Shiyu Zhang

Embroidered wearable antennas using conductive threads with different stitch spacings

This paper is focused on using conductive threads to design flexible antennas with textile features which means antennas can be embroidered directly into normal clothes. The fabric microstrip antennas are made from commercial conductive threads. The gain and efficiency of fabric antennas have been measured and compared with a reference copper patch antenna. Effects from different stitches geometries within the fabric antenna are discussed. The results demonstrate the feasibility of wearable antennas.

Embroidered Wire Dipole Antennas Using Novel Copper Yarns

This letter presents a method of fabricating wearable antennas by embroidering novel fine copper yarn. In this work, fine copper wires are first twisted together to create a physically strong and yet flexible thread. A digital embroidery machine was used to create dipole antennas. The dc resistance of the antenna arms along with the return loss, radiation patterns, and efficiency of the antennas have been measured. The results are compared to embroidered dipoles using commercially available conductive threads and etched copper antennas.

High performance flexible fabric electronics for megahertz frequency communications

This paper investigates the concept of using conductive threads for fabricating electronics including antennas at microwave frequencies. A number of commercial conductive threads have been considered. Digital embroidery has been used to create samples with different stitch types. This paper will provide a wide range of practical advice about fabricating samples using such materials. The threads have been examined by assessing their DC resistances at rest and while under physical strain and also the RF performance of transmission lines. The results show there is a wide range in performance between different conductive threads.

Embroidered Frequency Selective Surfaces on textiles for wearable applications

An assessment of a Frequency Selective Surface (FSS) for wearable applications is presented. The textile FSS array was created on 0.8 mm thick felt material using a fast and cost effective embroidery technique with conducting threads. This operates at 2 GHz with transmission coefficient lower than 10 dB. The FSS structure was also modelled using commercial simulation tools. This work is towards low-loss textile FSS structures for wearable applications.

3D-printed flat lens for microwave applications

This paper presents the design of a 3D-printed flat graded-index lens based on ray optics. The lens is comprised of several concentric dielectric rings with bespoke relative permittivities for transforming spherical waves into plane waves. 3D-printing was used to fabricate this lens with graded and tailored dielectric properties in a single process. The 3D-printed flat lens is low-cost and light-weight, but provides broadband and high gain performance. Measurement results show that the realised gain of the lens is 8 to 10 dB over the frequency band ranging from 12 to 18 GHz.

Repeatability of embroidered patch antennas

The repeatability of the embroidery technology in fabricating wearable antenna is discussed in this paper. Two groups of rectangular microstrip antennas have been embroidered by conductive threads with different stitch spacings. Each group contains 8 identical antennas with 16 antennas in total. The repeatability of resonate frequency, bandwidth, gain, antenna efficiency, radiation pattern and cross-polarization are measured for different stitch spacings. The results demonstrate the potential of applying embroidery to antenna mass manufacture.

On-body measurements of embroidered spiral antenna

This paper presents a compact and flexible embroidered spiral antenna that can be used for wearable applications. The antenna is embroidered by using a state of the art digital embroidery machine with multi-strand conducting thread Liberator™. The antenna has been measured on a Specific Anthropomorphic Mannequin (SAM) phantom and a real human. The measurement results show that the SAM phantom emulates the dielectric properties of the human body in a wide frequency band from 0.3 to 3 GHz. The far-field on-body performance of the antenna has been measured by placing the antenna on the SAM phantom in a tapered Anechoic Chamber. Near-field to far-field transformations have been used to produce the far-field performance including radiation pattern, directivity, rrealised gain and radiation efficiency.

Textile manufacturing techniques in RF devices

Wearable devices are designed to be low-profile, light-weight and integrated seamlessly into daily life. Comfort is one of the most important requirements for wearable devices. Textile-based radio frequency (RF) devices are soft, flexible and can be integrated into textiles of clothing. This paper summarises state of the art textile manufacturing techniques in RF components fabrication including antennas and frequency selective surface (FSS). The electromagnetic performance of embroidery, weaving and printing, combined with advanced conductive textile materials have been presented and compared.

3D printed flat lenses using synthetic artificial dielectrics

Flat lenses have the advantages of flat profiles, small volumes and ease of fabrication. The major challenge faced in fabricating these lenses, that are typically based on the Ray Optics (RO) design paradigm, is that the dielectric materials called for in these design are typically not available commercially. Artificial materials with the desired dielectric properties can be used to realize these flat lenses (R. K. Arya et al. APS/URSI, 2014). In this paper an alternative approach, namely the 3D printing technique is examined to fabricate dielectrics with three-dimensional control of local permittivity (J. Tribe et al. Electronics Letters, vol. 50, no. 10, 2014). Since the 3D printed dielectric materials are not only cost-efficient but are rapidly prototyped as well, they have become increasingly attractive for RF applications.

3D-printed millimeter wave lens antenna

In this work, we present a flat lens design using the Dial-a-Dielectric (DaD) and 3D-printing technique to realize the materials that are not available off-the-shelf. We design the proposed flat lens and compare its performance with that of the ray-optics (RO)-based lens. We find from the results that both designs show comparable performance.