Novel broadside trisection filters employing nonresonating nodes

This work presents novel filter topologies implemented in microstrip technology. The topologies combine printed line resonators with non resonating nodes (NRN) to implement transmission zeros in a very flexible way. Depending on the number of resonators and NRN, the filtering response exhibits a single transmission zero either below or above the passband, or two transmission zeros, one at each side of the passband. Several examples are designed and validated, using the new proposed structures.The authors thank Ministerio de Educación y Ciencia of Spain, which has supported this work under Grant TEC2007- 67630-C03-02

An interpolated spatial images method for the analysis of multilayered shielded microwave circuits

In this paper, an efficient interpolation method is presented in order to compute the Green’s function associated to electrical sources, when they are placed inside cylindrical cavities. The interpolation scheme is formulated in the frame of the spatial images technique recently developed. The original idea was to calculate, for every location of a point electric source, the complex values of the electric dipole and charge images, placed outside the cavity, to impose the appropriate boundary conditions for the potentials. In order to considerably reduce the computational cost of the original technique, a simple interpolation method is proposed to obtain the complex values of the images for any source location. To do that, a rectangular spatial subdivision inside the cavity is proposed. Each new sub-region is controlled by means of the exact images values obtained when the source is placed at the four corners of the region. The key idea is to use a bilinear interpolation to obtain the images complex values when the source is located anywhere inside this sub-region. The interpolated images provide the Green’s functions of the new source positions fast, and with high accuracy. This new approach can be directly applied to analyze printed planar filters. Two examples with CPU time comparisons are provided, showing the high accuracy and computational gain achieved with the technique just derived.This work was partially supported by the Spanish Ministry of Education and Science under Grant FPU-AP2006-015 and with the Project TEC2007-67630-C03-02

Analysis of inductive multiport microwave devices employing a novel double parallel plate approach

The authors present a novel surface integral equation approach to analyse inductive microwave devices with several parallel input­ output ports containing inductive metallic and dielectric obstacles. The technique decomposes the main problem into three subproblems, employ- ing different kinds of Green's functions. One of the subproblems uses the classical Green's func- tions of an infinite unbounded medium with the constitutive parameters of the dielectric obstacles. A novel point of the technique is the formulation of the two other subproblems with two different, 908 rotated parallel plate regions. In these regions the parallel plate waveguide Green's functions are used to simplify the modelling of the excitation problem. The second novel aspect of the work is in the treatment of these Green's functions, to smooth their behaviour, and to improve their con- vergence. Several numerical results are presented to demonstrate the usefulness of the algorithms proposed. Also, several results for inductive microwave devices are presented to show the practical value of the approach.Ministerio de Educación y Ciencia, Ref. TEC2007-67630-C03-02. Fundación Séneca, Ref. 08833/PI/0

Retribución de la alta dirección, estructura del consejo de administración y resultados

Resultados empíricos previos muestran distintas contradicciones cuando se relaciona la retribución de los miembros del equipo de alta dirección, la estructura del consejo de administración y los resultados alcanzados por la empresa. Un menor número de consejeros y una mayor proporción de consejeros externos se asocian a una mayor supervisión, pero no hay consenso sobre el efecto en el nivel retributivo del equipo de alta dirección. Esta falta de consenso se agrava cuando se analiza el efecto sobre los resultados. En este trabajo ofrecemos un marco teórico y un estudio empírico basado en la metodología de datos de panel, que permite explicar por qué los análisis previos difieren. En el contexto del mercado español se confirman las perspectivas del procesamiento de la información, que vinculan la sobredimensión del consejo con una mayor retribución del equipo de alta dirección. Asimismo, la mayor proporción de consejeros externos reduce el nivel retributivo del equipo de alta dirección al aumentar la supervisión y reducir el poder de los internos. Por último, se obtiene una relación cuadrática entre los resultados de la empresa y la retribución del equipo de alta dirección. Esta relación permite explicar, conjuntamente, un efecto positivo, defendido desde la teoría de la agencia, sobre los resultados de la empresa a niveles bajos de retribución de los miembros del equipo alta dirección y un efecto negativo, como consecuencia de una mayor discreción de éstos a niveles altos.Previous empirical results reveal various contradictions when relating top management compensation, board structure and levels of performance. While fewer directors and more external directors is associated with better supervision, there is no agreement on the effect on top management compensation level. This lack of consensus is even more noticeable when analysing the effect performance. This paper offers a theoretical framework and a panel data methodology based empirical study to account for how earlier analyses have differed. Given the great board dimension in the Spanish market, information processing perspectives are confirmed which link positively board size with higher top management compensation. Similarly, a higher proportion of external directors reduces top management compensation level since it improves supervision and reduces insiders’ power. Finally, a quadratic relation is obtained between performance and top management compensation. This relation explains both a positive effect, supported by agency theory on performance at low levels of management compensation, and a negative effect as a consequence of higher managers’ discretion at high levels

