Effects of Random Manufacturing Errors on the Performance of Contemporary Coherent Radiation Sources.

Abstract

The traveling wave tube (TWT) is a linear beam microwave vacuum electron device (MVED) and is a key element in telecommunication systems, satellite-based transmitters, military radar, electronic countermeasures, and communication data links. Variations in TWT performance due to random errors in the manufacturing process can drive up the cost. These errors provide a proportionately larger perturbation to the circuit as the frequency increases into the sub-millimeter wavelength regime and beyond. Previous studies calculated the standard deviation in the small-signal gain and phase of a TWT in the presence of small random, axially varying perturbations in the circuit phase velocity, but assumed zero space charge effects and synchronous interaction. This work relaxes the latter assumptions and calculates the ensemble-average gain and phase by two analytic approaches as well as a numerical calculation. The analytic theory resolved a previously unexplained puzzle where a significant fraction of samples with random circuit errors show a higher gain than an error-free tube. The effects of multiple internal reflections are also presented and their effects on the small-signal gain and phase are shown to be significant. Due to interest in the absolute instability of TWTs with such internal reflections, the absolute instability in a dielectric waveguide is investigated.

The magnetron is another type of MVED in a crossed-field configuration that is promising to deliver GWs of power in the GHz frequency range. The peer-to-peer configuration is an attractive method of phase-locking a large number of very efficient, lower power magnetrons. This thesis advances the theory a step further by examining the viability of peer-to-peer locking when two magnetrons in a peer-to-peer configuration suffer from a frequency chirp or contain a low frequency noise component. An argument is made that the analysis of temporal locking is analogous to the spatial locking experimentally observed in neighboring wires in z-pinch arrays. A framework for the interpretation of spatial locking found in these experiments is provided.