A Planar Integrated UWB/Reconfigurable Antenna with Continuous and Wide Frequency Tuning Range for Interweave Cognitive Radio Applications

This paper presents a planar ultra-wide band (UWB) sensing antenna accompanied with a monopole narrow band communicating antenna for interweave cognitive radio (CR) applications. The UWB antenna bandwidth covers the entire band specified for UWB applications (3.1–10.6 GHz). In addition to the varactor diode, a PIN diode is attached to the communicating antenna to expand the continuous frequency tuning of the varactor diode up to 3 GHz along the frequency range (3.3–6.3 GHz) including WiMAX, personal area network, and the 5 GHz wireless local area network. The UWB sensing antenna shape and the ground plane size of the communicating antenna are modified to reduce the mutual coupling between the two antennas to values less than − 15 dB. The measurements are well agreed with the simulation, and they verify the antenna suitability for CR systems. Moreover, the results show an omnidirectional power pattern for both sensing and communicating antennas which is compatible to the portable CR devices.