In this thesis we present a novel method for remote breathing detection using ultra-wideband(UWB) radar. This is a method that does not require any wearable sensors, makingit more comfortable and convenient for users. Furthermore, because of the penetratingcharacteristic of the transmitted signal through materials like walls, our system is usefulin emergency situations such as earthquakes, which require monitoring people who maybe trapped under rubble. In this thesis we present two new convolution-based methodsto extract breathing rate information from the received radar signal. We use two differenttemplate signals to detect a part of the received signal which contains breathing information.Using this information we are able to estimate the frequency of chest displacement.This method was tested on several people who were monitored while lying down on a bed.The subject’s position was determined and breathing rate was estimated. Experimental resultsincluding 20 different subjects are provided, showing that this is a viable method formonitoring breathing rate using a low-power UWB radar.i

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Piezoelectric energy harvester has become a new powering choice for small electronic device. Due to its piezoelectric effect, electric energy can be obtained from ambient vibrations. This thesis is intending to build a frequency-adjustable piezoelectric energy harvester system. The system is structured with two piezoelectric bimorph beams, which are connected to each other by a spring. The feasibility of the frequency-adjustable piezoelectric energy harvester has been proved by investigating effects of the spring, loading mass and impedance on the operation frequencies.

Ultra Wide Band (UWB) is a short-pulse electrical signal which is widely used for short distant wireless communication because its low path loss, good immunity to multipath propagation, and high data rate. The reason of using optical fiber as carrier is fiber can bust up the communication capacitance in long distance range because of high capacitance, low loss propagation. Thereby, the technique of UWB signal on fiber has become more and more important. In this work, a novel method using electro-absorption modulation with short termination for interface of optical fiber and generate UWB signal is proposed and demonstrated. The structure is simple.This method don¡¦t need employing any complicated frequency mixer, or complex systems. This work need to generate optical pulse with high energy, which is feded into the EAM. The signal can generate electrical pulse and build electrical field on EAM in the same time. The optical pulse is modulated by the electrical field on EAM. Using this way, we can generate UWB optical signal.

The maximum capacity of an optical fiber transmission system more than doubled every year to match the fast-growing communication need. The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1300nm to 1600nm. The fast increasing demand of communication capacity results in the emergence of wavelength division multiplexing (WDM) technology, which results in the need for ultra-wideband optical amplifier. Cr4+:YAG has a strong spontaneous emission that covers 1300nm to 1600nm. Besides, its absorption spectrum is between 900nm to 1200nm, which matches with the pumping source in current erbium doped optical amplifier. Such a fiber is, therefore, eminently suitable for optical amplifier applications. In this article, we will introduce the development of ultra-wideband optical amplifier using the double-clad Cr4+:YAG crystal fiber, which is grown by laser heated pedestal growth(LHPG) technique. Its material properties as well as optical gain will be characterized. By butt-coupling method, a low insertion loss of 4.2 dB was achieved in a SMF-CDF-SMF configuration, and it was measured to demonstrate a gross gain of 2.4 dB at 1 W bi-directional pump power. Moreover, theoretical models and numerical simulations have been developed to predict the experimental results. Numerical simulation indicates that the efficiency of mode overlapping between signal and pump is crucial to gain performance. The mode overlapping efficiency is about 25%~30% for our crystal fiber under current circumstances. In the future, we will make an attempt to reduce the index contrast between core and cladding for better mode overlapping efficiency. At the same time, we also try to grow crystal fiber of smaller core diameter to improve gain performance.

Ultra Wide Band (UWB) is a short-pulse electrical signal, which is widely used for short distant wireless communication due to its low path loss, good immunity to multipath propagation, and high data rate. The main target transmission area of UWB is within 10 meters. Using optical fiber as carrier can bust up the communication capacitance in long distance range because of high capacitance, low loss propagation, and TDM and WDM compatible properties of fiber. Thereby, the technique of UWB on fiber has become more and more important. In this work, a novel method using waveguide photodetector (WP) with short termination for interface of optical fiber and wireless is proposed and demonstrated. The structure is simple without employing any complicated frequency mixer, intermediate frequency, or complex systems. This work is divided into two parts: (1) generation of UWB electrical signals and (2) wavelength conversion of UWB through WP. In the former, a WP with short termination is used in the device. The photocurrent excited by short optical pulse is distributive generated through the waveguide, forming two opposite directions of electrical waves. By reflection on the short termination, the reversed phase of one electrical wave is added to another electrical wave through a delay line, forming a monocycle of UWB signal. By appropriate design on the length of waveguide, the band of 2-10GH is demonstrated, fitting the requirement of FCC (Federal Communications Commission). In the second part of this paper is the wavelength conversion of UWB. The active region of WG is multiple quantum wells (M.Q.W.), which is not only served as photo-absorption layer, but also can be used the electroabsorption material. By pumping M.Q.W.s with high optical power, the cross absorption properties can be applied for wavelength conversion. By pumping power of 12dBm, the wavelength-converted UWB signal is successfully demonstrated at range of 1545nm-1570nm. Using this method, the application of UWB on router of fiber optical network is expectable.

