fm envelope detector

hi all,
What is the ENvelope Detector For FM? How iTs work? Please Give the schematic and The reference...I really need it for my School Task

Thanks

Elits

Envelope detection is used to retreive modulation signal from AM signal, to demodulate it.
At FM it is first neccessary to convert FM to AM and use envelope detector as demodulator.
For FM to AM conversion a simple LC tank can be used. It is so tuned that FM signal frequency lies on a slope and not at the tank resonance.
The same principle is used at Foster-Seely discriminator and ratio detector.

See page 3

h**p://www.educatorscorner.com/media/Exp4a.pdf