Layered transition metals dichalcogenides such as MoS₂ and WS₂ have shown a tunable bandgap, making them highly desirable for optoelectronic applications. Here, we report on one-step chemical vapor deposited MoS₂, WS₂ and Mo_xW_1-xS₂ heterostructures incorporated into photoconductive devices to be examined and compared in view of their use as potential photodetectors. Vertically aligned MoS₂ nanosheets and horizontally stacked WS₂ layers, and their heterostructure form Mo_xW_1-xS₂, exhibit direct and indirect bandgap, respectively. To analyze these structures, various characterization methods were used to elucidate their properties including Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectrometry and high-resolution transmission electron microscopy. While all the investigated samples show a photoresponse in a broad wavelength range between 400 nm and 700 nm, the vertical MoS₂ nanosheets sample exhibits the highest performances at a low bias voltage of 5 V. Our findings demonstrate a responsivity and a specific detectivity of 47.4 mA W⁻¹ and 1.4 × 10¹¹ Jones, respectively, achieved by Mo_xW_1-xS₂. This study offers insights into the use of a facile elaboration technique for tuning the performance of Mo_xW_1-xS₂ heterostructure-based photodetectors.

This article derives design guidelines for radar absorbing materials (RAM) integrating connected, fishnet-like, resistive frequency selective surfaces (R-FSSs). While R-FSSs have been long used in the radar signature and electromagnetic interferences reduction, nevertheless the configuration where all the unit-cells are physically connected has not been yet thoroughly investigated for this aim. Indeed, the fishnet-like arrangement can guarantee extraordinary key advantages in terms of RAMs fabrication, especially for large production scales. Therefore, this article, by resorting to significant test-cases, aims at deriving practical design procedures to realize advantageous connections among adjacent FSS unit-cells. Specifically, the effects on the overall FSS impedance behavior of the geometrical variations in the unit-cell connections are deeply explored. To ensure the broad applicability of the presented guidelines, the study has been carried out by recurring to an equivalent circuit analysis, based on the transmission line theory, and on accurate full-wave simulations. To prove the practical significance of the developed guidelines, two prototypes of the same RAM based on a resistive and connected FSS have been fabricated. Both in a small flat panel and in a large-scale conformal arrangement, the electromagnetic reflection was drastically reduced in the band between 6 and 18 GHz, while significantly simplifying the fabrication process. In conclusion, the proposed research exhibits promising potential to enable an efficient large-scale fabrication for RAMs, by addressing the difficulties associated with the design of connected unit-cells.

This article presents a step-by-step design and modeling of a high-voltage pulse generator (PG) based on a Tesla transformer (TT) with an open-magnetic core to drive a low-impedance high-power microwave (HPM) source. Our design uses the off-resonance mode of operation for higher voltage transformation ratios. The pulse-forming line of the transformer is filled with deionized water for a higher energy density of the line and an increased output pulse duration. Maxwell equations are used to establish the transformer parameters such as the magnetizing and leakage inductances, and subsequently, the geometry of the TT for optimum power transfer between the resonant circuits. The required circuit parameters and geometry of the generator producing up to 250 kV and peak power of 9.3 GW when matched to a 6.7- $\Omega $ load were determined through analytical design and validated through simulations.

In this paper we present the latest results of a research program on the use of ground penetrating radar and machine learning-based algorithms for humanitarian demining in Colombia. We describe the experimental setup developed, which includes a polarimetric GPR-UWB unit, a radar positioning system, and a control unit. We describe as well a soil characterization campaign and an IED classification technique based on Support Vector Machine.

We introduce the Tapered-Impedance Half Impulse Radiating Antenna (TI-HIRA). This innovative version of the HIRA allows the direct connection of COTS, 50 Ω generators to the antenna, without requiring external transformers and without using the large, blocking, plates that would be required in the traditional constant-impedance case. The idea relies on the use of feeders having a characteristic impedance that increases progressively, as a function of the radial distance between the focal point and the parabolic reflector. The additional effort required for manufacturing the new profile is offset by the reduced number of electrical and mechanical parts required for operating the radiating system. Various impedance profiles for the feeders are presented and compared. The design is discussed and validated, both analytically and by full-wave simulations demonstrating that the performances of the original HIRA remains.

The performances of Vircators have been reported in different studies showing that a high discrepancy between the simulated and measured output peak power and radiating frequency can be encountered. Limited investigations have been reported where the one-variable-at-a-time methodology was applied. Performing a full analysis requires to apply statistical methods over a large number of experiments (simulation or measurement) which has been a challenge due to the computation time required to simulate Vircators. Recently, an surrogate model has been proposed to drastically reduce the computation time. In this paper, we propose to evaluate the performance variability of a Vircator considering mechanical manufacturing tolerances as well as the Pulsed Power source variability. The analysis is performed by means of well-spread stochastic methods (classical Monte Carlo, spectral techniques), and alternative sensitivity analysis approaches.