Synthesis, design, and fabrication techniques for reconfigurable microwave and millimeter-wave filters

As wireless communication becomes increasingly ubiquitous, the need for radio receivers which can dynamically adjust to their operating environment grows more urgent. In order to realize reconfigurable receivers, tunable RF front-end components are needed. This dissertation focuses on the theory, design, and implementation of reconfigurable microwave and millimeter-wave filters for use in such receivers. First, a theoretical framework is developed for absorptive bandstop filters, a new class of bandstop filters which overcomes some of the limitations of traditional tunable bandstop filters caused by the use of lossy tunable resonators. This theory is used in conjunction with silicon-micromachining fabrication technology to realize the first ever tunable bandstop filter at W-Band frequencies, as well as a state-of-the-art Ka-band tunable bandstop filter. The problem of bandwidth variation in tunable filters is then addressed. Widely-tunable filters often suffer from variations in bandwidth, excluding them from many applications which require constant bandwidth. A new method for reducing the bandwidth variation of filters using low-loss evanescent-mode cavity resonators is presented, and this technique is used to realize up to 90% reduction of bandwidth variation in octave-tunable bandstop filters. Lastly, a new differential coupling structure for evanescent-mode cavity resonators is developed, enabling the design of fully-balanced and balanced-to-unbalanced (balun) filters. An octave-tunable 3-pole bandpass balun filter using this coupling structure is presented. The balun filter has excellent amplitude and phase balance, resulting in common-mode rejection of greater than 40 dB across its octave tuning range

Synthesis, design, and fabrication techniques for reconfigurable microwave and millimeter-wave filters

As wireless communication becomes increasingly ubiquitous, the need for radio receivers which can dynamically adjust to their operating environment grows more urgent. In order to realize reconfigurable receivers, tunable RF front-end components are needed. This dissertation focuses on the theory, design, and implementation of reconfigurable microwave and millimeter-wave filters for use in such receivers. First, a theoretical framework is developed for absorptive bandstop filters, a new class of bandstop filters which overcomes some of the limitations of traditional tunable bandstop filters caused by the use of lossy tunable resonators. This theory is used in conjunction with silicon-micromachining fabrication technology to realize the first ever tunable bandstop filter at W-Band frequencies, as well as a state-of-the-art Ka-band tunable bandstop filter. The problem of bandwidth variation in tunable filters is then addressed. Widely-tunable filters often suffer from variations in bandwidth, excluding them from many applications which require constant bandwidth. A new method for reducing the bandwidth variation of filters using low-loss evanescent-mode cavity resonators is presented, and this technique is used to realize up to 90% reduction of bandwidth variation in octave-tunable bandstop filters. Lastly, a new differential coupling structure for evanescent-mode cavity resonators is developed, enabling the design of fully-balanced and balanced-to-unbalanced (balun) filters. An octave-tunable 3-pole bandpass balun filter using this coupling structure is presented. The balun filter has excellent amplitude and phase balance, resulting in common-mode rejection of greater than 40 dB across its octave tuning range

Ambient RF energy harvesting and efficient DC-load inductive power transfer

This thesis analyses in detail the technology required for wireless power transfer via radio frequency (RF) ambient energy harvesting and an inductive power transfer system (IPT). Radio frequency harvesting circuits have been demonstrated for more than fifty years, but only a few have been able to harvest energy from freely available ambient (i.e. non-dedicated) RF sources. To explore the potential for ambient RF energy harvesting, a city-wide RF spectral survey was undertaken in London. Using the results from this survey, various harvesters were designed to cover four frequency bands from the largest RF contributors within the ultra-high frequency (0.3 to 3 GHz) part of the frequency spectrum. Prototypes were designed, fabricated and tested for each band and proved that approximately half of the London Underground stations were found to be suitable locations for harvesting ambient RF energy using the prototypes. Inductive Power Transfer systems for transmitting tens to hundreds of watts have been reported for almost a decade. Most of the work has concentrated on the optimization of the link efficiency and have not taken into account the efficiency of the driver and rectifier. Class-E amplifiers and rectifiers have been identified as ideal drivers for IPT applications, but their power handling capability at tens of MHz has been a crucial limiting factor, since the load and inductor characteristics are set by the requirements of the resonant inductive system. The frequency limitation of the driver restricts the unloaded Q-factor of the coils and thus the link efficiency. The system presented in this work alleviates the use of heavy and expensive field-shaping techniques by presenting an efficient IPT system capable of transmitting energy with high dc-to-load efficiencies at 6 MHz across a distance of 30 cm.Open Acces

