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Independent Studies on Special Topics

Independent Studies:


Microwave FET Modeling
Project Assistant :   Scarlet Halabi
Project Director  :   Dr. Prasad Shastry
2002
This project was supported by a research grant from Fujitsu Compound Semiconductor, Inc.

ABSTRACT
   In this project, microwave transistor modeling is presented. This project involves the measurement procedures (i.e. measured DC and RF characteristics of the device), the parameter extraction of the model using the measured values, the design of model validation by comparing the measured data with the modeled data, as well as parameter optimization needed. Finally, a flow chart shows a summary of the modeling technique presented in this project.

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Transimpedance Amplifiers for Optoelectronic Applications
Project Assistant :   Shawn Parker
Project Director  :   Dr. Prasad Shastry
December 2000
This project was supported by a research grant from Fujitsu Compound Semiconductor, Inc.

ABSTRACT
   The optoelectronic field deals with the transition between optical and electrical components. Transimpedance amplifiers are used in optoelectronic applications. The optoelectronic conversion deals with two fundamental specifications that are used to define the term "Transimpedance Amplifiers". The optical devices generally have input impedances that vary significantly from the impedance levels encountered in RF/microwave circuits.
   The term transimpedance amplifier can be defined as an amplifier that provides gain and an impedance transformation. Bandwidth is a high priority in transimpedance amplifiers. These amplifiers have to maintain an acceptable response down to very low frequencies and still perform satisfactorily at high frequencies.
   Conventional amplifiers have been designed for transimpedance applications to provide the necessary bandwidth for high data rates. Optical devices typically have low input impedances.
   The distributed amplifier can meet the challenge of matching, and providing gain between these two very different impedance levels over an extremely wide bandwidth. The ability of the distributed structure in a distributed amplifier to provide extremely wideband matching is dependent on the gain cell.
   The constraints in the design of distributed transimpedance amplifier are the device characteristics and the biasing networks. Biasing networks are an extremely important part of the design. The biasing network could limit the low frequency response of the amplifier.

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Wide-Band Impedance Transformation Techniques
Project Assistant :   Shawn Parker
Project Director  :   Dr. Prasad Shastry
December 2000
This project was supported by a research grant from Fujitsu Compound Semiconductor, Inc.

ABSTRACT
   Impedance matching problems are encountered involved in most RF circuit designs. Impedance matching techniques can be divided into two categories: Narrow-band matching techniques and Wide-band matching techniques.
   This study focuses on wide-band matching techniques. The wide-band impedance matching techniques are significantly more compled than the narrow-band techniques. To fully understand wide-band impedance matching requires years of dedicated study. However, a designer can, in a shorter period, understand the principles of wide-band impedance matching. To understanding of the principles is adequate to intelligently utilize the impedance matching software packages.
   A summary of wide-band impedance matching techniques is provided in this report. The limits of the Bode-Fano criteria are presented to provide an understanding of the performance limits of a matching network. Two wide-band impedance matching techniques are presented. Both, the Real Frequency Technique (RFT), and the Q-Transform Technique (QTT) are used to design wide-band impedance matching networks. Examples of networks designed using each technique are presented and evaluated. The realizability of the networks is also discussed.

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Introduction to MMIC Design; MMIC Technology: Processing, Modeling and Component Design
Project Assistant :   Scarlet Halabi
Project Director  :   Dr. Prasad Shastry
December 2000
This project was supported by a research grant from Fujitsu Compound Semiconductor, Inc.

ABSTRACT
   The processes of fabricating GaAs MMICs are described in Chapter 1. Several options are described for each step in the process along with their advantages and disadvantages. The design of the MMIC is shown to be limited by the process technology that is available. The understanding of each process step leads to appropriate design considerations for the designer of GaAs MMICs.
   The fundamental information for MESFETs, HEMTs, and HBTs is reviewed in Chapter 2. The principles of operation of each device are described. The advantages and disadvantages as well as applications and limitations for each device are discussed. A comparative study of the different device models is included, and a study of the figures of merit is reported.
   The designs and simulations of a coupled line directional coupler and a square spiral inductor are presented in Chapter 3.

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MMIC Technology: Processing, Modeling and Layout
by :   Sasidhar Vajha
Advisor  :   Dr. Prasad Shastry
August 2000

ABSTRACT
   MMIC design Technology is presented in this report. Various linear and nonlinear models of popular microwave transistors (MESFETs, HEMTs, and HBTs) are presented in Chapter 2. Chapter discusses the design, implementation, and simulation of common MMIC components used in the circuits. All the designs are simulated using HP-ADS.

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PCS CDMA Receiver Front-End
by :   Sameer Naik
Advisor  :   Dr. Prasad Shastry & Dr. In Soo Ahn
August 1999

ABSTRACT
   With cellular networks in the 800-900MHz band reaching capacity limits, PCS(1800-1900MHz) is proving to be the best alternative for cellular operators. Spread Spectrum, CDMA (Code Division Multiple Access) enables one to incorporate many users within a relatively wide bandwidth. The intent of the Phase I of the project was to design, construct and test the subsystems for CDMA Receiver Front-End in the PCS band. The goal of the project was to transmit a CDMA signal from a transmitter (base station) and retrieve the information at the receiver. Another goal for this project was to design a duplexer as a part of the subsystem, fabricate and test the duplexer for its performance in the PCS band.
   The CDMA signal was transmitted at 1.93 GHz from a transmitter, and received at the receiver end. The signal was then passed through a duplexer, and a low noise amplifier. The CDMA signal was then downconverted to an IF frequency of 210 MHz. Further, the signal was amplified (with an automatic gain control) and demodulated to a baseband signal. The design and performance characteristics of the receiver front-end are presented in this report.

