Design of a Ka-band gyro-TWT for radar applications

Extending the bandwidth and average power capability of vacuum electron devices for the next generation of millimeter wave radars is a major research goal at the Naval Research Laboratory. Gyro-amplifiers such as the gyroklystron and gyro traveling wave-tube (gyro-TWT) appear to be ideal candidates for this purpose due to their high power handling capability relative to their conventional counterparts, i.e., klystrons and coupled-cavity TWTs. This paper presents the design of a high-average power compatible, Ka-band gyro traveling-wave-tube (gyro-TWT). This amplifier design employs the circular TE/sub 11/ mode and operates at the fundamental cyclotron harmonic. In addition, this design makes use of the distributed loss approach, which has recently been demonstrated to be effective in the suppression of spurious oscillations in gyro-TWTs. The design has been performed using the self-consistent, time-dependent, quasi three-dimensional code MAGY. The code has been successfully used to model gyroklystrons and benchmarked against gyro-TWT linear theory. The code is capable of addressing issues such as absolute instabilities and the effect of reflections, which have also been investigated for this design.