Browsing by Author "Dr. Michael B. Steer, Committee Chair"

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Analytic Models for Acoustic Wave Propagation in Air
(2008-01-07) Vetreno, JoAnna Ruth; Dr. Hamid Krim, Committee Member; Dr. Michael B. Steer, Committee Chair; Dr. Kevin Gard, Committee Member
Design and Characterization of Frequency Agile RF and Microwave Devices using Ferroelectrics
(2007-03-23) Nath, Jayesh; Dr. Gianluca Lazzi, Committee Member; Dr. Douglas W. Barlage, Committee Member; Dr. Angus I. Kingon, Committee Member; Dr. Michael B. Steer, Committee Chair
A methodology for the optimized design of tunable distributed resonators is introduced and verified. This technique enables maximum tuning with minimum degradation in quality (Q) factor. The concept of a network transformation factor and a new figure-of-merit for tunable resonators is introduced and applied to experimental data. The figure-of-merit quantifies the trade-off between tunability and Q factor for a given tuning ratio of the variable reactance device. As such, it can be extended to the design of filters, phase shifters, antennas, matching networks and other frequency-agile devices where resonant elements are used. Varactors utilizing Barium Strontium Titanate (BST) thin-film were designed and fabricated in integrated form and also in discrete form as standard 0603 components. High frequency characterization and modeling of BST varactors is described. A novel characterization technique for the intrinsic loss extraction of symmetrical two-port networks was developed and verified experimentally. Both integrated and discrete BST thin-film varactors were used to design, fabricate and characterize frequency-agile circuits. Tunable bandpass and bandstop filters and matching networks are described. A dual-mode, narrowband microstrip patch antenna with independently tunable modes was developed and characterized. Tuning and nonlinear characterization results are presented. Investigation for the use of BST thin-film varactors for voltage-controlled oscillators and phase shifters are also presented. Design parameters, fabrication issues, and processing challenges are discussed.
Implementation of Microwave Measurements Using Novel Calibration Techniques
(2003-05-19) Goswami, Aditya; Dr. Michael B. Steer, Committee Chair; Dr. Douglas Barlage, Committee Member; Dr. Griff Bilbro, Committee Member
NetA (Network Analysis) tools for calibration of microwave measurements has been implemented. NetA contains calibration and de-embedding procedures as data analysis MATLAB routines. The Through Line method for calibration of two ports has been used and the NetA process flow has also been explained. Complex characteristic impedance of the micro-strip transmission line has been calculated using the ETRL (Enhanced TRL)technique. Results have been simulated using NetA tools. A LabVIEW Implementation of NetA has also been implemented so as to enhance the usability of NetA and also provide the capability of Real--time microwave calibration and de-embedding.
An Integrated Tool For High Speed Circuits with Substrate Coupling.
(2003-06-04) Bollapragada, Rajesh; Dr. Michael B. Steer, Committee Chair; Dr. Douglas W. Barlage, Committee Member; Dr. Rhett W. Davis, Committee Member
An integrated environment for layout-oriented design of circuits for spatial power combining system is aimed in this study. The simulation environment would include a full-wave electromagnetic simulator and a circuit simulator, fREEDA, with a front engine, which is the major emphasis in this document. fREEDA implements local reference node instead of a global ground and this is crucial for distributed circuits. The models are implemented in object-oriented fashion and uses automatic differentiation. The same model can be used for DC, transient and harmonic balance analysis.
Integration of Interconnect Models in a Circuit Simulator
(2003-01-22) Mohan, Ramya; Dr. Gianluca Lazzi, Committee Member; Dr. Michael B. Steer, Committee Chair; Dr. Zhilin Li, Committee Member
A novel approach is implemented for synthesizing equivalent circuits. The approach called the Foster's approach finds its application in the transient simulation of distributed structures. The implementation is analogous to that of a Voltage Controlled Current Source, as it is a natural way to handle Admittance Matrix. The two main features of this method are its guaranteed causality and good numerical stability. The method is tested by simulating a six port power/ground plane and comparing the results with measurements. Also, different analyses types are compared and conclusions are made.
