An efficient integral equation technique for the analysis of arbitrarily shaped capacitive waveguide circuits

In this contribution a new and efficient integral equation formulation is presented for the analysis of arbitrarily shaped capacitive waveguide devices. The technique benefits from the symmetry of the structure in order to reduce the dimensions of the problem from three to two dimensions. For the first time, this technique formulates the waveguide capacitive discontinuity problem as a 2-D scattering problem with oblique incidence, combined with an efficient calculation of the parallel plate Green's functions. The numerical method allows the efficient evaluation of the electromagnetic fields inside the analyzed structures. Results for different practical capacitive waveguide devices are successfully compared with commercial software tools for validation of the proposed theory. Finally, a novel low-pass filter implementation based on circular conducting posts has been proposed. The field contour lines in the critical gaps of the new structure are curved due to the use of rounded posts. This could result in improved power handling capabilities with respect to standard corrugated low-pass filters. Copyright 2011 by the American Geophysical Union.This work has been developed with financial support from SENECA project reference 08833/PI/08, and CICYT project reference TEC2007-67630-C03.Quesada Pereira, FD.; Vera Castejon, P.; Alvarez Melcon, A.; Gimeno Martinez, B.; Boria Esbert, VE. (2011). An efficient integral equation technique for the analysis of arbitrarily shaped capacitive waveguide circuits. Radio Science. 46:1-11. doi:10.1029/2010RS004458S1114

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

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.The authors would like to thank ESA/ESTEC for having cofunded this research activity through the Network Partnering Initiative program and through the project "Multipactor Analysis in Planar Transmission Lines" (contract 20841/08/NL/GLC). We also are grateful to the Spanish government and the local Council of Murcia for their support through the projects CICYT Ref. TEC2010-21520-C04-04 and SENECA Ref. 08833/PI/08, respectively.Jimenez Nogales, M.; Marini, S.; Gimeno Martinez, B.; Alvarez Melcon, A.; Quesada Pereira, FD.; Boria Esbert, VE.; Soto Pacheco, P.... (2012). 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. Radio Science. 47(5):1-14. https://doi.org/10.1029/2012RS005008S114475Alvarez-Melcon, A., & Mosig, J. R. (2000). 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Fast S-domain modeling of rectangular waveguides with radially symmetric metal insets

This paper describes the application of the boundary integral-resonant-mode expansion (BI-RME) method to the modeling of rectangular waveguides with metal insets. It extends to more complicated radially symmetric insets, a method recently introduced by the authors, for the simple case of a cylindric post. In this extension, a self-consistent new theory is presented, which fully exploits the peculiarities of the considered class of structures, thus straightforwardly leading to the system equations. The efficiency of the BI-RME method, already demonstrated in the wide-band modeling of arbitrarily shaped waveguide components, is further enhanced in the particular application considered in this paper because the currents on the waveguide walls are not involved in the calculation. For this reason, the method-of-moments discretization of the field equations leads to a mathematical model of order much smaller than in the general BI-RME approach and in other boundary integral methods. Due to the state-space formulation of this model, a wide-band representation of the generalized admittance matrix of the structure is easily found in the form of a pole expansion in the S-domain by the calculation of a reasonably small number of eigensolutions of a matrix eigenvalue problem. The method is very fast and reliable, and permits the realization of a very efficient software, well suited for inclusion in computer-aided design tools for microwave circuit design. Some examples show the efficiency of the method, including the application to multiple and slanting insets and to the modeling of an evanescent-mode filter

Rigorous Investigation of RF Breakdown Effects in High Power Microstrip Passive Circuits

This work presents a new rigorous investigation of corona effects in microstrip components. To carry out the investigation, a new software tool has been developed. The new tool first calculates the electromagnetic fields in complex microstrip structures using a Volume Integral Equation (VIE) formulation. Novel numerical techniques have been incorporated in the VIE to increase the accuracy during the computation of the electromagnetic fields. This includes novel techniques introduced to treat the singularities of the Green's functions. Once the electromagnetic fields are computed accurately, corona effects in the relevant structures are investigated. For this, a numerical solution of the free electron density continuity equation has been implemented.The new software developed has been used, for the first time,in the study of corona effects in the neighborhood of coaxial to microstrip transitions, containing flat ribbons. Numerical results are validated through measurements, showing the accuracy of the developed models