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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.

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.

In this paper, we propose an alternative configuration for the design of bandpass inductive filters using transversal topologies. The structure is based on the use of a dielectric post asymmetrically placed on a cavity resonator. The input and output windows will couple energy to the TE102- and TE103-mode resonators at the same time, therefore obtaining the transversal topology. The proposed configuration is very compact, and allows to implement transmission zeros for maximum selectivity in an easy way. Results are validated with Ansoft’s finite-element High Frequency Structure Simulator tool, and with an integral-equation technique to demonstrate the validity of the proposed structure. This work was supported by the Comisión Interministerial de Ciencia y Tecnología under Spanish National Project TEC2004-04313-C02-02/TCM and under the Regional Seneca Project 02972/PI/05.

Experimental results are presented to show how a planar circuit, printed on a laterally shielded dielectric waveguide, can induce and control the radiation from a leaky-mode. By studying the leaky-mode complex propagation constant, a desired radiation pattern can be synthesized, controlling the main radiation characteristics (pointing direction, beamwidth, sidelobes level) for a given frequency, This technique leads to very flexible and original leaky-wave antenna designs. The experiments show to be in very good agreement with the leaky-mode theory. This work was supported in part by Spanish national projects ESP2001-4546-PE, TEC2004- 04313-C02-02-TCM and in part by regional Séneca project 2002 PB/4/FS/02.

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.

Different types of waveguide leaky-wave antennas, asymmetrically perturbed with printed-circuits, are studied in this paper. The capability to modify the leakage constant of the excited leaky-wave mode, while maintaining unchanged its phase constant, is studied in detail for each design. Several slot and strip configurations are proposed, in which the width and the position of the planar printed circuit perturbation is modified along the length of the antenna to obtain different tapering topologies. All of them are mechanically flexible to realize, thus simplifying the manufacturing process for millimeter wavelengths applications. The two-dimensional method used for the analysis is accurate for any geometry of the planar perturbation, and also allows for the computation of the whole spectrum of modes in these open waveguides. This makes possible to predict the appearance of unwanted channel-guide modes, and also allows for the study of the coupling effect between the desired leaky-wave mode and them. A tapered design is performed and compared with full-wave three-dimension simulations to validate the proposed technology. This work was supported in part by Spanish National projects ESP2001-4546-PE and TEC2004-04 313-C02-02/TCM and in part by Regional Séneca projects 2002 PB/4/FS/02 and PMPDI-UPCT-2004.

A modal series representation of spatial-domain electric field Green's functions for arbitrarily oriented electric current sources embedded in shielded multilayer media is presented. The Green's func- tions associated with planar excitations are briefly recalled, and the method to compute them is generalized to vertical current sources, yielding new components of the Green's function necessary for the anal- ysis of vertical metallizations embedded in waveguides or cavities. Universidad Politécnica Federal de Lausanne (EPFL)

El presente trabajo muestra los últimos avances en el campo de las antenas reconfigurables obtenidos por el Grupo de Electromagnetismo Aplicado a las Telecomunicaciones (GEAT). El paper presenta una novedosa antena leaky-wave (LWA) reconfigurable, diseñada en una tecnología planar de bajo coste denominada guía de onda integrada en sustrato (SIW). La antena se basa en el control electrónico de los modos de fuga excitados en la estructura, permitiendo controlar simultáneamente la dirección y el ancho de haz del lóbulo principal de radiación. En el trabajo se describen la metodología de análisis modal y se muestran resultados de simulación obtenidos a partir del diseño realizado para una frecuencia de operación de 5.5GHz. Centro Universitario de la Defensa. Escuela de Turismo de Cartagena. Escuela Técnica Superior de Ingeniería Industrial UPCT. Escuela Técnica Superior de Ingeniería de Telecomunicación (ETSIT). Escuela de Ingeniería de Caminos y Minas (EICM). Escuela de Arquitectura e Ingeniería de Edificación (ARQ&IDE). Parque Tecnológico de Fuente Álamo. Navantia. Campus Mare Nostrum. Estación Experimental Agroalimentaria Tomás Ferro