Investigation of Interconnect Characteristics in Mixed Signal Circuits
(2003-06-03) Gothi, Kuldip Shukdevbhai; Dr. Griff Bilbro, Committee Member; Dr. Gianluca Lazzi, Committee Member; Dr. Michael B. Steer, Committee Chair
Up to the early 1990s on chip digital signals had components much below 1 GHz,relatively short run lengths and widths of several microns. This situation has changed because of three main developments, primarily for digital circuits, but affecting analog circuitry because of the rise of mixed signal systems. The main developments are faster clocks, longer interconnect and fine lithography leading to interconnects having cross sectional dimensions of less than a micron. Planar structures such as microstrip lines are assuming very important role in the design of MICs and mixed signal circuits. Various design formulas for microstrip lines are investigated in this thesis. These formulas can be evaluated quickly and provide a designer with an intuitive feel for the various design parameters for microstrip lines. Various analytical formulas for microstrip dispersion are also compared with simulated results. Electromagnetic modeling tool from Sonnet® is used for high frequency electromagnetic analysis.
The Performance of Passive Lumped Element
(2010-04-30) Heo, Seung Kyun; Dr. Michael B. Steer, Committee Chair; Dr. David Schurig, Committee Member; Dr. Paul D Franzon, Committee Member
Lumped elements are the most widely used passive components in Radio Frequency (RF) circuits. The characteristics variation over change in frequency, however, limits their application. This limitation stems from the physical dimensions of lumped elements, which are, in general, 0603, 0402, and 0201 size in order to avoid the phase shift between the input and the output. By examining the Quality Factor (Q) and Self-Resonant Frequency (SRF), the performance of lumped elements can be determined. The quality factor contains the energy storing and dissipation terms, which vary according to frequency. This quality factor can be obtained using the S-parameters of lumped elements. It is difficult to obtain accurate measurement of a non-coaxial package device such as a lumped inductor, because it cannot be measured using a calibrated measurement system. A Print Circuit Board (PCB) fixture is thus considered to connect a Device Under Test (DUT) to 50 ohm connectors, and the effects of the fixture are then removed by performing a user fixture standards calibration. The combination of a port extension and calibration using a manufacturerâ€™s calibration kit is employed to collect one-port S-parameters. The best result is achieved using a SubMiniature version A (SMA) fixture that has a short line and good impedance matching This thesis presents an extraction method to derive the quality factor of lumped elements, and the quality factor is obtained using one-port S-parameters.
Transient Electrothermal Modeling of Digital and Radio Frequency Circuits.
(2006-08-24) Luniya, Sonali R.; Dr. Michael B. Steer, Committee Chair; Dr. Kevin G. Gard, Committee Member; Dr. Paul D. Franzon, Committee Member; Dr. Rhett Davis, Committee Member
Simulator technology for the high dynamic range, electrothermal modeling of electronic circuits is developed and applied to digital, radio frequency (RF) and microwave circuits. High-dynamic range is achieved using a combination of device models based on state-variables and utilizing automatic differentiation, precise error determination, and time step control. State-variables enable simpler and faster development of models less prone to implementation error. Automatic differentiation yields error free evaluation of the derivatives of circuit quantities with respect to each other and so removes any uncertainty in establishing the precise circuit condition. In transient analysis precise error determination and time step control is achieved by comparing two nonlinear solutions at each time point. A two-tone test of an X-band GaAs MESFET MMIC (Gallium Arsenide, Metal Semiconductor Field Effect Transistor Monolithic Microwave Integrated Circuit) was used to investigate and validate dynamic range. In the determination of the third-order intermodulation product in a two tone test a dynamic range of 165 dB was demonstrated. This high dynamic range was achieved through precise evaluation of the derivatives, accurate time step control and the circuit state, which is important in long electrothermal transient simulations. This minimization of accumulated numerical error is especially important in long electrothermal transient simulations. The 3D compact thermal models of the X-band MMIC LNA developed were verified with thermal images of the MMIC LNA taken with an infra red camera. The thermal models predict the temperature rise on various spots of the MMIC with less than 5% error. To perform an coupled electrothermal simulation at RF frequencies, a linear RC network based thermal macromodel of the MMIC was developed. The high dynamic range capability helped detect the small changes in the output voltage of the MMIC, at elevated temperatures. This thermal macromodel was applied to electrothermal simulations of an 3D thermal test chip designed with a 0.18 um Fully Depleted Silicon on Insulator (FDSOI) MOSFET (Metal Oxide Semiconductor Field Effect Transistor) technology. An experimentally validated state-variable based electrothermal model of a 0.18 um FDSOI MOSFET is implemented.