Miniaturized antenna and transponder based wireless sensors for internet of things in healthcare

Future medical and healthcare systems will be largely improved by the wide-spreading of internet of things (IoTs). One of the crucial challenges of IoTs for healthcare is at the wireless sensors. Miniaturization of sensor node profile, minimizing power consumption as well as lowering down design/production cost of antenna, RF circuits and sensor modules have become the key issues for realizing more exciting applications in medical and healthcare fields that never seemed to be possible before. In this dissertation work, we first focus on electrically small antenna (ESA) design and fabrication for medical telemetry. A comprehensive analysis of the radiation properties of a novel electrically small folded ellipsoidal ESA is presented, showing its ability to self-resonate and impedance match without external components. It will benefit various size-restricted applications especially with wireless medical implants. The second focus is on healthcare sensors using ESA as the sensing agent, which saves the power and cost by eliminating the need of extra sensing modules. Specifically, miniaturized helix ESAs are integrated with drug reservoirs to function as wireless transponder sensors for real-time drug dosage monitoring. We also introduce a system level innovation of a passive wireless harmonic transponder/harmonic sniffer/frequency hopped interrogator based sensing system. The μL- liquid level resolution and absolute-accuracy passive sensing is demonstrated in the presence of strong direct coupling, background scatters, distance variance as well as near-filed human body movement interference. Furthermore, we investigate how modern ubiquitous wireless sensor networks could take advantage of sensitive nanostructure materials for enhanced performance. Here we propose a new paradigm of chemically-gated mixed modulation on a single homogeneous graphene device in which the chemical exposure directly modulates an electrical carrier signal. To make the device ubiquitously reusable, a method of precisely tuning the charge neutrality point (Vcnp) is introduced by electrochemical calibration with gate voltage pulse sequence. Such chemically gated graphene modulator can be potentially used in a harmonic transponder as a passive ubiquitous sensor node for chemical and bio sensing applications. Overall the research work presented in the dissertation will help enable cost and power-efficient wireless sensor networks in future healthcare IoTs.Electrical and Computer Engineerin

Polarizable Particles and their Two-Dimensional Arrays: Advances in Small Antenna and Metasurface Technologies.

Metamaterials are subwavelength-structured materials designed to exhibit tailored electromagnetic properties. Metamaterials have allowed extreme control over constituent material parameters (i.e. permittivity, permeability, and chirality), which has enabled a myriad of counterintuitive physical phenomena. However, metamaterials typically suffer from high losses, difficulties in fabrication, and are bulky. This has led to the development of metasurfaces, which are the two dimensional equivalent of metamaterials. Metasurfaces can impart abrupt discontinuities on electromagnetic wavefronts, allowing electromagnetic fields to be tailored across subwavelength length scales. The building blocks of metasurfaces are subwavelength textured, polarizable particles. Near resonance, these particles support strong currents, which makes them excellent small antennas. In this thesis, a circuit model is developed that can model an arbitrary small antenna based on its frequency dependent polarizability. In addition, a direct transfer patterning process is developed that allows metallic patterns to be printed onto arbitrarily contoured substrates. This work will find immediate applications in a number of emerging technologies resulting from the rapid expansion of the mobile electronics industry. Next, extreme control of the polarization and profile of a wavefront is demonstrated using two-dimensional arrays of polarizable particles (i.e. metasurfaces). A new class of metasurfaces, referred to as metamaterial Huygens' surfaces, is shown to have a significantly improved efficiency over the state of the art. Metamaterial Huygens' surfaces utilize polarizable particles that exhibit both an electric and magnetic response, which allows for reflectionless wavefront control. Next, it is shown that simply cascading patterned metallic sheets can also provide high transmission and complete phase control. To demonstrate the design methodology, several different metasurfaces are developed that deflect incident Gaussian beams to a stipulated angle or convert an incident Gaussian beam into a vector Bessel beam. Further, utilizing sheets with anisotropic patterns provides additional magneto-electric coupling, which enables complete control of a wavefront (i.e. amplitude, phase, and polarization control). The experimental verification at frequencies ranging from microwaves to optics highlights the versatility of this work.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111395/1/carlpfei_1.pd

