Mutual coupling suppression in closely spaced antennas

A technique to significantly reduce the mutual coupling between closely spaced antennas operating at the same frequency band is presented. The method comprises the use of two ground-plane side walls that are erected vertically next to adjacent antennas. The side walls are defected with a lattice pattern of slots to form a defected wall structure (DWS). In addition, the adjacent antennas sharing a common ground plane are separated with a pair of slits in the ground plane. This technique implemented on closely packed antenna suppresses surface waves in the antenna´s operation band and can provide isolation of 56´dB, which was achieved with a DWS loaded with mushroom-shape slots separating two microstrip patch antennas. In this case, the inter-antenna spacing (centre to centre) is 0.272´_o and ground-plane size is 0.606 × 0.370 ×_o². Also investigated is the number of DWS slot loadings on isolation between adjacent antennas. Furthermore, the proposed technique is shown to substantially reduce mutual coupling between planar inverted-F antennas (PIFAs) and monopoles. The measured results validate the proposed technique and vindicate the simulation results.