A highly compact four-element monopole array with one-layer decoupling and matching network

The design of a highly compact four-element monopole antenna array operating at 2.45 GHz is provided. The four radiation elements are symmetrically placed and the minimum distance between them is 0.07λ. The input ports are decoupled by a simple decoupling network, which is a one-layer printed circuit board only containing transmission lines on low-cost FR 4 substrate. The proposed array shows good performance in port decoupling and matching, the coupling coefficient between the ports is below -20 dB, and the matching bandwidth is around 100 MHz.