Design of a dual port integrated antenna for cognitive radio applications

This paper presents an Ultra-Wideband (UWB) fractal antenna and a dual-band antenna integrated on a single substrate for cognitive radio applications. The UWB fractal antenna has an impedance bandwidth of 112.05%. The dual-band antenna has a bandwidth of 2.17% (3.503 GHz-3.58 GHz), suitable for WiMAX applications, and 2.32% (5.96 GHz-6.1 GHz) with resonant frequencies at 3.525 GHz and 6.02 GHz respectively. The dual-band antenna has a gain of 0.86dB and 2.27dB at frequencies of 3.525 GHz and 6.02 GHz respectively. Shorting pins are used in the antenna to reduce surface wave and to increase isolation between the two antennas. The isolation between the two antennas is found to be below -25 dB at 3.525 GHz and 6.02 GHz. The antenna has a compact dimension of 70mm × 50mm (1.16λ × 0.83λ). The observed VSWR value of the UWB antenna and the dual-band antenna is less than 2 for the required frequency range.