Hi there,

A question about FSK demodulation.
I have to decode a coherent FSK signal where fc=135kHz, the mark and space
frequency difference is 10kHz. The goal is to find a good trade-off between
speed and accuracy. The detection will have to deal with some environmental
noise, but still needs to perform (near) real-time.

I have looked at these method's:

1) zero crossing - looks a little to simple, don't think it will work well
enough in a noisy environment.
2) correlation demodulator - looks complex, do not have that much time.
3) short time DFT - to computationally intensive and due to FFT length not
real-time. 
4) arctan differentiated (quadrature demodulation) - my first choice.
5) full digital PLL - also seems rather complex.

My first choice goes to (4), seems relatively simple and accurate. This
method seems come up a lot on the internet, but no one really explains why
it is used.
Can anyone help me to define a good decision?


Thanks in advance,

mf