k band pass filter
TRANSCRIPT
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LOVELY PROFESSIONAL UNIVERSITY
CONSTANT K BAND PASS FILTER
TERM PAPER
2008
SUBMITTED BY
ASHISH KUMAR
B.TECH (E.C.E.) 4YRS.
SECTION B G1
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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
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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.
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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.
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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-
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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:
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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.
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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.
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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
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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.
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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
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