A Wavetrap-Based Decoupling Technique for 45° Polarized MIMO Antenna Arrays

A decoupling method using wavetrap technique for large-scale multiple-input multiple-output (MIMO) antenna arrays consisting of 45° polarized patch antennas is presented and studied in this article. To achieve high isolation responses among the array elements, simple wavetrap structures are proposed and positioned around every single patch element. With the presented decoupling scheme, the strong mutual coupling between both adjacent and nonadjacent patch elements is suppressed to a low level. Theoretical and numerical studies are carried out to verify the decoupling performance of the proposed architecture. For demonstration purposes, two practical examples of 1 × 8 and 4 × 2 45° polarized arrays centered at 4.9 GHz are developed, fabricated, and measured. The results indicate that all mutual couplings among the arrays are significantly suppressed to almost less than -25 dB from 4.8 to 5.0 GHz, with a small insertion loss of around 0.7 dB, making the proposed decoupling scheme attractive and valuable for phased array and massive MIMO systems.