Improved bandwidth and radiation efficiency of series‐fed patch array using cascaded inset‐fed mechanism

In this letter, a novel design approach of low-sidelobe series-fed patch antenna array is proposed which has enhanced bandwidth and radiation efficiency. It is based on the fact that the out-to-input voltage amplitude ratio of an inset-fed patch antenna element could be manipulated by changing the insert depth of the output microstrip line. Thus, by utilizing a cascaded inset-fed mechanism, the series-fed patch antenna array achieves voltage amplitude tapering for desired sidelobe suppression. The step-down transformer model and the cascaded step-down transformer model are presented to reveal the design approach as the equivalent circuit characterization of the antenna element. As a proof-of-concept, a 12-element series-fed patch antenna array operating 24 GHz with a 20 dB sidelobe level (SLL) is designed, simulated, and prototyped. It could be found that, in contrast to the conventional width-tapering patch antenna array, the proposed design achieves an impedance bandwidth broadening, from 1.7% to 2.5%, and a radiation efficiency improvement of 7% meanwhile.