Flexible Wearable Microstrip Patch Antenna based on Graded Dielectric Substrate Profile for Wireless Applications

Abstract

The aim of this paper is to investigate the possibilities of designing and fabricating a highly efficient and flexible wearable microstrip patch antenna operating at resonant frequency of 2.45 GHz. Copper Foil Tape (CFT) is used as a conducting medium in designing the patch and ground of antenna. While for designing the substrate, a graded profile based structures are made by combining two non-conducting fabrics i.e. Fleece-Curtain Cotton and Fleece-Polyester. The dielectric constant of these fabrics is measured with the help of ring resonator method. The proposed design models are simulated using CST simulator. To ensure the human body safety from antenna radiations in case of wearable applications, Specific Absorption Rate (SAR) is calculated on the simulated designs. Further some bending analysis of proposed antennas is also performed to ensure their applicability on different body parts like wrist, arm. Finally the proposed designs are fabricated and measured results are obtained using Agilent N5247A: A.09.90.02 VNA. TRL technique is used to calibrate the VNA with 3.5 SMA calibration kit.Simulated and measured results show good matching with each other in terms of resonant frequency, return loss, bandwidth and gain. The antenna designed using fleece-curtain cotton substrate achieved maximum bandwidth of 990 MHz, 2.22 dB gain and -34.99 dB value of S11 parameter. Voltage Standing Wave Ratio (VSWR) for all five antennas is less than 2. Hence the proposed antenna is a suitable candidate for wearable wireless applications.