Methods to reduce mutual coupling between antenna elements

Mutual coupling between antenna elements

Miniaturization of antenna arrays requires designers to place a large number of elements in a small area. This action creates what is known as mutual coupling, which in turn causes crosstalk and distortion, leading to degraded antenna performance and potential distortion of the radiation pattern. It is no exaggeration to say that this mutual coupling is the biggest obstacle to the miniaturization of antenna arrays. Over the years, antenna designers have found workarounds, but with limited success. Solutions include band gap and ground defect structures as well as 3D vias.

Zigzag Line Solutions

Recently, a promising new decoupling technique has emerged in the literature. It is called micromachined meanderline slots (ML). We use the popular EMWorks antenna software package HFWorks to test ML and study its decoupling efficiency.

Top and bottom views of a 2×1 patch array antenna with ML slots

A meander line (ML) slot is inserted between the antenna patches on the bottom ground plane to suppress surface currents.

S-parameters (S11 and S12) of the 2 × 1 patch array antenna with and without ML slots: Port 1 is excited, Port 2 is terminated with 50 Ω

The results show that ML is very effective in reducing coupling between antenna elements. In fact, the S21 graph clearly shows that adding the ML slots greatly improves the isolation between antenna elements. That is, the S21 is approximately 7.5 dB and 26 dB at 4.9 GHz without and with the ML slots, respectively. In addition to the S-parameters, the near electric field plot on the top plane, shown in the figure above, also shows that the coupling between elements is reduced if ML is used.

Therefore, ML is proposed to reduce coupling between elements in antenna arrays used in wireless communications, especially for 5G networks where miniaturization is crucial.