Strong demands for smaller, cheaper, and multifunction wireless systems have put very stringent requirements on passive devices, such as inductors and capacitors. This is especially true considering the size and weight of most radio frequency (RF) transceivers are mainly due to passives. RF micro-electro-mechanical-systems (MEMS) passives are addressing this issue by offering lower power consumption and losses, higher linearity and quality (<i>Q</i>)-factors, potential for integration and miniaturization, and batch fabrication. These advantages position RF MEMS passives as good candidates to replace conventional passives. Further, they also open an opportunity for using the passives as building blocks for lumped element-based RF circuits (e.g. Flters, couplers, etc.) which could replace the more-bulky distributed-element circuits.<p> This thesis presents the design, simulation, fabrication using the deep X-ray lithography process, and testing of thick-metal RF inductors and their applications to lumped-element low-pass Filter (LPF) circuits. The 70-um tall single-turn loop inductors are structurally compatible to a pre-existing RF MEMS capacitor concept and allow the two device types to be fabricated together. This compatibility issue is crucial if they would be used to construct more complex RF circuits.<p> At a 50-Ohm inductive reactance point, test results show <i>Q</i>-factors of 17- 55, self-resonant frequencies (SRF) exceeding 11 GHz, and nominal inductances of 0.4- 3 nH for 1-loop inductors and <i>Q</i>-factors of 11- 42, SRFs of 4- 22 GHz, and inductances of 0.8- 5.5 nH for 2-loop inductors. Further, test results reveal that high conductivity metals improve the <i>Q</i>-factors, and that low dielectric-constant substrates increase the SRFs.<p> In terms of LPFs, measurements show that they demonstrate the expected third-order Chebyshev response. Two nickel Filters on a quartz glass substrate show a 0.6-dB ripple with 3-dB frequencies (<i>f</i>-3dB) of 6.1 GHz and 11.9 GHz respectively. On an alumina substrate, they exhibit a 1.4-dB ripple with <i>f</i>-3dB of 5.4 GHz and 10.6 GHz respectively. The filters are 203- 285 um tall and feature 6- 6.5 um wide capacitance air gaps. These dimensions are different than the original designs and the filter performances were shown to be somewhat sensitive to these discrepancies. Compared to a distributed approach, the lumped-element implementations led to an area reduction of up to 95%.

Strong demands for smaller, cheaper, and multifunction wireless systems have put very stringent requirements on passive devices, such as inductors and capacitors. This is especially true considering the size and weight of most radio frequency (RF) transceivers are mainly due to passives. RF micro-electro-mechanical-systems (MEMS) passives are addressing this issue by offering lower power consumption and losses, higher linearity and quality (<i>Q</i>)-factors, potential for integration and miniaturization, and batch fabrication. These advantages position RF MEMS passives as good candidates to replace conventional passives. Further, they also open an opportunity for using the passives as building blocks for lumped element-based RF circuits (e.g. Flters, couplers, etc.) which could replace the more-bulky distributed-element circuits.<p> This thesis presents the design, simulation, fabrication using the deep X-ray lithography process, and testing of thick-metal RF inductors and their applications to lumped-element low-pass Filter (LPF) circuits. The 70-um tall single-turn loop inductors are structurally compatible to a pre-existing RF MEMS capacitor concept and allow the two device types to be fabricated together. This compatibility issue is crucial if they would be used to construct more complex RF circuits.<p> At a 50-Ohm inductive reactance point, test results show <i>Q</i>-factors of 17- 55, self-resonant frequencies (SRF) exceeding 11 GHz, and nominal inductances of 0.4- 3 nH for 1-loop inductors and <i>Q</i>-factors of 11- 42, SRFs of 4- 22 GHz, and inductances of 0.8- 5.5 nH for 2-loop inductors. Further, test results reveal that high conductivity metals improve the <i>Q</i>-factors, and that low dielectric-constant substrates increase the SRFs.<p> In terms of LPFs, measurements show that they demonstrate the expected third-order Chebyshev response. Two nickel Filters on a quartz glass substrate show a 0.6-dB ripple with 3-dB frequencies (<i>f</i>-3dB) of 6.1 GHz and 11.9 GHz respectively. On an alumina substrate, they exhibit a 1.4-dB ripple with <i>f</i>-3dB of 5.4 GHz and 10.6 GHz respectively. The filters are 203- 285 um tall and feature 6- 6.5 um wide capacitance air gaps. These dimensions are different than the original designs and the filter performances were shown to be somewhat sensitive to these discrepancies. Compared to a distributed approach, the lumped-element implementations led to an area reduction of up to 95%.

