The paper proposes a narrow-band polarization plane filter-rotator in a circular waveguide with minimal longitudinal dimensions ( λ/30) and a 2–3

The design of the 330 GHz continuous-wave clinotron oscillator with the modified circuit is presented together with the simulation results of the cold cavity including the circuit coupled to the power output. The simulations revealed the effective broadband conversion of the surface wave excited by the sheet electron beam moving above the grating to the TE $_{\text{10}}$ mode of the oversized output waveguide. The experimental studies of the clinotron oscillator demonstrated the operating frequency range from 280 to 335 GHz and the output power up to 110 mW. Finally, both simulation and experimental results revealed the excitation of the surface wave with one node of E -component along the grating lamella width that effectively transfers to TE $_{\text{20}}$ mode of the waveguide output.

Using the example of a waveguide metacell, it is shown that the introduction of additional rings of slots into a bilayer planar-chiral iris in a circular waveguide generates new resonances of the artificial optical activity (AOA). Their origin is the excitation of new eigenoscillations inside the bilayer gap and the corresponding rotation of the polarization plane at the output of the meta-object. Even with slight chirality of the layers, these rings increase the number of AOA resonances in the single-mode band. In loci of proximity and transformation of eigenoscillations inherent in planar-chiral bilayers, AOA maxima are observed with a rotation of the polarization plane up to 90°, and an expansion of the AOA band up to 10 % can be achieved.

Aperture eigenoscillations of a plane junction of a circular waveguide with a set of rectangular waveguides have been studied. They play a decisive role in generation of eigenoscillations of more complex waveguide components, which include considered plane junctions. It is shown that the real part of the frequency of an eigenoscillation can be reduced by increasing the number of rectangular waveguides arranged in compliance with rotational symmetry and/or their widths. The eigenoscillation can be shifted below cutoff of the circular waveguide in the case of two wide rectangular waveguides. It is shown that when rectangular waveguides are arranged along concentric rings, the number of eigenoscillations increases with an increase in the number of rings. In connection with research in nanoelectronics and metamaterials, where many effects arise in structures with holes of complex configuration, it can be assumed that the explanation of many regularities can be found in the behavior of aperture eigenoscillations of the corresponding interfaces.

A method of design of a broadband septum polarizer with a square common port is proposed. It is based on a classical configuration with a longitudinal stepped metal insert. The results of numerical optimization of its profile showed that it makes no sense to use more than four steps in the single-mode regime, since an increase in their number does not lead to an improvement in the characteristics of the device. It is shown that this limitation is absent in the multimode regime, and it is possible to achieve better device characteristics by increasing the number of steps. The design of a broadband septum polarizer with a bandwidth of 46.5% in the multimode regime is presented.

The possibility of using traditional (scalar) models of band-pass filters (BPF) of the millimeter range on "all-metal inserts" in design of three-dimensional modifications of such a BPF is estimated. The complication of the filter geometry is associated with the introduction of narrow grooves in each of the resonators, which provide a number of technological advantages in fabrication. It is proved that with all-metal inserts with a thickness of not more than λ/100, the results of the "vector" and "scalar" models completely coincide.

It is shown how the topology of the individual components of a two-layer 3D-chiral object affects the natural frequencies and the manifestation of the "artificial optical activity". Using the waveguide example, it is proved that the dihedral symmetry Dn with high n allows expanding the bandwidth of polarizer.

The polarization plane rotators located outside the transmission line volume are presented. Their work is based on the excitation of special (‘dihedral') eigen-oscillations in a waveguide object formed by two corrugated flanges with rotational symmetry. Such a topology provides 3D chirality of the composite object at an azimuthal shift of the flanges and rotation of the polarization plane by an arbitrary angle in the band of a few percent with minimal return loss. In circular and coaxial waveguides, a mechanical or electronic rearrangement of the PP by mutual rotation of the flanges or by the placement of controlled elements (media) into the object cavity is possible.

Numerical modeling data for the frequency selective surfaces whose elementary period contains one or two pairs of U-shaped slots are presented in the paper. A peculiarity of the numerical model implementation is discussed. In order to make the calculations rapid, a virtual waveguide is incorporated into the module that is responsible for the calculation of the scattering matrix of a plane junction of the Floquet channel and U-shaped waveguides. Numerical examples are given for a single-standing perforated screen and a two layer frequency selective surface. A possibility to generate a transmission response by the help of the resonant coupling via the first higher (not fundamental) mode of U-shaped slots is demonstrated.

The polarization plane rotators located outside the volume of a transmission line are presented. Their work is based on the excitation of special ("dihedral") eigen-oscillations in a waveguide object formed by two grooved flanges with rotational symmetry. When one of the flanges rotates relative to the other, the composite object becomes 3D-chiral and rotates the plane of polarization by a certain angle in the band of several percent with minimal reverse loss. In circular and coaxial waveguides, mechanical or electronic tuning of the polarization plane is possible by mutual rotation of the flanges or by placing the controlled elements (media) into the object cavity.

