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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.

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 couplers. This 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 2002 PB/4/FS/02.

In this paper, a neural-network-based method for the analysis of practical multilayered shielded microwave circuits is presented. Using this idea, a radial basis function neural network (RBFNN) is trained to approximate the space-domain multilayered media boxed Green’s functions used in the integral-equation (IE) method. Once the RBFNN has been trained, the outputs of the neural network (NN) replace the exact Green’s functions, during the numerical solution of the IE. The computation of the RBFNN output values is very fast in comparison with the numerical methods used to calculate the exact Green’s functions. This paper describes two novel strategies for efficiently training the RBFNN. In the first strategy, the input space of the RBFNN is divided into several spatial and frequency regions. The spatial subdivision is extended for the first time to both observation and source regions. In addition, the subdivision of the observation points regions is applied in a novel manner to the whole cross section of the metallic box. The second strategy combines the above region subdivision with an adaptive selection of the neurons variances in each region. The accuracy and the computational gain achieved with the NN method proposed makes possible the implementation of computer-aided-design tools that can be used for the analysis and design of integrated shielded microwave circuits (e.g., monolithic microwave integrated circuit devices) on a real-time basis.

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.

In this paper we present new contributions to the computation of the Green's functions arising in the analysis of mul- tilayered shielded printed circuits and antennas. First the quasi- static term of the spectral domain Green's functions is extracted so that the convergence of the reminder dynamic modal series is enhanced. Moreover, it is shown that by extracting a second-order quasi-static term the convergence is further improved. In regard to the quasi-static terms they are computed in the spatial domain by numerically evaluating the associated spatial images series. Then a new and efficient technique is developed for the summation of the slowly convergent modal series. The technique can be viewed as the application of the integration by parts technique to discrete se- quences and greatly accelerates the convergence rate of the series involved. It is shown that the new algorithm is numerically very robust and leads to a drastic reduction in the computational ef- fort and time usually required for the numerical evaluation of the shielded Green's functions. Universidad Politécnica Federal de Lausanne