Experimental Investigation of a Ku-Band Coaxial Transit Time Oscillator on Low Magnetic Field Operation

Low guiding magnetic field is conducive to miniaturization of high-power microwave (HPM) generators in the Ku-band, especially when they are designed to be suitable for lightweight permanent magnet packages. The Ku-band coaxial HPM generator proposed in this article is based on the transit-time effect. The coaxial structure can increase the radial dimensions of the device, thereby reducing the electron beam density and diminishing its requirement for magnetic field strength. The generator has a small number of cavities, and the compact structure is accompanied by a short uniform magnetic field area, which reduces the weight of the exciting coil and has the potential for lightweight permanent magnet packaging. At the low guiding magnetic field of 0.35 T, the microwave pulse with power of 644 MW, pulse duration of 36 ns, frequency of 12.84 GHz, and efficiency of 18.9% is generated in the experiment.