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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
191

Integrated Circuit and Antenna Technology for Millimeter-wave Phased Array Radio Front-end

Nezhad Ahmadi Mohabadi, Mohammad Reza January 2010 (has links)
Ever growing demands for higher data rate and bandwidth are pushing extremely high data rate wireless applications to millimeter-wave band (30-300GHz), where sufficient bandwidth is available and high data rate wireless can be achieved without using complex modulation schemes. In addition to the communication applications, millimeter-wave band has enabled novel short range and long range radar sensors for automotive as well as high resolution imaging systems for medical and security. Small size, high gain antennas, unlicensed and worldwide availability of released bands for communication and a number of other applications are other advantages of the millimeter-wave band. The major obstacle for the wide deployment of commercial wireless and radar systems in this frequency range is the high cost and bulky nature of existing GaAs- and InP-based solutions. In recent years, with the rapid scaling and development of the silicon-based integrated circuit technologies such as CMOS and SiGe, low cost technologies have shown acceptable millimeter-wave performance, which can enable highly integrated millimeter-wave radio devices and reduce the cost significantly. Furthermore, at this range of frequencies, on-chip antenna becomes feasible and can be considered as an attractive solution that can further reduce the cost and complexity of the radio package. The propagation channel challenges for the realization of low cost and reliable silicon-based communication devices at millimeter-wave band are severe path loss as well as shadowing loss of human body. Silicon technology challenges are low-Q passive components, low breakdown voltage of active devices, and low efficiency of on-chip antennas. The main objective of this thesis is to investigate and to develop antenna and front-end for cost-effective silicon based millimeter-wave phased array radio architectures that can address above challenges for short range, high data rate wireless communication as well as radar applications. Although the proposed concepts and the results obtained in this research are general, as an important example, the application focus in this research is placed on the radio aspects of emerging 60 GHz communication system. For this particular but extremely important case, various aspects of the technology including standard, architecture, antenna options and indoor propagation channel at presence of a human body are studied. On-chip dielectric resonator antenna as a radiation efficiency improvement technique for an on-chip antenna on low resistivity silicon is presented, developed and proved by measurement. Radiation efficiency of about 50% was measured which is a significant improvement in the radiation efficiency of on-chip antennas. Also as a further step, integration of the proposed high efficiency antenna with an amplifier in transmit and receive configurations at 30 GHz is successfully demonstrated. For the implementation of a low cost millimeter-wave array antenna, miniaturized, and efficient antenna structures in a new integrated passive device technology using high resistivity silicon are designed and developed. Front-end circuit blocks such as variable gain LNA, continuous passive and active phase shifters are investigated, designed and developed for a 60GHz phased array radio in CMOS technology. Finally, two-element CMOS phased array front-ends based on passive and active phase shifting architectures are proposed, developed and compared.
192

Fast Methods for Millimeter-wave Dielectric Resonator and Antenna Analysis and Design

Chen, Huanyu January 2009 (has links)
Ever-increasing interest in millimeter-wave and terahertz spectrum has prompted research and development of novel passive components working at these frequencies. Compared with the conventional planar components, non-planar dielectric devices become more attractive as frequencies increase due to their higher quality factors and dimensional tolerances. In this thesis, we present fast methods to analyze the millimeter-wave dielectric resonator and rod antenna. First, an analytical method has been developed to evaluate resonant frequencies, quality factors of the Whispering Gallery Mode (WGM) disk resonators and also the resonator-waveguide coupling. A numerical solver based on full-wave finite element method is implemented to verify the analytical result. This analytical model provides a solution for fast design and optimization of WGM resonators in filter and sensor applications. Secondly, a fast analytical approach based on local mode theory is introduced to calculate the radiation from tapered dielectric rod antenna. This efficient approximate model consumes much less computing resources and time, and demonstrates good agreements with full-wave numerical results. It supplies a quantitative way to understand the radiation mechanism and interaction between different parts of the antenna. Based on this, design criteria for the taper profile of rod antennas are given.
193

Design of a Cylindrical Cavity Resonator for Measurements of Electrical Properties of Dielectric Materials

