The increasing demands for improving magnetic resonance imaging (MRI) quality, especially reducing the imaging time have been driving the channel number of parallel magnetic resonance imaging (Parallel MRI) to increase. When the channel number increases to 64 or even 128, the traditional method of stacking the same number of radio-frequency (RF) receivers with very low level of integration becomes expensive and cumbersome. However, the cost, size, power consumption of the Parallel MRI receivers can be dramatically reduced by designing a whole receiver front-end even multiple receiver front-ends on a single chip using CMOS technology, and multiplexing the output signal of each receiver front-end into one channel so that as much hardware resource can be shared by as many channels as possible, especially the digitizer. The main object of this research is focused on the analysis and design of fully integrated multi-channel RF receiver and multiplexing technology. First, different architectures of RF receiver and different multiplexing method are analyzed. After comparing the advantages and the disadvantages of these architectures, an architecture of receiver front-end which is most suitable for fully on-chip multi-channel design is proposed and a multiplexing method is selected. According to this proposed architecture, a four-channel receiver front-end was designed and fabricated using TSMC 0.18μm technology on a single chip and methods of testing in the MRI system using parallel planar coil array and phase coil array respectively as target coils were presented. Each channel of the receiver front-end includes an ultra low noise amplifier (LNA), a quadrature image rejection down-converter, a buffer, and a low-pass filter (LPF) which also acts as a variable gain amplifier (VGA). The quadrature image rejection downconverter consists of a quadrature generator, a passive mixer with a transimpedance amplifier which converts the output current signal of the passive mixer into voltage signal while acts as a LPF, and a polyphase filter after the TIA. The receiver has an over NF of 0.935dB, variable gain from about 80dB to 90dB, power consumption of 30.8mW, and chip area of 6mm2. Next, a prototype of 4-channel RF receiver with Time Domain Multiplexing (TDM) on a single printed circuit board (PCB) was designed and bench-tested. Then Parallel MRI experiment was carried out and images were acquired using this prototype. The testing results verify the proposed concepts.

IEEE 802.15 High Rate Alternative PHY task group (TG3a) is working to define a protocol for Wireless Personal Area Networks (WPANs) which makes it possible to attain data rates of greater than 110Mbps. Ultra Wideband (UWB) technology utilizing frequency band of 3.168 GHz – 10.6 GHz is an emerging solution to this with data rates of 110, 200 and 480 Mbps. Initially, UWB mode I devices using only 3.168 GHz – 4.752 GHz have been proposed. Low Noise Amplifier (LNA) and I-Q mixers are key components constituting the RF front-end. Performance of these blocks is very critical to the overall performance of the receiver. In general, main considerations for the LNA are low noise, 50 broadband input matching, high gain with maximum flatness and good linearity. For the mixers, it is essential to attain low flicker noise performance coupled with good conversion gain. Proposed LNA architecture is a derivative of inductive source degenerated topology. Broadband matching at the LNA output is achieved using LC band-pass filter. To obtain high gain with maximum flatness, an LC band-pass filter is used at its output. Proposed LNA achieved a gain of 15dB, noise figure of less than 2.6dB and IIP3 of more than -7dBm. Mixer is a modified version of double balanced Gilbert cell topology where both I and Q channel mixers are merged together. Frequency response of each sub-band is matched by using an additional inductor, which further improves the noise figure and conversion gain. Current bleeding scheme is used to further reduce the low frequency noise. Mixer achieves average conversion gain of 14.5dB, IIP3 more than 6dBm and Double Side Band (DSB) noise figure less than 9dB. Maximum variation in conversion gain is desired to be less than 1dB. Both LNA and mixers are designed to be fabricated in TSMC 0.18µm CMOS technology.

With the increasing demand for high quality TV service, digital television (DTV) is replacing the conventional analog television. DTV tuner is one of the most critical blocks of the DTV receiver system; it down-converts the desired DTV RF channel to baseband or a low intermediate frequency with enough quality. This research is mainly focused on the analysis and realization of low-cost low-power front-ends for ATSC terrestrial DTV and DVB-H mobile DTV tuner systems. For the design of the ATSC terrestrial tuner, a novel double quadrature tuner architecture, which can not only minimize the tuner power consumption but also achieve the fully integration, has been proposed. A double quadrature down-converter has been designed and fabricated with TSMC 0.35µm CMOS technology; the measurement results verified the proposed concepts. For the mobile DTV tuner, a zero-IF architecture is used and it can achieve the DVB-H specifications with less than 200mW power consumption. In the implementation of the mobile DVB-H tuner, a novel RF variable gain amplifier (RFVGA) and a low flicker noise current-mode passive mixer have been proposed. The proposed RFVGA achieves high dynamic range and robust input impedance matching performance, which is the main design challenge for the traditional implementations. The current-mode passive mixer achieves high-gain, low noise (especially low flicker noise) and high-linearity (over 10dBm IIP3) with low power supplies; it is believed that this is a promising topology for low voltage high dynamic range mixer applications. The RFVGA has been fabricated in TSMC 0.18µm CMOS technology and the measurement results agree well with the theoretical ones.

