Impulsive interference in amplitude-modulation receivers

An analysis is made of the response of an a.m. receiver to impulsive interference (of the type generated by car ignition systems) using the Fourier integral theorem. Conclusions concerning the general behaviour of receivers are deduced from the formulae developed. The method is then applied to the calculation of the performance of noise suppressor circuits which are classified as amplitude, differential and delay limiters. Simple expressions are derived for estimating the suppression attainable in any particular case. Some experiments are described in which the performance of the first two types of noise suppressor was measured. There is shown to be fair agreement with the calculated values. A comparison is made between the behaviour of frequency modulated, pulse-length-modulated and suppressed amplitude-modulated systems with impulsive interference.