3 research outputs found
Bio-Radar Applications for Remote Vital Signs Monitoring
Nowadays, most vital signs monitoring techniques used in a medical context and/or daily
life routines require direct contact with skin, which can become uncomfortable or even
impractical to be used regularly. Radar technology has been appointed as one of the most
promising contactless tools to overcome these hurdles. However, there is a lack of studies
that cover a comprehensive assessment of this technology when applied in real-world
environments. This dissertation aims to study radar technology for remote vital signs
monitoring, more specifically, in respiratory and heartbeat sensing.
Two off-the-shelf radars, based on impulse radio ultra-wideband and frequency modu lated continuous wave technology, were customized to be used in a small proof of concept
experiment with 10 healthy participants. Each subject was monitored with both radars
at three different distances for two distinct conditions: breathing and voluntary apnea.
Signals processing algorithms were developed to detect and estimate respiratory and
heartbeat parameters, assessed using qualitative and quantitative methods.
Concerning respiration, a minimum error of 1.6% was found when radar respiratory
peaks signals were directly compared with their reference, whereas a minimum mean
absolute error of 0.3 RPM was obtained for the respiration rate. Concerning heartbeats,
their expression in radar signals was not as clear as the respiration ones, however a
minimum mean absolute error of 1.8 BPM for heartbeat was achieved after applying a
novel selective algorithm developed to validate if heart rate value was estimated with
reliability.
The results proved the potential for radars to be used in respiratory and heartbeat
contactless sensing, showing that the employed methods can be already used in some mo tionless situations. Notwithstanding, further work is required to improve the developed
algorithms in order to obtain more robust and accurate systems.Atualmente, a maioria das técnicas usadas para a monitorização de sinais vitais em
contexto médicos e/ou diário requer contacto direto com a pele, o que poderá tornar-se
incómodo ou até mesmo inviável em certas situações. A tecnologia radar tem vindo a ser
apontada como uma das mais promissoras ferramentas para medição de sinais vitais Ã
distância e sem contacto. Todavia, são necessários mais estudos que permitam avaliar esta
tecnologia quando aplicada a situações mais reais. Esta dissertação tem como objetivo o
estudo da tecnologia radar aplicada no contexto de medição remota de sinais vitais, mais
concretamente, na medição de atividade respiratória e cardÃaca.
Dois aparelhos radar, baseados em tecnologia banda ultra larga por rádio de impulso
e em tecnologia de onda continua modulada por frequência, foram configurados e usados
numa prova de conceito com 10 participantes. Cada sujeito foi monitorizado com cada
um dos radar em duas situações distintas: respirando e em apneia voluntária. Algorit mos de processamento de sinal foram desenvolvidos para detetar e estimar parâmetros
respiratórios e cardÃacos, avaliados através de métodos qualitativos e quantitativos.
Em relação à respiração, o menor erro obtido foi de 1,6% quando os sinais de radar
respiratórios foram comparados diretamente com os sinais de referência, enquanto que,
um erro médio absoluto mÃnimo de 0,3 RPM foi obtido para a estimação da frequência
respiratória via radar. A expressão cardÃaca nos sinais radar não se revelou tão evidente
como a respiratória, no entanto, um erro médio absoluto mÃnimo de 1,8 BPM foi obtido
para a estimação da frequência cardÃaca após a aplicação de um novo algoritmo seletivo,
desenvolvido para validar a confiança dos valores obtidos.
Os resultados obtidos provaram o potencial do uso de radares na medição de atividade
respiratória e cardÃaca sem contacto, sendo esta tecnologia viável de ser implementada em
situações onde não existe muito movimento. Não obstante, os algoritmos desenvolvidos
devem ser aperfeiçoados no futuro de forma a obter sistemas mais robustos e precisos
Design of an Ultra-wideband Radio Frequency Identification System with Chipless Transponders
The state-of-the-art commercially available radio-frequency identification (RFID) transponders are usually composed of an antenna and an application specific integrated circuit chip, which still makes them very costly compared to the well-established barcode technology. Therefore, a novel low-cost RFID system solution based on passive chipless RFID transponders manufactured using conductive strips on flexible substrates is proposed in this work. The chipless RFID transponders follow a specific structure design, which aim is to modify the shape of the impinged electromagnetic wave to embed anidentification code in it and then backscatter the encoded signal to the reader.
