A printed monopole antenna with multiple ground plane geometries for multi-protocol wireless and sweat sensing applications

A compact printed monopole antenna with multiple ground plane geometries is presented for multi-protocol wireless and sensing applications. The antenna, with physical dimensions of 25 × 20 × 0.8 mm3 and three different ground plane shapes, operates across the L, X, and Ku bands, with the capability to reject interfering bands. It consists of a circular radiating patch, a coplanar waveguide transmission line, and arrow-shaped slots, designed on a Rogers RO4003C substrate. The antenna, with its original ground plane shape, covers three −10 dB operating bands, including 8.2–10.64 GHz, 12.1–24 GHz, 25.54–30 GHz. Although the simulation indicates rejection bands at 10.65–12.1 GHz and 24–25.54 GHz, the measured results show an improved impedance match. After modifying the ground plane, the second configuration operates exclusively within the X band. The third design is optimized for the L and Ku bands and rejects the X band frequencies. Additionally, this work introduces a miniaturized antenna sensor suitable for non-invasive hydration monitoring via sweat analysis. By integrating the sensor into athletes’ shoes, it enables continuous, real-time monitoring during exercise, providing coaches with valuable insights to optimize hydration strategies and training intensity. The antenna sensor demonstrates a significant frequency shift in response to varying sweat concentrations, with a sensitivity of 20.57 MHz/1, allowing effective tracking of hydration levels throughout physical activity.