Investigation of vircator with time-frequency analysis

Precise measurement of the power generated by a virtual cathode oscillator has been a difficult task because of the ultra short duration of the microwave pulse and the complexity of its frequency spectrum. Here, we report a resolution of this problem through the time-frequency analysis of the output signal. The results reveal that the output spectrum is not only broadband in content, but also display a composition which varies significantly in a stepwise manner over the duration of the pulse. The resulting time-resolved spectrum sheds light on the physical processes involved. It also allows a proper account for the frequency sensitivity of the measuring apparatus and thereby an accurate determination of the output power from the experimental data.