Compact Reconfigurable UWB Slot Antenna for Cognitive Radio Applications

A very compact reconfigurable ultrawideband (UWB) stepped-slot antenna for cognitive radio (CR) applications is presented in this letter. The proposed antenna operates in two modes: UWB mode for sensing application and communicating mode for different narrow/wideband communication applications. The UWB mode of antenna is obtained by the creation of three resonances that lie in UWB spectrum. The narrow/wide communicating bands are obtained by different switching states of five p-i-n diodes. The impedance bandwidth of the proposed antenna in UWB mode is 2.8-10.7 GHz. The communicating bands (3.2-4.5, 4.3-7.8, and 7.9-11.2 GHz) cover the entire UWB spectrum. The proposed antenna has the compact size of 21 x 9 mm(2). A prototype of the designed antenna is fabricated and measured. Themeasured results are in good agreement with the simulated results that validate the proposed approach of reconfigurable UWB antenna design for CR applications.