PIER C | PIER Journals

2025-12-11 Latest Published

A Flexible Hexagonal Loop Monopole Antenna with Novel Embedded EBG for SAR Reduction in WBAN Download Full Article View Full Article

By Shital B. Gundre Varsha R. Ratnaparkhe

Progress In Electromagnetics Research C, Vol. 163, 11-19, 2025

doi:10.2528/PIERC25101505

Abstract

This paper introduces a novel compact, flexible hexagonal loop shaped patch antenna embedded with a novel electromagnetic bandgap (EBG) structure designed for ISM band operation, targeting 2.45 GHz wearable applications in close proximity to the human body. The EBG unit cell is formed using a rectangular patch which has nested U shaped slots with a stretched strip of inverted U shaped slot at bottom. Both hexagonal loop antenna and the 2 × 2 EBG array are simulated using Ansys HFSS (High Frequency Structure Simulator). A key aim of this research is to achieve the specific absorption rate (SAR) reduction. The effectiveness of the EBG array structure in reducing surface waves and dropping down the SAR is demonstrated using a multilayer human tissue equivalent phantom comprising skin, fat, muscle, bone layers, confirming obtained SAR values are within the safety limits set by regulatory authorities. The simulation results are verified and validated by the fabricated antenna experimental measurements. Furthermore, the antenna was experimentally assessed in terms of its performance under bending and in practical on-body conditions.

2025-12-10

PIER C

Vol. 163, 1-10, 2025

doi:10.2528/PIERC25091605

download: 12

Multi-Mode Dual Five-Phase Hybrid Excitation Motor High Efficiency Control Based on Gradient Descent

Yu Nan, Ye Yuan, Zhenzhen Kong, Xiaozhou Yang, Dong Mu and Fan Yang

The multi-mode dual five-phase hybrid excitation (MM-DFHE) motor, owing to its unique dual-stator configuration, is capable of operating in four distinct modes, offering exceptional operational flexibility. However, this flexibility introduces a control challenge, particularly in Mode IV where the auxiliary stator acts as both an exciter and a torque producer. The additional current variables in this mode lead to suboptimal current distribution, compromising efficiency and dynamic response. To address this, this paper proposes a novel low-loss current optimization control strategy. The key contribution is a Gradient Descent (GD) based online optimization algorithm that dynamically distributes the auxiliary excitation current, specifically tailored for the improved Mode IV operation. This approach resolves the trade-off between loss minimization and dynamic performance prevalent in conventional methods. Simulated and experimental results demonstrate that the proposed strategy reduces total copper loss by up to 13% compared to conventional methods.