Stretching, Amplification, and Compression of Microwave Pulses Using Helically Corrugated Waveguides

Abstract

We demonstrate the possible implementation of the chirped pulse amplification (CPA) method, which is widely used in optics, for the microwave frequency band. This method is based on the preliminary elongation of the incident pulse in the stretcher, sequential amplification of spectral components in a wideband amplifier, and final compression in a line with negative dispersion (compressor). A circuit is considered in which multifold, helically corrugated waveguides are used as an operating space in each section, including a stretcher, an amplifier, and a compressor. The dispersion characteristics of such waveguides can vary significantly when its geometrical parameters are changed, which makes it possible to ensure optimal dispersion characteristics in the stretcher and compressor, as well as the largest gain bandwidth in the amplifier. In addition, these dispersive elements allow us to avoid spurious reflection of the signal due to the absence of a stopband in the operating frequency range. Simulations within the framework of the coupledwave approach showed the prospects of the circuit proposed. In particular, using an experimentally realized 30-GHz gyro-TWT, the peak power of a 200-ns, 300-W incident pulse can be increased up to 4 MW, which is about six times higher than the power of the driving electron beam. With direct amplification (in the absence of a stretcher and a compressor) of the specified incident pulse in the same gyro-TWT, the output peak power does not exceed 250 kW.