The linear rectification of two amplitude-modulated signals and noise

The classical theory dealing with the passage of a modulated signal and noise through a linear rectifier is extended to include the case when the input consists of two amplitude-modulated signals and noise, all of which have been passed through a narrow-band filter. Methods are presented for approximating the modulation terms and also the coefficients appearing in the expansion of the auto-correlation function of the rectifier output. It is shown that these approximations lend themselves to rapid computation on a digital computer.