This paper contains measured data and empirical models for 2.5 and 60 GHz in-building propagation path loss and multipath delay spread. Path loss measurements were recorded using a broadband sliding correlator channel sounder which recorded over 39000 power delay profiles (PDPs) in 22 separate locations in a modern office building. Transmitters and receivers were separated by distances ranging from 3.5 to 27.4 m and were separated by a variety of obstructions, in order to create realistic environments for future single-cell-per-room wireless networks. Path loss data is coupled with site-specific information to provide insight into channel characteristics. These measurements and models may aid in the development of future in-building wireless networks in the unlicensed 2.4 and 60 GHz bands.

In-building wideband partition loss measurements at 2.5 and 60 GHz

This paper intends to present a summary of the technical issues arising in the exploitation of the 60 GHz mm-wave band for mobile and personal communications. The most significant applications proposed so far are surveyed, with particular emphasis placed on recent experimentation about millimeter-wave propagation for road/railway transportation as well as indoor scenarios. As a case study, the capacity of a (micro-)cellular Code Division Multiple Access (CDMA) network in the 60-GHz band is also evaluated in detail.

Mobile and Personal Communications in the 60 GHz Band: A Survey

We have measured (at 57.5 GHz) the reflection and transmission coefficients of typical walls, floor, ceiling, window, and partitions and have compared the measured reflection characteristics with the reflection characteristics estimated by multilayer dielectric models. Although the positional inhomogeneity of structures gives rise to some variation from one measured position to another, these positional variabilities are not large. The overall trend of reflection coefficients calculated by multilayer dielectric models thus agrees fairly well with the trend of the measurements. We have shown that the use of circular polarization can reduce the reflection even if the interior parts of the structure have complicated structures. In addition, the shadowing effects of several types of partitions were measured. The transmission coefficients of partitions depend on the materials. The transmission losses of plywood-made partitions are found to be fairly low.

Measurements of reflection and transmission characteristics of interior structures of office building in the 60-GHz band

The results of measurement and monitoring of reflection and transmission properties of cement-based specimens (blocks of mortar, concrete) obtained by using a simple and an inexpensive measurement system at microwave frequencies (X-band) are presented. Dependencies of the reflection and transmission coefficients on water-to-cement (w/c) ratio, preparing and curing conditions of the specimens are demonstrated. It is shown that the amplitudes of reflection and transmission coefficients, together with thickness of the specimens, determine the complex dielectric permittivity of the hardened cement-based specimens. The expected applications of the results for the determination of physical properties of cement-based materials are discussed. The causes and effects of measurement errors and uncertainties are also discussed.

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Measurement and monitoring of microwave reflection and transmission properties of cement-based specimens

The reflection characteristics and refractive indices of construction materials in the millimeter wave bands are needed for development of millimeter-wave application systems such as indoor communication systems and short-range sensing systems. Because so little experimental data of construction materials at millimeter-wave bands has been available, the authors have measured the reflection and transmission coefficients of a concrete plate, plasterboard, rock wool, a floorboard, a carpet tile, at 57.5, 78.5, and 95.9 GHz. The refractive indices of the materials that can be modeled as a homogeneous dielectric plate with a smooth surface were estimated by the combined use of reflection and transmission data. The refractive indices of a concrete plate, plasterboard, a floorboard, and rock wool at 57.5 GHz were found to be 2.55-j0.084, 1.50-j0.01, 1.98-j0.083, and 1.26-j0.005, respectively. These indices showed little frequency dependence in the measured frequency range, except for that of the floorboard, which varied about 10%. The authors also measured the reflection characteristics of materials with inhomogeneous structures or rough surfaces, and found that the specular reflection from a concrete plate and a floorboard can be reduced significantly by covering them with carpet tiles with rough surfaces.

Measurements of reflection characteristics and refractive indices of interior construction materials in millimeter-wave bands

The complex refractive index of concrete is measured at 57.5 GHz by the combined use of free-space reflection and transmission methods. The measured refractive index of the concrete 14 months after concreting was 2.55-j0.084. This index, in particular the imaginary part, is sensitive to the curing time after concreting and the water content. The transmission coefficient of a concrete plate, mainly determined from the imaginary part of the complex refractive index, is less than -20 dB/cm when the concrete is fresh and moist and reaches -9 dB/cm after aging for fourteen months. In contrast, the reflection coefficient of a concrete plate is less dependent on water content.

J. Polivka

Papers

Measurement of the complex refractive index of concrete at 57.5 GHz