A New Planar Microwave Sensor for Building Materials Complex Permittivity Characterization

Abstract

A new microwave sensor is proposed to characterize the complex relative permittivity of building non-magnetic materials and used in the characterization of three concrete samples. The proposed sensor structure consists of a log-periodic planar antenna with microstrip elements tilted forward by an angle β and printed, alternately, on the top and bottom sides of a dielectric layer. The operation principle is based on the measurement of the scattering parameters S11 and S21 in a free space propagation transmitter-receiver setup, for both cases with the material under test (MUT) sample (non-line-of-sight, NLOS) and without it (line-of-sight, LOS). A prototype is fabricated and measured to determine the scattering parameters of concrete samples. After measurements, the obtained results are used in the efficient and accurate Nicolson–Ross–Weir (NRW) method, making it possible to estimate the values of the complex relative permittivity of the concrete blocks. The sensor design is demonstrated from initial simulations to measurements for validation of the developed prototype. The obtained results for the complex relative permittivity of concrete are in agreement with those available in the literature and the difference between the simulated and measurement results for the sensor antenna resonant frequency is 4.71%. The used measurement setup can be applied to characterize different types of solid or liquid dielectric materials.

Differential Microstrip Sensor for Complex Permittivity Characterization of Organic Fluid Mixtures

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“…One of the important organic fluids of human biological liquids is urine [ 11 ]. Urine is a liquid waste of the body consisting of water, inorganic salts, and organic compounds [ 3 ]. Urine color, which depends on the proportion between metabolites and water, can be used to detect a person’s hydration state and early dehydration problems [ 12 ].…”

Determination of Time Domain Reflectometry Surface Sensors Sensitivity Depending on Geometry and Material Moisture

“…The relative dielectric permittivity (ε) of water is about 80.0 and is much higher than for other materials typically applied in the building industry [8][9][10]. The value of relative dielectric permittivity is frequency-dependent and decreases significantly for the frequency above 3 GHz [11][12][13]. The TDR measuring devices often utilize pulse signals with the rise time of approximately 0.3 ns, which corresponds to high-energy Fourier components emitted at around 3 GHz [11].…”

High-Resolution Detection of Rock-Forming Minerals by Permittivity Measurements with a Near-Field Scanning Microwave Microscope

“…Permittivity measurements can be classified in a large number of techniques [ 24 , 25 , 26 , 27 , 28 , 29 ], which can be categorized according to the measurable frequency range and the attributes of the materials to be characterized, such as dielectric losses, shape, or homogeneity [ 30 ]. Since rocks are heterogeneous materials, the approaches followed to measure their dielectric properties are very varied.…”