Subject and Purpose. Peculiarities of the electromagnetic wave scattering at screens perforated by U-shaped slots are the subject of the paper. Numerical modeling of frequency-selective surfaces with frequency characteristics given and research into the possibilities of the performance control of the screens by complicating their elementary cell geometry are the purposes of the paper. Method and Methodology. The numerical modeling is performed upon the MWD3 software package developed in the laboratory of computational electromagnetics of the IRE NASU. Based on the scattering mode technique and the mode-matching technique taking into account the electromagnetic field behavior near the edges, this software package enables calculations of scattering characteristics of both compound waveguides and gratings with piece-wise boundaries. Results. A virtual waveguide was incorporated into the MWD3 projection schemes, extending capabilities of the MWD3 software and making it possible to treat the frequency-selective surfaces with piece-wise boundaries without adding new building blocks. Numerical modeling of perforated screens with U-shaped slots was carried out. Conclusion. Configurations of single and double metal screens and, also, a compound grating formed by two screens separated by a dielectric layer were calculated in full agreement with the given task. The perforated screens provide essential reflectivity decrease at low frequencies and, also, a low insertion loss level in the given millimeter wave region. The obtained results can be of interest for specialists in antenna-feeder engineering and for MWD3 software users.

Purpose: Creating a radio telescope based on the MARK-4B antenna system being developed for telecommunication applications, determining the possibilities of using the broadband multirange operation of a beam wave-guided antenna system and to evaluate the antenna characteristics using the radioastronomical measurements. Design/methodology/approach: Acomprehensive analysis of all the MARK-4B systems allows to select the blocks and nodes to be replaced or upgraded. The analysis of the reflector and subreflector design, beam wave-guide, corrugated horn, and feeder system allows determining the possible frequency ranges of the radio telescope being created. Installing a broadband receiver with the stipulated calibration capabilities using cooled and uncooled load attenuators allows to determine the antenna system temperature. Guiding the antenna to the calibration sources and recording scans due to the Earth rotation eliminates the systematic errors or errors of the pointing system. In this way the width of the radiation pattern and the effective area of the radio telescope are determined. Findings: An analysis of the antenna design was made and the priority stages of the reconstruction of the MARK-4B antenna system were determined. The narrow-band transmitter and the C-band receiver were dismantled and a wide-band receiver (range 4.6 - 5.1 GHz) with a detector and the possibility of changing the signal integration time were installed. The observed results have allowed to initially estimate the system temperature mea-surements which allow us to hope that the RT-32 radio telescope (Zolotchiv, Lviv region, Ukraine) together with the cooled receiver will have low self noise. A new antenna pointing system has been calculated and installed which using in the C-band has allowed astronomical tests of the radiation pattern width (≈7.2') and the level of its side lobes (–12.5 dB), effective area (≈680 m2) and surface utilization factor (≈0.84). Conclusions: The completed measurements and calculations show that the MARK-4B antenna system allows to createhighly efficient radio astronomy instrument. The developed for now receiving and pointing systems for the RT-32 radio telescope testify to the high potential of Ukrainian science. Further cooperation between scientific research and high technologies will lead to the creation of an effective Ukrainian radio telescope of the centimeter wavelength range.

Open resonant systems as the oscillating circuits of the solid-state oscillators and characteristics of the quasi-optical oscillators themselves are the objects of the investigation. The aim of the work is to review the scientific results on the development and research of quasi- optical solid-state oscillators in the department of solid-state electronics from the inception of the idea to the development of real sources with enhanced spectral characteristics. Experimental and theoretical methods for studying the main parameters including spectrum, field topology of open resonators with resonant and non-resonant inhomogeneities are analyzed. For this purpose, the waveguide model of the resonator, the decomposition method and the generalized scattering matrix method, as well as experimental methods for measuring the spectrum, power and frequency, are used.

Purpose: Technical capabilities of the MARK-4B antenna system necessary for its further using as a 32-meter radiotelescope (RT-32) and making simultaneous spectral radioastronomical observations in the C and K frequency ranges, are investigated. Design/methodology/approach:The studies use the results of our own measurements made with the МАRK-4В antenna system, expert reviews, open information sources, technical documentation of the MARK-4B antenna system, radio astronomy and computer simulation methods and comparative analysis of this antenna main parameters with the corresponding parameters of the world’s best active radio telescopes. Combining different approaches allows us to determine the requirements for the receiving system, parameters of the spectrometer, calibration techniques and optimize the МАRK-4В antenna system modernization procedure. Findings: The radio telescope main parameters required for spectral observations in the C and K frequency ranges are determined. The antenna pointing system capabilities are specified. For the MARK-4B antenna system working frequency range, the main spectral lines of various molecules available for research have been considered. The transitions radiating the most intensive spectral lines are listed. The radio astronomical problems that can be solved using the MARK-4B in the mode of spectral observations are formulated. The required parameters of the spectrum analyzer and the receiver’s self-noise temperature are determined. Calibration techniques of the recorded signal are described, which are necessary for carrying out spectral observations. Conclusions: The here presented studies show that for making spectral observations based on the beam-waveguide MARK-4B antenna system, it is technically possible to create the RT-32 radio telescope with quality technical characteristics corresponding to the world-best analogs. Modernization of the beamwaveguide MARK-4B antenna system will allow at the first stage to create in Ukraine the dual-band radio-telescope permitting to make simultaneous spectral and/or continued observations in the C and K ranges. Henceforth, the amount of simultaneously working ranges can be increased.

