Integrated compact UWB and frequency reconfigurable antenna with high isolation for cognitive radio

Abstract

This paper presents the design of a compact ultra-wideband (UWB) antenna and a frequency reconfigurable antenna with high isolation for cognitive radio (CR) applications. The antenna prototype comprises a UWB antenna for sensing UWB spectrum and a frequency reconfigurable antenna for communication purposes. The proposed antenna has been designed on FR-4 substrate with a compact size of 25 × 36 × 1.6 mm3 (0.22λ0 × 0.32 λ0 × 0.014λ0), where λ0 is free space wavelength at 2.7 GHz. The −10 dB impedance bandwidth is realized for UWB antenna ranges from 2.7 GHz to 10 GHz and for frequency reconfigurable antenna in two frequency bands from 4.3 GHz to 5.5 GHz and 5.1 GHz to 6.8 GHz. A T-shaped stub is integrated into the ground plane to achieve high isolation between antenna element ports and the impedance bandwidth improvement. The proposed design attains high isolation of −21 dB over communication frequency range of frequency reconfigurable antenna and most of the UWB spectrum. The prototype has been fabricated and measured. The measurement results are in good agreement with the simulated results.