A study of secondary winding designs for the two-coil Tesla transformer

The multi-order response of the tuned secondary circuit of a Tesla transformer, following impulse excitation from its tuned primary circuit, is presented and analysed at the fundamental resonant frequency and at higher-order mode frequencies. A novel way of modifying the frequency response of the secondary coil is then investigated by utilising a technique normally applied to the design of a certain type of filter known as a helical filter. In general, these are used in radio and microwave frequency circuits in order to pass certain frequencies with little attenuation whilst significantly attenuating other frequencies. Design techniques, developed over several decades, modify and optimise the performance of such filters. The frequency response of the helical filter is modified by altering the geometry of the helical resonator component therein, which is typically in the form of an air-cored single-layer solenoid. A Tesla transformer whose secondary is constructed to be some form of single-layer solenoidal winding resonates at its designed frequency - its fundamental mode - but also at non-integer harmonics (higher-order anharmonic frequencies, also known as overtones). Those multi-order oscillatory voltages and currents energised in the secondary circuit have been identified and measured and research has determined the fundamental and higher-order mode frequencies and amplitudes for various experimental secondary winding configurations derived from helical filter design techniques. Applied to the Tesla transformer secondary winding, such techniques lead to a new design with a performance that is improved by the suppression of higher- order anharmonic frequencies whilst imparting little change to the fundamental response. It is anticipated that this feature will lead to Tesla transformers which exhibit enhanced spectral purity and which will be better suited to use in certain pulsed power applications than conventionally wound designs

Wireless power transmission para drones

Mestrado em Engenharia Eletrónica e TelecomunicaçõesDrones are unmanned aerial vehicles that have proliferated the market due to their low cost and the many applications that can already be associated to them. Besides the common use of these devices for playful activities, as aerial event recording, they demonstrate an enormous potential in other applications, such as military, as search and rescue or reconnaissance missions, or commercial, for example: surveillance and inspection of crops. However, most commercial devices currently available suffer from a major drawback in terms of their dependence of batteries which, in consequence of the large energy demand supplied to the drone's engines, quickly discharge. In addition, the weight of these batteries typically implies that more power is needed to keep the drone flying. This drawback can be overcome, or attenuated, using dedicated wireless power transmission systems that enable the devices to maintain flight without the need of batteries or simply charging them while in use. Throughout this dissertation a microwave wireless power transmission system working at 5.8 GHz will be described in detail, with emphasis on the design of the microstrip antenna array developed to allow directive transmission and the rectenna proposed for reception and power conversion. The proposed system allows the used quadcopter to boot and link with its remote control and demonstrates the potential to be adapted for other purposes.Drone é a designação normalmente atribuída a veículos aéreos não tripulados que se têm proliferado no mercado devido ao seu baixo custo e inúmeras aplicações. Além do seu uso em actividades lúdicas, como o já comum registo aéreo de eventos, demonstram um enorme potencial noutras aplicações, tanto militares, missões de busca e salvamento e reconhecimento de terreno, como comerciais, sendo exemplo a vigilância e inspecção de campos de colheita. No entanto, maioria dos dispositivos comerciais actualmente disponíveis padecem de uma grande limitação no que toca à sua dependência de baterias que, de modo a alimentar os motores do drone, rapidamente se descarregam. Além disso, o peso que estas baterias implicam levam a que seja necessária uma maior potência para que o drone se mantenha a voar. Estes problemas podem ser contornados, ou atenuados, recorrendo a sistemas de transmissão dedicada de energia electromagnética que possibilitem aos dispositivos manter vôo sem recurso a baterias ou carregando-as quando em uso. Ao longo desta dissertação será descrito em detalhe um sistema de transferência de energia sem fios projectado para trabalhar à frequência de 5.8 GHz, dando ênfase ao desenho de um agregado de antenas microstrip, desenvolvido para possibilitar uma transmissão directiva, e a rectenna proposta para recepção da energia electromagnética e sua conversão em corrente contínua. O sistema proposto possibilita ao quadricóptero ter energia suficiente para se conseguir ligar e estabelecer comunicação com o seu controlo remoto sendo que a arquitectura proposta demonstra potencial para ser adaptada em futuras abordagens