Este artículo presenta una nueva condición circuital, relacionada con las resistencias de radiación (R, G) del modelo equivalente de una celda CRLH L W, que fuerza a las antenas del tipo CRLH L W a radiar con una tasa de radiación constante en todo el espacio. Además, se demuestra que la condición propuesta elimina las fluctuaciones de la constante de fase que se producen alrededor de la frecuencia de transición, debido a la radiación en la dirección broadside. Simulaciones y medidas experimentales de un prototipo de este tipo de antenas son empleados para validar el nuevo método de diseño presentado. Destacar que la condición circuital propuesta permite diseñar celdas unidad CRLH L W mucho más estables. Centro Universitario de la Defensa. Escuela de Turismo de Cartagena. Escuela Técnica Superior de Ingeniería Industrial UPCT. Escuela Técnica Superior de Ingeniería de Telecomunicación (ETSIT). Escuela de Ingeniería de Caminos y Minas (EICM). Escuela de Arquitectura e Ingeniería de Edificación (ARQ&IDE). Parque Tecnológico de Fuente Álamo. Navantia. Campus Mare Nostrum

En este artículo se presenta un método nuevo para la predicción de la sensibilidad en filtros Butterworth pasobanda formados por cavidades acopladas. La sensibilidad del parámetro de reflexión respecto a variaciones en los coeficientes de acoplo se calcula en el prototipo pasobajo. A partir de este valor, es posible predecir el máximo error que se producirá en el parámetro de reflexión en el peor de los escenarios posibles. Además, se propone una aplicación práctica de la relación existente entre la sensibilidad y la energía almacenada en estructuras formadas por resonadores acoplados, permitiendo predecir la sensibilidad de un filtro Butterworth en línea utilizando únicamente el retardo de grupo. El nuevo método se ha validado en un filtro Butterworth de orden 6, que ha sido diseñado a modo de ejemplo. Centro Universitario de la Defensa. Escuela de Turismo de Cartagena. Escuela Técnica Superior de Ingeniería Industrial UPCT. Escuela Técnica Superior de Ingeniería de Telecomunicación (ETSIT). Escuela de Ingeniería de Caminos y Minas (EICM). Escuela de Arquitectura e Ingeniería de Edificación (ARQ&IDE). Parque Tecnológico de Fuente Álamo. Navantia. Campus Mare Nostrum

A broadband and low beam squint anisotropic magneto-dielectric 2D leaky-wave antenna excited by a vertical electric source is presented. A comparison of the TM dis- persion behavior of the structure for Drude/Lorentz dispersive anisotropic and an isotropic non-dispersive grounded slabs is performed. The isotropic slab is restricted to leaky-wave pointing angles near endfire with very low radiation performance due to the inherent endfire radiation null caused by the slab. As a result, its radiation is dominated by the space-wave, which leads to low directivity and beam scanning incapability. In contrast, the anisotropic meta-substrate provides a highly directive and efficient 2D leaky-wave radiation with great design flexibility. At its lower frequencies, it provides narrow-band full-space conical-beam scanning while at higher frequencies, it enables a designable angle fixed-beam with low-beam squint radiation. This antenna may find applications in broadband point-to-point communication and radar systems. Ministerio de Educación y Ciencia, Ref. TEC2007-67630-C03-02. Fundación Séneca, Ref. 08833/PI/08.

The radiation efficiency of a point electric source on a loss-less uniaxially anisotropic meta-substrate is computed by the mixed potential integral equation technique. For this purpose, the multilayered Green's functions of the structure are derived from the spectral domain transmission line model of the medium. The efficiency of the antenna is compared for different permittivities and permeabilities of the meta-substrate with fixed TE and TM wave numbers. It is shown that at certain frequencies the radiation efficiency is enhanced as the ratio of the permeability over permittivity is increased. This suggests that an antenna on a mushroom type meta-substrate or a meta-substrate which is constructed from the stacked split ring resonators (SRR) in the plane of the substrate may exhibit a high radiation efficiency close to the resonant frequencies of the metallic loops, as compared to a conventional substrate. Ministerio de Educación y Ciencia, Ref. TEC2007-67630-C03-02. Fundación Séneca, Ref. 08833/PI/08.

