The application of time-frequency analysis to high power microwave devices

摘要

Research is being condiucted on high power microwave devices (e.g. gyrotrons) at the University of Michigan. Of utmost concern is the phenomenon of pulse shortening. that duration of the microwave pulse is shorter than the duration of the cathode voltage. For years researchers have applied the Fourier transform to the heterodyned microwave signals. The problem with this technique is that a signal with multiple frequency components has the same spetrum as that of a signal with frequency components emitted at different times. Time-frequency analysis (TFA) using Reduced Interference Distributions provided an entirely differnt outlook in the community when it was recently applied to heterodyaned microwave signals. Results show, with unprecedented clarity, made hopping, mode competition, and frequency modulation due to electron beam votage flucturations. The various processes that lead to pulse shortening may finally be identified. Time resolved maximum intensity of the TFA has produced results very similar to the microwave power signal, verifying the utility of TFA in the analysis of the temporal evolution of power in each mode.