1,721,055 research outputs found
Modeling and realization of a 24-GHz FMCW radar for accurate target distance identification
No full textIn this work, the modeling and realization of a 24-GHz Radar based on the BGT24MTR11 chipset is presented. The model has been implemented with the Visual System Simulator (VSS) tool available inside the AWR software. Two modular implementations of the designed Radar have been proposed. One in which the Radar is driven by a DAQ card from National Instruments and one in which the Radar is controlled by a PLL circuit. The circuit model has been validated through a comparison with analytical and experimental measurements considering as target a metallic sphere. The better performance of the architecture with the PLL has been also evidenced by considering a scenario with a panel target
Wideband measurement of dielectric properties of wheat flour
No full textUse of electromagnetic (EM) fields in the food industry for food inspection as well as sterilization and drying is increasing. To develop such applications, the knowledge of the dielectric properties of food is fundamental. In the literature, there is scarcity of data on dielectric properties of powdered foods, with reported values that are usually at specific frequencies only. This article reports the development of an experimental framework to characterize the dielectric properties of powdered food over a wide range of frequencies. The used methodologies include the open-ended coaxial probe technique and waveguide systems: the first being intrinsically a broadband technique but strongly dependent on the type of material being tested, and the latter being a medium- to narrowband technique allowing a better control of the tested material. The proposed framework is then used to measure the dielectric properties of several types of flour between 500 MHz and 20 GHz. The measured properties are then characterized in terms of density and interpolated with a Cole-Cole dispersive model. From the measured results, the suitability of the proposed setup was demonstrated. Additionally, it was verified that the permittivity of flour does not depend on the brand and can be expressed as a function of the density of the material, following a mixture formula already proposed in the literature. Moreover, the proposed Cole-Cole fit is able to represent the frequency behavior of the real part of permittivity of flour with differences within 3% from the measured data
A comparison between multiple-input multiple-output and multiple-input single-output radar configurations for through-the-wall imaging applications
Full text linkThe performances of a multiple-input multiple-output (MIMO) radar, employing 16 equivalent antennas, and multiple-input single-output (MISO) radar, employing 10 antennas, for through-the-wall imaging applications are analyzed. In particular, imaging algorithms based on the Fourier transform (FT) and the multiple signal classification (MUSIC) available in the literature are compared with the FT-MUSIC hybrid algorithm recently developed by the authors. Three different investigations have been performed. The first, performed analytically, refers to a scenario in which a point scatterer is placed in free space, and the second, addressed numerically using the CST full-wave software, refers to a scenario in which two targets are present, while the last was executed in a real scenario where a metal panel is placed behind a tuff wall. All the algorithms and radar configurations were found to be suitable for accurately reconstructing the position of the investigated target. In particular, applying the FT technique, the MISO configuration has a lower cross-range half-power beamwidths (HPBW) than the MIMO one, while the range HPBW is the same for the two radar configurations. Despite the different number of elements present in the two radar configurations, similar range and cross-range HPBW are obtained for both configurations when MUSIC and FT-MUSIC techniques are employed. The field of view for FT and FT-MUSIC is about 45°, while it is less than 15° for the MUSIC algorithm. The HPBWs obtained with the experimental setup are very close to those obtained in the analytical study. Finally, the proposed experimental MISO radar acquires the data in half the time required by the MIMO one. The numerical results, confirmed by the experimental measurements, seem to indicate in the FT-MUSIC technique the one that provides the best performance for the considered radar configurations
Improvement and metrological validation of TDR methods for the estimation of static electrical conductivity
No full textAccurate measurement of the static electrical conductivity provides a great insight into the characteristics and quality status of various materials. To overcome some limitations of the traditional measurement methods, there has been a growing interest toward the investigation of enhanced techniques for measuring electrical conductivity. In this regard, time-domain reflectometry (TDR) has attracted considerable attention, also due to the possibility of simultaneously monitoring different physical parameters. Although initially introduced for monitoring soil properties, the application of the TDR-based technique might be an interesting and cost-effective means in many other fields. However, the accuracy of traditional TDR-based electrical conductivity measurements is strongly influenced by the preliminary calibration technique. On such basis, in this paper, two innovative approaches for a more straightforward and accurate evaluation of the electrical conductivity are presented. The first method relies on the combination of the TDR measurement with transmission-line modeling (TLM); the second method simply relies on a couple of independent capacitance measurements (ICMs) performed through an LCR meter. As a further goal, the metrological performance of this last method is compared with that of the traditional method, thus validating its applicability. Experimental results and related uncertainty analysis on various samples demonstrate that the proposed alternative method is definitely suitable for a simpler and accurate estimation of the static electrical conductivity, also when dealing with moistened soils. © 2006 IEEE
