High aperture efficiency symmetric reflector antennas with up to 60 degrees field of view

Abstract

A microwave single-reflector scanning antenna derived from an ellipse (rather than the usual parabola) which gives a much greater field of view is presented. This reflector combines reasonable scanning in one plane with good focusing in the other, and its scanning ability is superior to the torus and other single reflectors because it has much greater aperture efficiency and is thus smaller while having the same performance. The reflector surface is derived in two steps: a fourth-order even polynomial profile curve in the scan plane is found using least squares to minimize the scanned ray errors; then even polynomial terms in x and y that minimize astigmatism for both the unscanned and maximally scanned beams are added to form the three-dimensional surface. Numerical simulations of radiation patterns for a variety of antenna diameter and field-of-view cases give excellent results. The 60 degrees scan case with 30- lambda -diameter aperture has only 0.2-dB peak gain deviation from ideal and first sidelobe levels below 14 dB down from peak gain. The 17 degrees , 500- lambda case has only 0.8-dB gain variation and -14 to -11 dB sidelobe levels for approximately +or-68 beamwidths of scan, with focal length to aperture diameter ratio equal to about one. >