Multiband Reconfigurable Filtering Monopole Antenna for Cognitive Radio Applications

A compact frequency-agile multiband filtenna is presented in this letter. The proposed reconfigurable filtering antenna performs independent switching between four operating bands viz. 1.8 GHz (GSM), 2.4 GHz (Bluetooth), 3.5 GHz (WiMAX), and 5.2 GHz (WLAN). This switching allows the unused bands to be utilized by the secondary user, making the antenna suitable for cognitive radio applications. An elliptical wideband monopole antenna is excited through a reconfigurable bandpass filter (BPF) integrated onto the 50 Ω transmission line. The BPF comprises four distinct structures to tune to four different frequencies using p-i-n diodes. The proposed filtenna has the reflection coefficient less than −20 dB for all the desired operating bands. Furthermore, this multiband filtenna offers gain of about 1.1, 2.6, 3, and 3.4 dBi at the four frequency bands. The prototype filtenna is fabricated, and the simulation results are verified experimentally.