S. Sankaralingam

Determination of Dielectric Constant of Fabric Materials and Their Use as Substrates for Design and Development of Antennas for Wearable Applications

A novel approach to measure the dielectric constant of fabric substrate materials used for the development of wearable antennas (also called textile antennas) is presented in this paper. The technique reported here is based on the resonance method and focused on the use of microstrip patch radiator, which contains fabric material as its substrate. The accurate value of the dielectric constant of the fabric material can easily be extracted from the measured resonant frequency of the patch radiator. The dielectric constant values of six fabric materials, including jeans cotton, polyester combined cotton, and polyester, have been determined by this way. As an extended objective of this paper, initial investigations are done to study the performance/behavioral characteristics of wearable antennas in the Bluetooth industrial, scientific, and medical band. Two of the six textile antenna structures, developed to meet out the primary objective of determining the dielectric constant of fabrics, are tested, and their performance characteristics, such as impedance bandwidth, gain, efficiency, etc., are measured. In addition, another Bluetooth antenna employing polyester fabric substrate is designed considering its measured accurate value of dielectric constant and subjected to radiation pattern measurements. In general, all the measured antennas yield very good results, fulfilling the requirements for practical applications, and in particular, the third fabric antenna utilizing the accurate value of the dielectric constant determined shows superior performance characteristics compared to others, indicating the correctness of our approach. Thus, the suitability of fabric substrate materials for the development of textile antennas with microstrip patch configuration is also well demonstrated.

Development of Textile Antennas for Body Wearable Applications and Investigations on Their Performance Under Bent Conditions

Utilization of wearable textile materials for the develop- ment of microstrip antenna segment has been rapid due to the recent miniaturization of wireless devices. A wearable antenna is meant to be a part of the clothing used for communication purposes, which includes tracking and navigation, mobile computing and public safety. This pa- per describes design and development of four rectangular patch anten- nas employing difierent varieties of cotton and polyester clothing for on-body wireless communications in the 2.45GHz WLAN band. The impedance and radiation characteristics are determined experimentally when the antennas are kept in ∞at position. The performance deterio- ration of a wearable antenna is analyzed under bent conditions too to check compatibility with wearable applications. Results demonstrate the suitability of these patch antennas for on-body wireless communi- cations.

Development of wearable and implantable antennas in the last decade: A review

Utilization of wearable textile materials as antenna substrate has been rapid due to the recent miniaturization of wireless devices. A wearable antenna is meant to be a part of the clothing used for communication purposes, which includes tracking and navigation, mobile computing and public safety. This article portrays research on wearable and body mounted antennas designed and developed for various applications at different frequency bands over the last decade. A section is also devoted to describe the developmental scenario of implantable antennas for medical applications.

Experimental Results on Hiperlan/2 Antennas for Wearable Applications

This paper addresses the design and development of HiperLAN antennas meeting the IEEE 802.11a standards for wearable applications. Five such antennas are investigated for their performance characteristics, out of which three are conventional copper based antennas and the remaining two are fully fabric antennas. The results reveal that all the proposed antennas are suitable for HiperLAN applications yielding antenna gain in the order of 7{11dBi. This study demonstrates that fully fabric antennas outperform the copper based antennas.

A fully fabric wearable antenna for HiperLAN/2 applications

Electronics may soon be integrated into textiles in our near environment. These “Interactive Electronic Textiles” or “Smart Clothes” will benefit many wireless communication applications, leading to the development of body centric networks. Rapid progress in wireless communication promises to replace wired-communication networks in the near future in which antennas play a vital role. This paper deals with design, development and evaluation of a fully fabric wearable antenna suitable for HiperLAN/2 (5.8 GHz band) applications. This antenna yields promising results and demonstrate the use of textile materials as substrates and smart clothes as conducting layers for the design and development of wearable microstrip antennas.

A reconfigurable dielectric resonator antenna for polarization diversity applications

A circularly polarized rectangular dielectric resonator antenna is presented. Circular polarization is obtained by introducing a cross slot to generate two near orthogonal degenerate modes having similar amplitudes and 900 phase difference. Four pin diodes are placed across the slots to switch between two polarization states namely, Right Hand Circular Polarization (RHCP) and Left Hand Circular Polarization (LHCP). The antenna yields a measured impedance bandwidth of 26.3% in case of LHCP and 28.2% in case of RHCP. The antenna radiates with a gain of 4.21 dB exhibiting an axial ratio bandwidth of radiate with an acceptable gain over the entire band.

Preliminary studies on performance of a 2.45 GHz wearable antenna in the vicinity of human body

Impedance and radiation characteristics of 2.45 GHz wearable antennas in close proximity to a human body are studied in this paper. Three rectangular microstrip antennas namely wash cotton antenna, polyester antenna and polyester combined cotton antenna are considered in this preliminary study. Each of these three antennas is assumed to be placed in the vicinity of human torso with an air gap of 1 mm between torso and antenna. In this study, the human torso has been modeled as a lossy medium of fluid with permittivity and conductivity close to human torso at a frequency of 2.45 GHz. The results obtained indicate that the wearable antenna can provide required impedance and radiation characteristics even when it is placed in the vicinity of human body.

Impedance and radiation characteristics of circular patch wearable antennas at flat and bent positions

This paper describes design, development and evaluation of three electro-textile based circular patch wearable antennas for on-body wireless communications in the Bluetooth band. Performance characteristics are determined experimentally when these antennas are kept in flat position. All the three antennas are tuned to the desired frequency and they provide gain of 6.8–7.8 dBi. The performance characteristics of one of these antennas are analysed under bent conditions too, to check compatibility with wearable applications. The investigated antenna is robust against bending, yielding gain in the range 6.4–7.8 dBi. Results demonstrate the suitability of these fabric antennas for on-body wireless communications.

Efficient rectifier design on jute material for Wireless Power Transmission

In this paper, we are interested to the conversion part of a rectenna for Wireless Power Transmission applications involving wireless power transfer to low power consumption wireless device. The rectenna studied is a double diode rectifier operating at 2.45-GHz frequency. The specificity of this rectifier is its design on a textile material. We have chosen the jute as fabric material and we have measured its characteristics. The purpose is to demonstrate that this kind of fabric can lead to an efficient rectifier.

Design of high efficient double diode rectifier for wireless power transmission

In this work, we focus on the conversion part of a rectenna for wireless power transmission. We simulate and optimize a conversion circuit designed to operate in systems requiring relative high voltage (>15V) and high power (of about 0.5W). Furthermore, we propose a solution to reduce the surface of this circuit.