A waveguide with central frequency 868 MHz is used in transmission/reflection operation regime to accurately measure the behaviour of the complex permittivity of high complex permittivity granular materials and it has been frequencyextended up to 3 GHz using the Debye fitted relaxation model. It is shown that for highly granular high permittivity materials a waveguide based transmission/reflection technique is necessary to reduce the uncertainty of the extracted permittivity values. The technique is first described and validated with isopropyl alcohol and then applied to the characterization of cement based materials. This paper provides accurate data on the evolution of the complex permittivity of concrete and mortar from the moment of pouring until air dried condition is achieved.

This paper presents the design, manufacture and characterization of a novel 3D passive UHF-RFID tag for embedded applications. The prototype is fabricated using additive manufacturing techniques: 3D printing and copper electroplating. The design, manufacturing process and measurement setup are presented and discussed in detail. We propose a biconical antenna design with spiral strips embedded in the cones to provide compactness without breaking the symmetry of the component and to improve bandwidth. The antenna is matched to a commercial UHF-RFID integrated circuit. We incorporate a packaging design that consists of a dielectric coating, to provide proper operation in different media or surrounding environments with changing electromagnetic properties. The good agreement between experimental results and Finite Element Method simulations allows us to validate the whole process. Finally, a compact capsuletype RFID tag is proposed and its performance in different media is reported.

A cylindrical mode expansion of the fields produced by an embedded antenna is used to determine the dimensions of the antenna packaging in order to minimize antenna impedance changes when the antenna is immersed in a varying dielectric medium.

An RFID-based wireless system to measure the evolution of the setting process of cement-based materials is presented in this paper. The system consists of a wireless RFID temperature sensor that works embedded in concrete, and an external RFID reader that communicates with the embedded sensor to extract the temperature measurement conducted by the embedded sensor. Temperature time evolution is a well known proxy to monitor the setting process of concrete. The RFID sensor consisting of an UWB Bow Tie antenna with central frequency 868 MHz, matched to the EM4325 temperature chip through a T-match structure for embedded operation inside concrete is fully characterized. Results for measurements of the full set up conducted in a real-scenario are provided.

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There is an increasing need for safe and simple techniques for sensing devices and prostheses implanted inside the human body. Microwave wireless inspection may be an appropriate technique for it. The implanted device may have specific characteristics that allow to distinguish it from its environment. A new sensing technique based on the principle of differential resonance is proposed and its basic parameters are discussed. This technique allows to use the implant as a signal scattering device and to detect changes produced in the implant based on the corresponding change in its scattering signature. The technique is first tested with a canonic human phantom and then applied to a real in vivo clinical experiment to detect coronary stents implanted in swine animals.

Background Coronary artery disease (CAD) is the leading cause of death worldwide, and percutaneous coronary intervention with stenting the most widely performed procedure to treat CAD. However, current stent monitoring techniques are invasive and/or ionizing. Microwave spectrometry (MWS) may provide a non-invasive, non-ionizing and cost-effective alternative capable of detecting stent-related pathologies before fatal heart failure. Purpose To develop a new MWS-based technology to detect coronary stents in an in vivo swine model. Methodology First, using two new MWS devices, an in vitro experiment was carried out to demonstrate their ability of detecting the presence of: (1) a stent and (2) stent fractures (SF). To that end, an intact stent was distanced 3, 7, 11 and 15 mm from a MWS near-field probe in open-air conditions. Afterwards, three identical stents were piecemeal cut to emulate type I, II and III SF at different fractions of the stent's length (l): l/5, l/3 or l/2. Additionally, the stent was measured in a phantom substance, to simulate in vivo conditions: it was distanced from 0 to 40 mm in steps of 5 mm. Likewise, using a pair of MWS far-field antennas, the stent in phantom was measured at 10, 20, 30 and 40 mm. Finally, the MWS technology was assessed in vivo. To that end, six Landrace X Large White pigs were submitted to a stent implantation into the circumflex coronary artery (CX). The antennas measured the stent non-invasively, over the rib cage of the animals. MWS analysis were performed baseline (before stent implantation), and at 0, 3, 7, 14, 21 and 35 days of follow up. Measurements were performed only before ventricular systole to avoid differences in the stent position and deformation. Results In vitro, maxima and minima extrema in the microwave frequency response (see figure) were used to detect the stent. Type I and II SF produced 5 and 10% downshifts in the extrema frequencies with respect to the baseline values (unbroken stent), while type III produced 20% upshifts and a maxima splitting. Embedding the stent in phantom produced 25% downshift in the extrema frequencies. In vivo, the MWS antennas were useful to detect the stent presence into the CX artery during all time points of study, in all animals. Conclusions We have developed a new non-invasive and non-ionizing MWS technology capable of detecting the presence of a stent in a porcine model. Furthermore, we have proven how our technology can monitor structural damages in the stent (SF) and changes in its environment. This study proves the MWS potential to become a simple and yet effective method to arise stent-related pathologies in a pre-clinical stage; it could also provide physical insight about additional biological processes. Further improvements on the MWS device as well as in vivo measurements will ensure its consistency when monitoring human stents. Stent detection using MWS technique Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Fundaciό La MARATÓ de TV3, Generalitat de Catalunya, Red de Terapia Celular – TerCel, CIBER Cardiovascular, Spanish Agencia Estatal de Investigaciόn Unidad de Excelencia Maria de Maeztu, Sociedad Española de Cardilogía