A New Free-space Method For Measuring The Permittivity Of Walls In Indoor Buildings

The dielectric constant of the building walls is extremely important in the indoor electromagnetic environment modelling and electromagnetic wave propagation prediction.It also provides a basis for desiring indoors wireless communication system.This paper proposed two improved free-space methods for measuring the indoor dielectric constant of the real building walls,computing the dielectric constant by measuring the S-parameters.Compared with the traditional free-space method,the two methods proposed by this paper could calculate the dielectric constant of walls in narrow corners.which simplifies the configuration of the experimental system and reduces the error introduced by measurements as well.This paper gives a brief introduction about the basic theory and background knowledge of the free-space method at first,discussing the disadvantages of the traditional free-space method in measuring the dielectric constant in real indoor environment.It proposes two improved free-space methods:dual polarization measurement and dual parameter measurement and deduces the dielectric inversion formulas of the two methods.This paper also proposes the aluminum correction procedure for dual polarization measurement and the error correction factor for dual polarization,which raises the accuracy of the entire measurement system.An experiment to verify the validity of the proposed methods was designed and implemented.and the results proved that both methods achieved high accuracy.which can be applied to the on-site permittivity measurement.Based on the comparison between the dual polarization measurement.dual parameter measurement and the waveguide method,the paper deduces the error amplification function of the two improved methods.and draws the curves with Matlab.According to the results,the paper analyses the effect on the dielectric constant caused by the S-parameters measurements.