Array Amplitude Modulation: A numerical and experimental feasibility study
Abstract
Modulation is an integral part of digital communication. Communication systems are incorporated in many portable devices which have limited energy. As such, the study of increasing the energy efficiency of digital modulation is important. Of the forms of modulation, Quadrature Amplitude Modulation (QAM) is often used. Array Amplitude Modulation (AAM) is an idea put forth by D. Michael Zatman of QinetiQ North America[1] as a more efficient method of producing QAM. This work is a numerical and experimental feasibility study of using switching amplifiers to implement AAM. AAM uses a phased array to transmit a QAM signal. Each array element uses power-efficient nonlinear amplifiers to transmit the phase portion of the QAM signal. The amplitude portion of the QAM modulation is produced by switching some of the transmit amplifiers on and off. Several issues are introduced from this new method such as modulation method, small array quantization (SAQ), and steering error. These issues are investigated numerically and a custom method for demodulation is introduced to decrease error rates. It is concluded that the impact of steering error depends on the system's purpose and overcoming SAQ error is a performance trade-off between modulation complexity and array size. In addition to numerical investigations, a physical circuit is built as a proof-of-concept to test the feasibility of AAM. The circuit produces expected amplitude stability with relatively small phase noise. The system's performance is analyzed and recommendations for improvements are made. *Please refer to dissertation for footnotes.
Degree
M.S.M.E.
Advisors
Zoltowski, Purdue University.
Subject Area
Engineering|Mechanical engineering
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