Double-layer high-gain filter microstrip patch antenna

This paper proposes a dual-layer high-gain filtering microstrip patch antenna. The filter antenna exhibits high gain and good frequency selectivity. The filter section consists of a CQ filter composed of four open-loop rings, which exhibits good return loss and insertion loss. The antenna section is improved based on etched gaps in traditional rectangular patch antennas, comprising a rectangular loop patch and a rectangular patch with a pair of short-circuit vias, coupled by T-shaped microstrip lines, achieving higher gain. This dual-layer filter antenna demonstrates high gain and impedance matching within the operating frequency band, with two radiation nulls where the gain is very low, resulting in good edge roll-off characteristics.