Novel Techniques for Counteracting Multipath Interference Effects in Receiving Systems

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.