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The subject of this paper is the design and calibration of an open-ended coaxial probe for the nondestructive measurement of the dielectric properties of concrete. Measurements are made between 100-900 MHz, frequencies which are often used in geophysics and civil engineering for ground penetrating radar inspection. The probe is calibrated using measurements on saline solutions in conjunction with three different mathematical techniques for comparative study. Measurements of mortar and concrete specimens having different water/cement ratios were made in order to observe the standard deviations due to their heterogeneous nature. Similar to the case of relatively homogeneous rock specimens (limestone and granite), the standard deviation for heterogeneous concrete samples do not exceed 5%. In addition, the effect of the concrete's porosity on its dielectric properties was clearly observed: measured permittivity between 4-4.5 at 900 MHz for porous concrete, and between 6.5-7.5 at 900 MHz for dense concrete. [ABSTRACT FROM AUTHOR]

In this paper, a class of nonradiative dielectric (NRD)-guide discontinuities is studied toward the establishment of design rules of NRD-guide circuits and components for millimeter-wave applications. A mode-matching technique with a multimodal transverse resonance condition is formulated to derive a generalized scattering matrix that allows accounting for effects of higher order modes and intermode coupling. Transmission properties of an NRD structure featuring a multilayered dielectric in cross section are presented. Mode conversion and power transfer among principal NRD-guide modes are, in particular, characterized for design consideration of NRD-guide components and circuits. New sets of easy-to-use design curves are introduced, thereby allowing practitioners to choose appropriate dielectric materials and NRD-guide topologies. Equivalent-circuit models are extracted from the generalized S-matrix for some basic and practically useful discontinuities involved in the design of almost every NRD-guide component, which include open ends, junctions, steps, and gaps. Calculated results of the selected structures are found to be in a good agreement with measurements. Dispersion diagrams of periodic NRD structures are also given in this paper [ABSTRACT FROM PUBLISHER]