J. V. Morro

Efficient modal analysis of arbitrarily shaped waveguides composed of linear, circular, and elliptical arcs using the BI-RME method

This paper deals with the accurate and efficient modal analysis of arbitrarily shaped waveguides whose cross section is defined by a combination of straight, circular, and/or elliptical arcs. A novel technique for considering the presence of circular and/or elliptical segments within the frame of the well-known boundary integral-resonant mode expansion (BI-RME) method is proposed. This new extended BI-RME method will allow a more accurate solution of a wider number of hollow conducting waveguides with arbitrary profiles, which are usually present in most modern passive waveguide components. To show the advantages of this new extended technique, the modal chart of canonical (circular and elliptical) waveguides, as well as of irises with great practical interest (i.e., cross-shaped irises with rounded corners) has been first successfully solved. Next, a computer-aided-design software package based on such a novel modal analysis tool has first been validated with the accurate analysis of a referenced complex dual-mode filter, and then applied to the complete design of a novel twist component for K-band application based on circular and elliptical waveguides. A prototype of this novel device has been manufactured and measured for verification purposes.

Efficient Technique for the Cascade Connection of Multiple Two-Port Scattering Matrices

There are several practical applications in microwave engineering that require the cascade connection of multiple two-port scattering matrices. Many microwave devices are analyzed by segmenting the structure into small building blocks (steps, resonators, lines, etc.) that are characterized by means of the generalized scattering matrix. In order to obtain the reflection and transmission parameters of the entire structure, the scattering matrices of all the building blocks must be cascaded. Traditionally, the conversion of the scattering matrices to ABCD or T matrices has been used in order to perform the cascade connection. An alternative to this procedure is to perform a recursive connection by pairs of the scattering matrices. In this paper, we present a new technique for the efficient cascade connection of N monomodal or multimodal scattering matrices that reduces the computation time by 35% when compared to the cascading by pairs, and by 75% when compared with the use of ABCD matrices.

Hybrid Mode Matching and Method of Moments Method for the Full-Wave Analysis of Arbitrarily Shaped Structures Fed Through Canonical Waveguides Using Only Electric Currents

A new hybrid mode matching and method of moments formulation based only on electric currents is presented in this paper. The use of only one equivalent current allows the introduction of a new set of unknowns. The chosen new unknowns are the weights related to the scattered modes that emerge from the ports to the waveguides that feed the problem. Applying this new formulation, the matrices that must be inverted are smaller and the generalized scattering matrix can be obtained directly from the solution of the resulting system of equations so that no additional projection is needed to obtain the scattering parameters, as happens with traditional approaches with two equivalent currents. As a result, certain efficiency improvement is obtained, as can be seen when this technique is applied to the solution of H-plane problems in rectangular waveguide.

Automated design of waveguide filters using Aggressive Space Mapping with a segmentation strategy and hybrid optimization techniques

Microwave waveguide filters are key elements present in many communication systems. In recent times, increasing efforts are being devoted to the development of automated Computed Aided Design (CAD) tools of such devices. In this paper a novel CAD tool which improves the efficiency and robustness of the classical Aggressive Space Mapping (ASM) technique is presented. The use of a new segmentation strategy and the hybridization of various optimization algorithms is proposed. The CAD tool has been successfully validated with the design of a real H plane filter for an LMDS application.

Hybrid Mode Matching Method for the Efficient Analysis of Metal and Dielectric Rods in H Plane Rectangular Waveguide Devices

The paper presents a new accurate and efficient technique for the analysis of H-plane single or multiple rods in rectangular waveguides. The new method is based on a mode matching procedure that matches open space and guided modes along a circular boundary that encloses the rods. Since the EM fields around the obstacles are expanded using open space cylindrical modes, a full analytical (and highly efficient) solution can be obtained for dielectric or metallic circular posts. However, this technique can also cope with any arbitrary geometry of the H plane obstacles. In such a case, a numerical method should be used to characterize geometries other than circular in terms of cylindrical modes, and therefore the efficiency would be reduced. The method has been successfully applied to the analysis and design of several H plane filters with different topologies involving single centered and off-centered posts, as well as double post geometries.

