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Investigation into the use of high-efficiency switched-mode class E power amplifiers for high-dynamic range pulse-mode applications

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Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/7639

Investigation into the use of high-efficiency switched-mode class E power amplifiers for high-dynamic range pulse-mode applications

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Title: Investigation into the use of high-efficiency switched-mode class E power amplifiers for high-dynamic range pulse-mode applications
Author: Lai, Jesse
Advisor(s): Christodoulou, Christos
Committee Member(s): Gilmore, Mark
Leseman, Zayd
Feldner, Lucas
Department: University of New Mexico. Dept. of Electrical and Computer Engineering
Subject: dynamic range
efficiency
measurement
power amplifiers
pulse measurements
transmitters
LC Subject(s): Amplifiers, Radio frequency
Power amplifiers
Degree Level: Doctoral
Abstract: In typical communication and radar systems, the transmitter is operated in either a continuous wave or a pulsed mode where the transmitter is periodically turned on for a portion of time. These systems commonly use a power amplifier in the transmitter to raise the power level of the transmitted signal to a value sufficient to meet system sensitivity requirements. In high-dynamic range systems, the power amplifier pulse must turn off at a rate compatible with the system noise floor at the receive time. Some high-dynamic range systems are sensitive to signals greater than 120 dB below the transmit power level, and correlated energy that exists during the receive time can cause serious system consequences. The Class E high-efficiency power amplifier is an attractive candidate for pulse-mode systems, but it is unknown if the pulse profile characteristics are compatible with the stringent requirements of these systems. It is shown that the Class E amplifier mode allows generating a high-isolation pulsed signal simply by pulsing the input radio frequency (RF) signal. The unique properties of the switched-mode amplifier cause it to be off when it is not driven. A technique to characterize the pulse profile of an RF amplifier over a very wide dynamic range under fast-pulsing conditions is presented. A pulse modulated transmitter is used to drive a device under test with a phase coded signal coupled with a correlation technique that allows for an increased measurement range beyond standard techniques. A measurement receiver is described that samples points on the output pulse power profile and performs the necessary signal processing and coherent pulse integration, improving the detectability of low-power signals. A full measurement dynamic range of greater than 160 dB is achieved, extending the current state of the art in pulse profiling techniques. The pulse profiles of example Class E amplifiers are examined and compared to the results for the same amplifiers operating in a linear mode. It is discovered that the inherent trapping properties of the active device technology limit the usefulness of these specific amplifiers in a high-dynamic range pulsed system.
Graduation Date: December 2008
URI: http://hdl.handle.net/1928/7639


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