Permittivity and Conductivity Measurements of Building Materials at 5.8 GHz and 41.5 GHz

Abstract

The results of various experiments performed to characterize electromagnetic properties of typical building materials at BRAN (Broadband Radio Access Networks) and MVDS (Multipoint Video Distribution System) bands are presented and compared. Transmission and reflection coefficients were measured as functions of the angle of incidence, using a wideband sounder based on the swept frequency technique. A high precision angular positioning system was built and used in co-ordination with the measurement equipment.The dielectric constants (ε_r) were estimated by comparing values predicted with a multiple successive internal reflection model and measured transmission and reflection coefficients. It has been found that the variation of the dielectric constant value with the frequency does not necessarily follow the same trend for different materials. For example, the measured ε_r for plasterboard presents an increment withfrequency (2.02 at 5.8 GHz, 2.5 at 41.5 GHz – measured by theauthors –, 2.58 at 59.5 GHz, and 2.81 at 60.2 GHz – given byliterature –), while the values for glass follow a wanderingpattern (6.06 at 5.8 GHz, 5–10 at 10 GHz, 3.41 at 41.5 GHz, 7.51at 57.6 GHz, and 5.29 at 60.2 GHz). Moreover, the measuredε_r for a brick wall at 5.8 GHz (3.58) shows differenceswith values reported at 2 GHz (4.44).