Bioelectronic Sensor Nodes for Internet of Bodies

Energy-efficient sensing with Physically-secure communication for bio-sensors on, around and within the Human Body is a major area of research today for development of low-cost healthcare, enabling continuous monitoring and/or secure, perpetual operation. These devices, when used as a network of nodes form the Internet of Bodies (IoB), which poses certain challenges including stringent resource constraints (power/area/computation/memory), simultaneous sensing and communication, and security vulnerabilities as evidenced by the DHS and FDA advisories. One other major challenge is to find an efficient on-body energy harvesting method to support the sensing, communication, and security sub-modules. Due to the limitations in the harvested amount of energy, we require reduction of energy consumed per unit information, making the use of in-sensor analytics/processing imperative. In this paper, we review the challenges and opportunities in low-power sensing, processing and communication, with possible powering modalities for future bio-sensor nodes. Specifically, we analyze, compare and contrast (a) different sensing mechanisms such as voltage/current domain vs time-domain, (b) low-power, secure communication modalities including wireless techniques and human-body communication, and (c) different powering techniques for both wearable devices and implants.Comment: 30 pages, 5 Figures. This is a pre-print version of the article which has been accepted for Publication in Volume 25 of the Annual Review of Biomedical Engineering (2023). Only Personal Use is Permitte

Sensor-based management systems based on RFID technology

Παρατηρήσεις έκδοσης: λείπουν οι σελίδες 78, 102 από το φυσικό τεκμήριο.In this diploma thesis, the RFID technology is analyzed (operating principles, readers' and tags hardware, coding, modulation, anticollision procedures, frequencies, standards, applications). Moreover, a protocol to synchronize readers working in a multi-reader multi-tag environment is proposed. The protocol is applied to the store shelf scanning application and further refined to meet the requirements of this specific application

Wireless tools for neuromodulation

Epilepsy is a spectrum of diseases characterized by recurrent seizures. It is estimated that 50 million individuals worldwide are affected and 30% of cases are medically refractory or drug resistant. Vagus nerve stimulation (VNS) and deep brain stimulation (DBS) are the only FDA approved device based therapies. Neither therapy offers complete seizure freedom in a majority of users. Novel methodologies are needed to better understand mechanisms and chronic nature of epilepsy. Most tools for neuromodulation in rodents are tethered. The few wireless devices use batteries or are inductively powered. The tether restricts movement, limits behavioral tests, and increases the risk of infection. Batteries are large and heavy with a limited lifetime. Inductive powering suffers from rapid efficiency drops due to alignment mismatches and increased distances. Miniature wireless tools that offer behavioral freedom, data acquisition, and stimulation are needed. This dissertation presents a platform of electrical, optical and radiofrequency (RF) technologies for device based neuromodulation. The platform can be configured with features including: two channels differential recording, one channel electrical stimulation, and one channel optical stimulation. Typical device operation consumes less than 4 mW. The analog front end has a bandwidth of 0.7 Hz - 1 kHz and a gain of 60 dB, and the constant current driver provides biphasic electrical stimulation. For use with optogenetics, the deep brain optical stimulation module provides 27 mW/mm2 of blue light (473 nm) with 21.01 mA. Pairing of stimulating and recording technologies allows closed-loop operation. A wireless powering cage is designed using the resonantly coupled filter energy transfer (RCFET) methodology. RF energy is coupled through magnetic resonance. The cage has a PTE ranging from 1.8-6.28% for a volume of 11 x 11 x 11 in3. This is sufficient to chronically house subjects. The technologies are validated through various in vivo preparations. The tools are designed to study epilepsy, SUDEP, and urinary incontinence but can be configured for other studies. The broad application of these technologies can enable the scientific community to better study chronic diseases and closed-loop therapies

