A high power radial Ka-band transit time oscillator with nonuniform extractor

Abstract

The radial transit time oscillator is promising to realize high power output of millimeter-waves. However, the enhancement of the electric field in extractor and the microwave extraction are two main problems to be overcome. A high power radial Ka-band transit time oscillator is proposed in the paper. Increasing the third gap by integer multiples of half the wavelength, the nonuniform extractor will be introduced. In the extractor, the radial mode of the electric field in the modified extractor is the same as that in the uniform extractor. Due to volume increase of the beam-wave interaction region, this structure can improve power capacity to a certain degree. In particle-in-cell simulation, the proposed radial Ka-band oscillator can output high power microwave with the power of 1.0 GW, the frequency of 31.3 GHz and the efficiency of 33%. Besides, the modified structure can decrease the maximum radial electric field in extractor to 0.9 MV cm−1. As the diode voltage ranges from 350 to 450 kV, efficiency of the oscillator is larger than 20% and the center frequency will not change, which proves the steady operation of this device. To realize high output power, the materials with high conductivity need to be employed, such as copper and aluminum. Besides, the microwave channel goes through the inner space of the high current coils, this design can decrease the number of the support posts to 50 and increase the bandwidth where the transmission efficiency is larger than 99% to be over 1.8 GHz.