Generation of single and periodically repeated powerful ultrashort microwave pulses

Generation of powerful ultrashort microwave pulses (USP) is of interest for a large number of practical applications, including radars with high resolution, plasma diagnostics, spectroscopy etc. In order to achieve this purpose many methods well-known in laser physics can be implemented in microwave electronics. In the last decade significant progress was achieved in generation of microwave USPs based on classical superradiance (SR) of extended electron bunches. Using of this effect a new type of pulse sources has been developed, which are capable of producing uniquely short (under 0.2–1 ns) electromagnetic pulses at super-high peak powers exceeding 1 GW in the millimeter waves (Kaband) and 3 GW in the centimeter waves (X-band) with a repetition frequency up to several kilohertz [1]. A natural continuation of this research is related with the promotion of SR sources in shorter wavelengths ranges, where the oversized waveguides should be used. In the first part of this paper the results of the experimental observation of SR emission with excitation of a surface wave in the oversized periodically corrugated slow wave structures are presented. The experiments were based on a theoretical consideration in the frame of the quasi-optical approach. A periodic train of powerful ultrashort microwave pulses with a repetition frequency of 10–100 MHz can be generated in electron oscillators with a saturable absorber installed in the feedback loop [2]. The mechanism of pulse formation in this case is similar to the passive mode-locking [3] in laser physics where such pulses are also treated as dissipative solitons. The second part of this paper is devoted to the theoretical analysis of solitons generation in a mode-locked two-section microwave oscillator consisting of Cherenkov TWT and a Kompfner absorber in the feedback loop.