Tungsten trioxide (WO3) films are important for various optical devices and especially for electrochromic materials. Sputtered WO3 thin films were deposited on conductive glass substrate (ITO/glass) by RF sputtering from a WO3 target(diameter 2¡¨x 6 mm) in a reactive atmosphere of oxygen and argon flow ratio(0 to 1) mixture in a total gas pressure of 10m Torr. The RF power was 100W operating at 13.56MHz.We will improve the WO3 films by post-annealing in different atmosphere ambient. In addition, to prepare treatment solution of growing WO3 films were dissolved tungsten to aqueous which mixed hydrofluoric acid and nitric acid until it supersaturate. This solution was then diluted to 0.02 M of tungsten ions with distilled water. And we can get the treatment solution (WO3-HF aqueous). The WO3 thin films have been deposited at 40oC with the treatment solution (WO3-HF aqueous) which full of W ions, the 0.1M boric acid (H3BO3) solution and added aluminium metal by liquid phase deposition (LPD) technique. The deposition rate could be controlled to 45 nm/h. In our experiment, the WO3 films morphology and thickness was characterized by scanning electron microscopy(SEM), structure was characterized by X-ray diffraction(XRD), chemical properties was characterized by X-ray photoelectron spectroscopy(XPS) and Fourier transform infrared spectroscopy(FT-IR), optical properties was characterized by spectrophotometer(MP-100M), and electrochromic characterized by cyclic voltammetry(CHI627C). In our results, it will be improved the optical and electrochromic properties of sputtered-WO3 films by post-annealing in O2 ambient. we also have try a novel and very simple process for the thin films of WO3 by the LPD process. Adherent and conformal WO3 electrochromic films were prepared on ITO/glass from aqueous fluoride solution.

This dissertation presents research on synthesis, high-power microwave post-synthetic purification and high frequency characterization of Carbon Nanotubes (CNT). First, CNTs are synthesized using a Chemical Vapor Deposition system. The impact of substrate and methane flow rate on CNT growth is studied using Scanning Electron Microscopy, Transmission Electron Microscopy and Raman microscopy. Second, the microwave irradiation effects on purified HiPCO and CoMoCat Single-Walled CNT thin films are investigated. The measured drastic THz power transmission increase (>10 times) indicates a significant metallic content reduction after the irradiation. The Raman spectra also confirm the metallic-to-semiconducting ratio of Raman-active CNTs decreases by up to 33.3%. The observed microwave-induced effects may potentially lead to a convenient scheme for CNT demetalization. Third, Multi-Walled CNT papers are characterized from 8 to 50 GHz by rectangular waveguide measurements using a vector network analyzer. A rigorous algorithm is developed to extract the samples' effective complex permittivity and permeability from the measured S-parameters. Unlike other reported work, this method does not impose the unity permeability assumption. The algorithm is verified by finite-element simulations and the uncertainties for the characterization method are analyzed. The effective medium theory is then applied to obtain the intrinsic CNT properties. Furthermore, Terahertz Time-Domain Spectroscopy is used to characterize the samples from 50 to 370 GHz. Both transmission and reflection experiments are performed to simultaneously extract the permittivity and permeability. The extracted permittivity is fitted with a Drude-Lorentz model from 8 to 370 GHz. Finally, individual CNT characterizations at microwave frequency are studied. The impacts from impedance mismatching and parasitics on measurement sensitivity are systematically studied, revealing that the parasitic effect is possibly dominant above 10 GHz. A tapered coplanar waveguide test fixture is designed using Advanced Design System (ADS) to improve the impedance mismatching and minimize the test fixture parasitics, therefore optimize the measurement sensitivity. A de-embedding procedure to obtain the CNT's intrinsic electrical properties is presented and demonstrated with ADS simulations. In addition, the test fixture fabrication process is discussed, which is an ongoing research work. At the end, the conclusions of this dissertation are drawn and possible future works are discussed.

