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In this contribution we analyze the problem of the electromagnetic field radiated from apertures in metallic enclosures, fed by a coaxial cable, such as, for example, in PC environments. In particular, we develop an accurate model of the entire structure, including the coaxial line-loop-cavity coupling. The analysis is developed by means of two different methods, the Transmission Line Matrix (TLM) method and the Integral Equation (IE) method. The former is particularly suited to the modeling of arbitrarily shaped and complex structures, the latter is a rigorous approach based on the equivalence principle and leading to an integral equation formulation that is solved by the Method of Moments (MoM) approach. Theoretical results are compared with experimental ones showing very good agreement. The evaluation of the reflection coefficient and the input impedance of the structure (coaxial line-enclosure) leads to an equivalent circuit formulation, which is highly helpful for the engineering design of the entire structure.

This contribution deals with the application of the Method of Moment-Finite Difference Time Domain (MOM-FDTD) method, the Transmission Line Matrix-Integral Equation (TLM-IE) method and the Adapted Radiating Boundary (ARB) method to Electromagnetic Compatibility (EMC) problems. The essential theoretical aspects of the MOM-FDTD, TLM-IE and ARB methods are briefly described. The manner in which EMC problems can be modeled using the hybrid techniques is presented. Results are reported for the evaluation of the field radiated by a monopole antenna through an aperture into a shielded enclosure. Further developments of the hybrid methods are then discussed.

An accurate analysis and modeling of slot coupled patch antennas is proposed in this work. Two time- domain methods are used for the electromagnetic simulation of these structures, namely the hybrid Transmission Line Matrix-Integral Equation (TLM-IE) method and the Finite Difference Time Domain (FDTD) method. In order to establish the accuracy of these approaches, an antenna, working at the frequency of 10 GHz, is fabricated and tested. The measured data are then compared with those obtained from the numerical simulations of the same structure. The antenna is characterized in the hypothesis of infinite ground plane and by neglecting the dielectric losses. The scattering parameters, as well as the input impedance and the far field radiated by the antenna, are evaluated by adopting, for both methods, the same uniform grid. The computed results are found to be in a good agreement with the experimental results. The capability to simulate accurately this kind of structures could be applied to the understanding of more complicated effects, such as the ground plane truncation.

To evaluate the analgesic superiority and the safety equivalence of continuous fentanyl infusions versus fentanyl boluses in preterm infants on mechanical ventilation.In this multicenter, double-blind, randomized controlled trial, mechanically ventilated newborns (≤ 32(+6) weeks gestational age) were randomized to fentanyl (continuous infusion of fentanyl plus open-label boluses of fentanyl) or placebo (continuous infusion of placebo plus open-label boluses of fentanyl). The primary endpoint was analgesic efficacy, as evaluated by the Echelle Douleur Inconfort Nouveau-Né (EDIN) and Premature Infant Pain Profile scales. Safety variables were evaluated as well.Sixty-four infants were allocated to the fentanyl group, and 67 were allocated to the placebo group. The need for open-label boluses of fentanyl was similar in the 2 groups (P = .949). EDIN scores were comparable in the 2 groups; 65 of 961 (6.8%) EDIN scores were6 in the fentanyl group and 91 of 857 (10.6%) in the placebo group (P = .003). The median Premature Infant Pain Profile score was clinically and statistically higher in the placebo group compared with the fentanyl group on days 1, 2, and 3 of treatment (P.05). Mechanical ventilation at age 1 week was required in 27 of 64 infants in the fentanyl group (42.2%), compared with 17 of 67 infants in the placebo group (25.4%) (P = .042). The first cycle of mechanical ventilation was longer and the first meconium passage occurred later in the fentanyl group (P = .019 and .027, respectively).In very preterm infants on mechanical ventilation, continuous fentanyl infusion plus open-label boluses of fentanyl does not reduce prolonged pain, but does reduce acute pain and increase side effects compared with open-label boluses of fentanyl alone.

The coaxial suspended strip configuration in elliptical cross-section is found in transitions from ordinary coax to planar circuits and other geometries. Using elliptical coordinates makes the problem separable and leads to closed forms solutions for the fundamental TEM mode and the TE/TM higher modes: it is emphasized that the presence of the thin strip is dealt with analytically in this approach. Mode patterns and TEM characteristic impedance are reported. The cutoff frequencies vs. excentricity are computed for the first eight modes by both the present and the F.E.M. method finding excellent agreement.

Considering a standard InGaAs-AIGaAs PM HEMT, we report an accurate theoretical e.m. characterisation of propagation phenomena arising in this structure performed by means of a full-wave model. Some discussion of the carrier transport phenomena is also provided.

