Frequency modulation is widely used for radio transmissions for a wide variety of applications from broadcasting to general point to point communications. Frequency modulation, FM offers many advantages, particularly in mobile radio applications where its resistance to fading and interference is a great advantage. It is also widely used for broadcasting on VHF frequencies where it is able to provide a medium for high quality audio transmissions. In view of its widespread use receivers need to be able to demodulate these transmissions. There is a wide variety of different techniques and circuits that can be used including the Foster-Seeley, and ratio detectors using discreet components, and where integrated circuits are used the phase locked loop and quadrature detectors are more …
