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°.