Monopulse pattern‐forming method for an off‐focus RF sensor

Abstract

To improve the accuracy of the beam-pointing direction of the satellite-borne antenna, it is effective to attach an accurate RF sensor to such an antenna. On the other hand, it is not possible to place a monopulse horn for the RF sensor at the focal point of the antenna due to the use of the multihorn approach in the communication signal horn. Often the monopulse pattern is significantly degraded.In this paper, a method is presented for forming a desired monopulse pattern even under such an adverse condition. The least-square method is used for detennination of the amount of adjustment for the amplitude and phase for each horn. It is shown that the type of tracking receiver is related to the evaluation of the obtained pattern. At the same time, the tracking receiver is related to the evaluation of the obtained pattern. At the same time. the tracking receiver is modeled and a pattern evaluation method is proposed by observing the angular detection error at the output end of the tracking receiver. As an example, the present method is applied to the RF sensor displaced by six times the 3 d B beamwidth in an antenna with an aperture diameter of 350 wavelengths. It is found that a monopulse pattern is acquired with distortions as small as those for an RF sensor on the focal point and the angular detection error is about one-fourth the results in the conventional method if three constraint points on the difference pattern are chosen.As an RF sensor using the communication antenna, several types have been conceived for the feed horn, feed network, and tracking receiver. For instance, the feed horn can be a higher-order mode horn and a multihorn. The tracking receiver can be classified according to the 82 ISSN8756-662 1 /92/OOO2-OO82$7.50/0 1992 Scripta Technica, Inc.