Efficient Calculation of the Green's Functions for Multilayered Shielded Cavities with Right Isosceles-Triangular Cross-Section

An efficient calculation of the Green’s functions inside multilayered shielded cavities with right isosceles-triangular cross-section is presented. The method is entirely developed in the spatial domain, and it is based on image theory. The idea is to use the spatial-domain Green’s functions inside a multilayered shielded square box, in order to accurately obtain the Green’s functions for the right isosceles-triangular cavity. Image theory is then used to enforce the boundary conditions along the non-equal side of the triangle. It is shown that the new algorithm is very robust, with limited computational effort. Resonance frequencies and potential patterns of a triangular cavity have been calculated and compared with those obtained by other techniques, showing very good agreement. Finally, a transversal filter inside a multilayered triangular-shaped cavity is designed, manufactured and tested using the developed technique.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

2D to 3D rectangular waveguide filter designs from linear iterated prediction space mapping optimization

In this article, an optimization procedure is described to align electromagnetic (EM) three-dimensional (3D) models with two-dimensional (2D) models for the design of RF/microwave circuits. The optimization procedure is realized from a modified standard space mapping (SM) approach. The mapping function between the 2D and 3D parameter spaces is directly obtained from a linear iterated prediction method, which reduces the computational cost and also avoids inverse transformations. The linear iterated prediction 2D to 3D SM optimization of evanescent rectangular waveguide bandpass filters with inductive posts for the 2D models and non-inductive posts for the 3D models illustrate the advantages and the challenges of this approach. The proposed method is simple to be implemented, it requires a reduced computational cost and it can be useful for CAD environment with 2D and 3D circuit structure electromagnetic (EM) analysis.This work was supported by Ministerio de Educación y Ciencia of Spain (TEC2007–67630-C03–02/TCM)

A new neural network technique for the design of multilayered microwave shielded bandpass filters

In this work, we propose a novel technique based on neural networks, for the design of microwave filters in shielded printed technology. The technique uses radial basis function neural networks to represent the non linear relations between the quality factors and coupling coefficients, with the geometrical dimensions of the resonators. The radial basis function neural networks are employed for the first time in the design task of shielded printed filters, and permit a fast and precise operation with only a limited set of training data. Thanks to a new cascade configuration, a set of two neural networks provide the dimensions of the complete filter in a fast and accurate way. To improve the calculation of the geometrical dimensions, the neural networks can take as inputs both electrical parameters and physical dimensions computed by other neural networks. The neural network technique is combined with gradient based optimization methods to further improve the response of the filters. Results are presented to demonstrate the usefulness of the proposed technique for the design of practical microwave printed coupled line and hairpin filters

Application of the high-gain substrate-superstrate configuration to dielectric leaky-wave antennas

The high-gain substrate-superstrate configuration, which was proposed to increase the gain in printed circuit antennas, is applied to dielectric leaky-wave antennas (LWAs) to improve its frequency response. Analysis of a slitted suspended dielectric rectangular waveguide is carried out using a full-wave method. It is proved that the minimum values of the leakage constant of the leaky-wave mode for the suspended configuration are related to the high-gain resonance conditions. Moreover, it is found that the suspended LWA exhibits very small beamwidth variations in a large frequency bandwidth. It is well-known that inhomogeneous filled LWAs suffer from variation of beamwidth as the angle of maximum radiation is scanned with frequency. The proposed topology can be adjusted so that a flat response of the beamwidth can be obtained in a large frequency band, while maintaining the frequency-scanning behavior of the LWA.This work was supported by Spanish National Projects ESP2001-4546-PE and TIC2000-0591- C03-03, by Regional Seneca Projects 2002 PB/4/FS/02 and PMPDI-UPCT- 2004, and by the EPSON-Ibérica Foundation

Efficient integral equation formulation for inductive waveguide components with posts touching the waveguide walls

In this paper a surface integral equation technique is employed for the analysis of inductive waveguide problems containing metallic or dielectric objects of arbitrary shape, focusing on the case where these objects are connected to the waveguide walls. Using the extinction theorem, the main problem is split into two problems. In the first one the parallel plate waveguide Green’s functions are used. Because of the choice of these functions, the side of the object touching the waveguide wall is not considered for discretization in a method of moments analysis. The second problem is applied inside the dielectric object, and uses the free space Green’s functions. It is shown that an additional spatial image is needed to impose the proper boundary conditions for the fields on the side touching the waveguide wall in the original problem. Results show the importance of including this additional image in the formulation for the correct behavior of the fields. With the proposed technique, the paper explores some alternatives for designing specific filter responses using dielectric posts inside cavity filters. Comparisons with a commercial finite elements tool demonstrate the accuracy of the proposed integral equation formulation.This work has been developed with support from the Spanish National Project (CICYT) with Ref TEC2004-04313-C02-02/TCM, and the Regional Seneca Project with Ref 02972/PI/05

Analysis and design of periodic leaky-wave antennas for the millimeter waveband in hybrid waveguide-planar technology

