Theoretical and experimental studies of the resolution performance of multiplicative and additive aerial arrays

This paper describes some interim results of a theoretical and experimental study of multiplicative signal processing for receiving aerial arrays, such as those used in centimetric radar systems. Theoretical comparison is made between multiplication and other forms of demodulation such as linear and square-law rectification, in terms of the effect of demodulation on the ability of the directional array to resolve two closely spaced signal sources (or targets in a radar system). It is shown that the multiplicative system is superior to the other two systems for targets of approximately the same signal strength. It is also shown that improvements in resolution can result from the use of integration if the signals from the two sources are incoherent or partially incoherent. The effect of noise on resolution is briefly discussed and attention is drawn to the effect of the different directional responses of the different signal and noise products of demodulation. An experimental 8-element multiplicative array operating in the 3-cm band is described; this array is also capable of fast electronic scanning. Experimental directional responses of this array are presented for both single-target and multiple-target excitation, for static measurements and at electronic scanning rates of 2 kc/s.