A 3-D Printed Helix for Traveling-Wave Tubes

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 ( $\mu $ 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 $2\times 10^{{7}}$ 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.