Cheng Wang Chi. / "October 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 135-139) / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

The determination of the optimal location of transceivers is a critical design factor when deploying a wireless local area network (WLAN). The performance of the WLAN will improve in a variety of aspects when the transceivers' locations are adequately determined, including the overall cell coverage to the battery life of the client units. Currently, the most common method to determine the appropriate location of transceivers is known as a site survey, which is normally a very time and energy consuming process. The main objective of this research was to improve current methodologies for the optimal or near-optimal placement of APs in a WLAN installation. To achieve this objective, several improvements and additions were made to an existing computational tool to reflect the evolution that WLAN equipment has experienced in recent years. Major additions to the computational tool included the addition of the capability to handle multiple power levels for the transceivers, the implementation of a more adequate and precise representation of the passive interference sources for the path loss calculations, and the definition of a termination criterion to achieve reasonable computational times without compromising the quality of the solution. An experiment was designed to assess how the improvements made to the computational tool provided the desired balance between computational time and the quality of the solutions obtained. The controlled factors were the level of strictness of the termination criterion (i.e., high or low), and the number of runs performed (i.e., 1, 5, 10, 15, and 20 runs). The low level of strictness proved to dramatically reduce (i.e., from 65 to 70%) the running time required to obtain an acceptable solution when compared to that obtained at the high level of strictness. The quality of the solutions found with a single run was considerably lower than that obtained with the any other number of runs. On the other hand, the quality of the solutions seemed to stabilize at and after 10 runs, indicating that there is no added value to the quality of the solution when 15 or 20 runs are performed. In summary, having the computational tool developed in this research execute 5 runs with the low level of strictness would generate high quality solutions in a reasonable running time. / Graduation date: 2004

Roy A. Paananen. / "September 22, 1952." "Based on a thesis presented for the degree of Electrical Engineer, Massachusetts Institute of Technology, 1952." / Bibliography: p. 84-85. / Army Signal Corps Contract DA36-039 sc-100, Project 8-102B-0. Dept. of the Army Project 3-99-10-022.

Ultra-wideband technology (UWB) has received tremendous attention since the FCC license release in 2002, which expedited the research and development of UWB technologies on consumer products. The applications of UWB range from ground penetrating radar, distance sensor, through wall radar to high speed, short distance communications. The CMOS integrated circuit is an attractive, low cost approach for implementing UWB technology. The improving cut-off frequency of the transistor in CMOS process makes the CMOS circuit capable of handling signal at multi-giga herz. However, some design challenges still remain to be solved. Unlike regular narrow band signal, the UWB signal is discrete pulse instead of continuous wave (CW), which results in the occupancy of wide frequency range. This demands that UWB front-end circuits deliver both time domain and frequency domain signal processing over broad bandwidth. Witnessing these technique challenges, this dissertation aims at designing novel, high performance components for UWB signal generation, down-conversion, as well as accurate timing control using low cost CMOS technology. We proposed, designed and fabricated a carrier based UWB transmitter to facilitate the discrete feature of the UWB signal. The transmitter employs novel twostage -switching to generate carrier based UWB signal. The structure not only minimizes the current consumption but also eliminates the use of a UWB power amplifier. The fabricated transmitter is capable of delivering tunable UWB signal over the complete 3.1GHz -10.6GHz UWB band. By applying the similar two-stage switching approach, we were able to implement a novel switched-LNA based UWB sampling receiver frontend. The proposed front-end has significantly lower power consumption compared to previously published design while keep relatively high gain and low noise at the same time. The designed sampling mixer shows unprecedented performance of 9-12dB voltage conversion gain, 16-25dB noise figure, and power consumption of only 21.6mW(with buffer) and 11.7mW(without buffer) across dc to 3.5GHz with 100M-Hz sampling frequency. The implementation of a precise delay generator is also presented in the dissertation. It relies on an external reference clock to provide accurate timing against process, supply voltage and temperature variation through a negative feedback loop. The delay generator prototype has been verified having digital programmability and tunable delay step resolution. The relative delay shift from desired value is limited to within 0.2%.

This thesis aims to implement a linear wireless transmitter based on the envelope-following architecture. A class-E PA is utilized to replace the linear PA used in the traditional envelope-following transmitter for enhancing the average efficiency. The transmitter relies on a digital processor realized by FPGA to generate the baseband IQ signal and corresponding envelope signal. This way can not only achieve more accurate modulation accuracy and wider modulation bandwidth, but also use less analog components for the future convenience of realizing single-chip integration when compared to the traditional envelope-following transmitter. Furthermore, this thesis implements a predistorter in the digital processor to compensate the Vdd/AM distortion of class-E amplifier. Therefore, this transmitter can simultaneously achieve high efficiency and high linearity over a wide input power range. From the results measured in transmitting a QPSK-modulated CDMA2000 1x signal at a chip rate of 1.2288 Mcps, the transmitter incorporating an InGaAs pHEMT class-E PA can achieve 30~44 % in average efficiency (23~38 % in average PAE) with above 44 dBc in ACPR and below 4 % in EVM in the average modulated output power range from 7 to 21 dBm, while the transmitter incorporating a GaAs HBT can achieve 20~40 % in average efficiency (16~35 % in average PAE) with above 43 dBc in ACPR and below 5 % in EVM in the average modulated output power range from 4 to 18.5 dBm.