Compact system for measuring the dielectric properties of biological tissues at extremely-low and ultra-low frequencies
No full textThe aim of this paper is to describe a system designed for measuring the dielectric properties of biological tissues at extremely-low frequencies (ELF) and ultra-low frequencies (ULF), in particular in the 0.1 Hz - 1 kHz range. In this frequency range, literature data are very limited or absent, since measurement techniques are strongly affected by systematic errors. In order to carry out the aforementioned measurements, the paper presents the system design and metrological tests for assessing accuracy in complex impedance measurements. The uncertainty of the measuring system was determined using reference R-C circuits, showing extremely low errors as compared to high-accuracy multimeters and LCR meters. In order to obtain the sample complex permittivity, the system was calibrated in saline solutions to determine the cell constant K. Then, experimental results on the bioimpedance and related complex permittivity of bovine liver are shown, performed with the 4-electrode measurement technique to limit the effect caused by the electrodes polarization. In particular, measurements were performed in 20 tissue samples, obtained from 5 different livers. Both conductivity and relative permittivity results have been compared with the few existing literature data, finding a satisfactory agreement between the values obtained from the literature and those achieved by measurements with the proposed system
Extending Industrial Applicability of TDR Liquid Level Monitoring Through Flexible Probes
Full text linkIn the present work, an alternative probe configuration
to be used for time domain reflectometry (TDR)-based
monitoring of liquid level inside tanks is presented. The proposed
probe, which resorts to a bifilar transmission line configuration,
is flexible and adaptable to the surface of the containers to
be monitored. This feature, along with the other advantageous
characteristics of TDR, makes this probe configuration particularly
attractive for industrial applications. In this paper, to
test the applicability of the method, two different scenarios are
considered: monitoring of liquids contained in metallic tanks and
non-invasive monitoring of liquids in non-metallic tanks. Results
show that, in both cases, the proposed system has considerable
potential for being easily and effectively employed in practical,
industrial applications
An innovative method for TDR measurement of static electrical conductivity in granular materials
No full textTime domain reflectometry (TDR) is a robust approach for measuring static electrical conductivity of moistened granular materials. Although initially introduced for monitoring soil salinity, its application to granular materials might be an interesting and cost-effective means for monitoring the quality-status of various materials. However, the traditional approach requires tedious and time-consuming preliminary calibration measurements on reference liquids. In this paper, an innovative approach for the direct estimation of the electrical conductivity is presented. In fact, it is demonstrated that the suitable combination of the TDR measurement with a transmission-line modeling of the measurement setup, successfully leads to the avoidance of the preliminary calibration procedure. Investigations carried out on water and on moistened sand samples demonstrate that the performance of the proposed method in estimating the static conductivity is comparable with that achievable through the traditional approach. © 2009 IEEE
Complex permittivity measurements for moisture and salinity characterization of building materials
No full textIn this paper, preliminary results of complex permittivity measurements of clay-brick material will be presented. The general aim of the experimental project is to correlate the measured permittivity of construction materials with the content of water and salt, in order to obtain information on the condition of ancient walls by using non-invasive techniques. The complex permittivity values reported in this paper have been obtained by waveguide measurements on samples of clay-brick dried and then immersed in demineralized water or in a saturated solution of demineralized water and NaCl. © (2017) by the International Measurement Confederation (IMEKO)
Extending industrial applicability of TDR liquid level monitoring through flexible probes
No full textIn the present work, an alternative probe configuration to be used for time domain reflectometry (TDR)-based monitoring of liquid level inside tanks is presented. The proposed probe, which resorts to a bifilar transmission line configuration, is flexible and adaptable to the surface of the containers to be monitored. This feature, along with the other advantageous characteristics of TDR, makes this probe configuration particularly attractive for industrial applications. In this paper, to test the applicability of the method, two different scenarios are considered: monitoring of liquids contained in metallic tanks and non-invasive monitoring of liquids in non-metallic tanks. Results show that, in both cases, the proposed system has considerable potential for being easily and effectively employed in practical, industrial applications
Analysis and Experimental Characterization of an Alumina Woodpile-Covered Planar Antenna
No full textThe reflection scattering parameter, the gain, and the radiation pattern in the E- and H-planes, have been measured for a woodpile-covered patch, with the superstrate at different distances from the antenna. The main effect of the EBG on the antenna performances is an enhancement of about 10 dB in maximum gain. Experimental results are also presented for the transmission properties of woodpile cavities, and a comparison is reported with the Fourier Modal Method
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