Co-channel FM interference suppressed by using the amplitude-locked loop for digital communication

An amplitude-locked loop (ALL) is a high-gain. high-bandwidth servo-loop similar to a phase-locked loop (PLL) but operating in the amplitude domain rather than the frequency domain. The ALL has been used in combination with a PLL (the FM 201/5) and some additional circuitry to achieve a major improvement in frequency modulation technology. This includes co-channel interference (CCI), multipath interference and threshold extension. This work is the natural extension of this approach to digital communication systems