Design and optimization of flexible DGS-based microstrip antenna for wearable devices in the Sub-6 GHz range using the nelder-mead simplex algorithm

Abstract

• Flexible antenna Design: a flexible and wearable antenna with a defected ground structure (DGS) was developed, optimized, and experimentally validated for use in wearable devices. • Optimization Process: the antenna was optimized using the Nelder-mead simplex Algorithm. It operates at 2.185 GHz with strong signal quality (|S11| ≈ –22.34 dB) and a peak gain of 5.57 dBi. • Safety Assurance: SAR (Specific absorption Rate) analysis showed the antenna meets international safety standards, proving it is safe and effective for wearable applications. • Performance during Bending: the antenna's performance was tested under different bending conditions. It worked consistently well, showing it is both robust and flexible. • On-Body Testing: the antenna was tested on various body parts, including the hand, leg, and chest. It performed reliably in all cases, confirming its suitability for wearable use. • Applications in 5G: the results show that this antenna is ideal for wearable devices operating in the 5 G Sub-6 GHz frequency range, offering excellent performance, flexibility, and safety. This study introduces a Nelder-Mead Simplex Algorithm based low-profile, flexible, and wearable defected ground structure (DGS)-loaded deformed microstrip antenna for Sub-6 GHz 5 G applications. It is fabricated on a low-loss 20 mil Rogers RT/Duroid 5880 substrate and the antenna demonstrates robust performance with reflection coefficient magnitude (|S 11 |) of –22.34 dB with peak gain of about 5.57 dBi at resonant frequency ( f r ) of 2.185 GHz. Comprehensive key performance metrics such as |S 11 |, far-field gain patterns, and specific absorption rate (SAR) of the proposed antenna is demonstrated. The SAR for 1 g and 10 g tissues at various separation distances are analyzed and presented by utilizing human multilayer phantom model with antenna. Additionally, the lowest SAR is measured to be 0.0959 W/kg for 1 g of tissue and 0.0755 W/kg for 10 g of tissue when the antenna is placed 0.291λ 0 away from the model. The study also explores the proposed antenna performance under various bending conditions for the conformability analysis and in different on-body scenarios, with placement on the hand, leg, and chest. The measured |S 11 | values, particularly strong on the chest, underscore the antenna effectiveness for wearable technology.