The incorporation of Gallium Nitride (GaN) Power Amplifiers (PAs) into future high power aperture radar systems is certain; however, the introduction of this technology into multifunction radar systems will present new challenges to radar engineers. This dissertation describes a broad investigation into amplitude and phase transients produced by GaN PAs when they are excited with multifunction radar waveforms. These transients are the result of self-heating electrothermal memory effects and are manifested as interpulse instabilities that can negatively impact the coherent processing of multiple pulses. A behavioral model based on a Foster network topology has been developed to replicate the measured amplitude and phase transients accurately. This model has been used to develop a digital predistortion technique that successfully mitigates the impact of the transients. The Moving Target Indicator (MTI) Improvement Factor and the Root Mean Square (RMS) Pulse-to-Pulse Stability are used as metrics to assess the impact of the transients on radar system performance and to test the effectiveness of a novel digital predistortion concept. / Ph. D. / The incorporation of Gallium Nitride (GaN) Power Amplifiers (PAs) into future radar systems is certain, and will present new challenges to radar engineers. This dissertation describes a broad investigation into signal transients produced by GaN PAs when they are excited with a wide variety of RF pulsed waveforms. These waveforms are representative of those used by a radar system to conduct multiple functions or missions. The transients are primarily the result of changes in the GaN PA gain due to self-heating, and are manifested as differences in consecutive pulses. These pulse-to-pulse differences negatively affect the ability of a radar system to extract information from a received echo. A behavioral model based on a Foster network topology has been developed to replicate the measured signal transients accurately. This model has been used to develop a digital predistortion technique that successfully counteracts the transients mitigating the impact of the transients. The Moving Target Indicator (MTI) Improvement Factor and the Root Mean Square (RMS) Pulse-to-Pulse Stability are used as performance metrics to quantify the effect of the transients on radar system performance and to test the effectiveness of a novel digital predistortion concept.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/74445 |
| Date | 27 January 2017 |
| Creators | Tua-Martinez, Carlos Gustavo |
| Contributors | Electrical and Computer Engineering, Pratt, Timothy J., Zaghloul, Amir I., Silva, Luiz A., Mullins, Donald E., Buehrer, R. Michael, Foreman, Terry L. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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