A Free-Space Transmission Setup for Material Parameters Estimation with Affordable and Non-Synchronized Software-Defined Radios in the 0.85–1.55 GHz Band

Abstract

This paper describes a prototype of a free-space transmission setup for dielectric parameters estimation. The transmitter and receiver, both configurable by software and working in the range 0.85–1.55 GHz, are not synchronized, as they use different clocks. An estimation of the dielectric permittivity of a planar sample was obtained by comparing our measurements with a numerical model. A parametric study with different variables was conceived in order to find the best fit between measurements and simulations. Customized techniques were applied to deal with noise and inconsistencies found in the measurements. The genetic algorithm was used to adjust the constants that minimized the error between simulated and experimental data. Results for a reference sample of polymethylmethacrylate are presented and discussed. Although the accuracy of the proposed approach in recovering the dielectric parameters of the sample was relatively low, the simplicity and cost-effectiveness of this setup make it interesting for scenarios where a rough characterization of the material is sufficient.

Detecting Moisture in Bauxite Using Microwaves

“…The microwave analyser is mounted across a conveyor belt that is transporting bauxite ore from ship to factory, with a square-shaped transmitting antenna close below the belt and an identical receiving antenna approximately 0.6 m above, arranged so that transmitted signals pass through the ore mixture before arriving at the receiving antenna, as sketched in Figure 1. This is termed the free space transmission method, especially when used to determine dielectric properties [8], although our purpose here is rather to measure moisture content.

Figure 1 A sketch of the microwave analyser antennae mounted across a bauxite ore conveyor belt, showing key dimensions. The blue arrows illustrate microwave rays scattering from the rough ore surface, with some being lost to the environment.

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“…https://doi.org/10.1017/S1446181124000026 Published online by Cambridge University Press[8] Detecting moisture using microwaves…”