Antennas and Propagation

This Special Issue gathers topics of utmost interest in the field of antennas and propagation, such as: new directions and challenges in antenna design and propagation; innovative antenna technologies for space applications; metamaterial, metasurface and other periodic structures; antennas for 5G; electromagnetic field measurements and remote sensing applications

무선전력전송시스템을 구현하기 위한 실질적인 문제에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2014. 8. 남상욱.본 논문에서는 무선전력전송시스템을 구현할 때 고려해야 하는 실질적인 문제들의 해결책들을 제시하였다. 고효율의 무선전력전송시스템을 구현하기 위해서는 아직 해결되지 않은 문제들이 많이 남아있다. 적응형 정합 및 다수의 충전 문제들을 해결하기 위해서 새로운 방법들을 제안하였다. 또한 특성모드 방식을 이용하여 주변환경이 무선전력전송시스템에 미치는 영향을 분석하였다. 우선, 근접장 영역에서 무선전력전송시스템을 위한 적응형 정합방법들이 연구되었다. 거리의 변화에 따른 근접장을 이용한 무선전력전송시스템의 임피던스와 공진주파수의 특성에 대하여 분석하였다. 근접장의 영역에서 고효율의 무선전력전송을 위해서는 적응형 정합방법이 필수적이다. 이 논문에서는 동시 공핵정합 및 주파수 추적방식을 포함한 다양한 방식의 전력전송효율을 비교하였다. 분열된 공진주파수를 추적하는 방법을 이용하면 효율적인 적응형 정합이 가능한 사실을 발견하였다. 또한, 고효율의 무선전력전송이 가능한 거리를 확장시키는 개선된 주파수 추적방식을 제안하였다. 이론적인 결과들을 실험결과와 비교하여 검증하였다. 두 번째로, 효율적인 무선전력전송시스템을 위한 최적의 조건을 제시하였다. 그리고 수신기의 위치에 따라 송신기의 입력저항이 변할 때 무선전력전송시스템의 전력원으로 D급 전력증폭기를 사용하는 것이 유리하다. 실험을 통해서 이 논문에서 제안된 무선전력전송시스템을 증명하였다. 세 번째로, 무선전력전송시스템에서 다수의 수신기를 충전하는 방법을 제안하였다. 우선 근접장 영역에서 다수의 수신기가 가지는 주파수 특성을 분석하였다. 그 결과를 이용하여 시간분할방식의 무선전력전송시스템을 제안하였다. 제안한 방식을 이용하면 다수의 수신기에 고효율의 균등한 전력전송이 가능하다. 다수의 수신기를 충전할 경우 제안된 방식의 시스템의 유리하다는 결과를 확인하였다. 마지막으로 무선전력전송시스템의 주변환경에 대한 연구를 진행하였다. 주변환경의 영향을 분석하기 위해 특성모드 방식을 제안하였다. 전기적으로 작은 물체의 경우 그 물체의 전자기적인 반응은 소수의 특성모드만으로도 표현이 가능하다. 금속판과 작은 루프안테나의 시뮬레이션 결과와 제안된 이론을 통한 분석결과를 비교하여 검증하였다.This thesis presents solutions of the practical issues for implementation of wireless power transfer system (WPTS). There are many unresolved issues that remain in the implementation of highly efficient WPTS. To solve the adaptive matching and multiple charging problems, new methods are proposed. Also, to analyze the effect of surroundings of a WPTS, characteristic mode method was suggested. First, adaptive matching methods for a WPTS in the near-field region are investigated. The impedance and resonant frequency characteristic of a near-field power transfer system are analyzed according to coupling distance. In the near-field region, adaptive matching is necessary to achieve an effective power transfer. We compare the power transfer efficiencies of several schemes including simultaneous conjugate matching and frequency tracking. It is found that effective adaptive matching can be easily achieved by tracking