Adaptive beam-space nulling of multipath signals

A beam-space adaptive nulling technique that has potential for applications in communication circuits degraded by multipath signals is described. The technique is based on a well-known vector relationship in beam space. A linear transformation is used to prevent the degradation of the desired signal reception. Results are presented from tests of the technique that were conducted using real multipath data. The data used in these tests were recorded using a 32-element sampled aperture antenna (SAMPAR). These measurements were carried out on an over-water path. The direct signal, i.e. the signal that propagates via the shortest path from the transmitter to the receiver antenna, is selected as the desired signal; its reception is enhanced by suppressing the unwanted signals, i.e. the multipath signals that propagate via a reflection from the surface of the water. Examples are given in which the wanted and unwanted signals are separated by less than a beamwidth.<
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