The use of shorting posts to improve the scanning range of probe-fed microstrip patch phased arrays

This paper presents a thorough investigation of the use of shorting posts to improve the scanning potential of microstrip probe-fed patch arrays. A rigorous spectral domain integral equation (SDIE) technique is used to analyze the scan impedance and related radiation characteristics of several proposed shorting post-patch array configurations. It is shown that by using shorting posts, potential scan blindnesses can be removed and the useful scanning range of the array can be significantly extended beyond 80° in the plane of interest. Comparisons of the scan performance of several microstrip patch arrays containing up to three shorting posts are presented. Novel hybrid shorting post configurations are also proposed and examined, which provide excellent scanning potential in the three principal planes (E-, H-, and D-planes). These modified microstrip patches incorporate switching diodes and provide minimal scan impedance variation for scan angles near 80° in all three planes, as well as very low cross-polarization levels