College of Graduate and Postdoctoral Studies
http://hdl.handle.net/10388/380
Sun, 09 Dec 2018 09:03:10 GMT2018-12-09T09:03:10ZADAPTIVE LINEARIZATION OF EFFICIENT HIGH POWER AMPLIFIERS USING POLYNOMIAL PREDISTORTION WITH GLOBAL OPTIMIZATION
http://hdl.handle.net/10388/11615
ADAPTIVE LINEARIZATION OF EFFICIENT HIGH POWER AMPLIFIERS USING POLYNOMIAL PREDISTORTION WITH GLOBAL OPTIMIZATION
Analog frequency modulation (FM) or nearly constant envelope digital modulation schemes are used for most of the present generation mobile radio systems. Because of the almost constant envelope property, a high power-efficient nonlinear amplifier can be used for such systems. However, since high demand for cellular systems will lead to spectrum congestion, spectrally efficient linear modulation methods such as quadrature amplitude modulation (QAM) have been proposed for the future mobile radio systems. As these modulation methods are linear in nature, amplification must also be linear. Linear power amplifiers have poor power efficiency and are unsuitable for mobile transceivers where battery power must be conserved. To achieve both linearity and power efficiency, an efficient high power nonlinear amplifier must be linearized; predistortion is an effective technique for linearizing transmitter power amplifiers. Two types of predistortion linearizers, namely, the lookup table predistorter, and the polynomial
predistorter, have been reported in the literature. Polynomial predistorters have an advantage over lookup table predistorters, however, those reported in the past are limited to a polynomial of the fifth order, because of optimization problems, and only power amplifiers with nonlinearities of fifth order or less can be linearized using such linearizers.
Different types of polynomial predistortion linearizers are proposed in this thesis. Important features of these linearizers are: objective functions of quadratic shape are used for optimization, circuit imperfections can be compensated adaptively, the order of the predistorter is not limited to the fifth, and they are not limited to power amplifiers with fifth order nonlinearities.
First, an adaptive linearizer with amplitude and phase control circuits is introduced. The amplitude and phase control signals are generated using gain and phase polynomial functions. The power amplifier input and output signals are demodulated and used for optimizing the predistorter polynomial coefficients. The recursive least squares algorithm is employed for the optimization process. This linearizer, however, does not compensate for the predistorter and demodulator imperfections. A modified version of this linearizer is proposed which can compensate for imperfections adaptively. In this linearizer, the power amplifier output signal is demodulated using the predistorter input signal and the predistorter and demodulator imperfections are estimated by sampling the demodulated signals after updating the predistorter coefficients. The results of computer simulation show that the proposed linearizers are effective in compensating the amplifier nonlinearities, even in the presence of circuit imperfections. Spectrum spreading improvement of 52 dB is achieved at the edge of the filtered band after 60 iterations.
Next, an adaptive predistortion linearizer with a complex quadrature modulator is proposed. This linearizer has less circuit complexity than the one with amplitude and phase control circuits. A polynomial postdistorter is employed in the adaptation algorithm for optimizing the predistorter coefficients. Using this linearizer , spectrum spreading is improved by 50 dB at the filtered band edge after 600 iterations, in the presence of circuit imperfections. A modified version of this linearizer with convergence faster by an order of magnitude, is proposed.
It is shown that the spectral performance of the polynomial linearizer degrades rapidly near saturation. A new nonlinear function for the predistorter gain functions is proposed. Using this function, the power amplifier is linearized almost up to its saturated output power, and out-of-band power spectral density of 88 dB below that at the bandpass center frequency is achieved.
Tue, 01 Nov 1994 00:00:00 GMThttp://hdl.handle.net/10388/116151994-11-01T00:00:00ZINVESTIGATIONS OF MICROSTRIP PERIODIC STRUCTURES
http://hdl.handle.net/10388/11614
INVESTIGATIONS OF MICROSTRIP PERIODIC STRUCTURES
Periodic structures are used as microwave filters because of their inherent passband-stopband
characteristics. The structure exhibits alternative passbands and stopbands. The widths and positions of the passbands and stopbands are changed with the parameters of the structure. The analysis of non-planar periodic structure filters are well documented in the literature. Recently, investigations of these structures in the microstrip configuration have also been reported. The structures under consideration in the past investigations were microstrip lines with sinusoidally varying width and triangularly width modulated microstrip lines.
