Ralf Beyer

Automated design of waveguide components using hybrid mode-matching/numerical EM building-blocks in optimization-oriented CAD frameworks-state of the art and recent advances

Fast hybrid mode-matching/boundary-contour (MM/BC) and mode-matching/finite-element (MM/FE) waveguide building blocks are described for the optimization-oriented use in powerful circuit computer-aided design (CAD) tools and the automated design of waveguide components. The efficient electromagnetic (EM) CAD technique allows the accurate design of a comprehensive class of rectangular and circular waveguide components including realistic structures of higher complexity. The efficiency and flexibility of the hybrid CAD method is demonstrated at advanced EM design examples, such as broad-band circular-to-rectangular waveguide transitions including octagonal cross sections, waveguide resonator filters with rounded corners, optimum-shaped bends, dual-mode filters with coupling sections without tuning screws, ridged waveguide filters with rounded corners, and multiplexers. The designed components are directly amenable to cost-efficient fabrication techniques like computer-controlled milling methods. The theory is verified by available measurements.

Rigorous combined mode-matching integral equation analysis of horn antennas with arbitrary cross section

A combined rigorous method is presented for the analysis of horn antennas with arbitrary cross section and general outer surface. The horn taper is described by the mode-matching (MM) method where the cross-section eigenvalue problem is solved by a two-dimensional (2-D) finite element (FE) technique. For the exterior horn surface including the radiating aperture, the application of the Kirchhoff-Huygens principle yields two expressions for the admittance matrix which are based on the electric (EFIE) and the magnetic (MFIE) field integral equation, respectively. The equations are solved numerically by the method of moments (MoM). For the preferred EFIE formulation, the eigenvectors of the last waveguide taper section and RWG functions for triangular patches are utilized as basis-functions for the magnetic or electric surface current densities, respectively. The presented method is verified by available reference values or measurements for a waveguide radiator with a peripheral choke, a conical and a rectangular horn. Its flexibility is demonstrated at the example of a conical ridged waveguide horn.

Field-Theory Design of Circular Waveguide Dual-Mode Filters by a Combined Mode-Matching Finite Element Method

An efficiet hybrid mode-matching finite element method (MMFEM)is presented for the rigorous computer-aided design (CAD) of a comprehensive class of Microwave structures which are composed of homogeneous, waveguide elements with arbitrary cross-sections. This makes it possible to take advance of the MM method and the versatility of the FEM. To show the usefulness of the method, the rigorous design, of, circular, waveguide dual-mode filters is presented which are coupled by rectangular irises with rounded corners. The dual-mode coupling is achieved either by, 45° ridged circular waveguide sections or by asymmetrically located irises. The theory is verified by measurements.

Accelerated Simulation of Low Frequency Applications using Protheus/MLFMA

In order to extend the applicability of integral equation based methods to the analysis of complex structures at lower frequencies, an efficient formulation of the low frequency fast inhomogeneous plane wave algorithm has been implemented in the Protheus/MLFMA simulation tool. The seamless integration of the new low frequency method with the well known multilevel fast multipole algorithm within Protheus/MLFMA delivers a method capable of efficient accelerated wideband analysis for a large range of applications such as integration of communication antennas on ships, design of wideband antennas and EMC tasks.

Compact top-wall hybrid/coupler design for extreme broad bandwidth applications

A design approach for compact waveguide top-wall short-slot 3 dB hybrids is introduced to achieve high performance properties over extreme large bandwidths up to 30%. The hybrid principle relies on the dual mode propagation of TE 10 /TEM modes in a common coupling region. The CAD, established for this design task, is based on a combined finite element/mode-matching (FE/MM) method to accommodate with the particular constraints of the structure. Several hybrids have been designed for frequency bands from 4 to 40GHz. Validation of this novel CAD approach is demonstrated by a realized 12GHz design which exhibits accurate coincidence of computed and measured characteristics.

Cascaded Wide Stop Band Waffle-Iron Filter Designed with a MM/FE CAD Method

A hybrid mode-matching(MM)/finite element (FE) CAD method is applied for the fast CAD of ultra-wide stop band and high return loss waffle-iron filters. The design is based on cascaded waffe-iron sections with a different number of bosses in the cross-sections utilizing a new non-isotropic waffle-iron structure with individually optimized lengths. For the efficient optimization with regard to the S parameters, the generalized scattering matrix (GSM) combination technique is used with an automatic selection of localized and accessible modes. An overall block-LU-decomposition method allows one to calculate the field intensities within the waffle-iron sections. The optimization carried out by a robust direct search method achieved a waffle-iron filter with better than 30dB return loss between 7 and 8.3 GHz, and more than 70 dB rejection between 12 and 60 GHz. The theory is verified by excellent agreement with measurements.

The generalized scattering matrix separation technique combined with the MM/FE method for the efficient modal analysis of a comprehensive class of 3D passive waveguide circuits

A novel and versatile technique for the efficient modal analysis of passive waveguide structures, called the generalized scattering matrix separation (GSMS) technique, is introduced. Its combination with the well-proven hybrid mode-matching/finite element (MM/FE) method achieves the fast and rigorous modal analysis of a comprehensive class of three-dimensional waveguide components which include homogeneous segments of arbitrarily shaped cross-section and one or more side coupled rectangular waveguide ports. This combined method takes the higher order mode coupling between all discontinuities or ports into account and requires only one frequency independent application of the two-dimensional finite element (FE) method. The method is verified by excellent agreement with measurements.<<ETX>>

CAD of magic tee with interior stepped post for high performance designs

A CAD - based on the Finite Element/Mode Matching (FE/MM) method - is introduced for high performance Magic Tee designs that make use of an interior stepped post discontinuity in the branching region. The theoretical considerations of the approach are outlined. For validation a Magic Tee is designed and realized at 12 GHz exhibiting high performance properties over a 14 % bandwidth. Accurate coincidence of computed and measured responses verifies the CAD method.

Modal block-LU-decomposition technique for the efficient CAD of ridged waveguide filters

A mode-matching/block-LU-decomposition (MMLU) technique is presented for the fast calculation of the modal S-parameters of and the fields in waveguide components composed of step discontinuities and homogeneous sections. The MMLU approach leads to a numerically efficient block-tridiagonal matrix structure. Arbitrary cross-sections are included by the combination with the fast and flexible 2D FE method. The efficiency of the method is demonstrated at the CAD of advanced broadband higher-order mode suppression ridged waveguide filters. Excellent agreement with measurements verifies the theory.

Novel remote controlled dual mode filter providing flexible re-allocation of center frequency and bandwidth

A novel TE113 dual mode cavity filter design is introduced that provides remote controlled reallocation of center frequency and bandwidth. The reconfiguration principle1 considers both end-walls of the cavities to be independently moveable along the cavity axes. This allows convenient control of cavity resonance frequencies (cavity length) and filter couplings (i.e., field strength in front of the coupling means inside the cavity). Higher order filters are realized by side-wall cavity arrangements using synchronous movement of all cavity end-walls with only two actuation units. EM analyses and measured results of a 2-order filter design at 11.2GHz prove the feasibility of the new solution.