Introduction. Perfect polyphase unimodular sequences, i.e. sequences with ideal periodic autocorrelation and single amplitude of symbols are widely used in modern radio communications and radars. Among them a special place is occupied by perfect ternary sequences (PTSs) with elements {–1, 0, 1}. PTSs are quite numerous and their length in comparison with perfect binary sequences is not limited from above. There is a well-known review of PTS families undertaken by Fan and Darnell in 1996. However, over the past two decades numerous new PTS families have been discovered. Connections between PTSs and circulant weighing matrices have been established and certain theorems on the existence of PTS existence for certain lengths have also been obtained. Therefore, there is a need for a new modern review of existing PTSs.

Objective. This review of existing PTSs is intended for developers of radio electronic systems using perfect sequences.

Materials and methods. Domestic and foreign sources of information (books, journal papers, conference proceedings, patents) were considered and analysed. A Web search was carried out based on keywords using resources of Yandex and Google, as well as in digital electronic libraries (Russian State Library (RSL), IEEE Xplore Digital Library), conference materials (Digital Signal Processing and its Application (DSPA), Sequences and their Applications (SETA), etc.).

Results. In addition to the matter of collating an informational bibliography, the review shows the relationship between PTSs obtained at different times and their connection with circulant weighing matrices. The review also describes the generators of known PTS families (Ipatov, Hoholdt-Justensen, etc.).

Conclusion. A retrospective review of PTSs is herein presented and the generators of certain known PTS families have been considered. The results of the study are relevant for use in modern radio communications and radar systems and in CW and LPI radars in particular.

Introduction. Noise-proof coding is used in many communication systems to provide an acceptable level of performance. A particular feature of its use is the inclusion of redundant characters in a coded packet. It demands more transfer time and essentially better throughput of the channel than in the case of an uncoded packet transferring. A promising development is a software change in the configuration of radio communication system and the development of communication protocols. This is done to ensure the maximum load factor of the channel while ensuring an acceptable level of performance.

Objective. To improve radio system performance by updating communication protocols, in order to solve the problem of ensuring maximum channel load during signal formation and reception.

Materials and methods. The paper describes the structure of the protocol developed by the authors. It is applicable in software to control ionospheric radio communication system transceiver modules. The software was developed in LabView (VHDL language) cross-platform software environment and was studied by means of a radio interface simulation model.

Results. The study examined the corrective ability of codes in the case of a supplementary Gaussian channel with binary phase modulation (OFDM-modulation, 2PSK and 4PSK absolute phase manipulation) in the selection of an energy-efficient approach to the design of ionospheric radio communication system. The study developed the structure and the functional description of the protocol used in the software for the simulation model of software-configurable radio channel. The software operation can be carried out in Windows 7 and in later versions with bit depth x32/x64 under the MS VisualC++package. It was shown that the software thus developed can use the hardware and software controls of the transceiver module. SunSDR2 transceiver and antenna amplifier were included in the module.

Conclusion. The results obtained allow for the replacement of separately adjusted radio receivers and transceivers built on a complex super-heterodyne scheme. A limited number of hardware units operate under the control of the developed software. Further studies will be carried out to assess the passage of OFDM signals through multipath communication channels with Rician and Rayleigh fadings. The resulting model will allow for the assessment of noise immunity at different lengths of the cyclic prefix OFDM symbol and for observation of signal constellation behaviour under the influence of various instabilities.

Introduction. The frequency band around 60 GHz is one of the most promising to realize new generation communication systems with high data rate due to the utilization of a wide operational frequency band that significantly exceeds traditional frequency bands below 6 GHz. High interest in the development of 60 GHz communication systems is related to the recent evolution of MMIC technology that allows creating effective components for this band and the variety of planar devices. Both are typically realized on printed circuit boards and have interfaces that are based on microstrip lines. The wideband waveguide-to-microstrip transition is required to test various active and passive planar devices with microstrip interfaces in order to provide an effective interconnection between the standard waveguide interface of measurement equipment and planar microstrip structures.

Objective. The paper deals with the design of planar wideband waveguide-to-microstrip transition with low insertion loss level in the 60 GHz frequency band.

Materials and methods. The main objective is achieved by analyzing of discontinuities in waveguide-tomicrostrip transition structure and their influence on transition characteristics. The transition characteristics are analyzed using full-wave electromagnetic simulation and confirmed with experimental investigation of designed wideband waveguide-to-microstrip transition samples.

