Quasi-Reflectionless Tunable Filtering Antenna for Multicarrier Transceiver

In this letter, a tunable quasi-reflectionless filtering antenna is proposed. The device consists of a reflective microstrip bandstop filter (BSF) and a radiating patch antenna connected in a complementary-duplexer fashion. By terminating the output port of the BSF with another antenna and employing the patch antenna (antenna channel) as the radiator, a tunable quasi-reflectionless antenna is obtained. Since each element works at a specific frequency, the antenna array distributes spectrum resources to different antenna elements, which fits with the multicarrier base station application. The theoretical analysis by equivalent circuits is given. For verification, a dual-band prototype is fabricated and measured. The measured results agree well with the simulation. The filtering antenna exhibits a fractional bandwidth of 3.2% and a tuning range from 3.6 to 4.1 GHz for each band. The maximum radiation gain is 5.5 dBi, making it a good candidate for a multicarrier transceiver in sub-6 GHz 5G applications.