Experimental Investigation of a Q-Band Helix Traveling-Wave Tube With High Efficiency

In this article, the slow-wave structure (SWS) of a
${Q}$
-band helix traveling-wave tube (TWT) is designed with a variable scheme for helix pitch and inner diameter to obtain higher power, higher efficiency, and flatter gain. The four-stage depressed collector is also devised to further improve the device efficiency, and an efficient four-stage depressed collector design method (EFSDCDM) based on simulated annealing (SA) algorithm is proposed to determine the collector voltages. Thus, a hot-test experiment on a
${Q}$
-band helix TWT has been done. Under the conditions that the beam voltage and beam current are 8.9 kV and 58 mA, respectively, and the focusing magnetic flux density is about 4000 G, the experimental results clearly show that the following hold: 1) in the frequency range (from 37 to 41 GHz), the saturated output power of this
${Q}$
-band helix TWT is 82.4–83.4 W, the saturated device efficiency is 50.2%–54%, and the saturated gain is 42.8–46.8 dB and 2) when it is backed off 6 dB from the saturation, the output power is 20–20.1 W, the device efficiency is 19.6%–20.8%, and the gain is 53.9–47.5 dB. The
${Q}$
-band helix TWT developed here may be used in the next-generation wireless communication systems.