This work presents a full-wave integral equation approach specifically conceived for the analysis and design of laterally-shielded rectangular dielectric waveguides, periodically loaded with planar perturbations of rectangular shape. This type of open periodic waveguide supports the propagation of leaky-wave modes, which can be used to build leaky-wave antennas which exhibit many desirable features for millimeter waveband applications. The particularities of the leaky-mode analysis theory are described in this paper, and comparisons with other methods are presented for validation purposes. Using this leaky-mode analysis method, a novel periodic leaky-wave antenna is presented and designed. This novel antenna shows some important improvements with respect to the features of previously proposed antennas. The results of the designed radiation patterns are validated with three-dimensional electromagnetic analysis using commercial software.This work was supported by Spanish National projects ESP2001-4546-PE and TEC2004-04313-C02-02/TCM and Regional Séneca projects 2002 PB/4/FS/02. The authors would like to thank the EPSON-Ibérica Foundation for its stimulating support. and PMPDI-UPCT-2004. The authors would like to thank the EPSON-Ibérica Foundation for its stimulating support

Novel microwave network for the leaky-wave analysis of evanescent fields in stub-loaded structures

In this paper, a new transverse equivalent network for the modal analysis of stub-loaded leaky-wave antennas is developed. The derived network is useful for the study of the radiation of evanescent fields that occurs when they reach the top aperture of the parallel-plate stub. This transverse network is based, for the first time, on a nonhybrid formulation of the constituent parallel- plates modes of order 1 (TE 1 andTM 1 ). The obtained network is an alternative to the one based on hybrid TE 1 andTM 1 modes, and leads to a simpler transverse resonance equation. The new equivalent network is validated by obtaining leaky-mode dispersion curves for a previously studied leaky-wave antenna in nonradiative dielectric guide technology.This work was supported under the Spanish National Project TEC2004-04313-C02-02/ TCM, under the Regional Seneca Project 02972/PI/05, and under Regional Scholarship PMPDI-UPCT-2007

Numerical evaluation of the Green's functions for arbitrarily shaped cylindrical enclosures and their optimization by a new spatial images method

IIn this paper, a spatial image technique is used to efficiently calculate the mixed potential Green’s functions associated with electric sources, when they are placed inside arbitrarily shaped cylindrical cavities. The technique is based on placing electric dipole images and charges outside the cavity region. Their strength and orientation are thencalculated by imposing the appropriate boundary conditions for the fields at discrete points on the metallic wall. A method for the assessment of the potentials accuracy is proposed, and several optimization techniques are presented. Three cavities are analyzed to demonstrate the usefulness of the techniques. The cutoff frequencies and potentials patterns are compared to those obtained by a standard finite elements technique, showing excellent agreement. Finally, a band-pass filter based on coupled lines is analyzed, demonstrating the practical value of the technique.This work has been developed with support from the Spanish National Project (CICYT) with reference TEC2004-04313-C02-02/TCM, and the Regional Seneca Project with reference 02972/PI/0

Proyecto ARIAM: desarrollo de un radiotelescópio y de un taller de Radioastronomía e Ingeniería de alta frecuencia como herramienta para el fomento de la cultura científica y tecnológica en la UPCT

