A UWB directional antenna for microwave imaging applications

A compact ultra wideband (UWB) antenna with high fidelity for use in a near field microwave imaging system is presented. The antenna is composed of two elliptical conducting/resistive patches forming a dipole with a subtended angle between the two arms smaller than 90deg. This configuration resembles a "bunny-ear" antenna. A resistive layer is used to increase its front-to- back ratio and hence to reduce backward radiation. The antenna is assumed to operate in a liquid with a high dielectric constant to achieve the best matching with an irradiated body. The simulated and measured results show that the antenna covers the 2.4-10.6 GHz band with moderate gain (between 3.3 and 9.2 dB), good radiation efficiency (higher than 70%), high fidelity (more than 90%) and more than 10 dB front-to-back ratio.