Overmoded W-Band Traveling Wave Tube Amplifier.

摘要

We report on the design and test of an overmoded W-band TWT. The TWT was designed to operate in the rectangular TM31 cavity mode at 94 GHz. The unwanted lower order modes were suppressed using selectively placed AlN dielectric loading; simulations in 3-D CST Particle Studio confirmed the suppression. The 87-cavity TWT was designed to operate at 30 kV with 320 mA in a 2.5 kG solenoid magnet. The experiment was built in-house at MIT and operated with a 3 microsecond pulsed power supply. An initial beam test was implemented which confirmed operation at 31 kV with 306 6 mA of current detected at the collector and 88 % transmission. The TWT produced 21 2 dB system gain at 94.3 GHz and 27 W of saturated output power in zero-drive stable operation. The TWT had about 6 dB of additional loss due to the input and output coupling; taking that loss into account, the gain on the TWT circuit itself was 27 2 dB circuit gain. CST simulations for the experimental current and voltage predict 28 dB circuit gain, in good agreement with measurements. This experiment demonstrated the first successful operation of an overmoded TWT. The overmoded TWT is a promising approach to high power TWT operation at W- Band and to the extension of the TWT to terahertz frequencies.