<p>In this study, a novel and systematic methodology for the design and optimization of conductor-backed coplanar waveguide (CB-CPW) based low pass filter (LPF) is proposed. The width of the signal trace is continuously varied using a truncated Fourier series, and the adjacent gaps are designed in several types established on a specific optimization setup to obtain predefined electrical characteristics with maximum compactness taking into account physical constraints. Trust-region-reflective algorithm (TRRA), genetic algorithm (GA), and particle swarm optimization algorithm (PSO) are taken into account to minimize the developed bound-constrained non-linear objective function respectively.<br></p><p>All types are programmed and analytically verified in MATLAB. Solutions include design parameters such as the physical length and width of the structure, which will be drawn in AutoCAD later on. Also, the optimized layouts are exported to Ansys High Frequency Structure Simulation (HFSS) software for simulation and validation. Non-uniform CB-CPW LPFs are optimized and simulated over a frequency range of 0-6 GHz with a cutoff frequency of 2 GHz. Simulation results show a good agreement with the analytical ones.<br></p>

Recently, with advances in CMOS process, the RF receiver which is integrated into the SOC chip can effectively reduce production costs. When designing the wireless receiver, one of the most important technologies is to design channel-selection filter. Typically, the design of the channel-selection filter in multi-standard high-frequency will take up a large chip area and higher power consumption. Therefore, in order to reduce the area and power consumption, this thesis designed a low-power OTA and low-pass filter. This thesis presents a multi-mode wireless communication application in the receiver channel selection filter. This filter is designed to use the fifth-order Butterworth low pass filter, the filter range can be used in Bluetooth, cdma2000, wideband CDMA, and IEEE 802.11a/b/g/n wireless LAN. Using floating transistor architecture in the input stage of OTA can effectively increase the THD performance. Using MOS transistors operating in triode region and combined with current multiplier can achieve the voltage-to-current conversion. Using the trans-linear loop can reach a wide tunable range, and the OTA operating in weak inversion region can significantly reduce the transconductance. Implementation is to use the TSMC 0.18£gm CMOS process. Simulation results show that the successful operation of this filter can be between 650 kHz ~ 22MHz frequency range. The filter may have compatibility in different wireless communication applications. 14.5mW to 17.5mW, respectively, is the smallest to the largest power consumption. The supply voltage is 1.2 volts.

Most discrete time filters use Switched Capacitor structures, but Switched capacitor circuits have finite sampling rate and high power consumption. In this paper we use Switched Current structure to increase sampling rate and reduce power consumption. In this paper, we use a Class-AB structure to compose a double sampling third order low-pass filter. In this paper there are two integrator types. Modified backward Euler and modified forward Euler integrators were realized with double sampling technology from the backward Euler and forward Euler integrators. Compared with other circuits, the circuit has low power supply¡Blow power consumption ¡Bhigh sampling speed. We employ HSPICE and MATLAB to simulate and design the circuit. We use TSMC 0.35£gm process to implement this circuit. The power supply is 1.8V, the cut-off frequency is 3.6MHz, the sampling frequency is 72MHz, and the power consumption is 1.303mW.