En esta comunicación pretendemos dar a conocer una iniciativa de fomento de la cultura científica y tecnológica dentro del área de Radioastronomía e Ingeniería de Telecomunicaciones, que se ha denominado proyecto ARIAM (Aula-taller de Radioastronomía e Ingeniería de Antenas y circuitos de Microondas). Esta iniciativa tiene como punto de inicio el desarrollo de un Radiotelescopio de microondas por parte de los alumnos de último cursos de la Escuela Técnica Superior de Ingeniería de Telecomunicación (ETSIT) de la Universidad Politécnica de Cartagena (UPCT). El Radiotelescopio consta, básicamente, de una antena parabólica de unos 3 metros de diámetro, de un receptor de microondas de elevada sensibilidad y ganancia, y de un sistema de adquisición de datos y control del apuntamiento de la antena. Se trata de un proyecto de ingeniería complejo y de un reto tecnológico, que involucra el desarrollo de varios subproyectos de naturaleza multidisciplinar. Están implicadas áreas temáticas como la ingeniería de antenas, la ingeniería de circuitos de microondas, la instrumentación electrónica, la ingeniería mecánica, técnicas de adquisición y procesado digital de la señal, la ingeniería de control y de motores, la astrofísica… etc. La novedad y el interés docente estriban en que todos estos subproyectos están siendo dirigidos por profesores de la UPCT, y son desarrollados íntegramente por alumnos de esta misma Universidad, utilizando los conocimientos y los laboratorios disponibles en las instalaciones de la UPCT. Es la primera vez en España que un sistema tan complejo y tecnológicamente avanzado como un Radiotelescopio está siendo desarrollado íntegramente con recursos humanos y tecnológicos de una Universidad Pública. Un objetivo fundamental de esta iniciativa es el de trasladar a la sociedad murciana en general, y a los más jóvenes en particular, un mensaje claro y vital en estos momentos: nuestros actuales y futuros estudiantes universitarios tienen a su disposición los medios para adquirir los conocimientos y habilidades necesarias que permiten abordar proyectos tan interesantes como los que se describirán en la ponencia. En esta misma ponencia se resumirá el trabajo realizado hasta la fecha durante los cuatro años que lleva en marcha esta actividad. Se mostrarán los resultados obtenidos, tanto a nivel técnico como a nivel humano, haciendo hincapié en la respuesta que han dado los alumnos a esta propuesta y las habilidades que ellos mismos están desarrollando gracias a este proyecto. Cabe destacar el trabajo en equipo, el carácter multidisciplinar del mismo, el desarrollo de habilidades prácticas y competencias profesionales como el manejo de maquinaria de fabricación de circuitos y estructuras, o de instrumentación de testeo y ajuste de circuitos… etc. El Radiotelescopio será usado para difundir entre alumnos, profesores y público en general la tecnología que hace posible la concepción y puesta en marcha del mismo, así como la disciplina de la Radioastronomía, tan interesante como desconocida. Con este objetivo de difusión, todos los sistemas que están siendo desarrollados tienen una finalidad claramente divulgativa, buscando siempre la claridad de los conceptos que se pretenden transmitir. Asimismo, en la ponencia se describirán las posibilidades de ampliación y mejora del Radiotelescopio, de manera que se entienda por qué este proyecto está pensado para ser más que un mero instrumento de observación, parte de un aula-taller de aprendizaje y difusión de la tecnología de antenas y circuitos de alta frecuencia. Por supuesto, este Radiotelescopio además de para divulgación será usado para tareas científicas de observación del Universo, y en concreto para detectar las señales de microondas originadas por el hidrógeno atómico presente en las nebulosas que pueblan nuestra Galaxia. Además de ser un instrumento para astrofísicos y radioastrónomos profesionales, el Radiotelescopio estará a disposición de las asociaciones astronómicas amateurs regionales, como la Agrupación Astronómica de la Región de Murcia (AARM) o la Asociación Astronómica de Cartagena (AAC). Además, el Radiotelescopio formará parte del proyecto internacional SETI (Search of Extraterrestrial Intelligence), cuya misión es buscar posibles señales de radio extraterrestres que tengan un origen artificial. En la ponencia se mostrarán las bondades de este proyecto ARIAM para fomentar el interés por las carreras de Ciencia e Ingeniería en nuestra Región. Además, este proyecto cuenta con el apoyo de varias universidades del territorio nacional y del Instituto Astrofísico de Canarias, adquiriendo un carácter interterritorial. El desarrollo del Radiotelescopio de ARIAM ha sido financiado por la Fundación regional Séneca durante los años 2006, 2007 y 2008.El desarrollo de este Radiotelescopio no habría sido posible sin la financiación ofrecida durante los años 2006, 2007 y 2008 por la Fundación Regional Séneca [37]. De igual o mayor valor es la ilusión mostrada por todos los alumnos de la ETSIT de la UPCT que han colaborado o están colaborando en el proyecto ARIAM, los cuales nombramos por orden cronológico: Ricardo Alarcón Llamas (LNAs v1.0, curso 2005-2006), Pedro Enrique Ros Avilés (mixer v1.0, curso 2005-2006), Anna Kamasheva (LNA v2.0, curso 2006-2007), Gonzalo Peñafiel Beltrán (LNA v3.0, curso 2006-2007), Mónica Moragón Serano (oscilador, curso 2006-2007), Adrián Juan Heredia (bocina, curso 2006-2007), Francisco J. Sandoval Piqueras (mixer v2.0, curso 2006-2007), Javier Molero Madrid (sistema, curso 2007-2008), Jesús Mora Rodríguez (sistema, curso 2007-2008) y Marta Rodríguez García Rodríguez (sistema, curso 2007-2008). Asimismo, la dedicación de los profesores Fernando Quesada Pereira, Alejandro Álvarez Melcón, Jose María Molina García-Pardo, David Cañete Rebenaque y José Luis Gómez Tornero, de la ETSIT de la UPCT, ha sido vital para conseguir llegar hasta el punto en el que está el proyecto ARIAM

Two compact configurations for implementing transmission zeros in microstrip filters

This contribution presents compact structures for the implementation of transmission zeros using the zero shifting property. First, two open-loop resonators operating at different resonances are employed. Then, one of the open-loop resonators is substituted by a ( 4) short-circuited transmission line, thus resulting into a more compact structure. Properties of these configurations are discussed, and two manufactured prototypes have been sucessfully tested. The results showthe usefullness and validity of the new structures with high rejection capabilities.This work was supported by the Spanish National Projects ESP2001-4546-PE and TIC2000-0591-C03-03, and the Regional Seneca Project 2002, ref. PB/4/FS/0