Novel Method to Correct Radiation Pattern Distortion of Conformal Antennas

摘要

The radiation pattern of a curved phased array antenna is distorted when the beam is scanned. This is primarily due to the change of the appearance of the amplitude taper across the aperture which is a consequence of curvature. The approach described in this report, to correct for this phenomenon, is to adjust the aperture taper as a whole, rather than to adjust each individual radiating element separately. If an anti-symmetric taper is added in the proper proportion to a symmetric taper the original taper can be largely recovered. Typically the sum and difference aperture illuminations of an antenna can provide the needed symmetric and anti-symmetric functions. A relatively simple and practical technique of using the sum and difference networks in combination to correct for curvature effects is demonstrated. This technique uses a variable power divider to distribute the power is a prescribed proportion at an arbitrary scan angle to the sum and difference channels. The optimum amount of signal to be distributed to achieve the maximum restoration is found as a function of scan angle and curvature. The analysis is comprehensive, including effects due to the element pattern, antenna size, and the variation of apparent element density. Since attenuators are not used, the method has the added advantage of experiencing no loss of power. The technique can be used to improve any sum and difference illuminations. In this report cosine and sine illumination functions respectively are used.