the split resonant frequency. In addition, a modified frequency tracking method is proposed to extend the range over which the power is transmitted with high efficiency. The experimental results are in agreement with the theoretical results. Secondly, we found the optimal conditions for an efficient WPTS. Additionally, we found that a class-D PA has an advantage as a source when the input resistance changes with the position of the receiving antenna. The proposed WPTS was verified through the experimental results. Thirdly, a multiple charging method for a wireless power transfer system in the near-field region is proposed. We analyzed the frequency characteristics of multiple receivers in the near-field region. The results suggested that the time division WPTS can achieve efficient and equal power transmission at multiple receivers. We conclude that this system has an advantage for charging multiple receivers. Finally, the effect of the surroundings for a WPTS was investigated. The characteristic mode method was suggested to analyze the effect of the surroundings. For electrically small and intermediate size bodies, only a few characteristic modes are needed to characterize the electromagnetic behavior of the body. The theory is verified by a simulation with small loops and a metal plate.Abstract i Contents iii List of Figures vi List of Tables x 1. Introduction 1 1.1 WPT Scenario 4 1.2 Characteristics of WPT 6 2. Investigation of Adaptive Matching Methods for Near-Field WPT 11 2.1 Introduction 11 2.2 Impedance Characteristic of Coupled Antennas 14 2.3 Frequency Characteristic of Coupled Antennas 19 2.4 The Effect of Port Impedance 22 2.5 Measurements 26 2.6 Summary 31 3. Simple Efficient Resonant coupling WPTS Operation at Varying Distance between Antennas 34 3.1 Introduction 34 3.2 Characteristic of the Two coupled Antennas 36 3.3 Comparison of Source Types 45 3.4 Sinulation and Measurement 47 3.5 Summary 53 4. Analysis of WPT Characteristics for Multiple Receivers by Time Sharing Technique 56 4.1 Introduction 56 4.2 Frequency Characteristics of Multiple Receivers 58 4.3 Characteristics of the Time Division WPTS 61 4.4 Summary 64 5. Investigatoin of the Effect of Surroundings using Characteristic Mode Method for WPT 67 5.1 Introduction 67 5.2 Characteristic Currents 69 5.3 Modal solutions 72 5.4 Modified Z-matrix 75 5.5 Example 79 5.6 Summary 89 6. Conclusion 91 A. Appendix 94 A.1 Computaion of Generalized Eigenvalue Equation 94Docto

