An ultra-wideband Vivaldi antenna development for brain microwave imaging

This article presents a comprehensive analysis of a tiny, rectangular, and exponentially tapered slotted ultra-wideband (UWB) Vivaldi antenna developed explicitly for brain microwave imaging. The antenna comprises seven symmetric rectangular slots carved on both sides of the rear radiative wings of a tapered slot antenna. The antenna's total dimensions, which encompass the ground layer, are 0.39λ × 0.33λ × 0.007λ while operating at a lower frequency of 1.35 GHz. The simulated impedance bandwidth (IBW) is observed to have a range of frequencies between 1.35 and 5.50 GHz, with a fractional bandwidth (FBW) of 121.17%, where the magnitude of |S11|< - 10 dB. On the other hand, the measured IBW spans from 1.4 to 6.4 GHz, exhibiting an FBW of 128.20%. The antenna has a gain of 9.99 decibels isotropic (dBi) and possesses directional radiation properties, along with a front-to-back ratio (FBR) exceeding 30 dB. The analysis conducted in the time domain demonstrates little pulse distortion and a group delay of less than one nanosecond, indicating good performance. Additionally, the system exhibits a high-fidelity factor of 96.26% and maintains linearity in the transmission phase (S₂₁). Both simulation and experimental findings demonstrate the efficacy of the antenna for microwave-based imaging.