Authors: Asimina Kiourti, Jingni Zhong and John L. Volakis
Source: FERMAT, Volume 16, Communication 10, Jul.-Aug., 2016
Abstract: Broadband antennas are highly attractive for load-bearing applications, such as airborne and wearables. However, antenna design for such applications is very challenging due to requirements for 1) conformality, 2) lightweight, 3) robustness, and 4) tolerance to extreme weather conditions.
With this in mind, we present a novel 10:1 bandwidth conformal antenna based on a new class of conductive textiles (see Fig. 1). The antenna is a cavity-backed Archimedean spiral, 160 mm in diameter. It was ‘printed’ via automated embroidery of metal-coated polymer threads (E-threads), down to 0.12mm in diameter (A. Kiourti, C. Lee and J.L. Volakis, IEEE Antennas Wireless Propag. Lett., 2015). Doing so, the embroidery geometrical precision is as high as 0.1mm, viz. similar to typical Printed Circuit Board (PCB) designs. To enhance robustness, high-strength Kevlar fabric (εr = 2.6, tanδ = 0.006) was employed as the antenna’s substrate. Kevlar is a lightweight, low-loss, abrasion- and heatresistant material, making it suitable for extreme and flexible applications. The textile ground plane was placed at a distance of λlow / 40 from the spiral’s surface, where λlow refers to the wavelength at the lowest operational frequency (in this case, 0.3 GHz). Two 180 Ω resistors were soldered at the spiral ends to suppress wave reflections.
As per design, the textile antenna exhibits a 10:1 bandwidth (VSWR < 2), operating from 0.3 to 3 GHz. It also delivers a consistent circularly polarized realized gain of 8 dBi. This gain hold for most of the 10:1 band except near 300 MHz. Specifically, at low frequencies, the resistive termination decreases the antenna efficiency.
At the conference we will present spiral performance measurements, and several other antenna examples using the aforementioned embroidery process.
Keywords: Conformal Spiral Antenna, Conductive Textile Threads, LoadBearing Applications.
View PDF
Conformal Spiral Antenna Based on Conductive Textile Threads for LoadBearing Applications