A novel Ka-band coaxial transit time oscillator with internal extraction

In this paper, a Ka-band coaxial transit time oscillator (TTO) with internal extraction is proposed. Particle-in-cell simulation of this oscillator is performed to obtain results as follows: under the conditions of a diode voltage of 459 kV, current of 3.9 kA, and guiding magnetic field of 0.5 T, microwaves with an output power of 0.75 GW and a frequency of 31.4 GHz can be achieved with an efficiency of 42% and a saturation time of nearly 25 ns. Moreover, the asymmetric mode competition is suppressed in the preliminary experiments. The study of a Ka-band TTO aims to extend the working frequency of high power microwave sources to a higher level. Such a device has three merits. First, it implements high power and high efficiency. Second, the internal extraction of the microwave output decreases the over-mode ratio in the microwave extraction region. Third, the over-mode ratio of the internal extraction is smaller compared with the external extraction, which can effectively suppress asymmetric mode competition.