This thesis presents an application of the Ant Colony algorithm for optimizing filter placement and sizing on a radial distribution system to reduce power losses and keep the effective harmonic voltage values and the total harmonic distortion (THD) within prescribed limits. First, a harmonic load flow (HLF) algorithm is performed to demonstrate the effect of harmonic sources on total power loss. Then the Ant Colony algorithm is used in conjunction with HLF to place a selection of filter sizes available at each possible location so that both power loss and THD are minimized. As a result the optimal adjustment of location and size of the filter are determined. Results of computational experiments on standard test systems are presented to demonstrate improvement and effectiveness of using the filters at the optimal location. The methodology used can be easily extended to different distribution network configurations. / Master Thesis

The finite-difference time-domain (FDTD) method is one of most widely used computational electromagnetics (CEM) methods to solve the Maxwell's equations for modern engineering problems. In biomedical applications, like the microwave imaging for early disease detection and treatment, the human tissues are considered as lossy and dispersive materials. The most popular model to describe the material properties of human body is the Debye model. In order to simulate the computational domain as an open region for biomedical applications, the complex-frequency-shifted perfectly matched layers (CFS-PML) are applied to absorb the outgoing waves. The CFS-PML is highly efficient at absorbing the evanescent or very low frequency waves. This thesis investigates the stability of the CFS-PML and presents some conditions to determine the parameters for the one dimensional and two dimensional CFS-PML.The advantages of the FDTD method are the simplicity of implementation and the capability for various applications. However the Courant-Friedrichs-Lewy (CFL) condition limits the temporal size for stable FDTD computations. Due to the CFL condition, the computational efficiency of the FDTD method is constrained by the fine spatial-temporal sampling, especially in the simulations with the electrically small objects or dispersive materials. Instead of modifying the explicit time updating equations and the leapfrog integration of the conventional FDTD method, the spatial filtered FDTD method extends the CFL limit by filtering out the unstable components in the spatial frequency domain. This thesis implements filtered FDTD method with CFS-PML and one-pole Debye medium, then introduces a guidance to optimize the spatial filter for improving the computational speed with desired accuracy.

<p> Due to the high cost, telephone and cable television companies can only justify installing fiber optical networks to remote sites which serve up to a few hundred customers. For customers located at variable distances from the transmitting station, they will receive signals at different strengths. The signal stability and system reliability of FTTH network affected largely by the distance. We propose an effective solution for the enhancement of signal stability of FTTH network, which uses a semiconductor optical amplifier (SOA) coupled with an optical receiver.</p> <p> Before the signal reaches the optical receiver at the user end, signal strength is automatically adjusted through a semiconductor optical amplifier (SOA). Due to the special saturation property of SOA, the output optical signal will have very small fluctuation regardless the input optical signal power, the signal stability of FTTH network will be improved significantly. A set of simplified governing equations of SOA has been proposed and the corresponding numerical solver has been implemented. Although the main focus is primarily the SOA, a simplified optical receiver is also simulated, which comprises a PIN photodetector and a low pass filter (LPF). All simulations have been carried out in the time-domain with the frequency domain low pass filter modeled by a digital filter.</p> / Thesis / Master of Applied Science (MASc)