This paper is focused on the theoretical investigation of the relationship between the time average stored energy (t.a.s.e) in conventional lumped-element Chebychev low-pass prototype filters, and the sensitivity of the return loss with respect to properly tuned resonators. It is well known that the resonant frequencies are the most sensitive parameters in a filter to achieve the required return loss and often some form of manual adjustment is needed. Different degree transfer functions, and also different topologies, are investigated throughout the paper. It is shown that both, the t.a.s.e and the sensitivity behaviors are strongly related. This work provides some new insight in fundamental properties of passive filters and can be useful for the design of filters with reduced sensitivity for high power applications and tuningless filters, for example. Ministerio de Educación y Ciencia, Ref. TEC2007-67630-C03-02. Fundación Séneca, Ref. 08833/PI/08.

This work presents a novel leaky-wave antenna (LWA), conceived from the insertion of a dipole-based frequency selective surface (FSS) into a top-open rectangular waveguide. It is explained how the printed circuit has the ability to control the radiation rate of the leaky modes that propagate through this structure at a certain frequency. This attribute makes possible the tapering of the radiation diagram of the LWA. In particular, it is possible to reduce the sidelobes level. This feature will be illustrated by performing a cosine tapered design. Good agreement is observed when comparing the results obtained from leaky-mode theory with full-wave simulations. Finally, the limitations of this tapering procedure will also be presented. Este trabajo ha sido posible gracias al proyecto nacional TEC2007-67630-C03-02/TCM, el proyecto regional de la fundación Séneca 08833/PI/08, la beca nacional ―Salvador de Madariaga‖ (ref.PR2009-0336) y la beca regional PMPDI-UPCT-2009.

The use of ground planes is proposed inside the spatial images technique in order to calculate the multilayered shielded Green’s functions for rectangular enclosures. The positions of the ground planes are dynamically located, covering two walls of the cavity, as a function of the source position. Spatial mirror images, related to the ground planes, are used to perfectly impose the boundary conditions along these cavity walls. This completely removes the problems associated to the singular behavior of the source when it is placed close to a wall or a corner, improving numerical stability. In addition, the method leads to a very efficient computation (about 15 times faster than the original approach), due to the reduced number of non-mirror images that must be effectively computed. A multi-band filter in hybrid waveguide-microstrip technology is analyzed with the new method, showing excellent agreement with measured data.

The TM spectral transmission line model of a grounded meta-substrate with uniaxially anisotropic properties, corresponding to a composite right/left-handed sub-wavelength mushroom-type structure, is computed. The dispersion relation is found by the transverse resonance technique. It is analyzed and compared with the particular case of an isotropic grounded slab. The study is limited to the left-handed region of the meta- substrate, which corresponds to the frequency band where the permittivity and permeability are negative and most dispersive. The work considers only TM modes, for which the effects of dispersion and anisotropy are most significant. The leaky-modes in the anisotropic left-handed meta-substrate are shown to exhibit a leakage factor which may be conveniently designed to very low values for super highly directive leaky-wave antennas. Ministerio de Educación y Ciencia, Ref. TEC2007-67630-C03-02. Fundación Séneca, Ref. 08833/PI/08.

Metamaterial leaky-wave antennas (LWAs), which operate in their fundamental guided mode (ν = 0), have grown in popularity thanks to their full-space scanning possibilities [1]. Several technologies can be employed to practically implement this type of antennas, such us microstrip, CPW, CPS or mushroom-like periodically loaded waveguides [2]. In order to analyze these structures, equivalent circuit models may be used [1]. These models are able to accurately compute the propagation constant of the structure under analysis, but have some difficulties to obtain the radiation characteristics. Usually, time-consuming full-wave simulations are required for this last step. In this paper, a novel and efficient modal-based iterative circuital model is presented for the accurate analysis of the complex propagation constant related to mushroom-like CRLH LWAs.

Meta-substrates [1, 2] are artificial dielectric substrates with unusual properties. In [2] an anisotropic meta-substrate was proposed with the same fully-space scanning capability as leaky-wave antennas based on composite right/left-handed (CRLH) patterned transmission line (TL) structures. This meta-substrate is a mushroom type structure [3] with uniaxially anisotropic properties, where the wires perpendicular to the air-substrate interface exhibit a Drude permittivity and the loops between the adjacent mushrooms exhibit a Lorentz permeability. This paper presents a rigorous spectral TL approach analysis [4] of this meta-substrate, which is constituted of the anisotropic medium of Fig.1a, with the constitutive parameter tensors.

