The Multipolar Spectrum of a Microstrip Antenna Array Element Modifications

In this paper, we study the change in the multipolar spectrum of a circularly polarized microstrip antenna array during the application of classical methods for increasing the gain and reducing the cross-talk of neighbouring emitters. To examine how the changes in the geometry impact in the resulting set of internal modes, we decomposed of the antenna's far electric field into spherical harmonics. All the considered cases were divided into studying the standalone emitter and its nearest neighbor approximation. The paper describes the effect of the formation of a metal cavity behind the microstrip, as well as the addition of a parasitic patch in front of the antenna. Among other things, the effect of a perfect electric conductor mirror numerical approximation on the backside of the antenna array was also investigated. The results showed that by applying various operations that do not directly affect the resonant element itself, it is possible to control the modal composition of the entire system.