A COMPACT AND DIRECTIVE UWB ANTENNA FOR BIOMEDICAL APPLICATIONS

Ultra wideband (UWB) (3.1–10.6 GHz) microwave imaging systems offer much promise for biomedical applications such as cancer detection because of their good penetration and resolution characteristics. The underlying principle of UWB cancer detection is a significant contrast in dielectric properties, which is estimated to be greater than 2:1 between normal and cancerous tissue. UWB imaging systems have shown promising results in the detection of tumours for early breast cancer detection [1]. In UWB imaging systems, a very narrow pulse is transmitted from an UWB antenna and allowed to impinge on the body. As the pulse propagates through various tissues, reflections occur at interfaces between different tissues. This scattered signal can be received using another UWB antenna, or array of antennas, and used to map different layers of the body. For an accurate imaging system with high resolution and dynamic range, the transmitting/receiving UWB antenna should be planar, compact in size and directive with high radiation efficiency. Several UWB antenna designs have been proposed for the use in medical imaging systems [2-4]. Each has its own merits and drawbacks. Some of the proposed antennas have a non-planar structure while others have low gain and/or low radiation efficiency. The low efficiency is a major paramete