Reconfigurable Antennas

In this new book, we present a collection of the advanced developments in reconfigurable antennas and metasurfaces. It begins with a review of reconfigurability technologies, and proceeds to the presentation of a series of reconfigurable antennas, UWB MIMO antennas and reconfigurable arrays. Then, reconfigurable metasurfaces are introduced and the latest advances are presented and discussed

Network Methods for Analysis and Design of Resonant Wireless Power Transfer Systems

In this chapter we illustrate networks methods for the analysis an design of Wireless Power Transfer (WPT) systems. We begin with an introduction which compares the alternatives available for transfering electromagnetic power. In particular, we illustrate the advantages and disadvantages of the various possibilities: transmission lines, antennas, and mid-range reactive field couplings. Then, in the introduction, we also illustrate practical applications for WPT and discuss relevant papers published so far. In the second section, after introducing a basic structure for realizing WPT (see Fig.1), we discuss the relevant theory for WPT by considering a very simple network which, nevertheless, contains all the relevant phenomenology. We derive formulas for maximizing the efficiency of power transfer and we show the necessity of introducing matching networks. Several possible realizations of matching networks are then illustrated. In the next section we introduce appropriate methods, based on the ABCD matrix, for the narrow-band analysis of WPT systems including matching networks. An example of such a network is reported in Fig. 2. A section will be devoted to the input and output coupling design where we will provide new formulas for the design of the matching networks. In particular we show that, for a given type of resonators with a given quality factor Q and a given value of the coupling between the two resonators, we can find the optimal coupling coefficients which maximize the efficiency. An example of the results achievable when optimizing the input/output coupling is reported in Fig. 3. Having derived a procedure for attaining maximum efficiency, it is also possible to establish the theoretical limits that can be achieved for a given value of coupling and for specified values of the resonators Q. A section will be also devoted to the case of multiple transmitting and multiple receiving resonators. For this arrangement, which has practical relevance and is illustrated in Fig 5, we also introduce a rigorous general network model for its analysis. Several different types of resonators will be investigated and compared. Closed form formulas relevant to the resonators' design will be introduced and also fullwave analysis of resonators well be exploited. Theoretical results will be compared with measured ones and measurement methods will be discussed. One of the problems of WPT, i.e. the frequency shift occurring when resonators are placed at different distances, will be discussed and the solution will be outlined. This is very important in practice because allows to realize systems without the need of complex sources or difficult tracking mechanisms. Finally, we will also illustrate how to analyze, both in frequency and time domain, the network representations used for WPT

Antenna Systems

This book offers an up-to-date and comprehensive review of modern antenna systems and their applications in the fields of contemporary wireless systems. It constitutes a useful resource of new material, including stochastic versus ray tracing wireless channel modeling for 5G and V2X applications and implantable devices. Chapters discuss modern metalens antennas in microwaves, terahertz, and optical domain. Moreover, the book presents new material on antenna arrays for 5G massive MIMO beamforming. Finally, it discusses new methods, devices, and technologies to enhance the performance of antenna systems

Conformal antenna-based wireless telemetry system for capsule endoscopy

Capsule endoscopy for imaging the gastrointestinal tract is an innovative tool for carrying out medical diagnosis and therapy. Additional modalities beyond optical imaging would enhance current capabilities at the expense of denser integration, due to the limited space available within the capsule. We therefore need new designs and technologies to increase the smartness of the capsules for a given volume. This thesis presents the design, manufacture and performance characterisation of a helical antenna placed conformally outside an endoscopic capsule, and the characterisation in-silico, in-vitro and in-vivo of the telemetry system in alive and euthanised pigs. This method does not use the internal volume of the capsule, but does use an extra coating to protect the antenna from the surrounding tissue and maintain biocompatibility for safe use inside the human body. The helical antenna, radiating at 433 MHz with a bandwidth of 20 MHz within a muscle-type tissue, presents a low gain and efficiency, which is typical for implantable and ingestible medical devices. Telemetry capsule prototypes were simulated, manufactured and assembled with the necessary internal electronics, including a commercially available transceiver unit. Thermistors were embedded into each capsule shell, to record any temperature increase in the tissue surrounding the antenna during the experiments. A temperature increase of less than 1°C was detected for the tissue surrounding the antenna. The process of coating the biocompatible insulation layer over the full length of the capsule is described in detail. Data transmission programmes were established to send programmed data packets to an external receiver. The prototypes radiated at different power levels ranging from -10 to 10 dBm, and all capsules demonstrated a satisfactory performance at a data rate of 16 kbps during phantom and in-vivo experiments. Data transmission was achieved with low bit-error rates below 10-5. A low signal strength of only -54 dBm still provided effective data transfer, irrespective of the orientation and location of the capsule, and this successfully demonstrated the feasibility of the system