Teaching of advanced wave-propagation phenomena in open-space problems and waveguide devices using MATLAB GUIs

Interactive graphics and animations are fundamental tools for teaching electromagnetic concepts, especially to explain propagation phenomena. For this reason, the study of these phenomena needs advanced analysis tools. This article presents an accurate and efficient hybrid mode-matching method for the analysis of arbitrarily shaped structures with H-plane obstacles and discontinuities. An open-space spectral method is used to model the electric behavior of the H-plane problem. Next, the open-space modes are matched to guided modes, in order to obtain a multimode scattering-matrix representation of the structure. This new method is used to analyze the propagation in passive complex radio-frequency structures. The results from the analysis are integrated into a MATLAB graphical user interface (GUI), which has been designed to improve the teaching/learning process at the Universidad Politecnica of Valencia in Spain. These GUIs are thoroughly explained in the paper, and the improvements in the teaching/learning process are also discussed.

Modal computation of arbitrary waveguides composed of linear, circular and elliptical arcs

In this paper, the very accurate and efficient modal analysis of arbitrarily shaped waveguides, whose cross-section is defined by a combination of straight, circular and/or elliptical arcs, is solved. An extension of the well-known boundary integral-resonant mode expansion (BI-RME) method is proposed. Successful comparisons with available numerical and experimental data fully demonstrates the validity of the improved BI-RME method proposed.

New multimodel aggressive space mapping technique for the efficient design of complex microwave circuits

The well known aggressive space mapping technique has been widely used for the design of complex microwave circuits. Many extensions of ASM have been developed in recent times. These methods improve ASM either at the cost of increasing the number of fine model evaluations, or at the cost of decreasing the accuracy of the fine model. In this work, we present a new extension of ASM, the multimodel ASM (MASM) that uses several fine models of increasing accuracy. Following an iterative procedure, it gradually maps the coarse and the finest model, thus reducing the risk of divergence, and improving the overall efficiency and robustness of the design process, without reducing the accuracy of the results. The new MASM has been tested with the design of a six-pole H plane coupled cavities filter with rounded corners in the coupling windows due to die casting fabrication.

Online application for representation of the radiation pattern of antenna arrays

Students should learn how to plot the radiation patterns of arrays of antennas in undergraduate and graduate courses on antennas. Simple chalk plots do not provide a good idea of the radiation patterns, especially for three dimensions. The authors began to work with MATLAB GUIs in order to provide an application that achieved high-quality radiation-pattern graphics and good interaction with the students, allowing them to change the different parameters of the array and to visualize the whole process of pattern plotting. Nevertheless, we found that the students wanted to have the same application for testing and studying at home, but many of them did not have copies of the MATLAB environment. The authors then looked for a solution that was portable, free, and that did not require any specific software in order to run. In order to give access to the application via the Internet, we imported our functions in MATLAB to GNU Octave, an open-source software package with characteristics similar to MATLAB but freely redistributable under the terms of the GNU General Public License (GPL).

Hybrid mode matching method for the efficient analysis of rods in waveguided structures

Abstract Traditionally metallic waveguide filters have been used commercially for microwave applications. These filters have very reduced insertion losses within their operating frequency band and their construction is considerably economic. On the other hand, metallic filters have significant drawbacks, especially when they are designed for satellite and other spatial applications, since their weight and size may very often be too high and due to the lack of atmosphere, the Multipactor effect limits considerably the power that the filters can handle. This problems can be reduced by using new topologies of H-plane waveguide filters loaded with dielectric resonators. Nevertheless the analysis and design of these filters is far more complex than the one of all metallic filters, due to their special topology. Efficient mathematical tools are required for this analysis and this paper presents a new hybrid mode matching method for the efficient analysis of rods in waveguided structures.