Low-profile Dual-polarized Filtering Antenna with Improved Gain and Impedance Bandwidth using Characteristic Mode Analysis

Abstract

A low-profile dual-polarized filtering microstrip patch antenna (MPA) with improved gain and bandwidth is realized without requirement of filtering circuit. Herein, the characteristic mode analysis (CMA) method is adopted to analyze the antenna performances. Initially, the resonant modes of the MPA are deeply analyzed, which indicates that its resonant frequencies of CM1 and CM3 could be moved close to each other by loading slots and shorting pins, thus broadening the impedance bandwidth. Then, the influence of the slots on radiation patterns of the antenna is further studied. The results demonstrate that the non-broadside radiation beam of its CM1 could be reshaped as the broadside beam, and the sidelobe level of its CM3 could be reduced by cutting the slots, leading to the improved gain. After that, the effect of the pins on the gain-response is investigated, It shows that the gain nulls of the MPA could be controlled at both lower and upper bands, especially for the non-filtering scheme. Finally, the proposed dual-polarized antenna is fabricated and tested. The results prove that its impedance bandwidth reaches to about 7.4% with a low-profile of about 0.038 free-space wavelength. Besides, a stable enhanced gain of around 10 dBi is achieved over the operating band.