Design of Low-Profile Ultrawideband Conformal Array Antennas for Microwave Brain Imagers

This paper presents the design of low-profile ultrawideband conformal array antennas for microwave brain imaging applications. The radiating element features a double-layer folded log-periodic structure for bandwidth enhancement and size miniaturization. Taking advantage of the difference between the dielectric constants of the air and the brain or brain matched substance, the antenna exhibits the unidirectional radiation pattern with a high front-to-back ratio. The proposed low-profile radiating element has a size of around $91 \times 64 \times 1 \mathrm{~mm}^{3}$ and a wide operating bandwidth of 0.5-3 GHz, thus very suitable for conformal array design and high-resolution brain imagers.