Improving port isolation in dual-polarized microstrip patch antenna arrays

Abstract

In this thesis we present the design techniques mitigating the port isolation degradation in dual-polarized microstrip arrays. The advantages of using dual-polarized antennas are the frequency band reuse and simultaneous receive/transmit capability. To fully exploit these advantages the isolation between orthogonally polarized ports must be maximized and radiation cross-polarization minimized. To prevent the port isolation degradation due to presence of the feed network lines surrounding the radiator the "folded" feed optimized to maximize the port isolation is introduced. The analysis of the port isolation dependence on radiating element positioning and grouping as well as the layout of the non-mirrored sections of the feed network within the array is performed. Based on the design guidelines introduced in this thesis the 4x4 element dual-polarized microstrip patch array was manufactured and port isolation in excess of 40dB was measured over the impedance bandwidth. The effects of excitation amplitude taper and excitation phase progression on port isolation performance of the array are examined and the results presented.