L.A. Rud

Compact 90

Simple and compact rectangular waveguide 90deg twist is proposed. The twist transformer region is a square waveguide section with two square corner cuts. The twist full-wave model is based on the mode-matching and generalized S-matrix techniques. It is found that the optimized twists can provide the bandwidths of no less than 30% at the 30-dB return-loss level or 16% at the 40-dB level over a lower, middle, or higher part of the rectangular waveguide operating band. The twist lengths are five times less than the rectangular waveguide wavelength at the central frequency of the chosen operating band. Role of evanescent modes in the interaction of two small-distanced twist transitions is discussed. The design results are confirmed by the results of real device measurements.

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The new efficient numerical-analytical method of electromagnetic interior boundary value problem solving is presented with waveguide H plane angled bends as examples of implementation. The method essence consists in the analytical inversion of the main difference part of the initially derived ill-posed matrix equation of the first kind. As a result, the problem is reduced to the solution of the second-kind matrix equation with an invertible operator. The proposed method differs from other methods dealing with so-called modified Wiener-Hopf geometry structures. It is oriented to noncoordinate boundary value problems to which the ones of angular waveguide discontinuities are related. Detailed consideration of all parts of the numerical algorithm ensures its high efficiency. As application examples, the data for designing the matched truncated corners in a single-mode waveguide and the results of comparison of the known high-frequency heuristic estimations with the exact simulation of waveguide corners having a quasi-optical mirror are presented.

Twist Formed by a Double-Corner-Cut Square Waveguide Section

The opportunity of an effective usage of a stepped approximation for the calculation of cutoff frequencies and eigenfunctions of waveguides with complex cross-sections is shown. It is recognized that such an approach is productive for the analysis and optimization of polarizers based on sections of circular waveguides with rectangular ridges. The results of comparison with experimental data are represented.

Semi‐inversion method for an accurate analysis of rectangular waveguide H plane angular discontinuities

An efficient electrodynamic model and an optimization procedure for orthomode transducers based on a circular waveguide and step transitions in rectangular input arms is developed. The physical factors limiting the operating bandwidths of these transducers are determined. The effect of the number of sections in the step transitions on the characteristics of single-band transducers are investigated.

Stepped approximation technique in the problem on polarizer based on circular waveguide with rectangular ridges

Waveguide units with coordinate boundaries in the cylindrical coordinate system are widely used in microwave devices based on circular and coaxial waveguides. Besides the universal finite element methods more accurate and efficient algorithms were built for the analysis waveguides of this kind. However, all of the currently available algorithms were developed for the analysis of individual structures of interest, mainly for ridge waveguides. So far the general algorithm suitable for the analysis of any waveguide of this class has not been developed yet. In this paper we eliminate this gap by a generalization of the mode matching technique to the waveguides with coordinate boundaries in the cylindrical coordinate system taking into account field singularities. The final goal was to obtain a tool for fast calculation of the mode spectrum (up to hundreds) as it was previously built for the waveguides with piesewise Cartesian coordinate boundaries.

Orthomode transducers with a common circular waveguide

The results of the design and testing of circular polarization splitters (polarizers) of the Ka-, X-, and S-bands, intended for operation as constituent parts of a three-band feed of a radio telescope reflector antenna, are presented. In addition, the results of developing a set of polarizers intended for connecting to waveguide outputs of band-measuring horn antennas are presented. These polarizers are developed to measure the antenna feed patterns on the co- and cross circular polarizations.

Numerical determination of eigenmodes of an arbitrary waveguide with coordinate boundaries in cylindrical coordinate system

A highly efficient, full-wave electromagnetic model and CAD of ortho-mode transducers built on a circular waveguide and supplied with step transitions in input rectangular waveguide ports is proposed. A discussion on the inherent limitations of the achievable performance and critical parameters is presented. The capabilities of the CAD program are demonstrated by the design of dual-band OMTs with identical and different input waveguides.

Circular polarization splitters for three-band feed of radiotelescope reflector antenna

The attention to coaxial waveguide polarizers is caused due to developing multifrequency antenna systems, e.g. for radio telescopes, operating over two or more sufficiently spaced frequency bands. If the inner conductor is hollow and acts as a conventional circular waveguide, it can be used for transmitting a higher-frequency signal while the coaxial region provides the lower-frequency signal propagation. The further addition of outer cylindrical conductors allows increasing a corresponding number of frequency bands.

Electromagnetic simulation and design of dual-band ortho-mode transducers

A numerical algorithm for the analysis and optimization of broadband polarizers consisting of symmetrically placed rectangular ridges in a coaxial waveguide is developed. Because polarizer boundaries cannot be described in a single (cylindrical or Cartesian) coordinate system, the approach based on a stepped approximation of regular and ridged coaxial waveguides is proposed to apply. The factors influencing on accuracy and validity of obtained numerical results are established and discussed.

Design and optimization of broadband ridged coaxial waveguide polarizers

Septum polarizers (SPs), built on a square waveguide with stepped ridged waveguide junctions, have found many applications in antenna systems and polarization measurement equipments. In the present paper, the features of the developed CAD of compact square-waveguide SPs with a circular output waveguide and results of its design application are discussed. The SP configurations under consideration are combined by the following components: rectangular-to-rectangular, bifurcated square-to-ridged, ridged-to-ridged, square-to-square, and square-to-circular waveguide junctions. Exact numerical models for all the components are built on the mode-matching technique. The eigen-value problem for the single-ridged waveguide is solved using the moment method with basis and tested functions taking into account the field behavior near edges.