Theory of frequency modulation by synthetic antenna motion

The author presents the theory governing the method of simulating of synthesizing antenna motion over a specified aperture onboard a supporting platform by commutating among a number of discrete antennas arranged along a prescribed path of motion. The theory brings out the considerations and criteria for selecting the number and spacing of antennas to be commutated; the effects, and hence criteria, for specifying the pulse characteristics of the gating (or blending) time function that describes how each antenna is tapped (or switched on and turned off) by the commutator each time it is activated; the nature and performance characteristics of the blending corrective filter, or postcommutator sample interpolator, that will extract the desired Doppler-modulated signal if the spacing between successively activated antennas is such that no time-invariant blending function will extricate the desired sampling spectral zone for any but a very restricted type of signal; and the guidelines for resolving complications that may arise are in a number of special situations