Frequency tunable gyrotron using backward-wave components

We present a frequency tunable scheme for the gyrotron at millimeter/submillimeter regime. Unlike step-tunable type where oscillation jumps discretely in different transverse modes, this scheme allows a smooth tuning within a single transverse mode using its backward-wave component. The characteristics of backward-wave interaction will be shown. A proof of principle experiment was conducted with a sealed cavity. The result shows the oscillation frequency smoothly transitions over a wide range of 6 GHz from 134 to 140 GHz. The proposed mechanism is capable of producing medium output power with broad frequency tunability up to sub-terahertz region.