Pablo Soto

University of Valencia, Valenza, Valencia, Spain

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Publications (43)29.9 Total impact

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    ABSTRACT: 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.
    No preview · Article · Jan 2016 · IEEE Transactions on Microwave Theory and Techniques
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    ABSTRACT: 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.
    No preview · Article · Oct 2015 · IEEE Transactions on Microwave Theory and Techniques
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    ABSTRACT: In this paper, a new systematic technique to design manifold-coupled multiplexers in waveguide technology is proposed. The new technique uses generalized low-order electromagnetic (EM) distributed models, which constitute a half-way point between the fast, but imprecise, analytical models, and the more accurate, but costly, full-wave EM models. The method can be applied to contiguous and noncontiguous channel multiplexers, in both -plane or -plane configurations. This paper covers the complete design procedure for manifold multiplexers, starting from the required specifications and finishing with the physical dimensions. After explaining the general design technique for multiplexers with channel filters based on transmission-line resonators, the method is specialized for the design of classic multiplexers with circular-waveguide dual-mode filters. As a further application example, the same methodology is also used for the design of a nonconventional tuningless wideband multiplexer with a new type of rectangular waveguide filters. This paper is concluded with a comparison between simulation and measurements for the wideband multiplexer. Excellent agreement between measurements and simulations are demonstrated, thereby validating the complete design procedure.
    No preview · Article · Aug 2015 · IEEE Transactions on Microwave Theory and Techniques
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    ABSTRACT: 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.
    No preview · Article · Jul 2015
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    ABSTRACT: Abstract—In this work, ohmic losses present in arbitrarily shaped waveguide-based structures are rigorously considered. For such purpose, a software tool based on the perturbation of the boundary conditions on the metallic walls of the waveguides combined with an Integral-Equation (IE) analysis technique is proposed. In order to obtain the modal chart of waveguides with arbitrary cross-section, the Boundary Integral - Resonant Mode Expansion (BI-RME) method is also employed. To show the advantages of the proposed technique a computer-aided design software package based on this modal analysis tool has been applied to predict the propagation loss effects in complex waveguide components.
    Full-text · Conference Paper · May 2015
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    ABSTRACT: A very flexible and efficient computer-aided design (CAD) tool, specifically suited for advanced comb-line rectangular waveguide filters, is presented in this work. The developed software tool, which makes use of a full-wave analysis technique based on the Boundary Integral—Resonant Mode Expansion method, allows loading the considered comb-line resonators with any number of radially symmetrical partial-height metallic posts. The implemented CAD tool also allows dealing with coupling windows of arbitrary cross-section, thus drastically enhancing the flexibility of the CAD process. The excitation of the analyzed components, which is performed using generalized coaxial probes, has also been integrated in the implemented software tool, thus achieving a full-wave electromagnetic characterization of the whole component. Furthermore, a novel simple procedure to efficiently connect all the obtained wide-band matrices is proposed. To validate the accuracy and efficiency of this novel CAD tool, several new designs concerning advanced band-pass comb-line waveguide filters are presented. The accuracy of the developed CAD tool has been successfully validated by comparing the obtained results with numerical data provided by a commercial tool based on the finite-element method. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2015.
    No preview · Article · Apr 2015 · International Journal of RF and Microwave Computer-Aided Engineering
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    Full-text · Dataset · Jan 2015
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    ABSTRACT: Unilateral transducer constant power gain circles play an essential role in the design of radio-frequency amplifiers and active modulators, as they help to determine optimal impedance matching conditions to meet gain and stability specifications. It is shown that these gain circles are a subfamily of Apollonius circles. For better visualisation, unilateral transducer constant gain power circles have been plotted for the first time on the three-dimensional (3D) Smith chart. To this end, a natural relationship from an inversive geometry was required, in order to relate the gain circles with cutting planes for the 3D Smith chart.
