Leaky and Surface Waves in Multi-Layered Laterally Shielded Microstrip Transmission Lines

In this paper the leakage effects in open laterally- shielded multilayered microstrip transmission lines are investigated. Po- tential solutions are often reported to be difficult to find, since they are located in the complex propagating factor plane. To overcome this problem, a novel iterative algorithm is implemented to relate the solu- tions in the real axis of closed transmission lines with their correspond- ing complex open structure modes. The problem of modeling the leaky behavior of the open top wall is introduced, and a mathematical and physical explanation of the solutions is proposed. The advantage of this new technique is that it allows us to easily track the leaky solutions to their final location in the complex plane. Results are presented, includ- ing the field and power patterns associated to leaky waves, showing that the derived technique is indeed effective for the study of the complex modes excited in this type of structures.Universidad Politécnica de Cartagen

Nonorthogonality relations between complex hybrid modes: an application for the leaky-wave analysis of laterally shielded top-open planar transmission lines

In this paper, the orthogonality relations between complex modes are investigated to demonstrate the coupling effect that exists along a transverse direction ( -axis) between TE and TM hybrid modes when power storage, loss, or leakage occur in the longitudinal direction ( -axis) of a transmission line. As an example, the parallel-plate waveguide modes are used to study a laterally shielded top-open microstrip line. The study of leaky waves is a very interesting application of the novel orthogonality relations derived in this paper. This study is carried out using the correct and incorrect orthogonality formulations, showing that physically valid results are obtained only when the orthogonality relations derived in this paper are properly introduced in the formulation. A physical explanation of this novel coupling effect between TE andTM hybrid modes with respect to the -direction is given in terms of inhomogeneous plane waves. Comparisons with previous results for a laterally shielded slot-line antenna are presented to confirm the accuracy and usefulness of this novel proposed method

Análisis de modos de fuga en estructuras planares apantalladas lateralmente y diseño de nuevas antenas "Leaky-Wave" en tecnología híbrida impresa-apantallada

En esta tesis doctoral se estudian los modos de fuga en un tipo de guías de onda en tecnología híbrida. Esta tecnología híbrida consiste en combinar una guía rectangular dieléctrica apantallada lateralmente con circuitos planares impresos sobre el substrato de la guía dieléctrica. Se ha desarrollado un método de análisis electromagnético modal basado en el desarrollo de la función de Green de la guía de placas paralelas, en el que se resuelven las correspondientes ecuaciones integrales de campo eléctrico y/o magnético usando el método de los momentos. Este método tiene una alta carga analítica sin perder la rigurosidad de los resultados debido a su naturaleza de método de onda completa ("full-wave"). La búsqueda numérica de las constantes de propagación complejas de los modos de fuga es la tarea más costosa. Por ello se ha desarrollado un algoritmo iterativo para acelerar la búsqueda de los ceros complejos asociados a las soluciones de los modos de fuga, dotando de una enorme robustez al método de análisis propuesto. Los resultados obtenidos en este análisis modal son usados para diseñar nuevas antenas "leaky-wave" en la mencionada tecnología híbrida. El objetivo fundamental desde el punto de vista del diseñador de antenas es el de poder conseguir sintetizar una determinada respuesta eléctrica (dirección de apuntamiento, ancho de haz, eficiencia de radiación y nivel de lóbulos secundarios). Los resultados obtenidos demuestran que se puede controlar la respuesta de las antenas con mucha precisión y libertad. Se presentan diseños usando circuitos planares impresos de tipo "slot" (ranuras) y "strip" (tiras metálicas) en la banda de 5GHz y 50GHz. Los resultados obtenidos con el método propuesto se comparan con los obtenidos con una herramienta comercial de análisis electromagnético tridimensional basada en el método de elementos finitos. De esta manera se han validado todos los diseños, demostrando las mejoras de las antenas propuestas. También se ha expandido el método de análisis a circuitos impresos periódicos, usando una expansión en modos de Floquet para expresar la función de Green de la celda unidad. De esta manera se han propuesto nuevas antenas periódicas basadas en la tecnología híbrida. La tecnología propuesta presenta interesantes mejoras de fabricación y una mayor flexibilidad de diseño respecto de otras antenas "leaky-wave" propuestas en anteriores trabajos de investigación. Por último, en esta tesis se presentan dos programas desarrollados para asistir en el análisis de los modos de fuga y en el diseño de antenas "leaky-wave". La interfaz gráfica e interactiva de estos programas permite obtener resultados rápida y visualmente, en comparación con programas comerciales de análisis electromagnético, que al ser más genéricos necesitan de un mayor tiempo de cálculo. La presente tesis doctoral deja varias líneas futuras abiertas, entre la que cabe destacar el análisis y diseño de circuitos y antenas de microondas con propiedades zurdas ("metamateriales").Universidad Politécnica de CartagenaPrograma de doctorado en Tecnologías de la Información y Comunicacione

