A Forward-Wave Oscillator Based on Folded-Waveguide Slow-Wave Structure

A new concept of oscillator based on a folded waveguide slow-wave structure (FWG SWS) is studied. The resonant cavity of the oscillator is formed by a section of FWG SWS, a length-adjustable waveguide, and a waveguide loaded by multilayer dielectric. The beam is synchronized with the forward wave on the SWS. If an FWG traveling-wave amplifier (TWA) is driven by this oscillator, there is a possibility that the amplifier and the oscillator share the same design and the same art of manufacturing and power supplier. A forward-wave oscillator based on a design of a TWA in 2-mm band is calculated by both a 1-D nonlinear code and particle-in-cell (PIC) simulation. From both the code and the simulation results, when the oscillator is 30-pitch long, the operation voltage 22000 V and the start current is 3 mA at 138 GHz. When the oscillator is 22-pitch long, operation current 15 mA, and operation voltage 22400 V, simulation result shows that the output power is 58.32 W, and the efficiency is 17.26% at 133.2GHz. When both the voltage and length of the length-adjustable waveguide are tuned, the oscillator can operate within all the first dispersion band of the SWS. If only voltage is tuned, the oscillator can oscillate at several discrete frequencies.