A simple algorithm for sidelobe cancellation in a partially adaptive linear array

Abstract

The far-field lobes of the edge elements of a uniformly excited linear array are nearly equal in width to the sidelobes of the array itself, and hence the edge elements are ideal for cancellation of specific sidelobes of the pattern. This supports the concept of partial adaptivity using only the edge elements. This technique is suitable for real-time implementation because only the edge elements require direct control whereas the inner elements are controlled by PROM's. Other advantages are that the nulls produced specifically by control of the edge elements are deep and wide. Also the main beam gain is not much affected by the sidelobe cancellation.Keywords partial adaptivity, edge elements, real-time implementation, PROM's Disciplines Computer SciencesComments ©1988 IEEE. Reprinted, with permission, from "El-Azhary, I., Afifi, M. S., & Excell, P.S. Journal of IEEE Transactions on Antennas and Propagation, Vol.36, No.10 pp.1482-1486 Oct 1988 . Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder. VOL. 36, NO. 10, OCTOBER 1988 with the 0.1 mm claimed for our method. A further advantage of this technique is the fact that the basic observations, the taking of several photographs, requires relatively little time, so that the results will be reasonably free of thermal changes. Further, the observations can be made at a variety of antenna orientations, so that structural distortions could be observed. A drawback is the time required for the analysis: the photographs need to be digitized, and the data then processed before a set of panel adjustment instructions can be issued. A recent demonstration of the technique involving 110 points and six photographs required 50-min measuring time, and 2 0 4 1 1 reduction time. The number of points on a large radio telescope is more likely in the vicinity of 1OOO. Fraser [3] quotes 18 h for the time to scan the images of a 34-m antenna.Holography: This technique [3] has several advantages over the alternative schemes: it provides a true measure of the performance of the reflector/subreflector system, since it measures the phase variations across the outgoing wavefront. However, this method has a cost: high signal-to-noise is required, which in general translates to a requirement for long integrations and hence the operation may take several hours. Furthermore, interpretation in case of dual-reflector an...

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