Mutual coupling reduction using coupling matrix based band stop filter

Abstract

The capability of the coupling matrix-based band stop filter in mutual coupling reduction between the MIMO arrays is presented. Initially, a microstrip band-stop filter with 3 GHz center frequency is designed using coupling matrix method. This filter structure is then placed between 2×1 radiating patches separated by 0.22 λ in a reference MIMO antenna designed for 3 GHz WiMAX applications. Both array antennas with/without band stop filters are fabricated and the scattering parameters are obtained separately and plotted comparatively. A good agreement is achieved between measurement and simulation results, and about 28 dB isolation is observed at operating frequency after the proposed filter application. Besides, the Envelope Correlation Coefficient (ECC) is computed and surface current distributions are simulated for both cases. It is observed that ECC has dropped to almost zero and the surface currents induced in the second patch due to the first patch excitation are extinguished with the implementation of the proposed isolation wall. Finally, to clarify the advantages of our approach, a few related studies are summarized in a comparative table.