Improved Methods for Fourier-Based Microwave Imaging.

Fourier-based imaging has been widely adopted for microwave imaging thanks to its efficiency in terms of computational complexity without compromising image resolution. Together with other backpropagation imaging algorithms like delay-and-sum (DAS), they are based on a far-field approach to the electromagnetic expression relating to fields and sources. To improve the accuracy of these techniques, this contribution presents a modified version of the well-known Fourier-based algorithm by taking into account the field radiated by the Tx/Rx antennas of the microwave imaging system. The impact on the imaged targets is discussed, providing a quantitative and qualitative analysis. The performance of the proposed method for subsampled microwave imaging scenarios is compared against other well-known aliasing mitigation methods.

Compact Wearable Antenna with Metasurface for Millimeter-Wave Radar Applications.

Three metasurfaces (MTS) are designed to be combined with a series end-fed 1 × 10 array antenna with a modified Dolph-Chebyshev distribution for imaging applications in the millimeter frequency range, 24.05-24.25 GHz. A reduction in secondary lobes and an increase in FTBR can be achieved while preserving gain, radiation efficiency, SLL and size using an MTS-array combination. Moreover, as a result of each single-layer MTS-array combination, operation bandwidth is widened, with gain and radiation efficiency enhancement. The overall devices' size is 86.8 × 12 × 0.762 mm3. The envisioned application is collision avoidance in aid to visually impaired people at a medium-long distance.

A Portable Electromagnetic System Based on mm-Wave Radars and GNSS-RTK Solutions for 3D Scanning of Large Material Piles.

In this paper, a portable three-dimensional (3D) scanning system for the accurate characterization of large raw material (e.g., cereal grain, coal, etc.) stockpiles is presented. The system comprises an array of high resolution millimeter-wave radars and a cm-level accuracy positioning system to accurately characterize large stockpiles by means of a high-resolution 3D map, making it suitable for automation purposes. A control unit manages the data received by the sensors, which are sent to a computer system for processing. As a proof of concept, the entire sensor system is evaluated in a real environment for electromagnetically scan a scaled stockpile of coal, used in the industry for handling raw materials. In addition, a highly efficient processing adaptive algorithm that may reconstruct the scanned structure in real-time has been introduced, enabling continuous dynamic updating of the information. Results are compared with those from a photogrammetry-like technique, revealing an excellent agreement.

Paving the Way to Eco-Friendly IoT Antennas: Tencel-Based Ultra-Thin Compact Monopole and Its Applications to ZigBee.

An ultrathin, compact ecofriendly antenna suitable for IoT applications around 2.45 GHz is achieved as a result of exploring the use of Tencel fabric for the antenna's design. The botanical ecofriendly Tencel is electromagnetically characterized, in terms of relative dielectric permittivity and loss tangent, in the target IoT frequency band. To explore the suitability of the Tencel, a comparison is conducted with conventionally used RO3003, with similar relative dielectric permittivity, regarding the antenna dimensions and performance. In addition, the antenna robustness under bent conditions is also analyzed by measurement. To assess the relevance of this contribution, the ultrathin ecofriendly Tencel-based antenna is compared with recently published antennas for IoT in the same band and also, with commercial half-wave dipole by performing a range test on a ZigBee-based IoT testbed.

Comment on the Article "A Lightweight and Low-Power UAV-Borne Ground Penetrating Radar Design for Landmine Detection".

This reply aims to correct some incomplete/incorrect information provided in the article "A Lightweight and Low-Power UAV-Borne Ground Penetrating Radar Design for Landmine Detection", when the authors compare their results with some state-of-the-art contributions.

On the Broadening of Single-Layer Metasurface Bandwidth by Coupling Resonances.

In this contribution a new technique to increase the bandwidth of metasurfaces without increasing their profile is presented. This work takes advantage of the potential multiresonant behavior of a metamaterial whose unit cells comprise nested metallization geometries in the same layer. The novelty stems from the possibility of overlapping these resonances for increasing the bandwidth (instead of obtaining a multiresonant metasurface). Several guidelines to achieve the aforementioned bandwidth broadening, which are applicable to all metasurface designs, will be provided. An equivalent circuit model will be used to better explain the presented technique; then, it will be applied to several metasurface absorbers (MTAs), showing not only a bandwidth broadening but also an absorption reinforcement. Measurements will be also presented to corroborate the simulation results.

Zirconia-Based Ultra-Thin Compact Flexible CPW-Fed Slot Antenna for IoT.

