# FSK Demodulation Implementation

#### abdulwahab.hajar

Joined Jun 14, 2016
93
Hello everyone

I'm looking to implement an FSK demodulator, I did some research regarding FSK modulation and demodulation and I understood that essentially the concept of working is quite simple.
Where a digital 1 translates to a high frequency, and a 0 translates to a low frequency.
Taking a look at the available demodulation circuits, they all seem quite complex and not really explained furthermore, not many variations of the demodulator exist...

What I wanted to ask was whether a simpler approach would work, using a filter followed by a comparator...
since we know the frequencies which represent a digital 0 and 1, we can expect the filter's voltage output (response) to each frequency. Now we compare these voltages to a reference.. if it's higher than the reference we output a 1, else if it's lower we output a 0.

The issue which comes to my mind is... in the comparator what would be the reference? Furthermore, our input is an AC signal and in a comparator we would need to compare it to an AC signal as well right?

That's all for now
Thank you

#### crutschow

Joined Mar 14, 2008
26,735
The problem with a filter is its slow response time to the change in frequency.
That will significantly limit the data transmission rate below the maximum that can be obtained with other demodulation schemes.
Is demodulation/signal speed a concern for your application?

#### abdulwahab.hajar

Joined Jun 14, 2016
93
The problem with a filter is its slow response time to the change in frequency.
That will significantly limit the data transmission rate below the maximum that can be obtained with other demodulation schemes.
Is demodulation/signal speed a concern for your application?
I can't really be certain at this point, regarding the speed. I'll check.
What would be some other possible schemes of demodulation? and isn't demodulation using an algorithm (software) through a microcontroller easier, given that the algorithm already exists.

#### crutschow

Joined Mar 14, 2008
26,735
isn't demodulation using an algorithm (software) through a microcontroller easier, given that the algorithm already exists.
Likely true, if the micro is fast enough to do the demodulation.
What is the FSK data rate?