Two-dimensional Quasi-bessel beam synthesis and frequency-scanning leaky-wave launchers

In this paper, a technique to synthesize a 2D frequency-scanned high order Bessel beam in a parallel plates waveguide (PPW) scenario is presented. This technique is based on a one dimensional beam launcher, rather than the more typical axicons or the more recent metasurfaces and antenna arrays for 3D Bessel beam synthesis. With this launcher, it is possible to generate a 2D Bessel beams whose direction can be controlled by changing the frequency of the feeding signal in the Ku band from 14.5 GHz to 15 GHz. It is demonstrated how this can be done by combination of two leaky waves (LW), which can be created by the same 1D structure, scanning at different angles and launched to the PPW region. The beams are generated in a triangular area, with one of its sides being the launcher itself and the other sides are defined by the direction of radiation of each of the forming leaky wave

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

Microstrip leaky-wave antenna with control of leakage rate and only one main beam in the azimuthal plane

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

Printed-circuit leaky-wave antenna with pointing and illumination flexibility

A novel leaky-wave antenna, based on a periodic set of slots printed on a rectangular dielectric waveguide is conceived in this work. The antenna presents the ability to independently control the aperture illumination and the pointing direction, by only modifying the photoetched printed-circuit layout. The working mechanism is described using a leaky-mode dispersion analysis, and cosine-tapered designs are performed at 50 GHz. The radiation patterns are obtained using HFSS analysis to check the reduction of sidelobes levels, and the capacity to tune the pointing direction over a wide range of elevation angles.This work was supported by Spanish National Projects ESP2001-4546-PE, TEC2004-04313-C0202-TCM, Regional Seneca Project 2002 PB/4/FS/02, and the EPSON-Ibérica Foundation

A novel leaky-wave antenna combining an image NRD guide and a strip circuit

This letter presents a novel leaky-wave antenna which combines an image NRD (nonradiative dielectric) guide and a printed strip circuit. The proposed structure allows for an easier, cheaper and more flexible tapering mechanism than all previous leaky-wave antennas in NRD technology. The working mechanism is explained, and two different tapering strip-circuit topologies are proposed. Cosine tapered illuminations are designed using a two-dimensional leaky-mode analysis technique. Simulations with high-frequency structure simulator (HFSS) three-dimensional analysis are presented for validation purposes. Also, the influence of the feeding transitions for each printed-circuit design is studied. Results show the feasibility of one of the proposed designs, leading to a tapered radiation pattern with sidelobes level below 20 dB.This work was supported by Spanish National Projects ESP2001-4546-PE and TIC2000-0591- C03-03, and Regional Seneca Project 2002 PB/4/FS/02

Simple analysis and design of a new leaky-wave directional coupler in hybrid dielectric-waveguide printed-circuit technology

This paper presents a new theory to analyze and design a novel leaky-wave coupler based on a hybrid dielectric-waveguide printed-circuit technology. The analysis theory is based on a combined method of moments (MoM) geometrical optics (GO) technique, which makes use of the leaky mode complex propagation constant. This MoM-GO approach allows to easily obtain the response of the coupler, and to illustratively understand the working mechanism of the proposed structure. A coupler is designed to work at 5.5 GHz. Leaky mode results are compared with three-dimensional finite-element method simulations, showing the validity and accuracy of the new theory developed. This novel directional coupler presents interesting advantages when compared to previous wave couplersThis work was supported in part under Spanish National Project ESP2001-4546-PE and Spanish National Project TEC2004-04313-C02-02-TCM and under the Regional Séneca Project 2002PB/4/FS/02

Diseño de una Antena Leaky-Wave reconfigurable electrónicamenteen tecnología de guía de onda integrada en sustrato

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 Ferr