The use of ground planes is proposed inside the spatial images technique in order to calculate the multilayered shielded Green's functions for rectangular enclosures. The positions of the ground planes are dynamically located, covering two walls of the cavity, as a function of the source position. Spatial mirror images, related to the ground planes, are used to perfectly impose the boundary conditions along these cavity walls. This completely removes the problems associated to the singular behavior of the source when it is placed close to a wall or a corner, improving numerical stability. In addition, the method leads to a very efficient computation (about 15 times faster than the original approach), due to the reduced number of non-mirror images that must be effectively computed. A multi-band filter in hybrid waveguide-microstrip technology is analyzed with the new method, showing excellent agreement with measured data. Ministerio de Educación y Ciencia, Ref. TEC2007-67630-C03-02. Fundación Séneca, Ref. 08833/PI/08.

A new full-wave electromagnetic analysis method based on the Boundary Integral Resonant Mode Expansion (BI-RME) is presented in this paper. The technique allows the computation of the broad band circuital response of arbitrarily shaped cavity filters. The coaxial excitation of this kind of filters is rigorously modeled by taking into account the high order modes on the coaxial aperture. A singular decomposition algebraic procedure has been implemented in order to obtain the solenoidal and non-solenoidal counterparts contributions of the electric current density inside the cavity needed by the BI-RME formulation. This method is simple and avoids some issues associated to star and loop based functions which are typically used for the same purpose. This work has been developed with financial support fromSENECA project Ref. 08833/PI/08, and CICYT project Ref.TEC2007-67630-C03.

We present a simple analytical implementation of the static singular integrals arising in the volume/surface integral equation formulation for the analysis of mixed conducting and dielectric structures such as printed circuits with finite-size dielectric objects. The singularity of the Green's functions is extracted from the kernel of the integral equation as a static term. This term is then evaluated analytically for coincident rectangular cells in two and three dimensions. The new technique allows an accurate and efficient evaluation of method of moments (MoM) self-interactions compared to other methods previously used in the literature. Ministerio de Educación y Ciencia, Ref. TEC2007-67630-C03-02. Fundación Séneca, Ref. 08833/PI/08.

En este artículo se presenta un estudio sobre la Ingeniería de la Dispersión en el dominio de las microondas. Para ello, se emplean líneas de transmisión basadas en metamateriales, que proporcionan un comportamiento dispersivo en un gran ancho de banda. Los dispositivos o fenómenos que se presentan son tanto guiados (usando líneas de transmisión) como radiados (empleando las estructuras metamateriales como antenas leaky-wave). A diferencia del estudio en régimen armónico que se suele realizar sobre los metamateriales, todos los novedosos efectos presentados son de banda ancha, listos para implementarse en los recientes sistemas de comunicaciones UWB. Ministerio de Educación y Ciencia y (Fundación Séneca de la Región de Murcia). Código: TEC2007-67630-C03-02 y beca FPU-AP2006-015, y (08833/PI/08).

Este paper presenta filtros en guía de onda realizados mediante una innovativa técnica de fabricación conocida como "Selective Laser Melting" ó SLM. Se han fabricado dos tipos de filtros de quinto orden en guía de onda y con un ancho de banda de 0.9%. Ambos diseños tienen la misma respuesta en frecuencia pero diferentes geometrías internas. El segundo diseño hace uso de la libertad de geometría que ofrece esta nueva tecnología por lo que se han empleado técnicas de modelado de geometría para ayudar a reducir pérdidas. Gracias a la optimización de la geometría, es posible mejorar el factor de calidad en al menos un 15%. Asociación de Jóvenes Investigadores de Cartagena, (AJICT). Universidad Politécnica de Cartagena. Escuela Técnica Superior de Ingeniería Industrial UPCT, (ETSII). Escuela Técnica Superior de Ingeniería Agronómica, (ETSIA), Escuela Técnica Superior de Ingeniería de Telecomunicación (ETSIT). Escuela de Ingeniería de Caminos, Canales, y Puertos y de Ingeniería de Minas, (EICM). Fundación Séneca, Agencia Regional de Ciencia y Tecnología. Parque Tecnológico de Fuente Álamo. Grupo Aquiline

