Enhanced Bandwidth and Resonance Optimization of a Flexible Microstrip Antenna for ISM Applications

This paper presents the analysis and optimization of a flexible microstrip antenna to enhance its electrical performance for Industrial, Scientific, and Medical (ISM) band applications. The proposed design integrates inset slots on both the patch and ground plane, along with parasitic elements, to improve resonant frequency and bandwidth. Fabricated on Rogers RO4003C $(\varepsilon r=3.55)$ with dimensions of $20 \times 25 \times 0.2032 \text{mm}^{3}$, the antenna operates within the $5.725-5.875 \text{GHz}$ ISM band. Experimental results demonstrate an $S_{11}$ of −37.05 dB at 5.78 GHz and a bandwidth of $158 \text{MHz}(5.739-5.897 \text{GHz})$, covering 90.67 % of the ISM band. Theoretical, simulation, and experimental analyses confirm that embedding slots and parasitic elements significantly enhances performance. Additionally, the antenna maintains stable functionality under bending conditions, making it suitable for wearable and wireless body-area network (WBAN) applications. With its flexibility, optimized resonance, and broad bandwidth, the proposed antenna offers a robust solution for efficient and high-speed data transmission in ISM band communication systems.