Experimental Investigation of a Helical Traveling-Wave Tube Designed by Accurate Numerical Modeling

This paper presents cold-test characteristics of a traveling-wave tube (TWT) helical slow-wave structure (SWS) as predicted by a three-dimensional simulation code, HFSS, and the way in which they compare with measured data. LMsuite, which is a one-dimensional code, is utilized to predict the non-linear and large-signal performance of the helical TWT. Good agreement is demonstrated between the experimental and the code-predicted data based on accurate modeling. Simulations predict that the TWT produces 16.6 W of saturated power at 9 GHz when the input power is 40 mW. Experiments show that a saturated output power of 15.1 W is produced when an input power of 60.5 mW is injected at 9 GHz. The third-order intermodulation distortions (IMDs) are 12 dBc at the P1 dB compression point and 19 dBc at a 10-dB backoff point from the P1 dB point.