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.>

The theory of modulation by hopping or by commutation among a number of spaced antennas is presented. The theory brings out the important considerations and criteria for determining the separation of discrete antennas in time and/or space that produces a desired modulation. In addition, antenna hopping and commutation are proposed for generating direction-dependent spread spectrum to enhance receiving system anti-interference processing gain and/or transmitted signal camouflage and LPI, as well as to provide an effective means for channel monitoring and analytical probing.>

Discrete maltipath propagation is generally considered to impose severe limitations on the performance of receiving systems, and hence, on the information transmission capacity of a communication link. Much work has been directed to the problems of relieving multipath effects, generally concentrating on correction of the performance realized with the resultant of the multiple-path outputs. In this paper, the emphasis is on separating the outputs of a small number of discrete paths not only for freeing the output of at least one usable path, but also possibly for combining the various path outputs in constructive ways to take advantage of the additional signal energy that each path provides. Novel techniques for accomplishing this are described, based on converting directional and propagation-delay differences into very distinctive frequency differences by synthetic Doppler methods. These techniques are of course applicable to facilitate the separation of various time and frequency overlapping signals arriving from different directions.