A Complex Permittivity Estimation Method Based on Measuring the Radiation Pattern of a Monopole Antenna with a Material under Measurement on the Ground Plane

摘要

This letter presents a new complex permittivity value estimation method based on measuring the radiation pattern of a quarter wavelength monopole antenna. A material under measurement is placed on the ground plane of the monopole antenna, causing a radiation pattern change depending on a complex permittivity value, which consists of relative permittivity and loss tangent values. The measured radiation pattern is compared with parametrically simulated radiation patterns obtained by Finite Difference Time Domain analyses with respect to complex permittivity values. In this comparison, a mean square error criterion is employed. In the proposed method, the material under measurement is just placed on the ground plane, allowing nondestructive and contactless complex permittivity measurement. Furthermore, the proposed method makes it possible to measure complex permittivity values for powder and liquid materials. To confirm estimation accuracy of the proposed method, the complex permittivity value of a bundle of paper is measured; the estimated result is compared with that obtained by the cavity resonance method. The results agreed well, confirming the validity of the proposed method. The proposed method can also be used to validate measured values obtained by existing methods.