published_or_final_version / abstract / Electrical and Electronic Engineering / Master / Master of Philosophy

Thesis--University of Washington.

Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Modern satellite, wireless communication, and radar systems often demand wideband performance for multi-channel operation and the ability to steer multiple beams for multiple moving targets. This dissertation covers a variety of topics to design low-cost and wideband antenna systems. The main areas of study are microwave devices controlled piezoelectric transducers (PETs) and wideband baluns and balanced microwave circuits using parallel-strip lines. Some focus has also been given to the design of Rotman lens for multiple beam generation and Vivaldi antenna arrays for wideband two-dimensional scanning. The dielectric perturbation technique controlled by PET is introduced to design a wideband phase shifter and a QPSK modulator, and to tune the resonant frequency of a slot dipole. The designed PET-controlled phase shifters are used for beam steering in a dual beam phased array using a bidirectional feeding scheme and a five-beam phased array using a microstrip Rotman lens. Vivaldi-type antennas are commonly used to achieve wideband performance. Very wideband performance can be achieved using an antipodal tapered slot antenna because of its inherent simple wideband transition from microstrip line to parallel-strip line. An antipodal tapered slot antenna and a phased array are designed to span 10 to 35 GHz. In addition, a 4??4 two-dimensional antenna array is designed using wideband antipodal tapered slot antennas, and two sets of PET-controlled phase shifters for E- and H-plane scanning are fabricated to steer the beam. As a microwave system using wideband antenna array, a new low-cost and wideband phased array radar is developed using a modulated pulse over 8 to 20 GHz band. The double-sided parallel-strip line as a balanced line is presented. The parallelstrip line offers much flexibility for microwave circuit designs. This transmission line makes it possible to realize a low impedance line and allows the design of a compact wideband balun and junction. Wideband transitions (or baluns) from parallel-strip line to microstrip line, a typical unbalanced transmission line, are realized to cover several octave bandwidth. Balanced microwave filters and a hybrid coupler are developed using the parallel-strip line.

In this thesis, piezoelectric transducers were fabricated by depositing ZnO films on PET substrates. The optimal deposition parameters for ZnO films are sputtering pressure of 15 mTorr, RF power of 75 W and oxygen concentration of 60 %, which are determined by scanning electron microscopy and X-ray diffraction analysis. PET substrates of Young¡¦s modulus of 6.62 GPa are obtained by Nano Indenter. To fabricate a transducer with resonance frequency of 100 Hz, the cantilever length of 0.979 cm and vibration area of 1.4835 cm2 are calculated by Cantilever Vibration Theory. Copper layer was attached to ZnO/ITO/PET structure to form piezoelectric transducers. A mass of 0.57 g was attached to the transducer to increase the vibration amplitude. A vibration source of 100 Hz was provided to the piezoelectric transducer and then the experimental results were obtained by oscilloscope. The optimal thickness of ZnO films is 964.65 nm, at which the open circuit voltage is 1.87 V. A bridge rectifier was constructed by Shottky diode with product number 1N5711 along with a capacitor of 37 nF. After rectifying and filtering of device output, the maximum power of 0.0697£gW/cm2 was generated with the load resistance of 5 M£[ and the internal resistance of 4.3185 M£[.

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Thesis (M.S. in mechanical engineering)--Washington State University, August 2008. / Includes bibliographical references.

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Brand, Oliver; Committee Member: Adibi, Ali; Committee Member: Allen, Mark G.; Committee Member: Bottomley, Lawrence A.; Committee Member: Degertekin, F. Levent.

Thesis (Ph. D.)--Auburn University. / Abstract. Vita. Includes bibliographical references (p. 118-124).