Bandwidth-Driven Optimization of a Spiral UWB Antenna for Hemorrhagic Stroke Detection

This paper presents a microwave imaging system based on an eight-element spiral ultra-wideband (UWB) patch antenna array for hemorrhagic stroke detection. The proposed antenna, designed on an 8-mm polyimide substrate, operates over a 0.6-2.2 GHz frequency range and is numerically evaluated in CST Studio Suite using a realistic head phantom containing a stroke-mimicking inclusion. A monostatic radar configuration is employed in which each antenna sequentially transmits and receives microwave signals, and the collected reflection data are processed using a confocal Delay-and-Sum (DAS) reconstruction algorithm. The study investigates the influence of operating frequency range and bandwidth on the quality of reconstructed microwave images. Simulation results show that the low-frequency band provides improved penetration and reliable stroke localization, whereas the high-frequency band exhibits reduced detectability due to increased attenuation. The wideband configuration (0.7-2.0 GHz) achieves the most accurate localization by balancing penetration depth and spatial resolution. The system successfully detects both medium (4 cm) and small (2 cm) hemorrhagic strokes, demonstrating the potential of compact spiral UWB antenna arrays for portable and noninvasive microwave brain imaging.