Reconfigurable MIMO Filtenna for Spectrum Underlay Cognitive Radio

A two-port reconfigurable MIMO filtenna has been designed in this paper for Spectrum Underlay Cognitive Radio (CR) system. Also, the importance of having a sensing antenna in Underlay CR system has been discussed in this paper which is missing in the literature. The novelty of this paper lies in achieving both communicating and sensing antennas using a single-port filtenna. Such two single-port filtennas are arranged on a single substrate and sufficient isolation is maintained between them for two-port MIMO applications. Hence, the proposed reconfigurable two-port filtenna involves two technologies: one is CR and another one is MIMO. The designed two-port MIMO filtenna has dimensions of 55 × 80 mm
²
, The sensing antenna scans the wide range of frequencies from 0.8 to 4 GHz, whereas, communicating antenna exhibits stop-band frequency tunability from 2.5 to 3.5 GHz. Biasing circuitry and lumped elements (varactor diode) are used in achieving the frequency reconfigurability and the losses introduced by them are minimal. The proposed filtenna design has been fabricated and simulation results are experimentally verified. Throughout the antenna working band, peak gain and efficiency are more than 2 dBi and 75% respectively. Measured isolation between the antenna elements is more than 15 dB and the measured ECC between the two radiated signals is less than 0.5 in the working band, which proves the good MIMO performance of the proposed system.