We discuss the foundations and state-of-the-art of the method of analytical regularization (MAR) (also called the semi-inversion method). This is a collective name for a family of methods based on conversion of a first-kind or strongly-singular second-kind integral equation to a second-kind integral equation with a smoother kernel, to ensure point-wise convergence of the usual discretization schemes. This is done using analytical inversion of a singular part of the original equation; discretization and semi-inversion can be combined in one operation. Numerous problems being solved today with this approach are reviewed, although in some of them, MAR comes in disguise.

The method of analytical regularization in wave-scattering and eigenvalue problems: foundations and review of solutions

This article describes the historical evolution, and its theoretical and technological features of waveguide filters. All-metal waveguide filters have been widely used in satellite payloads since the advent of the first space communication systems four decades ago. In this period, such technology has been continuously evolving due to the increasing requirements demanded to these components. Special attention has also been paid to present the most recent advances in the development of CAD tools for satellite filters, which are based on full-wave electromagnetic analysis methods. Finally, the compact solutions for the input and output stages of satellite payloads are focused on, thus considering the evanescent mode waveguide filter technology.

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Waveguide filters for satellites

This paper presents an overview of the state-of-the-art of hybrid mode-matching (MM)/finite-element (FE)/method-of-moments (MoM)/finite-difference (FD) techniques applied for the rigorous, fast computer-aided design and optimization of waveguide components, combline filters, and coupled horns, as well as of slot arrays, and describes some recent advances Related aspects involve the inclusion of coaxial and dielectric structures for related filters, the extension to multiports at cross-coupled filters, the rigorous consideration of outer and Inner mutual coupling effects at coupled horn and slot arrays, the application of the multilevel fast multipole algorithm for the more efficient MoM calculation part of horns and horn clusters, and the utilization of the MoM for the design of arbitrarily shaped three-dimensional waveguide elements The described hybrid techniques combine advantageously the efficiency of the MM method with the flexibility of FE, MoM, and FD methods Topical application examples demonstrate the versatility of the hybrid techniques; their accuracy is verified by available measurements

Fast CAD and optimization of waveguide components and aperture antennas by hybrid MM/FE/MoM/FD methods-state-of-the-art and recent advances

The Advanced LOwer Hybrid Antenna (ALOHA) code, has been developed to improve the modelling of the coupling of lower hybrid (LH) waves from the antenna to a cold inhomogeneous plasma while keeping a fast tool. In contrast to the previous code Slow Wave ANtenna (SWAN) (that only described the interaction of the slow wave between the waveguides and the plasma in a 1D model), the equations are now solved in 2D including the contribution of both the slow and fast waves, with a low computational cost. This approach is completed either by a full-wave computation of the antenna that takes into account its detailed geometry or by a mode-matching code dedicated to multijunctions modelling, which is convenient in preliminary design phases. Moreover, ALOHA can treat more realistic scrape-off layers in front of the antenna, by using a two-layer electron density profile. The ALOHA code has been compared with experimental results from Tore Supra LH antennas of different geometries, as well as benchmarked against other LH coupling codes, with very good results. Once validated, ALOHA has been used as a support for the design of COMPASS and ITER LH antennas and has shown to be a fast and reliable tool for LH antenna design.

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ALOHA: an Advanced LOwer Hybrid Antenna coupling code

This paper discusses three emerging trends in the area of millimeter-wave (mm-wave) electromagnetic (EM) simulation and computer-aided design (CAD). Diakoptics techniques for frequency- and time-domain EM-simulation methods are needed for mm-wave circuit design. Development of artificial neural network (ANN) models is likely to result in an efficient use of EM simulators. Possible applications of knowledge-based tools are suggested for initial stages of the design process.

Emerging trends in millimeter-wave CAD

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.

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

Parallel and crossed rectangular waveguide broadwall couplers with apertures of arbitrary shape and number are analyzed rigorously by the efficient and flexible boundary-contour/mode-matching (BCMM) method. The modal S-matrix combination technique takes adequately into account both the finite wall thickness and the higher order mode interaction between the discontinuities. Examples with circular, elliptical, and cross apertures demonstrate the flexibility of the design method. The theory is verified with measurements.

J.M. Reiter

Papers

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

Modal analysis of parallel and crossed rectangular waveguide broadwall couplers with apertures of arbitrary shape