This report is a study of nonlinear circuits under two-signal conditions, with particular stress on the output spectral components generated, and on signal depression and hetero¬dyne interference effects in various individual circuits which form portions of a typical receiving system.nIt is shown that the degree of signal depression in an f-m system differs from that in an a-m system primarily because of the limiting circuits employed in the usual f-m system. With FM, when effective limiting is provided together with a linear-slope filter, the signal depression effects become greater owing to the combination of limiter and discriminator circuits. The limiters used in f-m reception produce output distortion components which contain signal Information. A wide-band discriminator circuit is necessary to retain as much of this information as possible. It is stressed that the annoying nature of the heterodyne in a narrow-band f-m system is a substantial detriment when compared to the heterodyne response in an a-m system.
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