A 2-D Self-Decoupling Method Based on Antenna-Field Redistribution for MIMO Patch Antenna Array

Abstract

In this letter, a novel method of 2-D self-decoupling at both <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> - and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> -planes is proposed based on the field-redistributed TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> -mode circular patch antenna. At first, it is demonstrated the marginal field of a patch is the main cause of coupling, and the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> -plane-coupled ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> -plane-coupled) array suffers from electric (magnetic) coupling. Then, it is discovered for the first time that the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> -mode circular patch antenna is immune to the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> -plane coupling because its fields are null at two marginal regions along <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> -plane. After that, the slot-loading for sidelobe reduction is further developed for field reshaping, and two cascaded slots help to generate two new marginal weak-field regions along the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> -plane. The initial strong electric coupling in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> -plane is thus eliminated. In particular, the proposed self-decoupling method is applicable for larger-scale 2-D arrays with arbitrary element numbers, and it is demonstrated by 1 × 4 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> -/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> -plane-coupled arrays and the 2 × 2 arrays. At last, a prototype of a 2 × 2 high-isolation multiple-input–multiple-output (MIMO) array with 0.2 mm patch-to-patch separation is fabricated and measured. The array can achieve intrinsic high isolation of more than 20 dB, element gain of 10.7 dBi, and cross-polarization level below −20 dBi without using any extra decoupling network.