A Self-Decoupled MIMO Patch Array With Consistent Radiation Patterns

It is challenging to simultaneously realize low mutual coupling and consistent radiation patterns in a multiple-input multiple-output (MIMO) patch array. This work addresses this issue by presenting a novel self-decoupled patch array with each antenna consisting of two differentially fed patches. Two characteristic modes can be stimulated, with modal currents superimposing in one antenna but canceling each other out in the other. Meanwhile, their modal patterns remain directed at the broadside and are not distorted, thus ensuring that each antenna in the array has a consistent radiation pattern without the need for extra EM structures. In addition, an H-shaped structure is included to enable a band-stop filter to prevent capacitive coupling across patches, hence improving self-decoupling performance. Importantly, the presented self-decoupling approach is scalable for MIMO arrays, including two, four, or even more antennas, without any modifications to antenna design or sacrificing its radiation and decoupling characteristics. Finally, a four-element, self-decoupled MIMO patch array was designed, fabricated, and measured. The measured results exhibit that the coupling between adjacent and non-adjacent antennas is less than −35 and −38 dB over their operation band of 5.8–5.97 GHz, respectively. Each antenna features a consistent and undistorted radiation pattern with a peak gain of more than 7 dBi at the broadside.