En este artículo se presenta una novedosa antena "leaky-wave" en guía de onda, basada en metamateriales. Para ello, la guía-onda se ha cargado con "slots" y "via-holes ", de tal forma que proporciona constantes de propagación tanto negativa como positiva, enfunción de lafrecuencia. Esta antena es capaz de modificar la dirección de la radiación en jimción de la frecuen cia de entrada, proporcionado un barrido completo del espacio. Para su análisis y diseño, se ha propuesto un método modal, combinado con condiciones de contorno de Floquet. De esta manera se consigue diseñar y analizar este tipo de antenas en cuestión de pocos minutos, evitando recurrir a herramientas de onda completa comerciales, que presentan unos tiempos de diseño de horas e incluso días. Medidas experimentales confirman el fenómeno de radiación previsto para la nueva antena, y validan la herramienta de análisis propuesta. Asociación de Jóvenes Investigadores de Cartagena, (AJICT). Universidad Politécnica de Cartagena. Escuela Técnica Superior de Ingeniería Industrial UPCT, (ETSII). Escuela Técnica Superior de Ingeniería Agronómica, (ETSIA), Escuela Técnica Superior de Ingeniería de Telecomunicación (ETSIT). Escuela de Ingeniería de Caminos, Canales, y Puertos y de Ingeniería de Minas, (EICM). Fundación Séneca, Agencia Regional de Ciencia y Tecnología. Parque Tecnológico de Fuente Álamo. Grupo Aquiline

This paper presents novel and compact implementations of bandpass filters using transversal topologies. The structures presented implement diferent transfer functions of order three in multilayered microstrip technology. In order to allow for easy implementation of the required coupling, multilayered broadside configurations are proposed. We demonstrate that with the proposed configurations, both dualband and quasi-elliptic responses can be easily synthesized, by only changing the sign of certain entries in the coupling matrix. To easily adjust the sign of the coupling, novel resonators are proposed, including simple half-wavelength transmission line resonators, meander line resonators and shortcircuited resonators. Experimental validations for both prototypes are presented, demonstrating the validity and usefulness of the proposed con gurations. The authors thank Ministerio de Educacion y Ciencia of Spain, which has supported this work with the Project TEC2007-67630-C03/TCM.

A novel composite right/left-handed leaky-wave antenna (CRLH LWA), based on periodically loaded parallel-plate waveguides (PPW) is presented. The loading is obtained by a rectangular grid of vertical wires and parallel slots etched in the upper metal plane of the PPW. A novel modal-based iterative circuit is proposed for the complete analysis and design of this type of antennas. The coupling between the antenna and freespace is rigourously modeled using a mode-matching technique, combined with the Floquet’s theorem. This provides a lossy dispersive CRLH unit-cell model, whose values are obtained using a quickly-convergent iterative algorithm. The proposed method is accurate, extremely fast and it takes into account the structure physical dimensions. A CRLH PPW LWA has been designed (without requiring any time consuming full-wave simulation), analyzed and fabricated using the proposed method. Very good agreement has been found between measurements and simulations, validating both, the antenna radiating phenomena and the proposed technique. Este trabajo ha sido cofinanciado por el Ministerio de Educación y Ciencia (Proyecto: TEC2007-67630-C03-02, Beca: FPU-AP2006-015).

In this paper, a numerical method has been proposed for the analysis of highlydispersive linear and non-linear metamaterial structures. Initially, pulse propagation along non-linear composite right/left-handed transmission line (CRLH TL) has been carefully studied. For this purpose, a dispersive CRLH line has been loaded with hyper abrupt diodes to achieve non-linearity. The characteristic impedance and propagation constant of each unit cell of the CRLH TL is then varied at each time-step, and the nonuniform line is analyzed. A novel interpolation scheme, based on the smooth behaviour of the propagation constant with small variations of the shunt capacitor has been proposed. This scheme has provided an 80% reduction of the computational cost maintaining high accuracy. A general example which combines dispersion and nonlinearity has finally been presented, validated and discussed. Secondly, the impulseregime radiation of a leaky-wave antenna has been analyzed and employed to describe a real-time spectrogram analyzer (RTSA). A calibration method for the system, which takes into account the directivity variation of the antenna with frequency, has been introduced. Numerical results have shown that the proposed technique provides an extremely fast and accurate tool to characterize leaky-wave based RTSA systems. 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.

