Pablo Soto

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.

Analysis, design, and experimental verification of microwave filters for safety issues in open-ended waveguide systems

Safety issues must be seriously considered in the practical implementation of microwave industrial systems with open ports. To preserve the radiation of these open-ended waveguide systems into permissible levels, bandstop microwave filters are widely used. In this paper, the accurate analysis, design, and experimental verification procedure of such filters are extensively studied. A singly and a doubly corrugated filter for continuous flow microwave industrial systems are designed. Two prototypes of such devices have been manufactured and experimentally verified.

Evaluation of time domain electromagnetic fields radiated by constant velocity moving particles traveling along an arbitrarily shaped cross-section waveguide using frequency domain Green's functions

[1] A technique for the accurate computation of the time domain electromagnetic fields radiated by a charged distribution traveling along an arbitrarily shaped waveguide region is presented. Based on the transformation (by means of the standard Fourier analysis) of the time-varying current density of the analyzed problem to the frequency domain, the resulting equivalent current is further convolved with the dyadic electric and magnetic Green’s functions. Moreover, we show that only the evaluation of the transverse magnetic modes of the structure is required for the calculation of fields radiated by particles traveling in the axial direction. Finally, frequency domain electric and magnetic fields are transformed back to the time domain, just obtaining the total fields radiated by the charged distribution. Furthermore, we present a method for the computation of the wakefields of arbitrary cross-section uniform waveguides from the resulting field expressions. Several examples of charged particles moving in the axial direction of such waveguides are included.

Accurate Synthesis and Design of Wideband and Inhomogeneous Inductive Waveguide Filters

In this paper, a new synthesis and design methodology is presented and applied for the fast and accurate design of inductive rectangular waveguide filters. By using this technique, the dimensions of both homogeneous and inhomogeneous filters can be successfully synthesized for almost any practical filter bandwidth, return loss, or filter order. This novel technique is based on a prototype with additional degrees of freedom, able to match the response of the different filter components in a wideband frequency range, and an elaborated design procedure that fully exploits this flexibility. During the design procedure, the prototype and the real structure are continuously aligned in order to have the same electromagnetic behavior and jointly evolve to obtain an equiripple response. Once the final prototype has been synthesized, excellent filter dimensions can be extracted that, in most cases, do not require further optimization. Examples will show the outstanding performance of the proposed design technique in terms of versatility, accuracy, and CPU time.

A 3-D Smith Chart Based on the Riemann Sphere for Active and Passive Microwave Circuits

This letter proposes a spherical 3-D Smith Chart suitable for representing both active and passive microwave circuits. Using the mathematical concept of the Riemann sphere, the extended reflection coefficient plane is transformed into the surface of the unit sphere. Since the proposed Smith Chart compiles the whole complex plane, all possible loads are included. A simple graphic tool is thus obtained that successfully unifies active and passive circuits. In addition, lossy lines with complex characteristic impedances can also be represented. The letter presents the 3-D Smith Chart, provides its main governing equations, and also enumerates its more important properties.

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.

Design of Compact Wideband Manifold-Coupled Multiplexers

The design of manifold-coupled multiplexers for wideband applications is considered in this paper. A systematic procedure, based on the sequential connection of filters to the manifold and subsequent adjustment of the interconnection elements, is presented. The filters are attached to the manifold without using stubs in order to minimize the effect of spurious resonances. The interconnection elements, the manifold, and the remaining filters are considered as the first inverter of each new filter that is attached. This technique has been applied to several practical examples. The obtained results validate the proposed design methodology.

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.

Design of Hybrid Folded Rectangular Waveguide Filters With Transmission Zeros Below the Passband

The design and physical implementation of hybrid folded rectangular waveguide filters providing multiple transmission zeros (TZs) below the passband are considered in this paper. These structures offer great flexibility to locate the TZs in a wide frequency range. Different implementations have been considered, each one offering certain advantages in terms of ease of manufacture, number of TZs, and their separation from the passband. A simple design procedure is also described. Measurements of a manufactured five-pole filter prototype and simulations fully validate the novel configurations proposed in this study.

Practical design of rectangular waveguide filters with a capacitive building block providing an extra transmission zero

This paper faces up the practical design of a class of rectangular waveguide filters using a recently proposed capacitive coupling scheme. Such a coupling scheme creates an E-plane stub in the waveguide resonator, and provides an extra transmission zero. First, a novel 2D building block including the capacitive window and the stub is identified. A parametric analysis of this block is then carried out to evaluate its performance, and also to obtain design guidelines for its use in practical applications. Finally, such guidelines are illustrated with the EM-based design of a novel constant-width filter topology of order 5, which provides 4 transmission zeros without cross-couplings and non-resonating nodes. The designed filter is fully validated with measurements of a manufactured prototype.