Compact Postwall Slotline-Based Stepped Impedance Resonator Decoupling Structure for Isolation Enhancement of Patch Antenna Array

A compact decoupling structure, implemented by the postwall slotline (PWS)-based stepped impedance resonator (SIR), is proposed for enhancing the isolation between patch antennas. A pair of SIRs is placed between microstrip antennas to cut off the coupling path, which enhances the decoupling performance greatly at resonance frequency. Meanwhile, designed with a combination of conventional slotline and the PWS, the decoupling structure has a compact profile and, thus, is suitable for miniaturized element space. A two-element patch array is designed and fabricated to verify the decoupling effectiveness of the proposed structure, by providing simulated and measured results. Measured realized gain of the antenna with proposed structure is about 5.1 dBi. High isolation of 30.4 dB at 5.7 GHz is achieved, and the edge-to-edge distance is 0.059λ0 with the decoupling structure. Moreover, with the decrease of element distance, isolation improvement will be significantly enhanced. The compact size and isolation performance show the potential of the structure to be applied in antennas arrays including multi-input-multi-output systems and adaptive arrays.