A tunable spatio-temporal Talbot imaging phenomenon, based on metamaterial composite right/left-handed (CRLH) leaky-wave antennas (LWAs), is presented. This phenomenon, reported for the first time in the microwave domain, is based on the combination of the conventional spatial monochromatic Talbot effect and the transient (polychromatic) character of the pulse radiation phenomenon in the LWA structure. When the elements of a periodic CRLH LWA array are fed simultaneously by an input pulse, the spatial beams corresponding to different temporal frequencies constructively interfere in space so as to form a self-imaged pattern constituted by narrow Talbot zones. This Talbot effect is spatial-temporal since the Talbot zones are localized both in space and time. Furthermore, the scanning law property of the LWA is exploited to provide an off-axis radiation, leading to a tunable Talbot distance. This phenomenon is analyzed theoretically, numerically validated and experimentally demonstrated for the case of narrow-band pulses Este trabajo ha sido cofinanciado por el Ministerio de Educación y Ciencia (Proyecto: TEC2007-67630-C03-02, Beca: FPU-AP2006-015).

This paper presents novel implementations of bandpass filters in multilayered microstrip technology. The structures presented implement transversal filter topologies of order three. In order to allow for easy implementation of the required couplings, multilayered broadside configurations are proposed. We demonstrate that with the proposed configurations, both dualband and quasi-elliptic responses can be easily synthesized, by only changing the sign of certain entries in the coupling matrix. To easily adjust the signs of the couplings, novel resonators are proposed, including simple half-wavelength transmission line resonators, meander line resonators and short-circuited resonators. Experimental validation for one prototype is presented, demonstrating the validity and usefulness of the proposed configurations. The authors thank Ministerio de Educación y Ciencia of Spain, which has supported this work under Grant TEC2007- 67630-C03/TCM

En este artículo se presenta un estudio sobre la propagación y la radiación de pulsos temporales en líneas de transmisión basadas en metamateriales CRLH. Esta nueva tecnología proporciona nuevas y originales soluciones en los recientes sistemas de banda ancha UWB. Usando una nueva formulación en el dominio temporal, se proponen dos novedosas aplicaciones. En primer lugar, el empleo de una antena CRLH leaky-wave como un analizador de espectros en tiempo real (RTSA) para caracterizar señales desconocidas, y en segundo, el uso de un array de antenas para obtener un barrido cuasi-instantáneo del espacio con un haz tipo “lápiz”. Este trabajo ha sido parcialmente financiado por el Ministerio de Educación y Ciencia (España). Los autores desean agradecer a Mr. Shulabh Gupta el apoyo, tanto técnico como personal, prestado en la realización de este trabajo.

El rápido avance de la radio y televisión digital está haciendo que los ingenieros y técnicos tengan que adaptar sus equipos de medidas, sus técnicas de instalación, y los conceptos tecnológicos adquiridos, para adecuarse a los nuevos requerimientos y parámetros de calidad de los servicios. En este contexto, el artículo aborda desde una perspectiva práctica diversos aspectos interesantes que hay que tener en cuenta a la hora de planificar la correcta instalación de sistemas de recepción digitales. La exposición se realiza desde la utilización de dos equipos muy útiles para el ingeniero y el técnico de telecomunicación, como son el analizador de espéctros y el medidor de campo, y cómo deben interpretarse las medidas obtenidas con estos equipos.

A novel tunable microwave broadband resonator, inspired from optical laser systems, is presented. In contrast to usual harmonic resonators, the proposed device is based on broadband composite right/left-handed (CRLH) metamaterial lines. This line, configured as a resonator, provides nonuniform spectral resonances due to the nonlinear nature of its dispersion curve. This is exploited in the impulse-regime, where the input pulse spectrum is discretized inside the resonator, with different spectral separation as a function of the carrier frequency. This discretization leads to a pulse periodicity in time, with a tunable output time period. Based on the new broadband resonator features, a pulse rate multiplication device is proposed. This device provides an increase in the repetition rate of a periodic input pulse, with the additional advantage of repetition rate tunability. Este trabajo ha sido cofinanciado por el Ministerio de Educación y Ciencia (Proyecto: TEC2007-67630-C03-02, Beca: FPU-AP2006-015).

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.

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.

