Low Cross Polarized and Matching Improved Ground Extended Defected Structure Wearable Antenna for Tactical Battlefield Communications

Abstract

In this paper, a flexible slot antenna of size 36 mm × 40 mm × 3 mm with high gain and low Specific Absorption Rate (SAR) is proposed. Wearable Antenna (WA) must achieve low cross-polarization, efficient impedance matching, high radiation gain, reduced SAR, and minimal return loss to ensure user safety and reliable performance in tactical communication environments. The proposed flexible antenna features a radiating patch with a combination of square and circular slots, fed by a Microstrip Patch (MSPA). Additionally, the extended ground plane incorporates a circular slot as part of a Defective Ground Structure (DGS). The circular slot is strategically positioned for optimal impedance matching and analysed. Textile felt is employed as the substrate, resulting in a return loss of less than -40 dB at 5.8 GHz. It is designed for tactical battlefield communications within the 5.725-5.875 GHz range, offering a bandwidth greater than 150 MHz and exhibiting a low cross-polarization radiation pattern. Simulated and measured S11 results demonstrate good impedance matching, supported by consistent gain variation across different theta angles. The far-field gain pattern comparison, with and without the circular slot DGS, along with SAR measurements at various distances, validates the antenna’s performance and safety for practical use. The proposed antenna exhibits a gain of 8 dBi and maintains a SAR value below the IEEE standard, while achieving desirable antenna parameters.