| Sumari: | A method for producing short duration high power microwave pulses is proposed. A circular waveguide with a helical corrugation on its inner surface can be used as a sweep-frequency based pulse compressor which is compatible with vacuum tubes. A 2.2 metre long copper helical waveguide was used to compress a 70ns, 1kW frequency swept pulse from a conventional TWT, driven by a swept solid-state source, to a 3ns 10.9kW pulse containing 44% of the energy of the input pulse, excluding sidelobes. A frequency modulation similar to that used here can be realized at the falling edge of a microwave pulse produced from a high-power (∼1 GW) BWO, indicating the potential of this type of compressor for producing multi-Gigawatt output pulses. The dispersion characteristics of the helically corrugated waveguide were investigated both experimentally and theoretically. A vector network analyser was used to experimentally measure the dispersion characteristics of complex waveguides and a particle-in-cell code was used to calculate the dispersion numerically. Good agreement between experimental results and theoretical predictions was observed.
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