Results. The designed transition is based on an electromagnetic coupling through a slot aperture in a microstrip line ground plane. The transition is performed without using blind vias in its structure that provides low production cost and al-lows integrating the WR-15 rectangular waveguide in a simple manner without any modifications in the waveguide structure. Results of the electromagnetic simulation are confirmed with experimental investigations of the fabricated waveguide-to-microstrip transition samples. The designed transition provides operation in the nominal bandwidth of the WR-15 waveguide, namely, 50…75 GHz with the insertion loss level of 2 dB and with less than 0.8 dB insertion loss level at the 60 GHz frequency.

Conclusion. The designed waveguide-to-microstrip transition can be considered as an effective solution for interconnection between various waveguide and microstrip millimeter-wave devices due to its wideband performance, low insertion loss level, simple integration and robustness to the manufacturing tolerances structure.

Introduction. In this work, we consider the problem of a radiator synthesis with the 50-Ohm port at the input in the frequency range of 0.9…5.8 GHz. At present, this frequency range is the most relevant for the electromagnetic environment analysis due to information exchange with the on-board equipment of unmanned aerial vehicles is most often realized in this frequency range.

Objective. The main objective of this work is the synthesis of a radiator for an ultra-wideband antenna array in the frequency range of 0.9…5.8 GHz.

Materials and methods. In this work, the method of full-wave electromagnetic simulation is used for the broadband radiator synthesis. The characteristics of the radiator are optimized by simulation and confirmed by experimental investigations of the radiator model. The antenna radiation pattern measurements are carried out in the anechoic chamber and standing wave ratio (SWR) is calculated by using the network analyzer.

Results. A non-analytical method of the model parametric optimization considering the SWR<2 criterion and using the latest tools of the full-wave electromagnetic simulation is proposed. The examples of the designed optimized model with the final values of all parameters are reported. The calculated distributions of the electric field over the antenna, calculated radiation patterns at several frequency points, and calculated SWR of the model are presented. The radiator model is made taking into account simulation and optimization results. The measured main cross-sections of the radiation pattern and SWR of the model are shown. Conclusion. In the present work, the broadband radiator model in the frequency range of 0.9…5.8 GHz is designed. The machining and brief comparative analysis of the calculated and measured antenna characteristics is carried out and demonstrated a good agreement. The advantages of the proposed method and designed radiator model are described. The results of this work are relevant in the tasks of observation, direction finding and signals reception from unmanned aerial vehicles. Key words: ultra-wideband antenna, Vivaldi antenna, microwave range, full-wave electromagnetic simulation><2 criterion and using the latest tools of the full-wave electromagnetic simulation is proposed. The examples of the designed optimized model with the final values of all parameters are reported. The calculated distributions of the electric field over the antenna, calculated radiation patterns at several frequency points, and calculated SWR of the model are presented. The radiator model is made taking into account simulation and optimization results. The measured main cross-sections of the radiation pattern and SWR of the model are shown.

Conclusion. In the present work, the broadband radiator model in the frequency range of 0.9…5.8 GHz is designed. The machining and brief comparative analysis of the calculated and measured antenna characteristics is carried out and demonstrated a good agreement. The advantages of the proposed method and designed radiator model are described. The results of this work are relevant in the tasks of observation, direction finding and signals reception from unmanned aerial vehicles.

Introduction. It has been previously reported that small-scale irregularities (SSI) in the polar ionosphere are elongated along the magnetic field and anisotropic in its cross-field direction. At the same time, the largest of the SSI cross-field axes tends to orient along the SSI drift direction. However, there is no evidence of direct correlations of SSI anisotropy and ionospheric drift directions in the middle latitudes.

Objective. A direct comparison of the experimental data of SSI shape with motion parameters of irregularities was measured at the same place (Moscow) at the same time. Previously, experimentally obtained values of SSI cross-field anisotropy orientation in the midlatitude ionosphere were compared only with the neutral winds model.

Materials and methods. A tomographic approach was used to determine SSI anisotropy parameters by processing radio scintillation signals during overfly by several navigation satellites emitting on frequencies of 150 MHz and 400 MHz. Estimations were obtained of the ratio between the ellipsoid axes and cross-field anisotropy orientations in the framework of the SSI model in a form of magnetic field-oriented ellipsoids with three different dimensions along and across the Earth's magnetic field. The parameters of irregularities were obtained by selecting model parameters at a time when the calculated logarithm dispersion of the satellite signals relative amplitude during orbit is the closest to the experimentally obtained curve. Estimations were obtained of the velocity and drift direction of medium-scale irregularities (MSI) by using DPS-4 ionosonde data acquired while decametre-wave radar studies of ionosphere from the Earth's surface. Simultaneous measurements of Doppler frequency shifts and incident angles of scattered waves allowed estimations of three components of the medium-scale irregularities drift velocity to be obtained.

