Digital Filter Design Part A.pptx

Digital Filter Design
[Digital Signal Processing]

© Copyright 2014 Dawar Awan
CECOS College of Engineering and IT dawar@cecos.edu.pk
What is Digital Signal Processor ?
Filter
│ A filter is a system that discriminates among the input frequencies by offering
different gain values to them i.e it is designed to enhance a certain frequency
band(s) or to attenuate a certain frequency band(s)
│ Based on their frequency discrimination, they are known as High pass, Low pass,
Band pass and Band stop filters
│ Notch and Comb filters are special types of Band stop filters
│ Digital filters can be broadly categorized into FIR and IIR types

Filter
High pass filter
A high-pass filter (HPF) is an electronic filter that passes signals with
a frequency higher than a certain cutoff frequency and attenuates signals with
frequencies lower than the cutoff frequency. The amount of attenuation for
each frequency depends on the filter design. A high-pass filter is usually
modeled as a linear time-invariant system. It is sometimes called a low-cut
filter or bass-cut filter. High-pass filters have many uses, such as blocking
DC from circuitry sensitive to non-zero average voltages or radio
frequency devices. They can also be used in conjunction with a low-pass
filter to produce a bandpass filter.

Filter
Low pass filter
A low-pass filter (LPF) is a filter that passes signals with a frequency lower than a
selected cutoff frequency and attenuates signals with frequencies higher than the
cutoff frequency. The exact frequency response of the filter depends on the filter
design. The filter is sometimes called a high-cut filter, or treble-cut filter in audio
applications. A low-pass filter is the complement of a high-pass filter.
Low-pass filters exist in many different forms, including electronic circuits such as
a hiss filter used in audio, anti-aliasing filters for conditioning signals prior to analog-
to-digital conversion, digital filters for smoothing sets of data, acoustic
barriers, blurring of images, and so on.

Filter
Band pass filter
A bandpass filter (BPF) is a system that passes frequencies within a certain range and
rejects (attenuates) frequencies outside that range.
These filters can also be created by combining a low-pass filter with a high-pass filter.
Bandpass filters are widely used in wireless transmitters and receivers. The main
function of such a filter in a transmitter is to limit the bandwidth of the output signal
to the band allocated for the transmission. This prevents the transmitter from
interfering with other stations. In a receiver, a bandpass filter allows signals within a
selected range of frequencies to be heard or decoded, while preventing signals at
unwanted frequencies from getting through

Filter
Band stop filter
In signal processing, a band-stop filter or band-rejection filter is a filter that passes
most frequencies unaltered, but attenuates those in a specific range to very low
levels. It is the opposite of a band-pass filter. A notch filter is a band-stop filter

Filter
FIR FILTERS
In signal processing, a finite impulse response (FIR) filter is a filter whose impulse
response (or response to any finite length input) is of finite duration, because it
settles to zero in finite time. This is in contrast to infinite impulse response (IIR) filters,
which may have internal feedback and may continue to respond indefinitely (usually
decaying).
The impulse response (that is, the output in response to a Kronecker delta input) of
an Nth-order discrete-time FIR filter lasts exactly N + 1 samples (from first nonzero
element through last nonzero element) before it then settles to zero.

Filter
Causal Discrete Time FIR FILTERS
For a causal discrete-time FIR filter of order N, each value of the output sequence is a
weighted sum of the most recent input values:

Filter
Properties FIR FILTERS
An FIR filter has a number of useful properties which sometimes make it preferable to
an infinite impulse response (IIR) filter
• Require no feedback
• Are inherently stable, since the output is a sum of a finite number of finite
multiples of the input values
• Can easily be designed to be linear phase by making the coefficient sequence
symmetric

FIR Filter

IIR Filters
INFINITE IMPULSE RESPONSE FILTERS (IIR)
Infinite impulse response (IIR) is a property applying to many linear time-invariant
systems that are distinguished by having an impulse response h[n] which does not
become exactly zero past a certain point, but continues indefinitely. This is in contrast
to a finite impulse response (FIR) system in which the impulse response does become
exactly zero at sample n > N for some finite samples, thus being of finite duration.
Common examples of linear time-invariant systems are most electronic and digital
filters. Systems with this property are known as IIR systems or IIR filters.

IIR Filters
Transfer function derivation of IIR Filters

IIR Filters

IIR Filter

Conclusion

Digital Filter Design Part A.pptx

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Digital Filter Design Part A.pptx