fir filter design - newbie

Hi baba,

One issue which causes headache to everybody is that "Matlab people" use Nyquist frequency as = 1. They never bothered to modify this anomaly despite their billions of profits. Everybody uses Fs = 1. (Nyquist is the point .5Fs of any system)

I mean in digital sampling systems, you don't need to bother about absolute frequency but just assume Fs=1 then any frequency point is a fraction relative to this 1 e.g. .1,.2,.3,...etc. Once you implement your real Fs say of 13.5MHz then the points relate accordingly e.g. (.1) becomes 1.35MHz and so on.

So make sure that you also double each point of your pdf values before entring them in Matlab(e.g. the point .4Fs => .8 in Matlab

As to the issue of group delay in cascaded filters(as written in your pdf), as long as you use symmetrical FIR then don't worry about it. A 7 tap symmetrical fir gives a constant delay of (7-1)/2 i.e. 3 sample periods.

I have the impression that 7 taps is too little but it could be just an exercise.

Regards.