High‐Gain Circularly Polarized Filtering Antenna Array Utilizing Aperture Coupling and Decoupled Resonant Structures

ABSTRACT To satisfy the miniaturization and high‐integration demands of wireless communication systems, this letter presents a novel aperture coupling circularly polarized (CP) filtering antenna array operating in the 2.45 GHz ISM band. Circular polarization is achieved by using a corner‐truncated radiating patch. The low‐frequency and high‐frequency radiation nulls introduced by U‐shaped slot and U‐shaped resonators can be independently tuned. The ground plane isolates the feeding network from the radiating patch, which realizes a fully decoupled design between filtering response and CP radiation performance. A 2 × 2 sequentially rotated‐feeding CP antenna array is designed to enhance the gain and expand the 3 dB axial ratio (AR) bandwidth. Measured results show that the antenna has a VSWR ≤ 1.5 bandwidth of 11.02% and an AR ≤ 3 dB bandwidth of 12.24%. The realized gain at center frequency is 11.15 dBic, and the selectivity on both sides of the passband is 183.3 dB/GHz and 169.2 dB/GHz, respectively. The proposed design exhibits independent tunable radiation nulls, low profile, and well‐overlapped impedance and AR bandwidths, making it highly promising for IoT, WLAN, and other wireless communication applications.