36 research outputs found
Design, Additive Manufacturing, and Electromagnetic Characterization of Alumina Cellular Structures for Waveguide Antenna
No full textIn this work, a design and additive manufacturing approach is successfully implemented to print via digital-light-processing cubic cellular alumina structures for antenna waveguides. Cellular structures’ porosity is varied during the design phase and different dielectrics are finally produced and inserted in antenna waveguides with the aim of decreasing the cutoff frequency in the range from 1 to 10 GHz. In parallel, the electromagnetic behavior of the cellular alumina structures into the antenna waveguide as the structure porosity varies is simulated. Printed samples are then tested in a laboratory setup. In the results obtained, it is shown that the antenna cutoff frequency increases as the porosity of the alumina cellular structures increases, also evidencing a linear correlation between their average dielectric constant and porosity. In this study, it is demonstrated that the dimensional accuracy achieved after the sintering process is essential because even a small (1%) deviation of the sintered sample size from the nominal ones, due to nonlinear shrinkage, highly affects their cutoff frequencies
Experimental analysis of dielectric structures with a two-step electromagnetic imaging method
No full textA novel two-step electromagnetic imaging method, suitable for the analysis of hidden inclusions in dielectric structures, is reported in this paper. In particular, two distinct steps compose the present technique. The first one extracts from the raw data an estimation of the scattered field due to the inclusions, and provides a first qualitative reconstruction of the structure under test. This information is then exploited by the second step, in which a quantitative inexact-Newton inversion approach retrieves a map of the dielectric characteristics of the examined region. Experimental data obtained with a tomograph prototype are used to validate the proposed inversion scheme
Detection of metallic bodies in dielectric structure by microwave imaging - Experimental results
No full textThis paper reports experimental results concerning the inspection of dielectric structures in which metallic inclusions are present. The investigation is based on a microwave imaging approach and the measured data have been obtained by using a prototype of a microwave tomograph. The reconstructed images of the structures under test have been constructed by using a nonlinear inverse scattering procedure based on a truncated Landweber method. The reported results concern in particular the inspection of wood materials with cylindrical metallic inclusions
A microwave tomographic system for wood characterization in the forest products industry
No full textNondestructive testing and evaluation techniques able to extract information about the internal structure of the samples under test are very important in the wood industry. Microwave imaging systems have been considered for a long time promising apparatuses for this task. In this framework, approaches exploiting the full scattering phenomena for creating images of the distributions of the dielectric properties of the targets have been developed in the last few years. In this paper, a prototype of microwave tomographic system is presented and several experimental validation confirming its suitability for the use in the wood and forest product industry are reported
Experimental assessment of a tomographic measurement system for quantitative microwave imaging
No full textIn-situ microwave tomography for parts’ cooldown monitoring in powder bed fusion of polymers
No full textISSN:2214-860
Design and Experimental Test of a Microwave System for Quantitative Biomedical Imaging
No full textDespite the numerous advancements in the field of microwave measurement systems and techniques for biomedical and industrial applications, the development of cheap and reliable microwave imaging devices is still a challenge. In this contribution, a tomograph prototype specir1cally designed for medical imaging is presented. An array of custom antennas is placed in contact with the target, and the scattered field data are collected by means of a computer-controlled switching board connected to a vector network analyzer. The acquired data are then processed with a combined qualitative/quantitative inversion scheme, whose final goal is to retrieve a spatial map of the dielectric properties of the sample. After the description of the developed system and an outline of the adopted inversion method, preliminary experimental results are shown in order to validate the effectiveness of the approach
A Tomograph Prototype for Quantitative Microwave Imaging: Preliminary Experimental Results
No full textA new prototype of a tomographic system for microwave imaging is presented in this paper. The target being tested is surrounded by an ad-hoc 3D-printed structure, which supports sixteen custom antenna elements. The transmission measurements between each pair of antennas are acquired through a vector network analyzer connected to a modular switching matrix. The collected data are inverted by a hybrid nonlinear procedure combining qualitative and quantitative reconstruction algorithms. Preliminary experimental results, showing the capabilities of the developed system, are reported
