Broadband Filtering Antenna With Asymmetric Feeding Structure

ABSTRACT A compact highly selective broadband filter antenna with an asymmetric feed structure is proposed. The radiating patch of the antenna unit consists of a central elliptical patch and a pair of semi‐annular patches, and the antenna forms multiple coupling paths from the feed ports to the radiating patches to generate a radiation null (6.28 GHz), which achieves the roll‐off rate of 193 dB/GHz. The innovation of this design is that asymmetric L‐shaped branches of about half a wavelength are added on both sides of the microstrip feedline of the antenna to expand the operating bandwidth and generate a low‐frequency radiation null (4.66 GHz), which achieves the roll‐off rates of 164 dB/GHz. The simulated results show that impedance bandwidth is 23.8% (4.77–6.06 GHz) with the peak gain of 5.86 dBi, which size is 0.5 λ 0 × 0.5 λ 0 × 0.09 λ 0 . Then, a 2 × 2 filtered antenna array is designed for experimental validation. The test results indicate that the impedance bandwidth of the antenna array is 21.5% (4.45–5.52 GHz), the in‐band gain is greater than 10 dBi and flat, and the out‐of‐band rejection level is greater than 20 dB. Attributed to the characteristics of easy and inexpensive manufacturing, the designed antenna has well application prospects in modern wireless communication systems.