A 60 degree scanning offset reflector antenna with high aperture efficiency

A new type of microwave offset reflector antenna which provides +or-30 degrees of scanning with reasonably high aperture efficiency is presented. This scanning reflector, like the torus antenna, combines reasonable scanning in one plane with good focusing in the other. Its scanning ability is superior to that of the torus and other single reflectors because it has much greater aperture efficiency and is thus smaller while being just as effective. A symmetric scanning reflector surface was derived in two steps: the fourth-order profile curve in the scan plane was found using least squares methods to minimize the scanned beam error; then, even polynomial terms which minimize astigmatism for both the unscanned and maximally scanned beams were added to form the three-dimensional surface. The offset design procedure is similar to that of the symmetric case. However, the offset geometry allows for odd order terms which do not exist in the symmetric case. Good results have been attained for +or-30 degrees scanning with a 30 lambda diameter illuminated aperture.<>