FM radio - Frequency Modulation

Frequency Modulation

First: Input signal.
Second: Carrier frequency.
Third: FM signal.
Fourth: High Pass Filtered.
Fifth: Rectified
Sixth: Final decoded signal, low pass filtered and gain boost.

Frequency modulation is the successor to amplitude modulation.

Its main advantage is that it is less vulnerable to amplitude changes in the signal, which is something that happens naturally for many different reasons (eg. nearby lightning storm affecting the radio signal).

Have you noticed how constant the amplitude of the FM signal is?(see figure above).

A sine wave can be mathematically described as Amplitude*sin(2*PI*frequency*time+phase).

We replace frequency by carrierFrequency+B*signal(time), where B is the modulation ratio. This results in a variating frequency that has a value between carrierFrequency +/- B*signal(time).

Stay tuned!

© ChillPill 2020, aka Paul Caron