Numerical simulation on Ku-band coaxial transit-time oscillator

When the operating frequency goes into higher band, the traditional high power microwave (HPM) generators are of smaller size and can support less power capacity and space-charge limiting. In order to solve these difficulties, a Ku-band coaxial transit-time oscillator was proposed. Using a coaxial structure, the space-charge limiting current and power capacity of the proposed device can be increased significantly. In comparison with a dual-cavity buncher, this proposed device with a trinal-cavity buncher can lead to a higher degree of beam current modulation. By using high frequency field software, the cold-cavity analysis was performed for buncher and extractor. The proposed oscillator was designed and optimized by a particle-in-cell (PIC) code. With the voltage 392 kV, the current 15.2 kA and the guiding magnetic field 0.6 T, the output power was 1.2 GW at the main frequency 14.184 GHz, and the efficiency of beam-to-microwave power conversion was about 20%.