    Full-text · Article · Oct 2014 · Electronics Letters
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    ABSTRACT: This paper presents a novel filter topology for the implementation of asymmetric responses with transmission zeros (TZs) in rectangular waveguide technology. It is based on a compact folded E-plane arrangement where adjacent resonators are capacitively coupled through rectangular slots, and non-adjacent resonators are coupled through simple inductive windows. The new folded configuration allows the introduction of transmission zeros above the passband, which can be easily controlled. High order filters can be designed by cascading an arbitrary number of resonators in a folded layout. Components based on this novel configuration are amenable to simple manufacturing processes and can be used in high-power environments. A triplexer containing filters implemented with the proposed topology has been designed. Measurements of a manufactured prototype are included to validate the use of this topology in practical applications.
    No preview · Conference Paper · Oct 2014
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    ABSTRACT: The accurate consideration of propagation losses in arbitrarily shaped waveguide-based structures is studied in this paper. For such a purpose, a software tool based on the perturbation of the boundary conditions on the waveguide metallic walls and on the boundary integral - resonant mode expansion method has been developed. To show the advantages of the proposed technique with respect to the classic power-loss method, the complex propagation wavenumbers of a double ridge and an elliptical waveguide have been first computed and compared with results of a commercial software based on the finite element technique. Next a circular, a sectorial shaped and a triangular shaped waveguide have been considered. Then, a computer-aided design software package based on this modal analysis tool has been applied to predict the propagation loss effects in complex waveguide structures, such as an evanescent mode ridge waveguide filter, a traditional dual mode filter with circular cavities and a twist component for K-band applications.
    Full-text · Article · Sep 2014 · IET Microwaves Antennas & Propagation
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    ABSTRACT: This paper proposes novel waveguide topologies for obtaining filter responses with arbitrary placed transmission zeros (TZs). These new structures have a good electrical behavior and allow fast simulation using EM techniques. Several topologies and their corresponding electrical models will be presented, together with amenable synthesis and design procedures. The simplicity of the layout raises these kind of filters as good candidates for useful applications requiring advanced filter characteristics.
    No preview · Conference Paper · Jun 2014
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    ABSTRACT: A novel multiplexer design technique which makes use of distributed models is proposed. For the first time, distributed models of dual mode filters are applied to the design of manifold multiplexers, with a large number of both contiguous or non-contiguous channels. After a brief review of the last advances in multiplexer design, the whole design process is described over a non-contiguous channel example. Finally, a contiguous channel case is presented.
    No preview · Conference Paper · Jun 2014
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    ABSTRACT: The authors have detected an error in Section IV-A in the above paper (ibid., vol. 59, no. 12, pp. 3601-3607, Dec. 2012). The analyzed rectangular waveguide in the actual version of the article is the WR137, instead of the WR90. As a consequence, the corrections presented here have to be implemented.
    No preview · Article · Jan 2014 · IEEE Transactions on Electron Devices
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    ABSTRACT: In this study, the efficient full-wave analysis of passive devices composed of circular and arbitrarily-shaped waveguides is considered. For this purpose, the well-known boundary integral-resonant mode expansion (BI-RME) method has been properly extended. Circular waveguides are used for resonant mode expansion, whereas the arbitrary contour is defined by any combination of straight, circular and elliptical segments, thus allowing the exact representation of the most widely used geometries. The proposed algorithm extends previous implementations of the BI-RME method based on circular waveguides by considering circular and elliptical arcs for defining arbitrary geometries. Similarly, it allows the efficient analysis of passive devices based on circular waveguides with arbitrary perturbations, thus providing more accurate results with less computational efforts than a rectangular waveguide-based BI-RME approach. The extended method has been successfully tested with several practical application examples, having compared its performance with the BI-RME method based on rectangular waveguides.