In this paper, 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 Green’s functions inside a multilayered shielded square box in order to accurately obtain the Green’s functions of the triangular structure. It is shown that the new algorithm is very robust, with limited computational effort. Cut-off frequencies and potential patterns of a triangular cavity have been calculated and compared to those obtain 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. Este trabajo ha sido cofinanciado por el Ministerio de Educación y Ciencia (Proyecto: TEC2007-67630-C03-02, Beca: FPU-AP2006-015).

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.

This paper uses a simple configuration to implement microwave transversal filters based on microstrip technology. The structure is of second order and implements two transmission zeros and two reflection zeros in the frequency response of the filter. The basic configuration consists of input and output ports coupled in a shunt configuration to two printed resonators of different lengths. A modification of the original structure is introduced to allow an additional direct coupling between the source and the load. Depending on the value and the sign of the coupling terms, different frequency responses can be obtained. In this way, small modifications in the basic structure allow to obtain band-pass or band-stop responses. Following this circuit topology, the paper discusses the possibilities to have transmission zeros in the real or in the complex plane and their effects on the frequency response and on the group delay of the filter. Also, two practical implementations in microstrip technology are proposed, and a third filter implementing group delay equalization is demonstrated. Measured results confirm theoretical predictions and validate the structures for practical applications. Ministerio de Educación y Ciencia, Ref. TEC2007-67630-C03-02. Fundación Séneca, Ref. 08833/PI/08

This paper is aimed at studying the electromagnetic radiation pattern of a multipactor discharge occurring in a parallel-plate waveguide. The proposed method is based on the Fourier expansion of the multipactor current in terms of time-harmonic currents radiating in the parallel-plate region. Classical radiation theory combined with the frequency domain Green's function of the problem allows the calculation of both the electric and the magnetic radiated fields. A novel analytical formula for the total radiated power of each multipactor harmonic has been derived. This formula is suitable for predicting multipactor with the third-harmonic technique. The proposed formulation has been successfully tested with a particle-in-cell code.

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.

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/08

We present an analysis procedure to obtain the modal dispersion curves of complex structures based on the introduction of metallodielectric frequency-selective surfaces (FSS) inside rectangular waveguides excited with TE0 modes. This type of structures can be used to conceive novel Electromagnetic-Band Gap (EBG) waveguides and low-profile high-gain leaky-wave antennas (LWAs). The analysis technique is divided in several steps, which have been implemented in a software tool using MATLAB®, and which are explained in detail in this work. The advantages and limitations of the proposed method are also described. Comparisons with full-wave simulations are presented to validate this analysis tool. Este trabajo ha sido posible gracias a la financiación y apoyo de los siguientes proyectos: proyecto internacional Royal Society Joint Project 2006/R2, proyectos españoles ESP2001-4546-PE y TEC2004-04313-C02-02-TCM, y el proyecto regional de la fundación Séneca 02972/PI/05.

A new time-domain Green’s function approach is used to characterize a composite right/left handed (CRLH) leakywave structure as a function of time under ultra-short modulated pulse excitation. This analysis is efficiently performed in the far-field region for both, a single CRLH element and for an array. Several novel broadband applications, such as a real-time spectrum analyzer (RTSA) (which exploits the unique frequencyspace mapping conversion of the CRLH) or an instantaneous radar scanning (based on the time-frequency relation of chirpmodulated pulses), are presented and discussed. Full-wave simulations and measurements are provided to validate the results. The semi-analytical formulation developed is compact, flexible and fast, avoiding stability conditions as in other completely numerical time-domain methods. Este trabajo ha sido cofinanciado por el Ministerio de Educación y Ciencia (Proyecto: TEC2007-67630-C03-02, Beca: FPU-AP2006-015).

An original leaky-wave antenna (LWA), conceived from a microstrip line which is laterally shielded by parallel plates, is presented in this paper. This structure shows, for the first time, that the leakage rate of a microstrip leaky-mode can be easily controlled while negligibly affecting the pointing direction. The antenna is based on the radiation from the second higher order mode of the microstrip line, which is perturbed by the addition of the two conductor walls to control the level of the leakage rate. The parallel-plates also serve as a mechanism to obtain a single main beam in the azimuthal plane, therefore improving the radiation pattern compared to common dual-beam second-higher order mode microstrip LWAs. The proposed antenna is analyzed by obtaining the corresponding leaky-mode complex propagation constant, which is calculated by a specific method of moments approach. The modal results obtained from the leaky-mode dispersion curves are validated with analysis performed on a three-dimensional structure using commercial finite element method solver. Also, a prototype is fabricated to experimentally confirm the advantages of this novel leaky-wave line source. This work was supported in part by the Spanish National project TEC2004-04313-C02-02/ TCM, in part by the Regional Seneca project 02972/PI/05, and in part by Regional Scholarship PMPDI-UPCT-2007.