Automatic student attendance registration using radio frequency identification (RFID)

Thesis (M. Tech.) - Central University of Technology, Free State, 2010The main aim of this research was to automate student attendance registration, thereby reducing human involvement in the whole process. This was made possible using Radio Frequency Identification (RFID) technology. The Central University of Technology uses student cards that are compatible for use with RFID technology. As a result, no initial investment (except for the existing personal computer’s and the constructed RFID reader) in infrastructure was required for this project. The basic working of the project was as follows. The students belonging to a specific class had their vital educational data (Student number, Name) entered into a database table at the time of registration. A student card containing a serial number, with reference to the data contained in the database table, was given to the students after registration. The students walk into their respective classes and scan their student cards with the RFID reader. The serial number stored in the student card is transferred to the reader and from there wirelessly to the main server using ZigBee technology. In the main server, using Java programming language, the card serial number is sent to the Integrated Development Environment (IDE). In this project the Netbeans IDE (Java platform) was used. The Netbeans IDE is connected to the Apache Derby database using Java Database Connector (JDBC), so the serial number (which is referenced to the educational data of the students) from the student card is automatically compared with the original database created at the time of registration. Once a match is confirmed between the two entries, the data is entered into a separate database table which serves as the basic attendance sheet for a specific day

Industrial and Technological Applications of Power Electronics Systems

The Special Issue "Industrial and Technological Applications of Power Electronics Systems" focuses on: - new strategies of control for electric machines, including sensorless control and fault diagnosis; - existing and emerging industrial applications of GaN and SiC-based converters; - modern methods for electromagnetic compatibility. The book covers topics such as control systems, fault diagnosis, converters, inverters, and electromagnetic interference in power electronics systems. The Special Issue includes 19 scientific papers by industry experts and worldwide professors in the area of electrical engineering

Improving the mechanistic study of neuromuscular diseases through the development of a fully wireless and implantable recording device

Neuromuscular diseases manifest by a handful of known phenotypes affecting the peripheral nerves, skeletal muscle fibers, and neuromuscular junction. Common signs of these diseases include demyelination, myasthenia, atrophy, and aberrant muscle activity—all of which may be tracked over time using one or more electrophysiological markers. Mice, which are the predominant mammalian model for most human diseases, have been used to study congenital neuromuscular diseases for decades. However, our understanding of the mechanisms underlying these pathologies is still incomplete. This is in part due to the lack of instrumentation available to easily collect longitudinal, in vivo electrophysiological activity from mice. There remains a need for a fully wireless, batteryless, and implantable recording system that can be adapted for a variety of electrophysiological measurements and also enable long-term, continuous data collection in very small animals. To meet this need a miniature, chronically implantable device has been developed that is capable of wirelessly coupling energy from electromagnetic fields while implanted within a body. This device can both record and trigger bioelectric events and may be chronically implanted in rodents as small as mice. This grants investigators the ability to continuously observe electrophysiological changes corresponding to disease progression in a single, freely behaving, untethered animal. The fully wireless closed-loop system is an adaptable solution for a range of long-term mechanistic and diagnostic studies in rodent disease models. Its high level of functionality, adjustable parameters, accessible building blocks, reprogrammable firmware, and modular electrode interface offer flexibility that is distinctive among fully implantable recording or stimulating devices. The key significance of this work is that it has generated novel instrumentation in the form of a fully implantable bioelectric recording device having a much higher level of functionality than any other fully wireless system available for mouse work. This has incidentally led to contributions in the areas of wireless power transfer and neural interfaces for upper-limb prosthesis control. Herein the solution space for wireless power transfer is examined including a close inspection of far-field power transfer to implanted bioelectric sensors. Methods of design and characterization for the iterative development of the device are detailed. Furthermore, its performance and utility in remote bioelectric sensing applications is demonstrated with humans, rats, healthy mice, and mouse models for degenerative neuromuscular and motoneuron diseases