A frequency selective surface (FSS) based on switchable slots in the ground plane is presented. The switching is done using an actuating MEMS bridge over the slot. The intent is to demonstrate the control of the resonance frequency of the FSS by deflecting the bridge. It is shown that by applying a voltage between the bridge and the ground plane, the bridge displaces and changes the system capacitance which in turn changes the resonance frequency. Two analyses are presented; (1) Electromechanical analysis to show how the bridge deflects by the voltage, (2) Electromagnetic analysis to show how the resonance frequency changes by the bridge deflection. The device was fabricated and tested. The measurement results are presented for two up and down positions of the MEMS bridge to verify the correctness of the theory and design.

This work aims to demonstrate the design and simulation of a Radio Frequency (RF) energy-harvesting circuit, from receiving antenna to the point of charge collection. The circuit employs a custom-designed antenna based around Koch fractal loops, selected for their small physical size, good multiband behaviour and ease of size scalability, as well as a power-efficient seven-element Greinacher rectification section designed to charge a super-capacitor or rechargeable battery for later use. Multiple frequency bands are tapped for energy and this aspect of the implementation was one on the main focus points. The bands targeted for harvesting in this thesis will be those that are the most readily available to the general Canadian population. These include Wi-Fi hotspots (and other 2.4GHz sources), as well as cellular (850MHz band), Personal Communications Services (1900MHz band) and WiMax (2.3GHz) network transmitters.

A frequency selective surface (FSS) based on switchable slots in the ground plane is presented. The switching is done using an actuating MEMS bridge over the slot. The intent is to demonstrate the control of the resonance frequency of the FSS by deflecting the bridge. It is shown that by applying a voltage between the bridge and the ground plane, the bridge displaces and changes the system capacitance which in turn changes the resonance frequency. Two analyses are presented; (1) Electromechanical analysis to show how the bridge deflects by the voltage, (2) Electromagnetic analysis to show how the resonance frequency changes by the bridge deflection. The device was fabricated and tested. The measurement results are presented for two up and down positions of the MEMS bridge to verify the correctness of the theory and design.

No description available.

The main purpose of this work is to explore whether and how much multichannel signal processing strategies can be beneficial for improving the detection procedure for auditory late response (ALR) in clinical applications in comparison with single channel recording. To achieve this target, four multichannel noise reduction methods based on independent component analysis (ICA) were proposed for noise reduction for multichannel recording of ALR. The four alternative component selection strategies introduced in this work are: Magnitude Squared Coherence (MSC) [based on coherency of the ICs with an evoking stimulus], the maximum Signal to Noise Ratio (Max-SNR) of ICs over a particular interval, the kurtosis (maximum non-Gaussianity of the ICs), and minimum entropy of the ICs. The proposed methods are applied for the noise reduction of auditory late response (ALR) data captured using 63 channel EEG from 10 normal hearing participants. The performances of the proposed methods for improving signal quality were compared with each other and also with the single channel alternatives. All automated component selection approaches produced high SNR for multichannel ALR data. MSC-ICs produced significantly higher SNR than Max-Kurt-ICs or Min-Entropy-ICs. However the performance of MSC-ICs and Max-Fmp-ICs were not significantly different. Therefore, the MSC-ICs approach was selected for further work. MSC-ICs were used for three different clinical applications: Finding hearing threshold level, exploring the effect of attention and exploring inter- and intra- subject variability. The results for MSC-ICs were compared to the single channel signal processing alternative of weighted averaging. The results confirm that the multichannel signal processing can significantly improve the detection procedure for threshold measurement and for measuring the effects of attention. However, no significant enhancement was found for detecting inter- and intra- subject variability with multichannel processing over single channel alternative. The MSC-ICs method was also used in an application for removing cardiac artifact from the ALR recordings and the results was compared with an existing artifact rejection platform based on constraint ICA (cICA). The results of this comparison show that the proposed method can significantly improve the quality of cardiac artifact rejection from ALR data. Finally, the use of MSC-ICs was explored for reducing the required time for recording ALR. Time reduction was investigated in two senses: 1. reducing the number of stimulus repetitions. 2. Optimizing the position and the number of the recording electrodes in multichannel recordings (potentially saving the time required to place many electrodes on the scalp). The results show that using multichannel processing can significantly reduce the number of stimulus repetitions and consequently the time of recording in comparison with the single channel alternative. Minimum required number of stimulus repetition (average over10 subjects) for having SNR equal to single channel processing at Cz was found to be 74 for un-weighted averaging and 85 for weighted averaging. Moreover, the results of optimal electrode placement procedure confirm that, the ALR can be recorded form the vertex (with the same SNR as when ALR is recorded using 63 channels) by using fewer numbers of electrodes. For the data set of this study (10 normal hearing adults) the same SNR as with 63 channels was achieved by using 40 channels. Placing 40 electrodes (instead of 63) on the scalp decreases the required time for recording ALR considerably, i.e. 53% improved.