S. A. Prikolotin

Ultra-compact 90° twist based on a pair of two closely placed flat chiral irises

A new ultra-compact device for rotating the polarization plane of planar electromagnetic wave in a square waveguide by 90° whose dimension is almost ten times less than wavelength is suggested. It is based on strong interaction of near-fields in two closely placed flat chiral irises. It is shown that this approach due to strong multi-mode and near-field interaction allows rotating the polarization plane by 90° in the several percent bandwidth with the loss level not worse than 0.1 dB.

Fast full 3D EM CAD of waveguide units based on the generalized mode matching technique

A unique 3D EM solver based on the generalized mode matching technique (MMT) and aimed to solve the problems of analysis and synthesis of a wide class of passive devices is presented. The high efficiency of the CAD software will be demonstrated at some typical examples.

Natural oscillations providing 90° polarization plane rotation by planar chiral double-slot irises

The common origin of the “enhanced transmission” through small holes and polarization plane rotation (“optical activity”) resonances peculiar for a pair of conjugated planar chiral irises is demonstrated. The eigenoscillation spectra are studied extensively from the “aperture” eigenoscillations of plane junctions responsible for the “enhanced transmission” through the planar chiral iris up to the eigenoscillations of “dihedral” symmetry formed in a composite double slot planar chiral iris. Their excitation results in polarization plane rotation of the dominant mode in a square waveguide. A new compact unit for TE01 to TE10 conversion operating within 5–10% frequency band is proposed and validated experimentally. All conclusions are valid for various types of metasurfaces based on the “fish-net” gratings.

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

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.

Eigen-oscillations of composite double-slot iris in a square waveguide and manifestation of enhanced transmission and “optical activity”

The widespread implementation of the powerful hardware and grid computing software in computational electromagnetics has spawned a wave of the publications devoted to the analysis of the complex three-dimensional structures, generating innovative applications. As an example, the analysis of a variety of objects, providing a giant “optical activity” (rotation of the polarization plane) due to topology complication can be cited [1].

Spectral properties of a rectangular waveguide section with a pair of two transversal ridges

Short metal ridges in a rectangular waveguide appeared to be promising units for different microwave filters providing complicated frequency response. In particular, a waveguide containing two rectangular even (or uneven) ridges was used [1] to provide high-quality resonant reflection of the incident mode. A pair of equal height posts in a rectangular waveguide was used lately [2] in order to design a bandpass filter generating an improved response with additional attenuation poles. A quasi-elliptic filter based on a pair equal height posts was reported recently [3]. Off-centered single post and slant single ridge were used successfully in a modern filter design as well [4, 5]. Nevertheless the physical nature of the phenomenon of an attenuation pole generation provided by all the mentioned resonant sections remained unrevealed. Here we use the spectral theory of open waveguide resonators [6-8] to solve this problem. Within the frames of the spectral theory a waveguide unit is considered as open waveguide resonator loaded by semi-infinite guides. Different resonant regimes are interpreted as a response on the excitation of the natural oscillations of the resonator. Similarly to [9], we expect that understanding the physical nature of the resonant phenomena makes their conditions and limitations more clear.

Plane-chiral pair with opposite rotations as a new way to rotate polarization up to 90°

A new approach to the problem of polarization transformation of a plane wave or waveguide dominant mode is proposed. The idea is based on the strong interaction of the fringing fields excited by irises with chiral right and left rotations, placed at a distance that is an order of magnitude shorter than the wavelength. Due to the multimode nature of the interaction we can provide 90 degrees rotation in bandwidth equal to several percents at the insertion loss level not worse than -0.1 dB.

Rotation of the polarization plane by double-layer planar-chiral structures. Review of the results of theoretical and experimental studies

This article provides examples that illustrate the search for different two-layer metamaterials that provide rotation of the polarization plane (“optical activity”). Selected objects show a twenty-year history of the search for a new principle of creation of polarization rotators based on planar metamaterials that were implemented in the form of thin-layered periodic structures. The manifestation of optical activity, presence or absence of satisfactory or perfect matching, the possibility of a multiband phenomena, the role of high spatial harmonics in “electromagnetics” of this effect are explained by the features of the eigen-oscillations that are excited in the gap of the multilayer structure.

Polarization Plane Rotation by Arbitrary Angle Using

A compact waveguide polarization rotator, able to turn the polarization plane by an arbitrary angle, is proposed. Its operational principle is based on a strong electromagnetic coupling between two conjugated quadruple-slot planar-chiral irises in a square waveguide by the below cutoff modes. The physical interpretation for the observed phenomenon is provided based on the analysis of the eigenoscillations of such a D4 symmetrical object considered as an open waveguide resonator. It is demonstrated that there exist two perfect matching points controlled by the iris geometry and width of the narrow gap between two planar chiral components. The reported unit has a bandwidth of several percent with return loss better than 20-30 dB. The conclusions of this work are fully applicable to double-periodical two-layer screens or metasurfaces having such square cells.

{ D}_{4}

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.