Reception of an f.m. signal in the presence of a stronger signal in the same frequency band, and other associated results

In frequency-modulation techniques, frequency is the controlling factor both for the information and the separation of signals. No use has been made of the fact that, when two signals are present, the instantaneous resultant varies in amplitude. This amplitude variation is related to both signals and therefore carries information. It can therefore be useful. A study along these lines has led to several possibilities described in the paper, including (a) receiving a weak f.m. signal in the presence of a strong one on the same channel, (b) reducing the interference caused by a weak signal on a strong one, and (c) transmitting a multiplicity of weak coded messages with a regular f.m. signal and in the same band. A comparative analysis of the band-width required by a number of multiplex systems using frequency modulation is also given.