A Wideband Filtering Bidirectional Slot Antenna With Parasitic Slots

This letter presents a design of a wideband filtering slot antenna with a bidirectional radiation pattern. The design starts from a conventional linear slot antenna. A capacitive coupling structure is utilized to make it easy to match the 50 Ω port. Then, parasitic slots are introduced to couple with the driven slot. Extra resonances are found to broaden the bandwidth. In addition, two radiation nulls are observed to improve the out-of-band suppression. Moreover, a transmission line model is derived. The coupling is modeled by an inductive/capacitive element, and the parasitic slot is modeled by a transmission line. They are connected in series, and the radiation null occurs at its resonance, which explains the mechanism of the filtering property. A prototype is fabricated and measured to verify our idea. The results show that the proposed antenna has a 10 dB bandwidth of 63.2%, an in-band gain of 3.5–5.6 dBi and an out-of-band radiation suppression more than 9.5 dB. The advantages of wide bandwidth, filtering property and easy fabrication make the proposed antenna suitable for various wireless communication systems.