Question: As indicated above, a band limited communication channel can be modeled as a linear filter whose frequency response characteristics match the frequency response characteristics of the channel. MATLAB may be used to design digital finite impulse response (FIR) or infinite impulse response (IIR) filters that approximate the frequency response characteristics of analog communication channels. Suppose that we wish to model an ideal channel having an amplitude response
A(f) = 1 for |f| ≤ 2000 Hz and A(f) = 0 for |f| > 2000 Hz
and constant delay (linear phase) for all f. The sampling rate for the digital filter is selected as F5=10 ,000 Hz. Because the desired phase response is linear, only an FIR filter could satisfy this condition. However, it is not possible to achieve a zero response in the stop band. Instead, we select the stop band response to be -40 dB and the stop band frequency to be 2500 Hz. In addition, we allow for a small amount, 0.5 dB, of ripple in the pass band.