Abstract
An analysis is presented on the output signal-to-noise ratios of the FM correlation system having an FM detector at each input channel of a conventional correlator, in which the input consists of a frequency-modulated signal combined additionally with stationary narrow-band Gaussian random noise.
First, a general expression is derived for the output signal-to-noise ratio. Next, as a practical case, a detailed calculation is made for the output signal-to-noise ratios when each input signal is the sinsoidal carrier frequency-modulated by a Gaussian random process and the integrating filter is of RC low-pass.
Some important characteristics are obtained as follows;
(i) For large input carrier-to-noise ratio the output signal-to-noise ratio has the constant value independent of the input carrier-to-noise ratio, but it is proportional to the product of the r.m.s. bandwidth of the input noise and the time constant of the RC low-pass filter, and the ratio of the r.m.s. bandwidth of the modulating signal to the r.m.s. bandwidth of the input noise.
(ii) For small input carrier-to-noise ratio the output signal-to-noise ratio is proportional to the square of the input carrier-to-noise ratio, the product of the r.m.s. bandwidth of the input noise and the time constant of the RC low-pass filter, and also to the square of the ratio of the r.m.s. modulation to the r.m.s. bandwidth of the input noise.