An ultra-thin compact flexible CPW-fed slot monopole antenna suitable for the Internet of Things (IoT) applications was achieved as a result of exploring the use of Zirconia-based ENrG's Thin E-Strate® for the antenna's design. The electromagnetic characterization of the novel material at the frequency range of interest was analyzed. A comparison was made concerning the required dimensions and the simulation results regarding impedance matching and radiation properties, for three different dielectric substrates: Novel flexible ceramic (ENrG's Thin E-Strate), rigid Arlon 25N, and flexible Polypropylene (PP). Two different metallization techniques-electrotextile-based and inkjet printing-were used in the fabrication of prototypes based on ENrG's Thin E-Strate. Return losses measured results for the fabricated prototypes with both procedures was compared, as well as with simulation. The best prototype on the ENrG's Thin E-Strate was compared with one on Arlon 25N, in terms of radiation properties in an anechoic chamber, and conclusions were drawn.

Correction: Elucidation of molecular kinetic schemes from macroscopic traces using system identification.

[This corrects the article DOI: 10.1371/journal.pcbi.1005376.].

RFID Technology for Management and Tracking: e-Health Applications.

Radio frequency identification (RFID) has become a key technology in the logistics and management industry, thanks to distinctive features such as the low cost of RFID tags, and the easiness of the RFID tags' deployment and integration within the items to be tracked. In consequence, RFID plays a fundamental role in the so-called digital factory or 4.0 Industry, aiming to increase the level of automatization of industrial processes. In addition, RFID has also been found to be of great help in improving the tracking of patients, medicines, and medical assets in hospitals, where the digitalization of these operations improves their efficiency and safety. This contribution reviews the state-of-the-art of RFID for e-Health applications, describing the contributions to improve medical services and discussing the limitations. In particular, it has been found that a lot of effort has been put into software development, but in most of the cases a detailed study of the physical layer (that is, the characterization of the RFID signals within the area where the system is deployed) is not properly conducted. This contribution describes a basic RFID system for tracking and managing assets in hospitals, aiming to provide additional details about implementation aspects that must be considered to ensure proper functionality of the system. Although the scope of the RFID system described in this contribution is restricted to a small area of the hospital, the architecture is fully scalable to cover the needs of the different medical services in the hospital. Ultra high-frequency (UHF) RFID technology is selected over the most extended near-field communication (NFC) and high-frequency (HF) RFID technology to minimize hardware infrastructure. In particular, UHF RFID also makes the coverage/reading area conformation easier by using different kinds of antennas. Information is stored in a database, which is accessed from end-user mobile devices (tablets, smartphones) where the position and status of the assets to be tracked are displayed.

Elucidation of molecular kinetic schemes from macroscopic traces using system identification.

Overall cellular responses to biologically-relevant stimuli are mediated by networks of simpler lower-level processes. Although information about some of these processes can now be obtained by visualizing and recording events at the molecular level, this is still possible only in especially favorable cases. Therefore the development of methods to extract the dynamics and relationships between the different lower-level (microscopic) processes from the overall (macroscopic) response remains a crucial challenge in the understanding of many aspects of physiology. Here we have devised a hybrid computational-analytical method to accomplish this task, the SYStems-based MOLecular kinetic scheme Extractor (SYSMOLE). SYSMOLE utilizes system-identification input-output analysis to obtain a transfer function between the stimulus and the overall cellular response in the Laplace-transformed domain. It then derives a Markov-chain state molecular kinetic scheme uniquely associated with the transfer function by means of a classification procedure and an analytical step that imposes general biological constraints. We first tested SYSMOLE with synthetic data and evaluated its performance in terms of its rate of convergence to the correct molecular kinetic scheme and its robustness to noise. We then examined its performance on real experimental traces by analyzing macroscopic calcium-current traces elicited by membrane depolarization. SYSMOLE derived the correct, previously known molecular kinetic scheme describing the activation and inactivation of the underlying calcium channels and correctly identified the accepted mechanism of action of nifedipine, a calcium-channel blocker clinically used in patients with cardiovascular disease. Finally, we applied SYSMOLE to study the pharmacology of a new class of glutamate antipsychotic drugs and their crosstalk mechanism through a heteromeric complex of G protein-coupled receptors. Our results indicate that our methodology can be successfully applied to accurately derive molecular kinetic schemes from experimental macroscopic traces, and we anticipate that it may be useful in the study of a wide variety of biological systems.