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 omega 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.