Li, Xiang, Jiang, Yan January 2010 (has links)
In microwave communications, the main aspects for affecting the dielectric losses in the materials are relating to the dielectric properties and the radiation frequencies. Normally, the different dielectric materials will lead to the different losses and reflections for microwave frequencies. To evaluate the dielectric properties from the different materials plays an essential role in the microwave engineering. There are many approaches can be used to measure the dielectric materials, e.g. capacitor methods, transmission line methods, cavity resonator methods, open cavity methods and so on. The cavity resonator method is one of the most popular ways for measuring the dielectric materials. In this thesis, some of the techniques will be reviewed, and the TM010 mode cylindrical cavity resonator with perturbation technique will be used for determining the dielectric properties. The design and measurements will be presented in both simulations and practice. With 1.2GHz cavity resonator, in the simulations, the dielectric permittivity for Teflon is measured as 2.09-0.0023i and 2.12-0.0116 in copper cavity and ferromagnetic cavity. Finally the sample is measured as 3.83-0.12i in practice.
194

Pulse Modulated Transmitter Architectures : Carrier Bursting

Chani Cahuana, Jessica Adaid January 2012 (has links)
No description available.
195

Fast Methods for Millimeter-wave Dielectric Resonator and Antenna Analysis and Design

Chen, Huanyu January 2009 (has links)
Ever-increasing interest in millimeter-wave and terahertz spectrum has prompted research and development of novel passive components working at these frequencies. Compared with the conventional planar components, non-planar dielectric devices become more attractive as frequencies increase due to their higher quality factors and dimensional tolerances. In this thesis, we present fast methods to analyze the millimeter-wave dielectric resonator and rod antenna. First, an analytical method has been developed to evaluate resonant frequencies, quality factors of the Whispering Gallery Mode (WGM) disk resonators and also the resonator-waveguide coupling. A numerical solver based on full-wave finite element method is implemented to verify the analytical result. This analytical model provides a solution for fast design and optimization of WGM resonators in filter and sensor applications. Secondly, a fast analytical approach based on local mode theory is introduced to calculate the radiation from tapered dielectric rod antenna. This efficient approximate model consumes much less computing resources and time, and demonstrates good agreements with full-wave numerical results. It supplies a quantitative way to understand the radiation mechanism and interaction between different parts of the antenna. Based on this, design criteria for the taper profile of rod antennas are given.
196

A Large-Stroke Electrostatic Micro-Actuator

Towfighian, Shahrzad January 2010 (has links)
Parallel-plate electrostatic actuators driven by a voltage difference between two electrodes suffer from an operation range limited to 30% of the gap that has significantly restrained their applications in Microelectromechanical systems (MEMS). In this thesis, the travel range of an electrostatic actuator made of a micro-cantilever beam electrode above a fixed electrode is extended quasi-statically to 90% of the capacitor gap by introducing a voltage regulator (controller) circuit designed for low frequency actuation. The developed large-stroke actuator is valuable contribution to applications in optical filters, optical modulators, digital micro-mirrors and micro-probe based memory disk drives. To implement the low-frequency large-stroke actuator, the beam tip velocity is measured by a vibrometer, the corresponding signal is integrated in the regulator circuit to obtain the displacement feedback, which is used to modify the input voltage of the actuator to reach a target location. The voltage regulator reduces the total voltage, and therefore the electrostatic force, once the beam approaches the fixed electrode so that the balance is maintained between the mechanical restoring force and the electrostatic force that enables the actuator to achieve the desired large stroke. A mathematical model is developed for the actuator based on the mode shapes of the cantilever beam using experimentally identified parameters that yields good accuracy in predicting both the open loop and the closed loop responses. The low-frequency actuator also yields superharmonic resonances that are observed here for the first time in electrostatic actuators. The actuator can also be configured either as a bi-stable actuator using a low-frequency controller or as a chaotic resonator using a high-frequency controller. The high-frequency controller yields large and bounded chaotic attractors for a wide range of excitation magnitudes and frequencies making it suitable for sensor applications. Bifurcation diagrams reveal periodic motions, softening behavior, period doubling cascades, one-well and two-well chaos, superharmonic resonances and a reverse period doubling cascade. To verify the observed chaotic oscillations, Lyapunov exponents are calculated and found to be positive. Furthermore, a chaotic resonator with a quadratic controller is designed that not only requires less voltage, but also produces more robust and larger motions. Another metric of chaos, information entropy, is used to verify the chaotic attractors in this case. It is found that the attractors have a common information entropy of 0.732 independent of the excitation amplitude and frequency.
197

