Improvement of FM demodulator with cochannel FM interference

Originally, frequency modulation (FM) was conceived to minimise the effect of additive noise. Since additive noise is the principal source of signal corruption in amplitude modulation (AM). The pre-cursor of frequency modulation. When the FM signal is received, the additive noise is removed by the action of a limiter. This process is a necessary part of FM demodulation. There are a number of ways to recover the modulating signal from the FM signal to improve cochannel interference (CCI). Without hard limiting, the signal is corrupted by both phase noise and by amplitude noise. It had not been possible to achieve FM demodulation without first using a hard limiter. Not until the realisation of the amplitude-locked loop (ALL)