Low profile ultra-wideband directional antenna operating in low microwave band for brain stroke diagnostic system

Worldwide, brain stroke is the leading cause of disability among adult. Present imaging systems do not offer a low cost and portable solution for the stroke diagnosis. Microwave imaging systems have the potential to provide that solution and substitute, or complement, existing systems. To achieve that target, a wideband antenna operating at the band used for that application with directional radiation for adequate penetration into the human head is needed. This paper introduces a novel ultra-wideband antenna design consisting of a folded dipole-like structure printed on two dielectric slabs of the same size. The antenna covers a 98% fractional bandwidth (0.77 to 2.25 GHz), which is used in head imaging. The antenna exhibits stable directional radiation patterns with an average gain of 4.5 dBi and front to back ratio of 8 dBi. The overall structure of the antenna is equivalent to 0.27i₀ × 0.121₀ × 0.05 k₀, where X₀ is the corresponding wavelength at 0.77 GHz, which is a compact and low profile arrayable design suitable for microwave-based head imaging.