Strut cross sections for minimizing noise temperature in reflector antennas

Symmetric reflector-antenna systems are widely used in numerous applications such as deep-space links, satellite communications, radio astronomy, radar, etc. In the majority of these applications, the system has either one or two reflectors, and in both cases the antenna entrance aperture is partially obstructed by the feed (single reflector), feed and subreflector (dual reflector), and their respective supporting structures (struts). This blockage decreases the overall antenna gain, increases the side-lobe and cross-polarization levels, and increases the antenna noise temperature. For physically-large shaped dual-reflector antennas designed for optimum gain and noise performance, simple ray-tracing considerations indicate that the plane-wave scattering is the dominant strut-noise source. Due to this, only the strut plane-wave scattering is considered. The main interest is in the determination of optimum (i.e., minimum noise) all-metallic strut cross sections, without detriment of their mechanical function. This is accomplished by optimizing the strut cross-section geometry to reduce the plane-wave scattering towards ground. However, with some modifications, the techniques presented can also be used to reduce the strut noise associated with the spherical wave scattering.