The work reported in this thesis is an investigation of microstrip periodic structures with rectangular and circular geometries. Closed form expressions for the ABCD parameters of a structure with N unit cells are derived. The input-output characteristics of the structures are very similar to a bandpass/bandstop filter. The design procedure for a periodic structure bandpass filter is presented. Bandpass filters are designed and fabricated. Theoretical results show agreement well with the measurement. The variations of the bandwidth and center frequency with the dimensions of the structures are studied.
Thu, 01 Nov 1990 00:00:00 GMThttp://hdl.handle.net/10388/116141990-11-01T00:00:00ZRECOGNITION OF COMPLEX TWO-DIMENSIONAL SHAPES USING GEOMETRIC PRIMITIVES AND THE HOUGH TRANSFORM
http://hdl.handle.net/10388/11613
RECOGNITION OF COMPLEX TWO-DIMENSIONAL SHAPES USING GEOMETRIC PRIMITIVES AND THE HOUGH TRANSFORM
The Hough Transform is a widely researched area of computer vision due to its unique promise for shape analysis in digital images. The Hough Transform is a robust technique for detection of geometric primitives in the presence of noise and partial occlusion.
The shortcomings of the Hough Transform include its high computational complexity and excessive storage requirements. Every year there are many new techniques proposed as improvements to the Hough Transform or any existing Hough techniques.
Complex objects can be decomposed into sub-objects, and sub-objects into further sub-objects. This decomposition can continue until geometric primitives are reached. For object recognition in digital images, lines are the lowest primitive constructed from the digital (pixel) information, and can then be used to construct other geometric primitives and sub-objects. This construction can be used to detect complex objects in digital images.
This thesis reviews existing Hough Transforms and explores their strengths and weaknesses. The research work introduces a new Hough Transform that uses a hi- erarchical (pyramid) approach to first detect simple geometric primitives which are then used together to construct more complex shapes for the purpose of object recognition.
This research provides a framework for complex object detection that is based on a model of human visual perception. Inside this framework is a discrete Hough transform that uses only discrete and local information for detection of line segments. The next level in the hierarchy uses the line segment information to detect circular and elliptical objects by directly computing all parameters directly from local information.
Sun, 01 Feb 1998 00:00:00 GMThttp://hdl.handle.net/10388/116131998-02-01T00:00:00ZCOLOR IN THE CONSTRUCTED RELIEF
http://hdl.handle.net/10388/11612
COLOR IN THE CONSTRUCTED RELIEF
Tue, 01 Jan 1985 00:00:00 GMThttp://hdl.handle.net/10388/116121985-01-01T00:00:00ZCOMPOSITE POWER SYSTEM ADEQUACY ASSESSMENT INVOLVING NON-UTILITY GENERATION AND POWER WHEELING
http://hdl.handle.net/10388/11611
COMPOSITE POWER SYSTEM ADEQUACY ASSESSMENT INVOLVING NON-UTILITY GENERATION AND POWER WHEELING
A significant component of the overall system electrical energy requirements of many power utilities is now being provided by Non-Utility Generators (NUGs) and power/energy purchases from neighbouring systems. A NUG is defined in this thesis as an independent power production facility or cogeneration facility, which is not owned by the utility in whose service area the facility is located. These facilities are small generating capacity components associated with load points within the utility system. NUG capacity additions can have considerable impact on adequacy at both the individual load points and the overall system.
The opportunity to wheel energy/power through the transmission facilities of one system in order to serve another system is one of the many possible uses and benefits of interconnection between neighbouring electric power systems. Wheeling of energy can also occur within a system when an independent power producer in a local utility system serves a load located at some other point in the system. Power wheeling transactions are recognised to have a definite impact on the utility's system losses depending upon the system topology, the amount of power/energy wheeled and the wheeling distance involved. These factors currently form the basis for determining service charges associated with power wheeling.
