fir filter for fsk demodulator

if you model two frequencies in Matalb, you can see how to convert them to two levels:

f1 = exp(j*2*pi*(0:1023)*.1);

f2 = exp(j*2*pi*(0:1023)*-.1);

f=[f1 f2]; %two symbols

plot(diff(unwrap(angle(f))),'.-')

the angle is that of I/Q stream. diff is easy (current sample - next sample).

the unwrap and angle are a bit tricky and is usually done in software but you can do it in vhdl by indirect methods. see:

http://www.dspguru.com/dsp/tricks/fixed-point-atan2-with-self-normalization

(http://www.dspguru.com/dsp/tricks/fixed-point-atan2-with-self-normalization)