La mitosis celular: una sorprendente frontera de la eficiencia

En este trabajo se presenta una frontera entre la eficiencia e ineficiencia de problemas abstractos en un marco computacional inspirado en la estructura y funcionamiento de las c´elulas de los organismos vivos. M´as concretamente, se justifica que una regla de reescritura, abstracci´on de la mitosis celular, proporciona un l´ımite de la tratabilidad de problemas, bajo el supuesto de que se verifique la conjetura P 6= NP. Como consecuencia relevante se obtienen nuevas herramientas que permiten atacar la resoluci´on de la citada conjetura en un marco absolutamente novedoso.Ministerio de Ciencia e Innovación TIN2009–13192Junta de Andalucía P08–TIC-0420

Analysis of Inductive Waveguide Microwave Components Using An Alternative Port Treatment And Efficient Fast Multipole

This paper presents a simple and alternative approach for the analysis of inductive waveguide microwave components. The technique uses a surface integral equation formulation, in which the contours of the waveguide walls and of the inner obstacles are all discretized using triangular basis functions. In order to avoid the relative convergence problem of other techniques based on mode matching, an alternative port treatment is used. The technique is based on the application of the extinction theorem using the spatial representation of the Green's functions in the terminal waveguides. In addition, the Fast Multipole Method is proposed in order to reduce the computational cost for large problems. Different complex structures are analyzed, including microwave bandpass filters with elliptic transfer functions, waveguide bends and T-junctions. Results show the high accuracy and versatility of the technique derived

Practical implementation of the spatial images technique for the analysis of shielded multilayered printed circuits

In this paper, a practical implementation of the spatial images technique for the analysis of shielded multilayered printed circuits inside convex cavities is proposed. A new method is introduced in order to automatically locate the images surrounding the structure in order to impose the appropriate boundary conditions for the potentials. The boundary conditions are imposed at discrete points along the cavity wall and, therefore, the technique proposed is an approximation to the exact cavity modeling. Furthermore, for the analysis of electrically long cavities, the use of several rings of images surrounding the entire cavity at different heights is employed. Using the special features of the formulation, a new method of moments implementation combined with the spatial images technique is proposed in order to efficiently analyze practical multilayered printed filters, considerably reducing the computational cost. Several examples with CPU time comparisons are provided, demonstrating the accuracy and efficiency of the new technique. A novel transversal filter in a trapezium-shaped cavity is designed, manufactured, and tested for the first time using the spatial images technique.This work was supported by the Centro de Investigación Científica y Tecnólogica (CICYT) under Spanish National Project TEC2004-04313-C02-02/TCM and under Regional Seneca Project 02972/PI/05

Multipactor radiation analysis within a waveguide region based on a frequency-domain representation of the dynamics of charged particles

A technique for the accurate computation of the electromagnetic fields radiated by a charged particle moving within a parallel-plate waveguide is presented. Based on a transformation of the time-varying current density of the particle into a time-harmonic current density, this technique allows the evaluation of the radiated electromagnetic fields both in the frequency and time domains, as well as in the near- and far-field regions. For this purpose, several accelerated versions of the parallel-plate Green’s function in the frequency domain have been considered. The theory has been successfully applied to the multipactor discharge occurring within a two metal-plates region. The proposed formulation has been tested with a particle-in-cell code based on the finite- difference time-domain method, obtaining good agreement.The authors would like to thank ESA/ESTEC for having funded this research activity through the Contract “RF Breakdown in Multicarrier Systems” ͑Contract No. 19918/06/NL/GLC͒

Enhanced topology for the design of bandpass elliptic filters employing inductive windows and dielectric objects

This work presents a new topology for the design of bandpass elliptic filters employing inductive windows and dielectric objects. The proposed filtering structure combines, for the first time, the modified TE 102 resonating mode with the modified TE 201 mode. The TE 201 mode is excited by placing a wide dielectric post inside a waveguide cavity. The main advantage of the new topology is that two transmission zeros can be synthesized in the insertion loss response of the filter, for a second order structure. Also there is a high flexibility on the location of the transmission zeros. They can be synthesized along the frequency axis for maximum selectivity, or as a pair of complex poles for phase equalization.The authors thank Ministerio de Educación y Ciencia of Spain, which has supported this work under Grant TEC2007- 67630-C03-02/TCM

Numerical evaluation of the Green's functions for arbitrarily shaped enclosures

In this paper, a new spatial method has been implemented for the efficient calculation of the mixed potential Green's functions associated to electrical sources, when they are placed inside arbitrarily-shaped cylindrical cavities. The technique consists of placing electric dipole images and charges outside the cavity, imposing, at discrete points of the metallic wall, the appropriate boundary conditions for the potentials. Results show that the numerical convergence is attained fast. The cut-off frequencies and potential patterns for a trapezium-shaped waveguide are compared to those obtained by a standard finite elements technique, showing excellent agreement. Furthermore, a printed planar filter shielded in a square cavity has been analyzed with the new Green's functions, showing the practical value of the new theory.This work has been supported by Spanish National project CICYT-TEC2004-043 13-C02-02/TCM, and by Fundacion Séneca project, Ref. 02972/PI/0