Microwave pulse compression using a helically corrugated waveguide

There has been a drive in recent years to produce ultrahigh power short microwave pulses for a range of applications. These high-power pulses can be produced by microwave pulse compression. Sweep-frequency based microwave pulse compression using smooth bore hollow waveguides is one technique of passive pulse compression, however, at very high powers, this method has some limitation due to its operation close to cutoff. A special helical corrugation of a circular waveguide ensures an eigenwave with strongly frequency dependent group velocity far from cutoff, which makes the helically corrugated waveguide attractive for use as a passive pulse compressor for very high-power amplifiers and oscillators. The results of proof-of-principle experiments and calculations of the wave dispersion using a particle in cell particle-in-cell (PIC) code are presented. In the experiments, a 70-ns 1-kW pulse from a conventional traveling-wave tube (TWT) was compressed in a 2-m-long helical waveguide. The compressed pulse had a peak power of 10.9 kW and duration of 3 ns. In order to find the optimum pulse compression ratio, the waveguide's dispersion characteristics must be well known. The dispersion of the helix was calculated using the PIC code Magic and verified using an experimental technique. Future work detailing plans to produce short ultrahigh power gigawatt (GW) pulses will be discussed

Single-cavity gyromultipliers

Several new configurations of self-exciting gyro-multipliers are proposed. These schemes allow concurrent excitation of radiation at fundamental and harmonic frequencies in a single resonator. It is shown that such an approach simplifies the experimental setup and promises high device efficiency. Experimental proposals based on some of the schemes are presented

Special Libraries, April 1933

Volume 24, Issue 3https://scholarworks.sjsu.edu/sla_sl_1933/1002/thumbnail.jp

Temporal Dynamics of Mode Interaction in Submillimeter-Wave Second-Harmonic Gyrotron

Competition of the operating modes at the second cyclotron harmonic with spurious modes at fundamental is studied numerically for the cases of gyrotron and traveling opposite spurious modes in the gyrotron FU II. This competition limits significantly the output power at the second harmonic. The results are in good agreement with experiments

Design of mm-wave slow-wave devices with sheet and hollow electron beams

The frequency increase of the slow-wave electron devices is accompanied by inevitable increase of the electron current density and ohmic losses which strongly restricts the attainable power. In recent years, the use of the spatially-developed sheet electron beams is considered as the major way to develop the medium-power slow-wave devices at mm and sub-THz waves. Hollow electron beams is another configuration which could be used for this purpose. The designs of the oscillators and amplifiers in Ka-band and W-band with both sheet and hollow electron beams are considered and compared