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Design and application of an advanced fully active harmonic load pull system using pulsed RF measurements and synchronised laser energy

Casbon, Michael Anthony 2018. Design and application of an advanced fully active harmonic load pull system using pulsed RF measurements and synchronised laser energy. PhD Thesis, Cardiff University.
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Abstract

The objective of this work was to advance the design of Active Harmonic Load-Pull systems to facilitate accurate modelling of RF semiconductors, with specific regard to time dependant behaviours. Pulse capability is added, to extend the thermally safe operating region, investigate thermal behaviour, and reduce the thermal loading on the system components. The safe operation region extension is demonstrated with a GaAs die, the thermal aspects of behaviour are illustrated with GaN on SiC, GaN on Si and GaN on diamond die. A violet laser is added, which releases some types of trapped charge, helping to reveal the full potential of the device. The thermal transient response of the device is thereby exposed, and the trap filling times may be studied. The application of this to GaN die with and without Source Coupled Field Plates is described. The relevance of the light wavelength is briefly investigated. A novel wafer probe station is described, providing access to the backside of the wafer for photonic trap release and the measurement of hot electron electroluminescence, as RF measurements are conducted on the front side. Replacing the drain RF and DC circuits with a fixed resistor, and stepping the gate voltage allows the device to be held at any point on the load-line and then moved to another, here this demonstrates that the residual “knee-walkout” on a GaN on SiC part with an optimised source coupled field plate is not a thermal effect, and must therefore be due to trapped charge, despite the field plate. A low loss diplexer/ bias tee combination with very good DC supply memory properties is described, demonstrated with a InAlN/GaN die at Ka band. Accurate measurement of harmonics is vital to waveform engineering. Here a novel method of increasing the effective dynamic range of the system is presented.

Item Type: Thesis (PhD)
Date Type: Submission
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: GaN Charge Trapping; 3dB Coupler; Electroluminescence; Harmonic Equaliser; Pulsed Harmonic Loadpull; Memory Effects.
Date of First Compliant Deposit: 11 October 2018
Last Modified: 11 Oct 2018 11:08
URI: http://orca.cf.ac.uk/id/eprint/115731

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