This dissertation presents a hybrid quadrature polar modulator (HQPM) to drive the power amplifier (PA) highly efficiently in a wireless RF transmitter with good potential for multi-mode operation. For enhancing the efficiency, a Class-E PA is used in the transmitter. The HQPM consists of a quadrature modulator for processing the RF modulated carrier and a Class-S modulator for processing the supply-voltage signal. The quadrature modulator and the Class-S modulator deliver the output signals with envelope variation before being inserted into the RF-input terminal and the supply-voltage terminal of Class-E PA, respectively, causing the double envelope modulation to distort the modulated RF signal at the PA output. Therefore, a digital predistorter is proposed to be embedded in the HQPM for compensation. The use of such predistorted HQPM techniques can help reducing the average DC and RF input powers and the output feed-through levels so as to enhance power added efficiency and adjacent channel power rejection quite remarkably.

beta-Bungarotoxin (beta-BuTx), the presynaptic neurotoxin purified from the venom of Bungarus multicinctus, consists of two dissimilar polypeptide subunits. A phospholipase A2 subunit named A chain, and a non-phospholipase A2 subunits named B chain. The A chain and B chain are covalently linked by one disulfide bridge. Although it has been widely accepted that the toxic effect of beta-BuTx is attributed to the disturbance of presynaptic transmitter release, however the inhibition of transmitter release by beta-BuTx is still obscure. Here we investigate the mechanism that mediates facilitation of transmitter release at the neuromuscular junction induced by beta-BuTx, using Xenopus nerve-muscle coculture. Application of beta-BuTx and isotoxins BM12, BM13 led to a marked increase in the frequency of spontaneous synaptic currents (SSCs) after a short period (12~18 min) of latency. The synaptic potentiation induced by these toxins was abolished when Ca2+ in the medium is substituted by Ba2+ (a potent phospholipase A2 inhibitor). Application of PLP-BM12 and PLP-BM13, which have been chemical-modification to lose their PLA2 activity from BM12 and BM13, failed to potentiate the transmitter release.

Historically, the collared peccary (Tayassu tajacu) occurred throughout much of Texas including the northern portion of the Texas Hill Country. Remaining peccary populations were extirpated in much of their former range due to over harvest and habitat loss. In 2004, efforts to restore peccary populations to the Texas Hill Country began when Texas Parks and Wildlife Department biologists translocated 29 collared peccaries into the 2,157 ha, Mason Mountain Wildlife Management Area (MMWMA). I evaluated the success of peccary translocations for mixed and intact family groups by comparing survival, ranges, and dispersal of translocated, radio-tagged peccaries. In addition, I evaluated two release methods (soft versus hard) to determine differences in population demographics. I found that peccary ranges and dispersal patterns did not differ (P > 0.05) between intact and mixed groups or release method (soft versus hard). However, I did find that peccary fidelity to release sites was greater for soft releases of family groups. Individuals from the soft release group dispersed the shortest distance and stayed on MMWMA. Only 2 individuals from the hard releases stayed on MMWMA while the rest (19 individuals) dispersed 4-8 km. Future peccary translocations should emphasize the release method employed and family structure of individuals released to improve translocation effectiveness in establishing populations in target areas.

This thesis consists of two subjects of research: eliminating, by avoidance or removal, the effects of different types of interference on small signal recording, and a body-sensor transmitter application utilizing piezo sensors. The first topic demonstrates ECG signal and noise signal recording in the presence of various types of interference. A low-pass filter is proposed to remove power-line interference of ECG signals, and a switch between high-pass filters before amplification is proposed to avoid motion artifacts in the ECG signal. Finally, a low-cost noise recording system for educational uses that can record and analyze the noise of resistors and amplifiers in the LabVIEW program is proposed. The second topic concerns the application of a body-sensor transmitter. The sensor uses piezo film and combines the characteristics of piezo film with the characteristics of the human body and can exchange information by capacitor coupling. The signal used in the body-sensor transmitter is designed for a fixed frequency using narrow band-pass filters and is received by receivers via four methods as confirmation. Finally, the charge amplifier designed to detect signals is fabricated using a 0.35£gm 2P4M CMOS process.

In this thesis we have proposed a variable-length multiobjective genetic algorithm to solve heterogeneous wireless transmitter placement with multiple constraints. Among many factors that may affect the result of placement, we focus on four major requirements, coverage, cost, data rate demand, and overlap. In the proposed algorithm we release the need for the upper bound number of transmitters that is a major constraint in the existing methods and achieve better wireless transmitter placement while considering the transmitter position and design requirement simultaneously. In experiments, we use the free space propagation model, the large scale propagation model which considers the shadowing effect, and the extended Hata-Okumura model to predict the path loss in a real two dimensional indoor environment, and an outdoor environment and even a real three dimensional outdoor environment. Experimental results show that the proposed algorithm can find many feasible solutions for all test cases under four objectives.