Effect of bending and padding on the electromagnetic performance of a laser-cut fabric patch antenna

Abstract

A fabrication and characterization procedure is detailed for a flexible planar antenna integrated into textiles by interfacing thin metal-coated fabric sheets on a polyester fabric substrate. From the full-wave electromagnetic simulations and measurements, it is observed that the low dielectric dissipation in the porous woven polyester enables the fabric antenna to achieve a high gain of 8.4 dBi. It is comparable to other antennas fabricated with engineered substrates of low-loss polymer composites. Using this antenna, the impact of cylindrical concave bending deformation is observed in terms of the impedance matching and radiation performance. The simulated and measured results agree reasonably well. A 1.2% frequency shift is observed when the antenna is bent concavely along its length, while bending along its width showed only a marginal impact. On the other hand, the gain is reduced by as much as 1.0 and 0.5 dB when the antenna is bent along its length and width, respectively. The impact of padding layers was also investigated when placed above the radiating patch and below the ground plane. Because the textile padding layers have complex permittivity closer to air due to their highly porous structure, it is expected to observe only small influence on the radiation performance. However, the simulations and measurements show that padding the radiating patch lowers both the operating frequency and the realized gain by up to 1.6% and by up to 0.9 dB, respectively, due to dielectric loading and dissipation.

Relationships between structure and microwave dielectric properties in cotton fabrics

“…With the recent booming of wearable electronics and e-textiles, the dielectric properties of textile materials have been featured in the research and development of textile-based microwave interfaces [1]. Wearable microwave interfaces such as antennas and transmission lines have been inherently integrated into fabrics by weaving [2], knitting [3], embroidering [4] and interfacing [5] electrically conductive yarns and fabrics. These approaches to add electronic functionalities to conventional fabrics not only enable constructions of flexible and lightweight devices in a highly wearable form with the pre-existing textile manufacturing techniques [6], but could also enhance electronic performance.…”

“…For instance, certain textile fabrics including cotton were reported to have dielectric properties desirable for the fabrication of microwave devices [1,5]. The highly porous nature of fabric structure results in a permittivity close to that of air which enables development of a microwave systems having low dielectric loss [1,5].…”

“…These approaches to add electronic functionalities to conventional fabrics not only enable constructions of flexible and lightweight devices in a highly wearable form with the pre-existing textile manufacturing techniques [6], but could also enhance electronic performance. For instance, certain textile fabrics including cotton were reported to have dielectric properties desirable for the fabrication of microwave devices [1,5]. The highly porous nature of fabric structure results in a permittivity close to that of air which enables development of a microwave systems having low dielectric loss [1,5].…”

The effect of bending on laser-cut electro-textile inductors and capacitors attached on denim as wearable structures

“…3–8 Among these challenges, the effects of mechanical strains such as bending or stretching on the embedded electrical components should be evaluated to ensure their correct operation when shaping to the human body. 9–11…”

“…[3][4][5][6][7][8] Among these challenges, the effects of mechanical strains such as bending or stretching on the embedded electrical components should be evaluated to ensure their correct operation when shaping to the human body. [9][10][11] Recently, researchers have developed various types of textile antennas at higher frequency bands that realize off-body communications, 12 such as patch antennas applied in protective clothing for firefighters and basic attachments for standard clothes 13,14 and on jeans fabric. 15 Wearable ultra-high frequency (UHF) radiofrequency identification (RFID) antennas have also been developed and implemented on smart textiles for various applications, and the maximum read range is up to 16 m for patch UHF RFID antenna circuits with microchip connections.…”