Measurement of the electrical constitutive parameters of materials using antennas

A general technique is presented for measuring the electrical constitutive parameters of a material using a monopole (dipole) antenna. A normalized impedance that is only a function of the dimensionless parameterkh(wavenumber length) is defined for the antenna. The normalized impedance is expressed as a rational function, and the coefficients in this function are determined from a measurement of the impedance in a standard medium. The impedance measured in a material with unknown constitutive parameters is used with the rational function to form a polynomial inkh. The constitutive parameters of the medium are determined from a root of this polynomial. The measurement technique is implemented for a rational function of order three. The constitutive parameters of the alcohol 1-butanol and saline solutions were measured over a range of frequencies using the technique with cylindrical and conical monopole antennas. The measured constitutive parameters are in good agreement with those determined by previous investigators.