Empirical evaluation of loss mechanisms in high frequency helix circuits

The intrinsic rf losses in each of a series of experimental helix circuits were measured to evaluate loss mechanisms in the helix tape and dielectric support rods. The effects of helix material, helix surface finish, and rod material were measured over the frequency range of 10 GHz to 20 GHz in a test vehicle similar in design to circuits used in I-J band TWTs. The nonresonant perturbation measurement technique permitted separation of conductor losses from dielectric losses while avoiding errors common to other measurement methods. A by-product of the measurement technique was the circuit wavelength used to normalize the loss data.