# FSK demodulator by integration if the samples per symbols is 2

Say I have a binary FSK with +f and -f frequencies and I have two samples per symbol.

Let's consider the "1) multiply with +f/-f then 2) integrate over the number of samples per symbol, 3) take absolute value, 4) take the difference" demodulator.

Lets call this type of demodulator Integrating FSK Demodulator.

If I have only two samples per symbol, then is the Integrating FSK Demodulator the same as if I would just use a differential FM demodulator (which takes 2 consecutive samples into account) ?

If they are different, what is the difference ?

• I'm not sure, but in my opinion to answer your question you should find out: i. are Integrating Demodulator and Differential Demodulator has different structure but contain the same components; ii. does all components perform linear transformation? If it's true then they both perform equal transformations (in my opinion). – Gluttton Jan 15 '16 at 10:53
• Integrating demodulator is non linear due to the "taking absolute value". Differential demodulator is on the other hand linear. So probably they are different, but I am not sure. – jhegedus Jan 15 '16 at 11:16
• Or wait gnuradio.org/redmine/projects/gnuradio/repository/revisions/… this seems non linear actually. Why is the Differential demodulator implementation in gnu-radio. – jhegedus Jan 15 '16 at 11:22
• Correction, 'Why' = ', which' in previous comment, but I could not edit it, due to being too old. – jhegedus Jan 15 '16 at 11:28