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MMIC Technology : Processing, Modeling and Layout
by :   Shawn Parker
Advisor : Dr. Prasad Shastry
May 1999

ABSTRACT
   The process of fabricating GaAs MMICs is described in this report. Several options are described for each step in the process along with their advantages and disadvantages. The design of the MMIC is shown to be limited by the process technology that is available. The understanding of each process step leads to appropriate design considerations for the designer of GaAs MMICs. The fundamental information for MESFETs, HEMTs, and HBTs is reviewed. The design and layout of a microstrip inductor and coupled line filter are presented to illustrate the design of layouts.

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MMIC Technology : Processing, Modeling and Layout
by :   Edward Cullerton
Advisor : Dr. Prasad Shastry
May 1998

ABSTRACT
   The process of fabricating GaAs MMICs is described in this report. Several options are described for each step in the process along with their advantages and disadvantages. The design of the MMIC is shown to be limited by the process technology that is available. The understanding of each process step leads to appropriate design considerations for the designer of GaAs MMICs.
   The fundamental information for MESFETs, HEMTs, and HBTs is reviewed. The design and layout of a microstrip inductor and coupled line filter are presented to illustrate the design of layouts.

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Microwave Planar Antennas And Transmission Lines
by :   Mahmoud Basraoui
Advisor : Dr. Prasad Shastry
May 1994

ABSTRACT
   This report is the result of a research project regarding planar transmission lines and planar antennas. The purpose of this report is to present the reader with the underlying information of planar structures that are well under use in microwave integrated circuits. Analysis, modelling, and design are important for any subsystem development. Useful design approaches and various aspects of planar transmission lines can be accessed from part one of this report. As well, design approaches and various information regarding planar antennas can be found in part two. The topic of antenna array systems is discussed in the last chapter of part two. Two types of transmission lines were designed experimentally, and information regarding the measurements as well as antenna measurements are included in the appendix.

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Microwave Transistors and Circuit Applications
by :   G.Brubaker
Advisor : Dr. Prasad Shastry
December 1993

ABSTRACT
   This paper presents linear and non-linear device models used to simulate the behaviour of MESFETs, HEMTs, and HBTs. Applications of the models are shown for amplifier design. Other microwave circuits are shown where models are used to simulate their behaviour.

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MMIC Technology : Processing, Layout Design and Packaging
by :   G.Brubaker
Advisor : Dr. Prasad Shastry
August 1993

ABSTRACT
   In this special topics course, the student is expected to learn GaAs MMIC layout design skills using EEsof CAE tools as well as obtain the knowledge on GaAs MMIC processing and packaging techniques by reading published material on the subject.
   Learning the layout design skills will involve working on selected MMIC layout design projects. Exposure to GaAs MMIC processing and packaging techniques will involve studies of published books and papers on the subject matter. The student is expected to keep a good record of his work. The student is expected to confer with the instructor at least once a week and report on the progress being made until the course in completed. The student is expected to: Give 3 seminar talks one each, on layout design, processing and packaging at the end of the course. Submit a report at the end of the course encompassing the topics covered by the course.

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Microwave Antenna Measurements
by :   Mahmoud Basraoui
Advisor : Dr. Prasad Shastry
December 1993

ABSTRACT
   Antennas serve as critical interface between hardware and space, and evaluating their performance requires a combination of optical, mechanical, and electronic techniques. In this report, Test procedures for the measurement of antenna properties operating in the "microwave" region will be investigated. The parameters commonly of interest to describe an antenna system's performance are polarization, the pattern (amplitude and phase), gain, beam direction, efficiency, null depth, impedance, and reflection coefficient or the voltage standing wave ratio (VSWR) and current distribution. Ranges used for measurements are outdoor ranges (evaluated and ground) and indoor ranges (anechoic chamber and near-field). The experimental results found using the test procedures are needed to validate the theoretical data.

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Wideband Microwave Distributed Circuits Analysis and Design
by :   G. Brubaker
Advisor : Dr. Prasad Shastry
May 1992

ABSTRACT
   This paper presents distributed paraphase amplifier, oscillator circuit based on distributed topology, distributed mixer circuit, circulator/transmit-receive module based on distributed topology, noise considerations in distributed amplifiers, power and efficiency considerations in distributed amplifiers, cascode distributed amplifiers, band-pass distributed amplifiers, dual-gate distributed amplifiers and wideband power dividers and combiners.

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Bandpass Distributed Amplifier Design guidelines
by :   Ashok Kumar Kajjam
Advisor : Dr. Prasad Shastry
December 1991

ABSTRACT
   In this report, GaAs FET Band-pass Distributed Amplifier design guidelines are presented. The report focuses on fundamental design considerations. The design approach presented enables one to examine the trade-offs between variables and arrive at the appropriate design for a specified gain and band-width. The analysis enables the designer to predict the gain of the amplifier form the design curves for a given number of devices. The 3-db bandwidth of the amplifier can be determined form the Normalized Frequency response curve.

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Design Considerations for Achieving Optimum Gate Voltages in Distributed Amplifiers
by :   Srinivas Reddy Ponnala
Advisor : Dr. Prasad Shastry
December 1991

ABSTRACT
   This paper presents a report on the design considerations for achieving optimum gate voltages in Distributed Amplifiers. The analysis is carried out for an exponential distribution of series capacitors in the gate-line. This results in an increased gate voltage excitation till the last device as compared to an uniform distribution of series capacitors.

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