Magnetic Transduction for RF Micromechanical Filters

Forouzanfar, Sepehr 21 February 2012 (has links)
The use of electrostatic transduction has enabled high-Q miniaturized mechanical resonators made of non-piezoelectric material that vibrate at high and ultra high frequencies. However, this transduction technique suffers from large values of motional resistance associated with the technique, limiting its use for interfacing to standard 50 RF circuits. Piezoelectric transduction has advantages over the electrostatic method because of its comparable to 50 motional resistance. However, the technique requires use of thin film piezoelectric materials with the demonstrated Qs that are much lower than their corresponding non-piezoelectric resonators. This research proposes use of electrodynamic transduction, reports analytic and experimental studies on electrodynamic transduction for RF application, highlights the method’s advantages, and lists the contributions. The use of Lorentz-force transduction for RF micromechanical filters proposed in this work is pursued by experimentally evaluating the transduction technique implemented for microfabricated designs. By fabricating single and coupled microresonators in a few different fabrication technologies, including CMOS35, the performance of the Lorentz-force driven microresonators is studied. Using a laser vibrometer, the actual performance, including the displacement and velocity of the moving points of the microstructures’ surfaces, are measured. The mode shapes and resonance specifications of the microstructures in air and vacuum derived by laser vibrometer provide data for characterizing the employed Lorentz-force transduction technique. Furthermore, the results from the electrical measurements are compared to the micromechanical resonators’ frequency response obtained from the mechanical measurements by laser vibrometer. The significantly low values of motional resistance computed for the differently fabricated designs demonstrate the advantage of Lorentz-force transduction for RF filter applications. Should a device similar in size be driven electrostatically, the motional resistance would be multiple orders of magnitude higher. This research reports the experimental results obtained by examining a Lorentz- force transduction application for developing RF micromechanical filters. The results demonstrate the Lorentz-force transduction’s advantages over other transduction methods used for RF μ-mechanical filters. Compared to electrostatic transduction, the Lorentz-force method provides greater electromechanical coupling, multiple orders of magnitude lower motional resistance, the independence of the filter center frequency from the bias voltage, higher power handling, and no requirement for bias lines, which decreases the work in microfabrication. Unlike piezoelectric transduction, the electrodynamic technique requires no piezoelectric material. Use of non-piezoelectric materials provides more flexibility for resonator material in the IC-compatible fabrications. Power handling in electrodynamic transduction has fewer limitations than other transduction techniques because the higher power needed in electrostatic or piezoelectric methods requires a higher voltage, which is limited by the breakdown voltage. The higher power in Lorentz-force-based transduction demands a larger current. The larger current produces heat that is removable by applying an appropriate cooling technique.
198

