FM Receiver

570

05:31:48

The blue line is the input to the modulator and the green line is the output from the demodulator. The switch is the connection between the modulator and demodulator. The 10pF capacitor at the end of the RC network should actually be 100uF. In reality, the input signal would be amplified to clipping so that it always stayed at constant amplitude and then it would be filtered before being demodulated. That way, the receiver wouldn’t mistake difference in input amplitude for difference in frequency because the input wouldn’t change in amplitude.

published 8 years ago

hurz

8 years ago

What you demodulate is the amplitude. Put a limiter amplifier somewere into the chain which takes away the amplitude and try to demodulate.

jason9

8 years ago

Yes, I demodulate the amplitude. This is because instead of directly demodulating the frequency I first send it through a band pass filter to turn it from FM to AM to make it simpler to demodulate.

hurz

8 years ago

Can you mark the airinterface e.g. with a switch for more detailed discussions?

jason9

8 years ago

I put the switch in.

hurz

8 years ago

I have made some changes and inserted a limiter amplifier check this http://everycircuit.com/circuit/5584041318547456

jason9

8 years ago

I see. I just realized that the limiter is necessary because the FM modulator also partially works as an AM modulator as well. It still works to some extent, just not quite as well.

jason9

8 years ago

At least this is still a good demonstration of the concept, even if it has a few errors.

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