This dissertation comprises a multidisciplinary research encompassing the design of low-cost chipless RFID transponders with a novel frequency coding technique, unlike usually disregarded in literature, this approach considers the communication channel effects and assigns a unique frequency response to each transponder. Hence, the identification codes are different enough, to reduce the detection error and improve their automatic recognition by the reader while working under normal conditions. The chipless RFID transponders are manufactured using different materials and state-of-the-art mass production fabrication processes, like printed electronics. Moreover, two different reader front-ends working in the ultra-wideband (UWB) frequency range are used to interrogate the chipless RFID transponders. The first one is built using high-performance off-theshelf components following the stepped frequency modulation (SFM) radar principle, and the second one is a commercially available impulse radio (IR) radar.
Finally, the two readers are programmed with algorithms based on the conventional minimum distance and maximum likelihood detection techniques, considering the whole transponder radio frequency (RF) response, instead of following the commonly used approach of focusing on specific parts of the spectrum to detect dips or peaks. The programmed readers automatically identify when a chipless RFID transponder is placed within their interrogation zones and proceed to the successful recognition of its embedded identification code. Accomplishing in this way, two novel fully automatic SFM- and IRRFID readers for chipless transponders. The SFM-RFID system is capable to successfully decode up to eight different chipless RFID transponders placed sequentially at a maximum reading range of 36 cm. The IR-RFID system up to four sequentially and two simultaneously placed different chipless RFID transponders within a 50 cm range.:Acknowledgments
Abstract
Kurzfassung
Table of Contents
Index of Figures
Index of Tables
Index of Abbreviations
Index of Symbols
1 Introduction
1.1 Motivation
1.2 Scope of Application
1.3 Objectives and Structure
Fundamentals of the RFID Technology
2.1 Automatic Identification Systems Background
2.1.1 Barcode Technology
2.1.2 Optical Character Recognition
2.1.3 Biometric Procedures
2.1.4 Smart Cards
2.1.5 RFID Systems
2.2 RFID System Principle
2.2.1 RFID Features
2.3 RFID with Chipless Transponders
2.3.1 Time Domain Encoding
2.3.2 Frequency Domain Encoding
2.4 Summary
Manufacturing Technologies
3.1 Organic and Printed Electronics
3.1.1 Substrates
3.1.2 Organic Inks
3.1.3 Screen Printing
3.1.4 Flexography
3.2 The Printing Process
3.3 A Fabrication Alternative with Aluminum or Copper Strips
3.4 Fabrication Technologies for Chipless RFID Transponders
3.5 Summary
UWB Chipless RFID Transponder Design
4.1 Scattering Theory
4.1.1 Radar Cross-Section Definition
4.1.2 Radar Absorbing Material’s Principle
4.1.3 Dielectric Multilayers Wave Matrix Analysis
4.1.4 Frequency Selective Surfaces
4.2 Double-Dipoles UWB Chipless RFID Transponder
4.2.1 An Infinite Double-Dipole Array
4.2.2 Double-Dipoles UWB Chipless Transponder Design
4.2.3 Prototype Fabrication
4.3 UWB Chipless RFID Transponder with Concentric Circles
4.3.1 Concentric Circles UWB Chipless Transponder
4.3.2 Concentric Rings UWB Chipless RFID Transponder
4.4 Concentric Octagons UWB Chipless Transponders
4.4.1 Concentric Octagons UWB Chipless Transponder Design 1
4.4.2 Concentric Octagons UWB Chipless Transponder Design 2
4.5 Summary
5. RFID Readers for Chipless Transponders
5.1 Background
5.1.1 The Radar Range Equation
5.1.2 Range Resolution
5.1.3 Frequency Band Selection
5.2 Frequency Domain Reader Test System
5.2.1 Stepped Frequency Waveforms
5.2.2 Reader Architecture
5.2.3 Test System Results
5.3 Time Domain Reader
5.3.1 Novelda Radar
5.3.2 Test System Results
5.4 Summary
Detection of UWB Chipless RFID Transponders
6.1 Background
6.2 The Communication Channel
6.2.1 AWGN Channel Modeling and Detection
6.2.2 Free-Space Path Loss Modeling and Normalization
6.3 Detection and Decoding of Chipless RFID Transponders
6.3.1 Minimum Distance Detector
6.3.2 Maximum Likelihood Detector
6.3.3 Correlator Detector
6.3.4 Test Results
6.4 Simultaneous Detection of Multiple UWB Chipless Transponders
6.5 Summary
System Implementation
7.1 SFM-UWB RFID System with CR-Chipless Transponders
7.2 IR-UWB RFID System with COD1-Chipless Transponders
7.3 Summary
Conclusion and Outlook
References
Publications
Appendix A
RCS Calculation
Measurement Setups
Appendix B
Resistance and Skin Depth Calculation
Appendix C
List of Videos
Test Videos
Consortium Videos
Curriculum Vita