A novel second-order decoupling network for two-element compact antenna arrays

A novel broadband decoupling network for two tightly coupled antennas is proposed in this paper. An intentional coupling is introduced by inserting a second-order coupled resonator filter network between two coupled antennas. With properly controlled magnitude and phase, this coupling can cancel the existing mutual coupling between the two antennas. A prototype is realized on an FR4 PCB for demonstration purpose. Measurement results indicate that both port matching and decoupling can be achieved simultaneously. Specifically, return loss of no less than 6dB and isolation of more than 20dB can be achieved for 11% fractional bandwidth. Moreover, measured radiation efficiency and envelop correlation at the center frequency are 74% and -56dB respectively. The proposed decoupling network is suitable for diversity antennas and other size-limited multi-antenna systems.