The GTEM cell is proving a useful tool for characterizing the electromagnetic scattering of objects under laboratory conditions. In this contribution, we present an analytical model of the discontinuity posed by a conducting cube in the cell, evaluating the scattered fields that are compared with experimental data, showing very good agreement. Moreover, an analytical model of the fundamental quasi-TEM mode is proposed and compared with accurate numerical computation.

Aim of this work is to model electrostatically doped carbon nanotubes (CNT), which have recently proved to perform as ideal PN diodes, also showing photovoltaic properties. The new model is able to predict the optical absorption of semiconducting CNT as function of size and chirality. We justify theoretically, for the first time, the experimentally observed capability of CNTs to detect and select not only a well defined set of frequencies, as resulting from their discrete band structure, but also the polarization of the incident radiation. The analysis develops from an approach proposed in a recent contribution. The periodic structure of CNTs is formally modeled as a photonic crystal, that is characterized by means of numerical simulators. Longitudinal and transverse components of the electric field are shown to excite distinct interband transitions between well defined energy levels. Equivalently, for a given energy of the incident radiation, absorption may show polarization ratios strongly exceeding unity.

In this contribution, we measure and compare the polarization properties of 3-D photonic crystal fibers and of a classic single-mode polarization maintaining fiber. The polarization-maintaining property depends on the cross-section geometry of the fiber and is therefore related to the strong intrinsic birefringence and to the well-defined principal axis of the fiber.

Finding several higher modes in ferrite-loaded waveguide becomes mandatory when dealing with discontinuities in accurate component design. It is well known, however, that this is a very difficult task in practice. In this contribution, we report a novel approach to this problem based on the explicit eigenvalue formulation of the vector telegrapher's equations applied to the anisotropic uniform waveguide and discretised by using the actual modes taken at cutoff as an expanding set. Theoretical results are compared with existing ones for the case of a longitudinally magnetised fully and partially loaded waveguide with very good agreement. The resulting algorithm is compact and it requires extremely low computational effort to evaluate as many modal characteristics and vector fields as required.

An accurate investigation of a microstrip H-shaped antenna is presented, coupled by means of an aperture or via-hole to a microstrip feed-line. The EM analysis is performed by means of the hybrid transmission line matrix-integral equation method. The calculated S-parameters are compared to measured results and to those obtained by the generalised transverse resonance-diffraction method.

The interfacing between optical cavities and mechanical systems has given rise to the rapid development of cavity optomechanics, which aims to confine light into small volumes by means of high-Q resonant recirculation [1], [2]. The purpose of an optomechanical system is to investigate the interaction of light with a mechanical oscillator. Its highly interdisciplinary nature leads to several potential applications in various fields of research, especially in quantum processing.

We present an accurate e.m. model of T-Gate TW-FET's and necessary conditions for obtaining exponentially growing waves. This model takes into detailed account device geometry, the effect of carrier velocity saturation in the high field region, conductor and dielectric losses and small signal channel current. >

We introduce a novel EM solver for the accurate analysis of complex problems in the areas of MMIC and optical integrated circuits. The basic idea is to construct a unique tool which involves two efficient 3D full-wave methods, GTRD (generalized transverse resonance diffraction) and TLMIE (transmission line matrix integral equation), acting in the frequency and time domains, respectively. This tool is integrated in EM3DS, an existing tool based on the GTRD method, and is equipped with a user-friendly graphic interface and pre/post-processing instruments. The accuracy of the solver is demonstrated by modeling complex structures like MEMS, RF-package and photonic band gap.

In this contribution we present an accurate investigation of three different techniques for the modeling of complex planar circuits. The EM analysis is performed by means of different electromagnetic full-wave solvers in the time-domain and in the frequency-domain. The first one is the transmission line matrix (TLM) method. In the second one the TLM method is combined with the integral equation (IE) method. The latter is based on the generalized transverse resonance diffraction (GTRD). In order to test the methods we model different structures and compare the calculated S-parameters to measured results, with good agreement.

In this contribution we introduce a rigorous and efficient method producing exact TLM boundary conditions for closed homogeneous waveguides. This approach uses the modal expansion of the EM field and the modal transfer functions between different planes. The absorbing condition is imposed by sampling the modal coefficients on arbitrary planes inside the TLM-domain and translating them to the terminal planes. Accuracy and efficiency of the method are demonstrated for the H-plane junction and for thick inductive irises in rectangular waveguide, providing excellent wide-band match of the fundamental mode as well as of higher order modes excited by the discontinuity.