Mon, 01 Jun 1992 00:00:00 GMThttp://hdl.handle.net/10388/116111992-06-01T00:00:00ZAN EXPERIMENTAL FEASIBILITY INVESTIGATION OF A LOW COST ULTRASONIC FLOW MEASUREMENT TECHNIQUE
http://hdl.handle.net/10388/11610
AN EXPERIMENTAL FEASIBILITY INVESTIGATION OF A LOW COST ULTRASONIC FLOW MEASUREMENT TECHNIQUE
Currently conventional paddle wheel flowmeters are used to measure the flow rate in prairie grain farm sprayers. These flowmeters experience relatively short operating life due to failure of the paddle bearing. Wear on the paddle bearing and the bushing is caused by grit in the water used for spraying. One way to avoid this problem is to measure the flow with a meter that has no moving parts.
There are a variety of techniques that can be used to measure flow. Ultrasonic flow measurement is one of the promising techniques. It has advantages of being
nonobstructive and no moving parts. But it is relatively expensive compared with other flowmetering devices.
In this thesis, an ultrasonic flow measurement system is proposed as a relatively simple scheme which could be implemented with low cost. It makes use of the different phase delays experienced by ultrasonic waves travelling with and against the flow in a pipe. The differential phase is proportional to the flow rate.
To investigate the feasibility of the proposed scheme in a practical situation, an ultrasonic flow system was constructed and its reciprocity and triple transit were tested to ensure the setup system was working properly. An electronic measuring system consisting of a transmitter, a receiver and a switch array was designed and developed in printed circuit boards to implement the technique. The measuring system was then briefly calibrated by a standard flowmeter.
It was proved that the system had fairly good linearity between its differential phase output and the flow rate. The system repeatability was found to be influenced by fluid temperature and the flow system setup. The experimental test results clearly demonstrated the proposed scheme was feasible and could be exploited practically for the prairie grain sprayer applications.
Thu, 01 Aug 1996 00:00:00 GMThttp://hdl.handle.net/10388/116101996-08-01T00:00:00ZRODIN'S INFLUENCE UPON MY SCULPTURE
http://hdl.handle.net/10388/11609
RODIN'S INFLUENCE UPON MY SCULPTURE
Fri, 01 Jan 1982 00:00:00 GMThttp://hdl.handle.net/10388/116091982-01-01T00:00:00ZA PROBABILISTIC TECHNIQUE FOR OPERATING RESERVE ASSESSMENT USING SYSTEM OPERATING STATES
http://hdl.handle.net/10388/11608
A PROBABILISTIC TECHNIQUE FOR OPERATING RESERVE ASSESSMENT USING SYSTEM OPERATING STATES
Operating reserve assessment in an electric power system is normally performed using deterministic criteria. Deterministic approaches do not include an assessment of the actual system reliability as they do not take into account the probabilistic or stochastic nature of system behavior and component failures. Probabilistic techniques, however, respond to the significant factors which affect the reliability of a system. Deterministic criteria are, however, easier for the system operator to understand, than a risk index determined using probabilistic techniques. In order to alleviate the difficulty in interpreting the risk index and provide
more applicable information for the system operator, deterministic considerations can be included in the probabilistic assessment.
A probabilistic technique is illustrated in this thesis to assess the operating reserve requirements in a system. This technique combines deterministic criteria with probabilistic indices to monitor the system wellbeing. In this approach, the generation system is classified into different system operating states. A risk index designated as the Generating System
Operating State Risk (GSOSR) is defined in this thesis as the probability of residing in an undesirable operating state. The technique together with the effect on the GSOSR and the system operating state probabilities of factors such as lead time, system peak load, load forecast uncertainty and generating unit derated states are illustrated in this thesis. The inclusion of rapid start and hot reserve units and interruptible loads in the analysis can affect the GSOSR and the system operating state probabilities. The effects of these factors have been incorporated in the operating reserve assessment using the concept of area risk curves. The effect of various degrees of postponability on the GSOSR and the system operating state
probabilities are also discussed. Two reliability test systems, the RBTS and the IEEE-RTS, have been utilized in the wide range of studies presented in this thesis.
