Improved modeling of permittivity measurement cells

The impedance of metallic cavity, which contains a material, the complex permittivity of which is ε*, is a rational functional of the complex variable (ε*-ε₀,/ε₀). Since the poles and the residuals of this function are all real, it can be written as a ratio of two polynomials, with real coefficients. The degrees of the polynomials can be chosen so that the experimental values fit the theory with a desired accuracy. It is shown that formulas of this type can be used for calibrating any dielectric measurement cell, avoiding the establishment of an equivalent circuit of the cell