Phase Principle for Detecting NarrowBand Gaussian Signals

In many branches of science and technology one is often confronted with the problem of detecting a weak, narrow-band Gaussian signal in the presence of receiver noise. For example, this problem occurs in the fields of radio and radar astronomy, radar detection, and radio communication. The classical solution to this problem utilizes the timehonored square-law detector. The output of the square-law detector is proportional to the total power applied at its input. One detects the presence of a Gaussian signal in the presence of receiver noise by monitoring the total power. When the total power is relatively high the signal is supposed to be present. Present-day radiometers use this principle. In this paper we shall describe a phase principle for detecting a narrowband Gaussian signal in the presence of receiver noise. We shall show that the phase principle leads to a phase detector whose performance is comparable to the square-law detector when gain fluctuations are negligible. Furthermore, the phase detector is relatively insensitive to system gain fluctuations; whereas the square-law detector is highly sensitive to system gain fluctuations. That is, the phase detector enjoys this important property shared by the polarity-coincidence correlator, 1,2 the phase detector analyzed by Huggins and Middleton, 3 and the zero-cross143