Among PWM power conversion topologies, the single-switch forward topology is the one that has been most widely used for decades. Its popularity has been based on many factors, including its low cost, circuit simplicity and high efficiency. However, several issues need to be addressed when using the forward converter such as the core reset, the voltage spikes caused by the transformer leakage inductance, and the pulsating input current waveform. The transformer is driven in a unidirectional fashion in the forward converter; a tertiary forward converter (TFC) is an example of this. Therefore, the third winding and reset diode must be provided with an adequate period of reset time so that the flux can be fully reset by the end of each switching cycle to prevent core saturation. Also, due to the utilization of a transformer, leakage inductances cannot be avoided. The energy stored in the leakage inductance during current ramp-up is not transferred to the load, and is not recovered during its discharge phase. As a result, the VDS waveform has a voltage spike and undesirable high-frequency oscillation. Therefore, a higher voltage-rating switch should be used to reduce the risk of high-voltage breakdown. Although a switch with amply high voltage ratings is available, it would tend to have a higher on-resistance, RDS(ON), resulting in increased conduction losses. Moreover, selection of a switch with higher voltage ratings than necessary may needlessly increase the cost of the design. Usually an additional circuit such as a snubber circuit or a clamp circuit or the soft-switching technique is used to absorb these voltage spikes. Consequently, the leakage inductance is intentionally minimized in the PWM power conversion technique so that it will not degrade the circuit performance. In contrast, the leakage inductance of the transformer may enhance rather than detract from circuit performance with a resonant power conversion technique. To date, however, no single-switch forward converter has been claimed to be able to enhance the converter performance with the PWM power conversion technique by utilizing the leakage inductance. Therefore, research on the utilization of the transformer leakage inductance in the PWM forward converter is needed. Two techniques, input current ripple reduction and an embedded filter, are proposed to enhance the performance of forward converter using the PWM technique. By inserting a capacitor between two primary windings of the TFC, an input current ripple reduction technique is proposed and a forward converter with ripple reduction (FRR) is presented in this research work. Because the voltage of the capacitor is clamped to input voltage, the capacitor becomes a second voltage source to share part of the load current. As a result, the input current ripple is reduced. Moreover, the capacitor voltage is clamped both at the static and dynamic states; thus the excessive voltage stress on the main switch S1 of the FAC during low-line to high-line step transient is eliminated. Furthermore, without an external LC filter, the EMI noise levels can be further reduced as a result of the embedded notch filter formed by the transformer leakage inductance and clamp capacitor if the notch frequency is designed to be the same as the switching frequency. With the help of the clamp capacitor, therefore, the leakage inductance can enhance rather than detract from the converter performance. The input current ripple can be reduced further by employing the proposed techniques. Two sets of the clamp capacitors and the leakage inductances are utilized, and the current ripple can even be cancelled if the condition is met. Consequently, the input current becomes a non-pulsating waveform and a forward converter with ripple cancellation (FRC) is presented. Moreover, without an external LC filter, the EMI noise levels can be further attenuated as a result of the embedded low-pass filter formed by the transformer leakage inductances and clamp capacitors. Again, the leakage inductance can enhance the converter performance just as the resonant converter does. In addition to providing the analysis and design procedure, this work verifies the performance of the presented converters, the FRR and the FRC, by the experimental results. By employing the proposed techniques, eight new topologies have been extended for different power conversion applications. Each member of the FRR and the FRC families is able to enhance the converter performance, in ways such as the elimination of the voltage spikes on the main switch without a snubber circuit and the improvement of the EMI performance with small filter components. Consequently, the cost can be reduced and the space of the converter can be saved. / Ph. D.

The safety concern of aging aircraft is a rising issue in terms of both safety and cost. An aircraft structure failure during flight is unacceptable. A method needs to be developed and standardized to test the integrity of both commercial and military aircrafts. The current method to test the structure of an aircraft requires the aircraft to be taken out of service for inspection; this is costly due to the inspection required to be performed and the lost use from downtime. A novice idea of an on-site structural health monitoring (SHM) system has been proposed to test the integrity of aircraft structure. An on-site system is a system that can be used to perform inspection on an aircraft simultaneously while the aircraft is in use. This SHM system uses the principles of active lamb wave and passive acoustic emission through the use of piezoelectric sensors as the sensing elements. Piezoelectric sensors can be used both as an input device and as a sensing element. This research focuses on the development of the major data acquisition electronic components of the system. These components are charge amplifier, high pass filter, low pass filter and line driver. A charge amplifier converts a high impedance signal to a low impedance signal. A high pass filter attenuates the low frequency content of a signal, while a low pass filter attenuates the high frequency content of a signal. A line driver converts a low current signal to a high current signal. All of these components need to operate up to a frequency of 2 MHz. Off-the-shelf electronics will be used for prototyping as custom components will not be feasible at this point of the research. / Master of Science