Simple Technique for source reflection coefficient measurement while characterizing active devices

This paper describes a simple, yet rigorous technique for fast and accurate determination of the source reflection coefficient during the characterization of microwave active devices. The solution consists in measuring the waves at the DUT reference plane under two different bias conditions. Since the DUT small signal impedance value depends on the bias voltage, the waves at the DUT input port changes as well. We proved that their measurements give enough information to compute the source reflection coefficient with accuracy suitable for most applications. The correction for systematic errors is based in the traditional error-box model and it does not require any exotic calibration procedures. Experimental results are presented and compared to data obtained with more traditional technique

Novel software techniques for automatic microwave measurements

Although many microwave measurement techniques are heavily based on special purpose software, the application of modern software techniques like object oriented programming and new programming language like C++ is seldom used. The impact of such new software solutions can drastically improve the overall design of a microwave test set. The paper presents the design and implementation of a new multiport network analyzer with particular attention to the control program architecture. The use of Object Oriented Programming techniques results in a clear and easy to maintain solution which boosts both the user interface and the overall test set organizatio

On methods to determine bounds on the Q-factor for a given directivity

This paper revisit and extend the interesting case of bounds on the Q-factor for a given directivity for a small antenna of arbitrary shape. A higher directivity in a small antenna is closely connected with a narrow impedance bandwidth. The relation between bandwidth and a desired directivity is still not fully understood, not even for small antennas. Initial investigations in this direction has related the radius of a circumscribing sphere to the directivity, and bounds on the Q-factor has also been derived for a partial directivity in a given direction. In this paper we derive lower bounds on the Q-factor for a total desired directivity for an arbitrarily shaped antenna in a given direction as a convex problem using semi-definite relaxation techniques (SDR). We also show that the relaxed solution is also a solution of the original problem of determining the lower Q-factor bound for a total desired directivity. SDR can also be used to relax a class of other interesting non-convex constraints in antenna optimization such as tuning, losses, front-to-back ratio. We compare two different new methods to determine the lowest Q-factor for arbitrary shaped antennas for a given total directivity. We also compare our results with full EM-simulations of a parasitic element antenna with high directivity.Comment: Correct some minor typos in the previous versio

LA TASA DE EGRESO DE QUIENES INGRESAN POR APLICACIÓN DEL ARTÍCULO 7º DE LA LEY DE EDUCACIÓN SUPERIOR Y SU RELACIÓN CON LA TASA DE QUIENES INGRESAN CON ESTUDIOS SECUNDARIOS COMPLETOS

Este trabajo es uno de los resultados del proyecto de investigación en que nos encontramos trabajando, que tiene por objeto estudiar el desempeño académico que tuvieron quienes ingresaron en la Universidad Nacional de Luján (UNLu) sin acreditar estudios de nivel medio completo, en el marco del artículo 7º de la Ley 24.521 (LES). Al mismo tiempo, nos proponemos comparar el desempeño académico observado en estos estudiantes con el de quienes ingresaron acreditando estudios completos. En esta oportunidad presentamos el resultado de analizar la tasa de egreso, calculada por cohorte, de los ingresantes mayores de 25 años que no acreditaron estudios completos de nivel medio, de las cohortes comprendidas entre los años 1996 y 2005, ambas inclusive. Por otra parte, se efectuó el mismo estudio para quienes ingresaron en esas cohortes pero habiendo acreditado estudios secundarios completos, con el objeto de comparar la tasa de egreso de las dos poblaciones. Los resultados alcanzados mostraron que, para las diez cohortes estudiadas la tasa media de egreso difiere en 3 puntos, a favor de quienes ingresaron con estudios de nivel medio completo. Por otra parte, para alguna de las cohortes la tasa es superior para quienes ingresaron sin acreditar estudios completos

Optimal Planar Electric Dipole Antenna

Considerable time is often spent optimizing antennas to meet specific design metrics. Rarely, however, are the resulting antenna designs compared to rigorous physical bounds on those metrics. Here we study the performance of optimized planar meander line antennas with respect to such bounds. Results show that these simple structures meet the lower bound on radiation Q-factor (maximizing single resonance fractional bandwidth), but are far from reaching the associated physical bounds on efficiency. The relative performance of other canonical antenna designs is compared in similar ways, and the quantitative results are connected to intuitions from small antenna design, physical bounds, and matching network design.Comment: 10 pages, 15 figures, 2 tables, 4 boxe

