A 3-D Printed Helix for Traveling-Wave Tubes

Abstract

In this work, a 3-D printed copper helix for a traveling-wave tube (TWT) is reported. The fabricated helix was designed to be used in a TWT operating at millimeter-wave frequencies (60–80 GHz). The helix was realized with an additive micromanufacturing technique ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> AM). Measurements were also performed to estimate the losses of the printed material and evaluate the RF performance of deposited copper. Simulations showed that a TWT based on the 3-D printed helix can have a gain of about 30 dB at 66 GHz and a 1-dB bandwidth of about 5 GHz. The estimated losses from RF measurements reveal an RF copper conductivity of about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 10^{{7}}$ </tex-math></inline-formula> S/m, measured in air without any surface cleaning steps, which is a very good value and comparable to bulk copper conductivity in the millimeter-wave range.