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.