Tuning-Range Extension Strategies for Varactor-Based Frequency-Reconfigurable Antennas

OnlinePublTuning range extension strategies for varactor-based frequency-reconfigurable planar patch antennas are presented. The three tuning range optimization methods described in the paper include cooptimization of antenna dimensions and varactor properties, exploitation of multiple radiation modes, and reduction of parasitic capacitance. The first two strategies are emphasized by briefly reviewing two previously reported wide tuning range frequency-agile planar antennas. Importantly, the influence of parasitic capacitance on reducing the tuning range of the varactor-based frequency-reconfigurable antennas is then demonstrated by examining two antennas. The three tuning range extension methods are then combined to further expand the frequency tuning range of a reported frequency-reconfigurable antenna. The antenna has been re-designed, fabricated and experimentally characterized to demonstrate enhanced performance, which validates the proposed techniques, and their simultaneous application to reconfigurable antenna designs.Quoc Hung Dang, Nghia Nguyen-Trong, Christophe Fumeaux, Shengjian Jammy Che

Signal processing algorithms for ultra-wideband wireless communications

Electrical Engineering, Mathematics and Computer Scienc

A frequency-reconfigurable wearable textile antenna with one-octave tuning range

A reconfigurable wearable textile antenna with wide frequency tuning range is demonstrated in this work. Frequency agility is realized by adding a coplanar reconfiguration module to a planar inverted-F antenna (PIFA) constructed in textile technology. The reconfiguration module consists of a small flexible printed circuit board (PCB) which integrates a tuning circuitry with commercial snap-on buttons as electronic-to-textile connectors. Using this module equipped with a varactor diode, the frequency reconfigurability of the PIFA is investigated and optimized parametrically for maximum tuning range, exploiting a smooth transition from a quarter-wave to a half-wave patch resonant mode. A fabricated prototype demonstrates a very wide tuning range of approximately 70% (or one octave) with stable directive radiation characteristics, as predicted by simulations. The robust performance and mechanical stability of the reconfigurable antenna in various on-body and bending configurations validates the viability of the antenna tuning concept and the practicality of the proposed coplanar reconfiguration module.Quoc Hung Dang, Shengjian Jammy Chen, Damith Chinthana Ranasinghe and Christophe Fumeau

Modular integration of a passive RFID sensor with wearable textile antennas for patient monitoring

An integration and modularization solution for a passive computational radio frequency identification (RFID) module is proposed for wireless patient monitoring. In the proposed integrated configuration, all the electronic components are encapsulated within the cavity of a textile antenna. This forms a compact protected embodiment suitable for concealment in a hospital garment, with the aim of being unobtrusive to older patients. In addition, modularization of the sensor and textile antenna is introduced through a convenient snap-on attachment method for the computational RFID module. This is in harmony with simple assembly techniques and facilitates maintenance. Importantly, the resulting customizable configurations, for example, in terms of antenna form factor and materials, can be tailored to suit application requirements, such as performance and disposability. The experimental results demonstrate that the proposed wireless wearable sensor can operate with an antenna broadside gain of 2.74 dBi within a wide bandwidth extending over 893–964 MHz to support seamless worldwide operation across the ultrahigh-frequency (UHF) industrial, scientific, and medical (ISM) bands. The wearable sensor embodiment characterized in the context of a monitoring system attains excellent performance in terms of received signal strength, data read rate, and batteryless operational range.Quoc Hung Dang, Shengjian Jammy Chen, Damith Chinthana Ranasinghe and Christophe Fumeau

Shorting Strategies For Wearable Textile Antennas: A Review of Four Shorting Methods

Date of current version: 4 May 2021Shorting vias are standard components in planar technologies, but their implementation is not straightforward in wearable textile electronics technologies. In this article, four different shorting strategies for wearable flexible textile antennas, namely those based on embroidered metalized wires, folded strips of metalized fabric, eyelets, and snap-on buttons, are investigated. These shorting methods are applied to design different selected antenna structures, specifically two variations of a quarter-wavelength patch antenna and a monopolar patch antenna with edge shortings. The simulated and experimental results demonstrate how these four shorting strategies can be effectively used in flexible wearable textile antenna designs. Each method exhibits different strengths and weaknesses in terms of complexity, efficiency, mechanical stability, and modularity. The analysis aims at guiding designers in the selection of the most appropriate shorting method for their specific application, considering the efficiency of the folded strips, the fabrication simplicity of the eyelets, the mechanical stability of the embroidered vias, and the modularity of the snap-on buttons.Quoc Hung Dang, Shengjian Jammy Chen, Baoqi Zhu, and Christophe Fumeau

A Low-Complexity Blind Multiuser Receiver for Long-Code CDMA

Receivers for long-code systems are for computational reasons usually based on simple matched-filter techniques, and hence suffer from multiaccess interference. Decorrelating RAKE and MMSE receivers do not have this problem but have not been widely studied due to the apparent complexity of the inversion of a large code matrix. Tong, van der Veen Dewilde, and Sung (IEEE Tr. Signal Proc., 2003) derived a blind decorrelating RAKE receiver (DRR) and channel estimation algorithm for long-code CDMA systems, and showed how it can be efficiently implemented. In this paper, we continue on that work. We propose both single-user and multiuser blind source-channel estimation algorithms by making use of an iterative estimation scheme initialized by the DRR. Simulation results show significant improvement, even in heavily loaded systems. Moreover, with an implementation based on time-varying system theory, the proposed algorithm can be implemented efficiently at a cost similar to the RAKE.Electrical Engineering, Mathematics and Computer Scienc

A reconfiguration module with coplanar snap-on connection for wearable textile antennas

A reconfiguration module based on a small printed circuit board (PCB) and commercial snap-on buttons for reconfigurable flexible textile antennas is proposed. The concept consists of a small PCB loaded with a reconfigurable circuitry including active and lumped components, which is combined with a pair of commercial male snap-on buttons for electrical connection to conductive textiles. The reconfiguration module can provide a secure and robust coplanar electrical connection between rigid electronics and flexible textile conductors, which is usually challenging for textile antennas. To validate this module concept, a frequency-reconfigurable planar inverted-F antenna using a varactor-based module realization is designed and simulated. The antenna is predicted to exhibit a frequency tuning range of 24.9% from 2.14 to 2.75 GHz with efficiency from 60.1% to 89.4%.Quoc Hung Dang, Shengjian Jammy Chen, Damith Chinthana Ranasinghe and Christophe Fumeau

Designing batteryless wearables for hospitalized older people

Older people have expressed a clear desire for unobtrusive wearable monitoring devices. Emerging batteryless sensor technologies such as sensor enabled RFID (Radio Frequency Identification) create new opportunities for building unobtrusive wearables for older people. This study aims to: i) uncover user perceptions and acceptability of a batteryless wearable sensor concept for hospitalized older people; and ii) present the construction of a new textile integrated wearable sensor incorporating user feedback. We recruited 40 older people (age: 81.0 ± 7.0 years) to wear our initial sensor prototype and used two modified versions of validated questionnaires to evaluate user perceptions and acceptability. Our results showed: i) allowing older people to experience the system created the opportunity for them to develop confidence and trust in the sensing technology, even when they were initially anxious and skeptical: and ii) the first design prototype should ideally be modified to reduce its visibility. To this end, we built a new wearable sensor design.Asangi Jayatilaka, Quoc Hung Dang, Shengjian Jammy Chen, Renuka Visvanathan, Christophe Fumeaux, Damith C. Ranasingh

Signal model and receiver algorithms for a transmit-reference ultra-wideband communication system

Electrical Engineering, Mathematics and Computer Scienc