Mon, 01 Mar 1993 00:00:00 GMThttp://hdl.handle.net/10388/116081993-03-01T00:00:00ZDESIGN AND TEST OF A MULTIPLE-VALUED LOGIC CMOS STANDARD CELL LIBRARY
http://hdl.handle.net/10388/11607
DESIGN AND TEST OF A MULTIPLE-VALUED LOGIC CMOS STANDARD CELL LIBRARY
Multiple-valued logic (MVL) circuits can be designed and implemented, utilizing 4 levels of logic, in current mode CMOS technology to compete with and improve upon conventional binary logic in certain target areas. The chosen technology is important to the success of MVL in augmenting and contributing to the semiconductor logic framework. CMOS is the technology selected for the implementation of the MVL standard cell library in this thesis. It is essential that these circuits can coexist with and perform the functions of existing binary logic circuits, the majority of which are fabricated in CMOS. The design and simulation and/or test of a number of multiple-valued logic standard cells are performed to verify the thesis statement.
The MVL designs are made up of six basic elements; the switch, constant, current mirror, threshold, summing node and voltage reference circuits. Built upon the these basic components are the MVL operators including the min, max, tsum, literal, complement of literal, cycle, level restorer and t-gate circuits. In addition, the binary- to-quaternary encoder and quaternary-to-binary decoder circuits are designed, further demonstrating the compatibility between MVL and binary logic. Methods are provided for combining the operators and basic components to synthesize functions via existing binary tools and representations; the Karnaugh map and the sum of products form. Each of the circuits are presented with detailed design specifications. All circuits are simulated with HSPICE and the results verifying operation are graphed. Standard cell library VLSI layout diagrams are presented with accompanying descriptions for a subset of the
operators and basic elements. Test results confirming the basic functionality of the fabricated standard cell circuits are also presented.
The complete design of two implementations of a quaternary full adder are developed and simulated to reveal optional design methodologies available in MVL, and to confirm the validity of the application of MVL design for realizing functions.
Mon, 01 Jan 1996 00:00:00 GMThttp://hdl.handle.net/10388/116071996-01-01T00:00:00ZULTRASONIC MEASUREMENTS FOR THE EVALUATION OF THERMAL FATIGUE DAMAGE
http://hdl.handle.net/10388/11606
ULTRASONIC MEASUREMENTS FOR THE EVALUATION OF THERMAL FATIGUE DAMAGE
An ultrasonic test system was assembled to evaluate the ability of ultrasonic measurements to measure thermal fatigue damage in composite material systems. The ultrasonic test system used a modification of the sing-around technique. The sample to be studied was placed between a transmitting and a receiving transducer, and the time between the first peak on the transmitted waveform and the first peak of the received waveform was measured as the transit time through the sample. The peak to peak voltage at both transducers was also measured, and used to define an attenuation.
Cyclic thermal fatigue loading was carried out on three fibre-reinforced plastics, two uniaxial and one randomly oriented. Before any loading, and at intervals during loading, measurements of ultrasonic velocities and attenuations at frequencies of 3.00, 4.00, and 5.00MHz were performed. These measurements were made for a number of samples, normalized, and averaged. Generally it was found that ultrasonic attenuations increased and ultrasonic velocities decreased with increasing number of thermal fatigue cycles. This depended on the material tested and the propagation direction of the ultrasound. Scanning electron microscopy (SEM) was used as a qualitative tool to examine specimens after fatigue to provide information on the modes of stress relief in the specimens.
It was found that ultrasonic attenuation is sensitive to thermal fatigue damage in these materials. The main mode of damage is fibre-matrix debonding at the fibre ends, occasionally accompanied by matrix cracking. This is demonstrated by the SEM examinations of the fatigued specimens. A damaged surface layer in the uniaxial composites did not have a great effect on the bulk properties of the specimens, and ultrasonic velocities were not always sensitive to damage, due to the nature of the stress relief.
Tue, 01 Sep 1992 00:00:00 GMThttp://hdl.handle.net/10388/116061992-09-01T00:00:00Z