Reduction of mutual coupling between closely spaced PIFAs

A new approach for reducing mutual coupling between planar inverted-F antennas (PIFAs) is proposed. The approach consists of placing a resonator in between the PIFAs. The signal from the first antenna is scattered by the resonator and couples to the second antenna creating another path for mutual coupling, the phase and amplitude of which may be varied to suppress the existing coupling between the antennas. The simulation and experimental studies show that the proposed technique is able to reduce mutual coupling to about −25 dB from −3.5 dB when the antennas are placed as close as λ/11. Reduced mutual coupling between closely spaced antennas may find applications in MIMO, multi-antenna systems and phased arrays.