Broad-band simultaneous measurement of the complex permittivity tensor for uniaxial materials using a coaxial discontinuity

A technique is presented for simultaneously measuring the complex values of the permittivity tensor of uniaxial materials. A gap in a coaxial line is filled with the material under test. Complex elements of the permittivity tensor are computed from measurements of the S-parameters (S₁₁ and S₂₁ ) made on the gap taking into account higher order modes excited at the discontinuity. The authors demonstrate that this problem is reduced to two systems, each containing three equations with three unknowns. Computer time is therefore reasonable without affecting accuracy. Measured complex permittivity data from 45 MHz to 18 GHz are presented. Good agreement between calculated and generally accepted values is obtained