes high

frequencies well, but attenuates (reduces the

amplitude of) frequencies lower than the

cutoff frequency. The actual amount of

attenuation for each frequency varies from

filter to filter. It is sometimes called a low-

cut filter; the terms bass-cut filter or rumble

filter are also used in audio applications. A

high-pass filter is the opposite of a low-pass

filter, and a band-pass filter is a combination

of a high-pass and a low-pass.

Fig 15 high pass filter

Fig 16 output

It is useful as a filter to block any unwanted

low frequency components of a complex

signal while passing the higher frequencies.

The meanings of 'low' and 'high' frequencies

are relative to the cutoff frequency.

Fig 17 plotting

CONSTANT K BAND PASS FILTER:


7/12

A band-pass filter is a device that passes

frequencies within a certain range and rejects

(attenuates) frequencies outside that range.

An example of an analogue electronic band-

pass filter is an RLC circuit (a resistor

inductorcapacitor circuit). These filters can

also be created by combining a low-pass

filter with a high-pass filter.

Fig 18. Band pass filter

Fig 19 band pass

Fig 20 wave

Bandpass is an adjective that describes a type

of filter or filtering process; it is frequently

confused with passband, which refers to the

actual portion of affected spectrum. The two

words are both compound words that follow

the English rules of formation: the primary

Meaning is the latter part of the compound,

while the modifier is the first part. Hence,

one may correctly say 'A dual bandpass filter

has two pass bands'. An ideal bandpass filter

would have a completely flat passband (e.g.

with no gain/attenuation throughout) and

would completely attenuate all frequencies

outside the passband. Additionally, the

transition out of the passband would be

instantaneous in frequency. In practice, no

bandpass filter is ideal. The filter does not

attenuate all frequencies outside the desired

frequency range completely; in particular,

there is a region just outside the intended

passband where frequencies are attenuated,

but not rejected. This is known as the filter

roll-off, and it is usually expressed in dB of

attenuation per octave or decade of

frequency. Generally, the design of a filter

seeks to make the roll-off as narrow as

possible, thus allowing the filter to perform

as close as possible to its intended design.

Often, this is achieved at the expense of pass-

band or stop-band ripple.

The bandwidth of the filter is simply the

difference between the upper and lower

cutoff frequencies. The shape factor is the

ratio of bandwidths measured using two

different attenuation values to determine the

cutoff frequency, e.g., a shape factor of 2:1 at

30/3 dB means the bandwidth measured

between frequencies at 30 dB attenuation is

twice that measured between frequencies at 3

DB attenuation.


8/12

Outside of electronics and signal processing,

one example of the use of band-pass filters is

in the atmospheric sciences. It is common to

band-pass filter recent meteorological data

with a period range of, for example, 3 to 10

days, so that only cyclones remain as

fluctuations in the data fields.

Fig 21 diagram

Fig 22 diagram

Bandpass filters are one of the simplest and

most economical ways to transmit a well-

defined band of light, and to reject all other

unwanted radiation. Their design is

essentially a thin film Fabry-Perot

Interferometer formed by vacuum deposition

techniques, and consists of two reflecting

stacks, separated by an even-order spacer

layer. Each one of these structures is referred

to as a cavity, and some filters may contain

as many as eight cavities. There are many

different variations of the Fabry-Perot type

bandpass filter, but for this catalog, we will

only consider the all-dielectric and metal-

dielectric type

All-dielectric type consists of two highly

reflecting mirrors separated by a dielectric

spacer layer. These reflecting mirrors are

constructed of alternating high and low

refractive index materials and the reflectance

of the stack is sometimes in excess of

99.99%. By varying the thickness of the

spacer layer and or the number of reflecting

layers, one can alter the central wavelength

and bandwidth of the filter. This type of filter

displays very high transmission in the

passband, but, has a limited range of out-of-

band blocking. To compensate for this

deficiency, an additional blocking component

is added, which is either all-dielectric or

metal-dielectric depending upon the required

blocking range. This additional blocking

component will eliminate any unwanted out-

of-band radiation but it will also reduce the

overall throughput of the filter.

The metal-dielectric type is similar to the all-

dielectric type except that it utilizes a metal

spacer layer instead of a dielectric layer.

Although this type of filter has excellent out-

of-band blocking and high passband

transmission, it lacks the sharp cut-on and

cut-off slopes of the typical two and three

cavity filters. The metal-dielectric type is

mainly used for bandpass filters in the

ultraviolet. However one version, the induced

transmission type, is used as an additional

Blocking component when rejection is

required to the far infrared.


9/12

Fig 23filter

Fig 24 elements

Fig 25 dia

USES:

The constant bandpass filter could be used as

power transmitter system in modulator

configuration. Reflective Bandpass Filter is

designed to provide superior performance for

low and medium power transmitter systems

in a modular configuration. This filter has

four sections designed, assembled and

shipped fully tested.

Fig- 25 power transmitter

It is used as Alpine SBE-1243BP in alpine

equipment.

Fig-26 alpine

It could be used as kits for laptops, TV, etc

Fig-27

It could be used in tuning of radios and any

other tuning operated equipment.

Fig-28 tuning operating

It could be also used as fm bandpass, in

frequencies operating.

Fig-29 fm bandpass

It could also used as helix bandpass


10/12

Fig-30 helical bandpass

It could be used in waveguide bandpass.

Fig-31

It could be used in r & s bandpass.

Fig-32 r& s

It could be used in power bandpass.

Fig-33 power

It could be used in universal bandpass.

Fig-34 universal

In combline bandpass to operate equipments.

Fig-35

It could be used in RF bandpass also.

Fig-36 RF band pass

CONCLUSION:

The filters are used to amplify, attenuate, or

reject a certain range of frequencies of their

input signals.the bandpass is a essential &

important for these circuits are used as phase

shifters and in systems of phase shaping and

time delay. Filters such as the above can be

cascaded with unstable or mixed-phase filters

to create a stable or minimum-phase filter

without changing the magnitude response of

the system. Analog filters process

continuous-time signals, i.e., signals that are

defined at every instant of time. There are

many types of analog filters, such as passive,

active, biquadratic, and switched-capacitor.Digital filters process discrete-time signals,

which are those that are defined only at

specific instances of time.


11/12

REFERENCES:

1. www.google.com2. www.educypedia.com3.

www.googleimages.com

4. www.amazon.com5. www.efy.com6. www.electroworld.com7. Circuits & networks

Sudhakar shyam mohan, TMH

8. Linear integrated circuitsj.s.katre


12/12

Documents

k band pass filter