Theory and Hot Test of High-Power Broadband Helix Traveling-Wave Tube Based on a Double-Graded Radius and Pitch Circuit

The classical Pierce’s 1-D small-signal theory of backward-wave gain, generalized to allow axially varying the double-graded radius and pitch circuit characteristics, is applied. Numerical calculations demonstrate that the double gradient circuit can effectively suppress the backward-wave oscillation (BWO). Furthermore, the hot test experiment is carried out to predict the performance of the tube. The hot test results show that this helix traveling-wave tube (TWT) based on the double-graded pitch and radius circuit has achieved over 5.06 kW of output power, and the corresponding device gain achieves more than 34.1 dB in the frequency range of 8-18 GHz.