Single-patch and single-layer square microstrip antenna with 67.5% bandwidth

A square microstrip patch antenna with broadband operation is demonstrated. With an air-filled substrate of thickness around 0.1λ₀ and one patch edge shorted by three symmetrical shorting pins, the antenna achieves an impedance bandwidth (return loss ⩽-10 dB) of 67.5%. The broadband feature of the antenna is mainly realised by exciting three resonant modes in a single patch and making them sufficiently close to one another. Details of the antenna design, equivalent circuit, and typical characteristics are presented and discussed both theoretically and experimentally