Pedro Vera Castejón

Numerical evaluation of the Green's functions for cylindrical enclosures by a new spatial images method

A spatial images technique is used to efficiently calculate the mixed potential Greens functions associated to magnetic sources when they are placed inside a circular cylindrical cavity. The technique places magnetic dipole images and charges outside the cylindrical region. Their strength and orientation are then calculated by imposing the appropriate boundary conditions for the fields at discrete points of the metallic wall. In this paper, the basic technique is combined with spatial domain multilayered Greens functions formulated with Sommerfeld integrals. This allows the analysis of practical multilayered circuits shielded in circular cavities. Convergence results are shown to demonstrate the usefulness of the technique. Two practical microwave circuits are also analyzed to show the validity of the formulation.

A Novel Low-Pass Filter Based on Rounded Posts Designed by an Alternative Full-Wave Analysis Technique

A new low-pass waveguide filter topology is proposed based on capacitive posts using rounded shapes. The new structure is designed using a technique that benefits from a full-wave integral equation simulation tool for arbitrarily shaped capacitive microwave circuits. This integral equation method enables one to apply an efficient filter design technique employing iris geometries other than rectangular discontinuities, such as the one based on rounded posts proposed in this work. A prototype using circular posts has been manufactured and measured obtaining excellent results as compared with predictions, thus demonstrating the practical feasibility of the new proposed filtering structure. A new filter using elliptic capacitive posts was compared in terms of multipactor risk against similar filters based on traditional rectangular windows and on rectangular posts. Simulation results indicate that the new proposed concept using rounded shapes leads to geometries that can double multipactor thresholds as compared with traditional filters.

Integral-Equation Formulation for the Analysis of Capacitive Waveguide Filters Containing Dielectric and Metallic Arbitrarily Shaped Objects and Novel Applications

This paper presents an integral-equation formulation specialized for the analysis of capacitive waveguide circuits, which include arbitrarily shaped conducting and homogeneous magnetic/dielectric objects. The technique benefits from the symmetry of the structure by formulating a 2-D scattering problem with oblique angle of incidence, combined with the use of the parallel-plate Green’s functions. As practical applications, the paper proposes novel low-pass filter designs loaded or coated with dielectric and magnetic homogeneous materials. If the filter is properly designed, the use of these materials could improve the filter response, selectivity, or out-of-band performance, and power-handling capabilities. Some novel filter design implementations, showing these kinds of benefits, are presented for the first time in this paper. For validation, a commercial full-wave simulator is employed, showing the validity, accuracy, and computational efficiency of the novel software tool.

Analysis of microstrip to circular waveguide transitions by a new spatial images method

A new spatial images procedure has been applied to the analysis of microstrip to circular waveguide transitions. The numerical technique is based on the utilization of stratified image rings, where the weights and orientations of either discrete charges or dipole images are determined. This is accomplished by enforcing the scalar and vector potential boundary conditions on the cavity walls. The results obtained with the new Greens functions have been compared to those given by a standard integral equation method based on the free space Greens functions, and a finite elements implementation. Good agreement is shown between the different techniques, thus demonstrating the usefulness of the new approach.

Integral equation analysis of capacitive waveguide circuits

This contribution presents a formulation based on the integral equation technique for the analysis of waveguide circuits containing capacitive obstacles, and including material bodies, such as dielectric or magnetic posts. The formulation is very efficient, since it reduces the 3D structure to a 2D problem by using a mixed spatial and spectral formulation. Results show high accuracy and efficiency in the analysis of lowpass filters in waveguide technology. Using the software tool, several new applications in the area of waveguide lowpass filters are introduced. This includes the use of magnetic materials to implement resonant irises, and the use of dielectric materials to reduce multipactor risk in high power applications.

A novel technique for the numerical evaluation of the Green's functions associated to cavity backed antennas in circular waveguides

In this contribution a simple and effective technique for the numerical calculation of the Greens functions in cylindrical shaped enclosures is developed. The technique is based on the numerical imposition of the boundary conditions for the fields at the cylindrical walls, using the theory of images. Numerical results for the Greens functions inside a cylindrical cavity are presented, including convergence test of the algorithm. Results show that numerical convergence is attained fast, therefore demonstrating the usefulness of the developed algorithm.