A 100GHz grooved circular empty cavity for low loss dielectric substrate measurements in W band

A 100GHz grooved circular empty cavity is proposed for the low loss dielectric substrate measurements by the cut-off circular waveguide method. The influence of the excitation holes for the coaxial cable with a small loop are investigated by a 3D electromagnetic simulator. The diameter of the excitation hole is determined base on the calculated results, and two kinds of four 100GHz grooved circular empty cavities are fabricated. Comparative experiments of the cavities with the different excitation holes validate the simulated results. Moreover, the complex permittivity of a PTFE plate is measured using the fabricated four cavities by the cut-off circular waveguide method around 85GHz. It verifies that the proposed 100GHz cavity for the cut-off waveguide method is useful for the complex permittivity measurement of low loss dielectric substrates in W band.