High-performance UWB Vivaldi antenna on FR4: A cost-effective solution for wearable technologies

• Vivaldi Tapered Slot Antenna (VTSA) is designed using a low-cost FR4 substrate, offering an affordable solution for wearable UWB devices. • The antenna offers an 18.81 % compactness, a 36.16 % and a 16.63 % gain improvement compared to a VTSA using the costlier Rogers RO4003C substrate • Edge slots improve compactness and bandwidth, while directors enhance gain and stabilize radiatio. The antenna showed low SAR on flat and curved human phantoms, ensuring safe UWB body-centric use. • The antenna achieves S11 < -10.56 dB (3.66–20.42 GHz), 8.1 dBi gain, stable patterns, and 0.83 ns group delay, make it ideal for wearable UWB. This paper introduces a novel Vivaldi Tapered Slot Antenna (VTSA) designed for wearable Ultra-Wideband (UWB) applications, utilizing a cost-effective FR4 substrate with a thickness of 0.8 mm. The proposed design achieves an 18.81 % size reduction (38.3 mm × 27.06 mm × 0.8 mm), a 36.16 % bandwidth (BW) increase, and a 16.63 % gain improvement compared to a VTSA using a Rogers RO4003C substrate (42.9 mm × 28.28 mm × 0.813 mm). The key contributions of this work include the effective use of the affordable FR4 substrate to achieve high performance, improvements in antenna compactness and BW through innovative slot designs, and the enhancement of gain and radiation pattern stability through the addition of directors to the slots. These modifications significantly boost the antenna's performance while maintaining a compact design. The antenna's suitability for wearable applications was validated through testing on flat and curved human phantoms made of skin, fat, and muscle, showing low Specific Absorption Rate (SAR) values across the UWB spectrum, confirming its safety for body-centric use. Measured results include S 11 values below -10.56 dB over the 3.66–20.42 GHz range, a peak gain of 8.1 dBi, stable radiation patterns, and an average group delay of 0.83 ns. Simulations using Computer Simulation Technology (CST) were validated by experimental testing, demonstrating the antenna's potential for wearable and body-centric applications.