A simple filtering patch antenna based on stub‐loaded resonator

In this article, a simple coaxial‐feed filtering patch antenna based on stub‐loaded resonator is investigated and analyzed. Owning to the addition of a pair of parasitic stubs, the original rectangular patch antenna acquires a new resonance point and an out‐side radiation null beyond the upper band edge. Then, by establishing a transverse path (introducing connected stubs), the radiating and filtering responses at lower band have been enhanced accordingly. In short, it operates like a three‐order filter with two‐constrained radiation nulls along the passband outside. The novel design has been verified by machining and testing, which meets the expected lately. A fractional bandwidth of 28% and a stable realized gain of 5.8 dBi in‐band are finally measured, and more it also reaches a higher radiation efficiency of 83%. Besides, it exhibits a unidirectional radiation pattern with a low‐cross polarization less than −20 dB in the boresight direction.