A 4-to-4 Decoupling Feeding Network With Port-Pairing Capability for Compact Phased Arrays

In this article, a 4-to-4 decoupling feeding network (DFN) is proposed for closely spaced array elements. With extra coupling paths provided by the DFN, mutual coupling between adjacent and nonadjacent elements can be effectively suppressed. A full matrix of mutual coupling is adopted to synthesize the DFN. In particular, the coupling coefficients are expressed as functions of the DFN’s S-parameters, and hence, they can be effectively improved by optimizing the DFN. The proposed DFN has good port-pairing capability, which enables wide-angle beam scanning. A four-element rectangular patch antenna array is simulated and measured to verify the decoupling effect of DFN. After applying the proposed DFN, mutual coupling between all array elements is reduced by 7–23.8 dB. The realized gain of the array at all scan angles can be improved by ~0.6 dBi. In addition, the proposed DFN is applied to array elements with wide beamwidth to demonstrate its usefulness for wide-angle scanning arrays. Assisted by the DFN, the beam-scanning range of the wide-angle scanning array can be improved from ±60° to ±68°.