Study of Stepped Impedance Resonator on Microwave Filter Components

Chang, Yu-Chi 24 June 2011 (has links)
This dissertation divides into three parts: (a) design and research of asymmetric stepped impedance resonator (SIR); (b) design and fabrication of dual-band and ultra-wide band (UWB) bandpass filters (BPFs) and (c) design and fabrication of millimeter wave filters. (a)design and research of asymmetric stepped impedance resonator. In the first part of the dissertation, we propose an asymmetric SIR, and the effect of electrical length ratio and impedance ratio on the performance of frequency has been discussed in detail. The insertion loss and spurious can be controlled by the structural parameters of asymmetric SIR which decreases the length of resonator effectively and achieves the reduction of whole size. Additionally, this characterization of the asymmetric SIR can be extensively applied on the interconnection of RFIC. (b) design and fabrication of dual-band and ultra-wide band (UWB) filters. In the second part of the dissertation, we propose dual-band and UWB BPFs by using asymmetric SIRs. The designed dual-band BPF is conformed to the standard of wireless local area network (WLAN), and the designed UWB BPF is conformed to the standard that Federal Communications Commission (FCC) defined. The structural parameters of asymmetric SIR can be adjusted accurately by the theoretical equations we calculated. Then, the ideal performance can be achieved. (c) design and fabrication of millimeter wave filters. In the third part of the dissertation, we propose the design of millimeter wave filters fabricated by the standard of complementary metal-oxide semiconductor (CMOS). Asymmetric SIRs are used to design the microwave filter to estimate that the feasibility of system on chip (SoC). Finally, some suggestions are made in the future work on technology for system on chip (SoC).
199

Distributed Feedback and Feedforward of Discrete-Time Sigma-Delta Modulator

Chiu, Jih-Chin 23 July 2012 (has links)
This paper presents a distributed feedback and feedforward of discrete-time delta sigma modulator applications in the radio. We know the delta-sigma modulator using oversampling and noise shaping technique, thus we can relax the specifications of the components. This paper described the architectural differences and compare, the in-band signal is less sensitive to noise interference, and improve the resolution of the circuit. In the resonator, a simple structure with a small number of capacitor in resonator circuit. This paper uses the TSMC 0.18£gm process parameters to the simulation, implementation, and measurement. Our fourth-order discrete-time delta-sigma modulator specifications as follows: the input signal frequency is 10.7MHz, the sampling frequency is 42.8MHz, the signal bandwidth is 200kHz, oversampling rate is 107, and one bit quantizer.
200

Study on the Dielectric Properties of Organic/Inorganic Composites with the Development of Measurement Method

Wu, Chia-Ching 05 August 2009 (has links)
Polyetherimide/(Ba0.8Sr0.2)(Ti0.9Zr0.1)O3 (PEI/BSTZ8291) composites are fabricated using PEI, dispersant, solvents, and BSTZ powder. The effects of the content of BSTZ8291 filler on the chemical, physical, mechanical and dielectric properties of PEI/BSTZ8291 composites are studied in this paper. As the content of BSTZ filler increases from 10 wt% to 70 wt%, the relative permittivity of PEI/BSTZ8291 composites at 1 MHz increase from 2.58 to 17.71. The measurement of relative permittivity of PEI/BSTZ8291 composites is developed using the ¡§Rectangular Cavity Resonator¡¨ method from 1 GHz to 13.5 GHz. The relative permittivity is calculated by observing the frequencies of resonant cavity modes. The relative permittivity of PEI/BSTZ8291 composites is almost unchanged as the measured frequency increases from 1 GHz to 13.5 GHz. The presented characteristics are better than those of polymer/BaTiO3 composites. The improvement in the tensile strength of PEI/BSTZ8291 composites may be caused by the increased interactions between neat PEI and BSTZ8291 ceramic powder, and no phase separation phenomenon occurred. The Young¡¦s modulus of the PEI/BSTZ8291 composites is improved by about 58% as the content of BSTZ8291 filler from 0 to 50 wt% and the elongation at break of the composites decreases as the content of BSTZ8291 filler increases, indicating that the composite becomes somewhat brittle as compared with neat PEI. PEI/BSTZ8291 composite substrates are developed for the applications of circularly polarized (CP) antennas. A CP antenna with a simple structure is developed as the ultra high frequency (UHF) band radio frequency identification (RFID) reader application. The fabricated antenna has an impedance bandwidth spanning from 901 to 949 MHz, which covers the entire band of Taiwan UHF-RFID frequency. The measured return loss, Smith chart, axial ratio, radiation patterns and CP gain characteristics of antennas fabricated on PEI/BSTZ8291 composites are excellent in the band of Taiwan UHF-RFID frequency. It is demonstrated that the CP antenna fabricated on PEI/BSTZ substrate has the better characteristics and small size than those fabricated on FR4 substrate.

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