A Cascaded W-Band Gyro-TWT With the Configuration of Coaxial and Circular Waveguides

To realize a high-gain wideband millimeter-wave amplification, we present and simulate a <inline-formula> <tex-math notation="LaTeX">${W}$ </tex-math></inline-formula>-band gyrotron traveling wave tube (gyro-TWT) with cascaded coaxial- and circular-waveguide amplifiers. The amplifiers are operated in a coaxial and circular TE01 mode, respectively, and driven by two 60-kV gyrating electron beams with a pitch factor of 1.2 but different beam currents of 1 and 10 A. They are designed to possess relatively low individual gains below all oscillation thresholds to maintain high stability and achieve a high total cascaded gain for the whole gyro-TWT. A coupling circuit is adopted to cascade these two sections, converting the coaxial TE01 mode to the circular one with a −3-dB bandwidth of 6.8 GHz (94.1–100.9 GHz). particle-in-cell (PIC) simulation shows that the designed gyro-TWT can achieve a maximum saturated output power of 239.8 kW at 100 GHz, with a gain greater than 60 dB over a −3-dB bandwidth of 8.0 GHz (94.5–102.5 GHz).