A novel structure for the implementation of compact transversal bandpass filters is proposed in this paper. This new proposal consists of a hybrid structure, based on the combination of two different technologies: the waveguide and microstrip. It is shown that the novel hybrid microwave filter is able to implement both a second- and third-order filtering function with up to two or three transmission zeros, respectively. In this way, a practical implementation of a fully canonical transversal filter with a third degree response is for the first time directly achieved. In addition, the way to control the positions of transmission zeros with the new technology is treated in this paper. It is shown that symmetric or asymmetric responses and also filtering functions with a complex pair of transmission zeros can be easily obtained. To demonstrate the validity of this novel structure, several implementation examples are presented. A prototype has been designed, manufactured, and successfully tested, showing the practical validity of the new structure. This work was supported by the Centro de Investigación Científica y Tecnológica under Spanish National Project TEC2004-04313-C02-02/TCM and under Regional Seneca Project 02972/PI/05.

Radomes are usually made of lossy dielectric materials, and their accurate analysis is often cumbersome because of their typical large electrical size and geometrical complexity. In real reflector antenna structures, there are always complex interactions between the radome, the reflector surfaces and the directional feeds, which are typically neglected for the sake of simplicity. In this paper we will consider all such interactions in a very accurate way, thus requiring a high number of unknowns for the numerical solution of the problem. To overcome such drawback, an integral equation formulation based on the Equivalence Principle in combination with the wavelet transform has been employed, obtaining finally a robust and accurate CAD tool for the rigorous analysis of arbitrarily shaped radomes containing continuous and discrete electromagnetic sources. It will be shown that the use of wavelet-like bases substantially improves the numerical efficiency and memory requirements of the original integral equation method. For verification purposes, the results obtained with the new technique are successfully compared with examples taken from the literature. Complex antenna structures are then discussed in order to prove the usefulness of the new method. This work has been supported by Ministerio de Educación y Ciencia, Spanish Government, under the Research Projects Ref. TEC2004/04313-C02-01 and TEC2004/04313-C02-02.

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/05

In this paper we propose to use the Surface Integral Equation technique for the analysis of arbitrarily shaped Hplane obstacles in rectangular waveguides, which can contain both metallic and/or dielectric objects. The Green functions are formulated using both spectral and spatial images series, whose convergence behavior has been improved through several acceleration techniques. Proceeding in this way, the convergence of the series is not attached to the employment of any particular basis or test function, thus consequently increasing the flexibility of the implemented technique. In order to test the accuracy and numerical efficiency of the proposed method, results for practical microwave circuits have been successfully compared with other numerical approaches. The authors would like to thank Alcatel Alenia Space (Madrid, Spain) for having provided data of the lossy dielectric loaded evanescent waveguide filter. They also wish to acknowledge the economic support of MEC, Spanish Government, through the coordinated Research Project TEC2004/04313-C02.

En este artículo se presenta una nueva familia de filtros de microondas, implementados en tecnología híbrida guiaonda-microstrip. Estos filtros combinan por primera vez la resonancia de la cavidad que encapsula al circuito, con la resonancia proporcionada por una línea microstrip impresa, obteniéndose diseños con máxima selectividad, compactos y ligeros, ideales para aplicaciones por satélite. Se incluyen también dos ejemplos de diseño de éstos novedosos filtros, que han sido fabricados y analizados, obteniéndose unos resultados satisfactorios que demuestran el valor práctico de la tecnología presentada. Ministerio de Educación y Ciencia (España) y la Fundación Séneca (Murcia).

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.

En este artículo revisamos las características más importantes relacionadas con la modulación empleada en el nuevo sistema de Televisión Digital Terrestre. Veremos las especificaciones más importantes, y revisaremos sus capacidades para rechazar señales indeseadas y evitar los efectos negativos de la propagación multitrayecto. A través de un programa de simulación estudiaremos, con un caso práctico, su robustez ante la interferencia de canales de televisión analógicos adyacentes.