Behavioral Model and Predistortion Algorithm to Mitigate Interpulse Instabilities Induced by Gallium Nitride Power Amplifiers in Multifunction Radars

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Date

2017-01-27

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Publisher

Virginia Tech

Abstract

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.

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Keywords

III-V semiconductors, gallium compounds, mean square error methods, power amplifiers, synthetic aperture radar, Foster network topology, GaN NMIC, GaN power amplifiers, amplitude transients, behavioral modelling, digital predistortion technique, gallium nitride

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