    No preview · Article · Jan 2013 · IET Microwaves Antennas & Propagation
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    ABSTRACT: The aim of this paper is to study the multipactor radio-frequency breakdown voltage in several ridge and multiridge waveguide configurations. First, multipactor susceptibility charts for several types of ridged waveguides have been computed using the commercial software FEST3D. Next, these charts have been used to predict multipactor threshold values for a bandpass filter and a quasi-low-pass filter both containing ridge waveguide sections. Furthermore, multipactor simulations using FEST3D are carried out to calculate the multipactor threshold of the aforementioned structures. A good agreement between predictions and simulations has been found for both filter examples.
    No preview · Article · Dec 2012 · IEEE Transactions on Electron Devices
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    ABSTRACT: Abstract This paper analyzes and compares voltage and power wave reflection coefficients using a visual representation which fully exploits that both coefficients are directly related to the geometry of direct inversive transformations in the extended impedance plane. In order to compare the two concepts for complex impedance ports, the 3D Smith chart tool is used in premiere. The paper gives a geometrical and more intuitive insight of these two parameters and proposes a novel tool for handling both types of reflection coefficients.
    No preview · Conference Paper · Dec 2012
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    ABSTRACT: 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.
    Full-text · Article · Oct 2012 · Radio Science
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    ABSTRACT: The mathematical theory of the 3D Smith chart unifies active and passive microwave circuit design on the surface of a Riemann sphere. The reflection coefficient plane is mapped stereographically through the South Pole on the surface of a unit sphere. The infinite region of the normalized impedance or z-plane is due to the open circuit, because the magnitude of the input impedance grows to infinity as the load tends to an open circuit. Since in practical applications, impedances can be found close to the open circuit, it is rather uncommon to use the z-plane to perform a visual representation of loads. The 2D Smith chart successfully compiles in a bounded region the unit circle and all of the passive loads with the matched load in its center. Although the passive loads are the more common ones, certain applications involve the use of active devices, whose impedances can be very far from the unit circle.
    No preview · Article · Jul 2012 · Microwave Journal
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    S. Marini · M. Mattes · B. Gimeno · P. Soto · V.E. Boria
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    ABSTRACT: In this paper, propagation losses effects present in rectangular waveguide structures are rigorously considered. For this purpose, a new formulation based on the perturbation of the boundary conditions on the metallic walls of the waveguides combined with an Integral-Equation (IE) analysis technique is proposed. Following this advanced technique, the drawbacks of the classical power-loss method are overcome and a complex modal propagation constant is computed. To validate this theory, we have successfully compared our results with numerical data of lossy hollow waveguides. Next, a Computed-Aided-Design (CAD) software package based on such a novel modal analysis tool has been used to predict the propagation losses effects in a 2-pole symmetric bandpass filter.
    Full-text · Conference Paper · Oct 2011
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    ABSTRACT: Most of the circuit prototypes used in practical applications were proposed many decades ago, when the present computational resources were not available. Simplicity was a key factor in their conception. Although these traditional prototypes model the real structures, they usually neglect second-order effects, the frequency dependence of the filter parts and, in some cases, they do not have an exact correspondence with the physical structure. All of these inaccuracies can affect the equivalence between the prototype and the real filter, thus degrading the initial structure extracted from the synthesized prototype. Optimizations carried out from poor initial dimensions are computationally burdensome and more liable to provide a filter with unsatisfactory response. The synthesis methods reviewed in this article are based on prototypes designed to faithfully represent the real components. These prototypes include elements to model the relevant effects of the structure in the particular designs to be carried out. Moreover, accurate EM simulators are used to find an almost exact equivalence between the prototype and the filter parts. Although more elaborate synthesis techniques are usually required, these enhanced prototypes and synthesis procedures can be used to extract outstanding initial structures. The design is essentially solved after the dimensional synthesis of the component since, at most, only a slight and fast final refinement is needed (using an EM optimizer or the tuning elements included in narrowband filters). The examples shown in this article reveal the capabilities of these methods to overcome the limitations of classic circuit synthesis.
    No preview · Article · Oct 2011 · IEEE Microwave Magazine