Subject and Purpose. The study of various kinds of microwave devices and the description of the most interesting designs. Methods and Methodology. The fast numerical-analytical methods are used in the study of devices. They allowed identifying fine physical effects and achieving the optimal characteristics of these devices. The main achievements of the laboratory of computational electromagnetics obtained in recent years are described in the paper. Results. A simulation system based on numerical-analytical methods is developed. It covers a wide class of problems with a discrete spectrum (waveguides and periodic structures). It also includes the ability to model antenna devices excited by complex feeder systems. With its help, a wide range of passive microwave devices was designed, including frequency and polarization-selective nodes, mode and polarization converters used from microwaves up to the terahertz range. Particular attention is paid to the developments being studied in the new sections of radiophysics based on extraordinary transmission and optical activity. Conclusions. The most interesting devices studied in the laboratory of computational electromagnetics in recent years are described in the paper. Many of them are designed for the first time.

The possibility to design a tunable polarization plane (PP) rotator in waveguides with circular symmetry is proven. The appearance of artificial "optical activity" in the interaction of a pair of conjugated planar chiral irises by the fringing fields is used. The rotator can be reconfigured by rotating the irises relative to each other providing the rotation of the PP up to cross-one. Being relatively narrowband, the rotator has a longitudinal dimension lambda(0)/50-lambda(0)/10.

Three versions of two-layer polarization plane rotators in a circular waveguide based on the internal fringing field interaction are considered. They work on the excitation of unusual eigen-oscillations within the gap between a pair of peculiar four-slot metal irises. The subjects for comparison were the range of rotation angles, the possibility to provide good matching, and the ability of rotators to be tuned by mutual iris-to-iris rotation. The best properties were found in the case of the conjugated planar-chiral irises.

The results of the study and development of quasi-optical solid-state oscillators are: the level of frequency noise is not more than 115...120 dB/Hz; power of generation at the first harmonic is up to 130...150 mW at a frequency of 40-50 GHz; at the second harmonic – up to 10 mW at a frequency of 60...90 GHz; generation power is not less than 3 mW at a frequency of 150 GHz; long-term frequency instability is 3·10–8 at active temperature control ΔT ~ 0.1 °C. The paper analyzes the areas of application of solid-state quasi-optical oscillators: heterodynes in receiving devices, refractometry, dielectrometry and other fields where high stability and low level of frequency noise are needed. The perspective directions of the search for new physical phenomena to create nonlinear elements in the terahertz frequency range are determined.

Subject and purpose. Open resonant system as the oscillating circuit of the solid-state oscillators and characteristics of the quasi-optical oscillators properly are the object of investigations. Purpose of article is review of works being fulfilled at the solid-state department over period 1979 and to the present day. The intent of the paper is to give the indication prerequisites of the creation of high-stabilized millimeter wave sources and way of this problem solution. Method and methodology. Theoretical and experimental methods of study of main parameters of open resonators with resonant and nonresonant inhomogeneities such as spectrum, field topology of open resonators are the waveguide model of resonator, decomposition method, generalized scattering matrix method, and experimental technique of the power, frequency, and spectrum measurements. Results. Results of study and development of quasi-optical solid-state oscillator are: the level of frequency noise is no more than –115…120 dB/Hz; power of generation at first harmonic is up to 130…150 mW at frequency of 40…50 GHz; at second harmonic – up to 10 mW at 60…90 GHz; generation power is no more than 3 mW at frequency of 150 GHz ; long-term frequency instability is 3×10–8 at active control temperature DТ ~ 0.1 °С. Conclusion. In the paper it is analyzed an application area of solid-state oscillators. They are local oscillators in receiving units and radiometers, refractometry, dielectro-metry, and fields where high stability and low level of frequency noise are needed. The promising lines are inquired, they are search of new physical properties for nonlinear element creating at Terahertz frequency band.

In this paper, we propose a simple design of a planar-chiral screen based polarization plane rotator that enables a polarization conversion at two assigned frequency bands simultaneously. The rotator is composed of a pair of conjugated double periodic perforated screens separated by a short distance. Two groups of four rectangular slots are cut along a perimeter of the screen periodical cell. Polarization rotation frequencies are controlled by choosing appropriated dimensions and placements of the slots' groups. At the same time, we report that even a rotator with equal slots belonging to different (outer or internal) quadruples enables a dual-frequency operation as well.