High-Frequency Circuits for Environments Affected by Radiation

Abstract

The reluctance of previous governments to make adequate provision for the long-term storage and disposal of nuclear waste has resulted in an imminent and significant decommissioning burden, as existing “temporary” solutions are well beyond the end of their useful lives. It is preferable to use remote handling solutions for decommissioning, in order to ensure worker safety; however the susceptibility of electronic devices to radiation damage is often unclear. This document discusses factors affecting the survivability of electronics in radio-active environ- ments, and the design of GaAs circuits suitable for high-speed communications applications in such an environment. Techniques for performing accurate RF measurements and electromagnetic simulations are also discussed. Measurements of the designed devices are presented. Results of irradiation testing of a silicon rotary encoder and GaAs pHEMT transistors, on a related process to that used for the aforementioned circuits, are also presented, demonstrating Mrad hardness for the GaAs devices and krad hardness for the silicon; although the silicon and GaAs results are not directly comparable they are nevertheless of interest to illustrate the difference in radiation hardness between the two technologies, and the GaAs results suggest that the communications circuits designed on the process are likely to be highly radiation-tolerant. Neither the hardness of the encoders tested nor the GaAs process considered are believed to have been measured before. Analysis of a novel technique for improving the performance of certain common RF circuit elements at high frequencies, using stubs of an unusual form of lossy transmission line, is also described; an improvement in the matching of a load standard over frequency is demonstrated in simulation.

Date of Award	31 Dec 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Barry Lennox (Supervisor)