Analog Circuits Cookbook, 2nd Edition

7

RF circuits and techniques

Homodyne reception of FM signals

Direct conversion FM design

Although many people are familiar with homodyne (direct conversion) reception of CW and SSB signals, it is not immediately obvious that FM signals can be received by direct conversion. But with some crafty signal processing, the original baseband modulation can indeed be recovered.

Homodyne or direct conversion reception has always attracted a good deal of attention, especially in amateur circles (Hawker, 1978). It has the attraction of simplicity, both in principle and in hardware terms. Figure 7.1 shows a simple homodyne receiver which could in principle be simplified even further by the omission of the rf amplifier (at the expense of a poorer noise figure) ...