Load pull techniques for millimetre-wave device characterization

Load-pull experimental characterisation of active devices under non linear operation is a well proved technique still used in designing power amplifiers. When applied to the MMIC, this technique shall require special solutions to be extended to on-wafer devices up to millimetre waves. The paper presents an overview on the traditional load pull measurement techniques focusing the attention on millimetre wave application. An example of a fully automatic on-wafer system is described along with the more useful calibration techniques. By means of this test set a very detailed characterisation of devices can be carried out in short time, by setting the loads either at the fundamental or at the harmonic frequencies with independent controls

Characterization of multilayer stack parameters from X-ray reflectivity data using the PPM program: measurements and comparison with TEM results

Future hard (10 -100 keV) X-ray telescopes (SIMBOL-X, Con-X, HEXIT-SAT, XEUS) will implement focusing optics with multilayer coatings: in view of the production of these optics we are exploring several deposition techniques for the reflective coatings. In order to evaluate the achievable optical performance X-Ray Reflectivity (XRR) measurements are performed, which are powerful tools for the in-depth characterization of multilayer properties (roughness, thickness and density distribution). An exact extraction of the stack parameters is however difficult because the XRR scans depend on them in a complex way. The PPM code, developed at ERSF in the past years, is able to derive the layer-by-layer properties of multilayer structures from semi-automatic XRR scan fittings by means of a global minimization procedure in the parameters space. In this work we will present the PPM modeling of some multilayer stacks (Pt/C and Ni/C) deposited by simple e-beam evaporation. Moreover, in order to verify the predictions of PPM, the obtained results are compared with TEM profiles taken on the same set of samples. As we will show, PPM results are in good agreement with the TEM findings. In addition, we show that the accurate fitting returns a physically correct evaluation of the variation of layers thickness through the stack, whereas the thickness trend derived from TEM profiles can be altered by the superposition of roughness profiles in the sample image

Two-dimensional two-component plasma with adsorbing impurities

We study the behavior of the two-dimensional two-component plasma in the presence of some adsorbing impurities. Using a solvable model, we find analytic expressions for the thermodynamic properties of the plasma such as the $n$-body densities, the grand potential, and the pressure. We specialize in the case where there are one or two adsorbing point impurities in the plasma, and in the case where there are one or two parallel adsorbing lines. In the former case we study the effective interaction between the impurities, due to the charge redistribution around them. The latter case is a model for electrodes with adsorbing sticky sites on their surface

Effect of slow-moving landslides on a vaulted masonry building: The case of San Carlo Borromeo church in Cassingheno (Genova)

This paper presents the structural analysis of San Carlo Borromeo church, a masonry building located in Cassingheno (Genoa, Italy) in an area affected by a slow-moving landslide. A deep knowledge of the building in terms of geometry, structural configuration, history and construction phases was acquired by means of on-site surveys and archival research. The crack patterns were surveyed in detail and the deformations were studied through a point cloud obtained from a LIDAR survey. The comparison between the landslide direction and the damage observed showed discrepancies and suggested the presence of foundation settlements due to other phenomena. To identify the actual causes of damage, a finite element model (FEM) of the building in its hypothetical undeformed configuration was created. The geometry of such configuration was reconstructed starting from the point cloud obtained from the LIDAR survey and removing geometrical defects such as leaning of walls, deformation of vaults and inclination of tie-rods. To simulate the effects produced by the landslide and the foundation settlements on the building over time, nonlinear analyses were performed by imposing different displacement fields at the foundation plane in multiple steps. The damage predicted numerically was then compared with the one experienced by the building, showing good agreement

Advances in paclitaxel combinations for treating cervical cancer

Introduction: Cervical cancer is the fourth common cancer in women worldwide. While, in the past, locally advanced stage disease was treated by pelvic radiotherapy, nowadays the National Cancer Institute strongly recommends chemoradiation protocols. Weekly cisplatin was previously the standard of care in this setting; however, the low response rate and the short median progression-free survival (PFS) of patients have led researchers to investigate combinatory regimens. Area covered: This article is based on literature searches up until April 2019, with current trial registers also analyzed. All data available on this topic has been summarized in this narrative review. Expert opinion: In recent years, it has been demonstrated that cisplatin-based doublets, and in particular, cisplatin plus paclitaxel, are superior to cisplatin as a monotherapy in terms of response rate and progression-free survival of patients with advanced cervical cancer. This double regime combined with bevacizumab is also considered the first-line option for metastatic or recurrent disease. Dose-dense paclitaxel in neo-adjuvant chemotherapy combinations is a promising option in patients with locally advanced cervical cancer. Exploration of novel biological therapies and in vitro combinations based on the use of paclitaxel is warranted