Minimization of the plane-wave scattering contribution of inverted-Y strut tripods to the noise temperature of reflector antennas

The article is concerned with determining the metallic strut cross section of inverted-Y tripods used to minimize the plane-wave scattering contribution to the noise temperature of ground-station reflector antennas and radio telescopes. This is accomplished by numerically optimizing the cross section for minimum ground-noise pickup over the antenna elevation-angle operation range. Advantage is taken of the fact that although the struts' cross-section perimeter can be comparable to the operation wavelength, their electrical lengths are usually long. This allows the struts' scattering characteristics to be determined by solving standard two-dimensional field integral equations. The article concentrates on the top strut of an inverted-Y configuration since it is responsible for the dominant ground noise pickup associated with the plane-wave scattering. Numerical simulations are presented to substantiate this fact and a simple and convenient broadband closed-form representation for the minimum-noise top-strut cross section is derived and tested.