am and fm modulation and demodulation

[theillestengineer]

Im looking for websites that give an fm demodulator with the theory behind it. Where is the math behind fm demodulation? Im not talking about superhet receivers, the math can easily be understood. If a circuit is given where you have a tank circuit followed by one or two transistors with feedback, where is the math to support fm demodulation in any website? Im trying to design an fm demodulator, but to identify the math has been difficult. Can you help me? The circuit Im referring to I could not find online.

 

[klystron]

AM demodulation : an envelope detector : diode into RC circuit
FM demodulation : cut off slope of bandpass filter converts change in frequency to AM signal and then an envelope detector : diode into RC circuit

 

[FvM]

A classical method measures the phase shift between the input signal and a tank circuit loosely coupled to the signal, or in other words a bandpass. Phase characteristic of a bandpass doesn't involve difficult mathematic in my opinion. There are different methods to measure the phase shift of course. Synchronous rectification (multiplying one signal with the sign of the other) is a straightforward one.

 

[theillestengineer]

I looking towards designing a demodulator without the use of a diode and an RC circuit. Any ten year old can do this. We are all engineers, innovators. Lets try to use our imagination and find some other way to generate the message signal out of the modulated signal with a circuit configuration given to us and applying all circuit analysis theorems to get an explanation as to why it demodulates. Im heavy on theory. It explains to me what I cant and can do. I live off of it. Where can I find a website that explains the theory behind demodulation with a circuit given. Engineering is not just putting parts together and hoping it works, otherwise, it is all guess work and Im in the wrong field of work. Can anyone help, I would really appreciate it. Here is a circuit to consider,

**broken link removed**

 

[FvM]

I don't see the linked "AM-Receiver" related to your question, particularly after reading your comments.

The AM receiver is a very unspecfic demodulator, performing AM demodulation as a parasitic effect of an amplifier stage. From your comment, I would rather expect that you are looking for a kind of FM demodulator with clearly specified behaviour instead of accidental FM demodulation effect.

Usage of "diode and an RC circuit" is a more superficial attribute of FM demodulators in my opinion. One point is to refer to the involved circuit principle, the others are implementation details.

 

[theillestengineer]

Demodulation has to have mathematics to identify it as a demodulator. Just like superheterodyne receivers. Im looking to demodulate an AM or FM signal using analog parts, transistor, passive elements, and without the use of any IC, which I can implement. Thats the problem I am having.

 

[WimRFP]

You may search on Foster Seeley detector, ratio detector, quadrature detector, pulse count detector, phase locked loop, etc.