17-08-2012, 04:41 PM
FIR Filter Design
FIR Filter Design.ppt (Size: 274 KB / Downloads: 70)
Introduction
In digital signal processing, there are two important types of systems:
Digital filters: perform signal filtering in the time domain
Spectrum analyzers: provide signal representation in the frequency domain
In this and next chapter we will study several basic design algorithms for both FIR and IIR filters.
These designs are mostly of the frequency selective type
Multiband lowpass, highpass, bandpass and bandstop filters
Preliminaries
The design of a digital filter is carried out in three steps:
Specifications: they are determined by the applications
Approximations: once the specification are defined, we use various concepts and mathematics that we studied so far to come up with a filter description that approximates the given set of specifications. (in detail)
Implementation: The product of the above step is a filter description in the form of either a difference equation, or a system function H(z), or an impulse response h(n). From this description we implement the filter in hardware or through software on a computer.
Why we concentrate on a lowpass filter?
The above specifications were given fro a lowpass filter.
Similar specifications can also be given for other types of frequency-selective filters such as highpass or bandpass.
However, the most important design parameters are frequency-band tolerance (or ripples) and band-edge frequencies.
Whether the given band is a passband or stopband is a relatively minor issue.
Advantages of a linear-phase response
Design problem contains only real arithmetic and not complex arithmetic;
Linear-phase filter provide no delay distortion and only a fixed amount of delay;
For the filter of length M (or order M-1) the number of operations are of the order of M/2 as we discussed in the linear phase implementation.