In this paper, a two-dimensional material-based diode for microwave detection at 2.49 GHz with photodetector capabilities is presented. The diode consists of a molybdenum disulphide monolayer/graphene monolayer heterojunction transferred onto a silicon/silicon dioxide substrate, and patterned by means of nanolithography techniques to obtain a geometrical self-switching diode. The interaction between the two monolayers gives rise to a double-stage device, which behaves as a back-toback diode in the [-3, +3] V range, and as a tunnel diode when exceeding +10 V. The heterojunction can be reproduced on large scale due to its CMOS compatibility; it does not need any particular doping process thanks to its geometrical nature and can be used efficiently as microwave detector up to 10 GHz, with the best performance around the ISM 2.45 GHz band. Last, a rigorous equivalent circuit model based on the Foster’s method is provided, which relies on the measured scattering parameters at high frequencies. This way, the device can be exploited in circuit-based numerical tools for the design of complex microwave front-ends

A single molecule made of carbon atoms, namely C100, has been rigorously simulated for application in quantum electronics and related devices. A self-consistent calculation, using density functional theory and a master-slave perturbation approach, has been done in order to characterize the curren-voltage curves of the above nano-scale component, that could be the building block for future device concepts based on quantum transport. Charging effects, quantum tunneling, ballistic transport, are shown to characterize the device under study, making it an important element of a potential scalable platform for unconventional electronics with extremely high charge sensitivity.

This is the preprint version of the paper in which we demonstrate theoretically the efficient conversion of surface acoustic waves (SAW) generated on a substrate by an RF electric signal into the acoustic waves of a nanobeam. This paper is published under the referenceJournal of Physics D: Applied Physics 52 (32), 2019

The GTEM (GigaTEM) cell is proving a useful tool for simulating free space scattering of objects under laboratory conditions. The authors present an efficient numerical algorithm for the characterization of the discontinuities presented by perfectly conducting cubic or spherical objects. Numerical results are compared with experimental data (provided by EMC Baden), showing very good agreement.

We report on full-wave techniques in the frequency (energy)-domain and the time-domain, aimed at the investigation of the combined electromagnetic-coherent transport problem in carbon based nanostructured materials and devices viz. graphene nanoribbons. The frequency-domain approach is introduced in order to describe a Poisson-Schrödinger / Dirac system in a quasi static framework. Thetime-domain approach deals with the full-wave solution of the combined Maxwell-Schrödinger / Dirac system of equations. From the above theoretical platforms, home-made solvers are provided, aimed atdealing with challenging problems in realistic devices / systems environments, typical of the area of radio-frequency nanoelectronics.

We present a full-wave analysis of an infinite array of free-standing rectangular patches. The patches are thick and made of nonperfectly conducting material. The rigorous analysis involves the evaluation of the induced volume currents and is capable, in principle, of handling arbitrarily shaped geometries. For the case of a normally incident wave, the computed results are in very good agreement with experimental data reported in literature.

In graphene, the two-dimensional electrons and holes are described by the Dirac equation with a vanishing effective mass. As a consequence, under particular operative conditions, the electromagnetic response of graphene can be strongly nonlinear. We recently developed a method that accounts for deterministic electromagnetic field dynamics together with the quantum coherent transport in the nanoscale environment. We analyze the response of the system to harmonic plane wave and observe the frequency multiplication effect, resulting from the nonlinearity of the electromagnetic response. Theoretical results are compared with ones reported in the literature.

We present an accurate modeling of complex vertically integrated structures based on the new LTTC (low-temperature cofired ceramic) multilayer technology. The EM analysis is performed by means of different electromagnetic full-wave solvers in the time- and frequency-domains, namely: i) finite difference time-domain (FDTD); ii) transmission line matrix (TLM); iii) transmission line matrix integral equation (TLM-IE); iv) generalized transverse resonance diffraction (GTRD). We analyze a stacked patch antenna and a spiral inductor. The calculated S-parameters and Q-factors are compared to measured data showing good agreement.

We introduce a new TLM node approach for the analysis of wave-propagation in electro-optical devices. The present model accounts for both permittivity and permeability tensors of the material. The node scattering matrix is derived by using centered differences and averages. The novel aspect is that stub-loaded reactances are derived by consideration of the refractive-index ellipsoid.

Data on features of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in children and adolescents are scarce. We report preliminary results of an Italian multicentre study comprising 168 laboratory-confirmed paediatric cases (median: 2.3 years, range: 1 day–17.7 years, 55.9% males), of which 67.9% were hospitalised and 19.6% had comorbidities. Fever was the most common symptom, gastrointestinal manifestations were frequent; two children required intensive care, five had seizures, 49 received experimental treatments and all recovered.