A Compact Wideband Three-Slot Filtering Antenna Based on Mixed Electric and Magnetic Couplings

In this article, a compact wideband three-slot filtering antenna is proposed. The antenna consists of a U-shaped driven slot, a folded resonant slot, and a linear resonant slot. A microstrip feedline with a shorting via is employed to excite the antenna. Mixed electric and magnetic couplings enable the driven slot to couple to the two resonant slots. Three resonant frequencies lie within the passband, resulting in wideband operation. The lowest resonant frequency is determined by the folded resonant slot, while the highest resonant frequency is determined by the linear resonant slot. The center resonant frequency is influenced by the combined effects of the U-shaped driven slot, the folded resonant slot, and the linear resonant slot. A low-frequency radiation null at 1.68 GHz and a high-frequency radiation null at 3.19 GHz are generated. These two radiation nulls enable the proposed antenna to achieve excellent filtering performance. A prototype was fabricated and measured. The measured results are in good agreement with the simulated ones. The measurements show that the proposed three-slot filtering antenna exhibits a relative impedance bandwidth of 39.1%. The out-of-band suppression levels reach 12.5 dB and 14.8 dB in the lower and upper sidebands, respectively. The proposed three-slot filtering antenna is suitable for applications in wireless communication systems.