Broadband voltage-controlled oscillators are critical to the design of millimeter wave frequency synthesizers. This thesis proposes a design technique that can be used to significantly extend the achievable frequency span of an oscillator. A dual-band oscillator topology is described that can be configured to operate in one of two modes, by an electrical reconfiguration of the negative resistance core around the resonant tank, without switching passive elements within the tank itself. The configuration helps to minimize the difference in phase noise performance between the two modes, while achieving a wide tuning range. To verify the concept, a mm-wave VCO that operates at 30-GHz is designed in a commercial 0.18-um CMOS technology, with an approximate simulated tuning range of 20%. A dual-mode oscillator is also designed in a 0.13-um technology at 60-GHz. / text

The commercialization of wide band-gap devices such as silicon carbide and gallium nitride transistors has made it possible for power electronics applications to achieve unprecedented performance in terms of efficiency and power density. However, the device characteristics which make this performance possible also create secondary consequences in these high-performance applications. One such consequence which is particularly difficult to manage in the context of power electronics applications is the occurrence of self-sustained oscillation. This problem has been recognized in the power electronics literature, but heretofore has not received an extensive analytical treatment. This dissertation provides a comprehensive analytical treatment of the self-sustained oscillation phenomenon, logically separated into two components: an initial forced cycle and the subsequent oscillatory behavior. A large-signal model has been developed in order to predict the occurrence of the initial forced cycle based on a set of estimated initial conditions derived from a user-specified operating point. The establishment of the initial forced cycle as predicted by the large-signal model creates the bias conditions necessary for the analytical treatment of the subsequent oscillatory behavior. For this purpose, a small-signal model is presented which describes this phenomenon on the basis of recognizing the wide band-gap device and a minimal set of parasitic components associated with the gate and drain circuits as an unintended negative conductance oscillator. In the context of established oscillator design theory it has been shown both analytically and with simulation that negative differential conductance exhibited by the parasitic model explains the conditions under which self-sustained oscillation is likely to occur. Both the large-signal and small-signal models are shown to demonstrate good agreement with empirical results from pulsed switching experiments obtained over a wide range of operating conditions. In addition, a catalog of known solutions to the problem of self-sustained oscillation is presented, along with a discussion of a method by which the current work can be used by application designers to preclude the occurrence of this phenomenon in practical systems by design.

The increasing demand for efficient cancer treatment inspired the researchers for new investigations about an alternative treatment of cancer. Microwave ablation is the newest ablation technique to cure cancer. This method is minimally noninvasive and inexpensive compared to the other methods. However, current microwave ablation systems suffer due to narrowband nature of the antenna (dipole or slot) placed at the tip of the probe. Therefore, this study developed an ultra-wideband ablation probe that operates from 300MHz to 10 GHz. For this purpose, a small wideband antenna is designed to place at the tip of the probe and fabricated. These probes are tested at ISM frequencies (2.4 GHz and 5.8GHz) in skin mimicking gels and pig liver. Microwave ablation probe design, simulation results, and experiment results are provided in this thesis.

The main purpose of this thesis is to estimate the direct path in dense multipath Ultra Wide-Band (UWB) environment. The time-of-arrival (ToA) estimation algorithm used is based on Generalized Maximum-Likelihood (GML) algorithm. Nevertheless, GML algorithm is so time-consuming that the results usually take a very long period of time, and sometimes fail to converge. Hence, the schemes that would improve the algorithm are investigated. In the schemes, the search was executed in sequential form. Two threshold parameters are to be determined¡Xone is about the arrival time of the estimation path while the other is the fading amplitude of the estimation path. The thresholds are determined in order to terminate the sequential algorithm. The determination of thresholds is based on error analysis, including the probability of error and root-mean-square error. The analysis of the probability of error is subject to the probability of false alarm and the probability of miss. However, a trade-off problem on the probability of false alarm and the probability of miss exists in the process of determining thresholds. The thresholds are determined according to the requirement of the probability of error. We propose an improvement scheme for determining the two thresholds. In the proposed scheme, candidate pairs are evaluated within an appropriate range. The root-mean-square error value for each pair of thresholds is calculated. The smallest error, corresponding to the desired thresholds, is chosen for use in ToA estimation. From the simulation results, it is seen that, when SNR falls between -4dB and 16dB, the improvement proposed scheme results has the smaller estimation error.