Electrical and Computer Engineering ETDs

Author

Jesse Lai

Publication Date

1-29-2009

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.

Keywords

Amplifiers, Radio frequency, Power amplifiers

Sponsors

Sandia National Laboratories

Document Type

Dissertation

Language

English

Degree Name

Electrical Engineering

Level of Degree

Doctoral

Department Name

Electrical and Computer Engineering

First Advisor

Christodoulou, Christos

First Committee Member (Chair)

Gilmore, Mark

Second Committee Member

Leseman, Zayd

Third Committee Member

Feldner, Lucas

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