Simple Patch Antenna with Filtering Function Using Two U-Slots

Abstract

In this study, two U-slots of different sizes are used to combine the filtering function with a patch antenna. The U-shaped slots are etched into the patch, and currents in the opposite direction exist around these slots. Therefore, the currents cancel each other out, and a radiation null is formed. As a result, two radiation nulls are implemented on the left and right sides of the passband. To demonstrate the novelty of the proposed concept, a filtering patch antenna with a center frequency of 3.21 GHz and a 10 dB impedance bandwidth of 19.9% is designed and fabricated. High suppression levels of 25.33 and 19.32 dB in the lower and higher stopbands, respectively, are achieved. Therefore, a sharp band skirt and good selectivity are exhibited in the boresight gain response. The two radiation nulls are located at 2.4 and 3.7 GHz and can be independently adjusted.