Broadbanding a gyro-traveling-wave tube by chiral-dielectric material loading

Loading the circular waveguide interaction structure of a gyro-traveling-wave tube (gyro-TWT) with chiral material was proposed to show the possibility of widening the device bandwidth. Outlines to obtain the dispersion relation of a circular waveguide enveloping a chiral-dielectric rod and a chiral-dielectric tube were presented, which further interpreted in special cases for the circular waveguides loaded with a chiral-dielectric coaxial rod (structure I) and with a chiral-dielectric wall-lining (structure II). A computer code was developed in MATLAB to solve the dispersion relations and the solutions were substituted into the Pierce-type small-signal gain equation of a gyro-TWT for the device-gain calculation. The electromagnetic analysis of the structure has been validated against simulation. The dispersion shaping and the broadbanding were presented for the two structures. The structure I was found to be more sensitive to chirality parameter than structure II.