A Compact High-Selectivity Wideband Filtering Antenna With Multipath Coupling Structure

Abstract

A compact wideband filtering patch antenna with high selectivity is presented. The proposed filtering antenna contains a rectangular patch rounded by a pair of U-shaped patches, and is fed through two coupling slots etched on the ground. By introducing these elements, four in-band resonances are generated and the impedance bandwidth are expanded. Besides, multiple coupling paths are constructed from the feeding port to the radiating patches to form three radiation nulls at the band edges. Moreover, a modified composite right/left-handed transmission line unit is used as the feedline to further suppress the out-of-band radiation level. The performance of the proposed filtering antenna is verified by both simulation and measurement. It exhibits a 21.5% (4.45–5.52 GHz) measured impedance bandwidth with a compact size of 0.4 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.4 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free-space wavelength at 5 GHz). Besides, the measured average gain and out-of-band suppression level are 4.8 dBi and 15.9 dB, respectively. Obviously, this filtering antenna can be used to build a compact multiband antenna array to reduce the interference between different bands.