Results. There was evidence of a good correlation between the drift direction of medium-scale irregularities and cross-field anisotropy orientation of small-scale irregularities. The difference in the drift directions of MSI and in the orientation of the cross-field axes of SSI varied from 3 to 10 degrees (provided the spatial coincidence of the ionosphere regions where the measurements were carried out).

Conclusion. In constructing a model of the radar backscattering signal in the HF band, the correlation between the cross-field anisotropy orientation of the elongated irregularities and their drift direction can be useful when there is a lack of information on ionospheric irregularities.

Introduction. Relativistic, high intensity and small emittance electron bunches are the basis of a future linear collider and free electron laser projects. Drive beam generation in a wakefield structure employing for power extraction and acceleration low loss dielectrics like microwave ceramics, fused silica and Chemical Vapor Deposition (CVD) diamond were considered.

Objective. We report here our experimental testing of a ceramic material with extremely low loss tangent at GHz frequency ranges allowing the realization of high efficiency wakefield acceleration. We also present Barium Strontium Titanium oxides (BST) ferroelectric material, which is a critical tuning element of the 400 MHz superconducting radiofrequency (RF) tuner developed and tested by the CERN/Euclid Techlabs collaboration. The materials discussed here also include quartz and CVD diamonds that are capable of supporting the high RF electric fields generated by electron beams or pulsed high power microwaves. These materials have been optimized or specially designed for accelerator applications.

Materials and methods. The ceramic materials for accelerators, commonly used for the dielectric based accelerating structures, have to withstand high gradient accelerating fields, and prevent potential charging by electron beams. Correspondingly, the ceramic materials, fused silica and CVD diamond were tested with high power wakefield accelerating structures at Argonne Wakefield Accelerator of Argonne National Laboratory. Some of the presented here ceramic materials were tested at X-band 11.4 GHz magnicon high power source.

Results. Low loss microwave ceramics, fused silica, and CVD diamonds have been considered as materials for dielectric based accelerating structures to study of the physical limitations encountered driving > 100 MV/m at microwave and ~ GV/m at THz frequencies in a dielectric based wakefield accelerator. Various ceramic compositions were high power and electron beam tested at X-band 11.4 GHz magnicon power source and Argonne Wakefield Accelerator correspondingly. Special attention was paid to the CVD diamond cylindrical Ka-band 35 GHz wakefield structure development. Finally, the dielectric based structure tuning was demonstrated by varying the permittivity of the BST ferroelectric layer by temperature changes and by applying an external direct current electric field across the ferroelectric. This allows us to control the effective dielectric constant of the composite system and therefore, to control the structure frequency during operation. The same type of ferroelectric material was used for the Ferroelectric Fast Reactive tuner (FE-FRT) development. In a world first, CERN has tested the prototype FE-FRT with a superconducting cavity, and frequency tuning has been successfully demonstrated.

Conclusion. Recent results on the development and experimental testing of advanced dielectric materials for accelerator applications are presented. Low loss microwave ceramics, quartz and CVD diamond are considered. We presented our experimental results on wakefield generation in microwave frequency ranges with the dielectric based accelerating structures. Special attention was paid to the experimental results on high power testing at X-band of the externally powered dielectric based components. Finally, we present here first experimental demonstration of ferroelectric tunable microwave ceramic for accelerator application, which includes both tunable dielectric wakefield accelerating structure and ferroelectric based fast high power tuner for superconducting cavities. The experimental results presented here are critical for the advanced dielectric wakefield accelerating structures and other components development intended for the future linear collider projects.

Introduction. Microacoustic sensors based on surface acoustic wave (SAW) devices allow the sensor integration into a wafer based microfluidic analytical platforms such as lab-on-a-chip. Currently exist various approaches of application of SAW devices for liquid properties analysis. But this sensors probe only a thin interfacial liquid layer. The motivation to develop the new SAW-based sensor is to overcome this limitation. The new sensor introduced here uses acoustic measurements, including surface acoustic waves (SAW) and acoustic methamaterial sensor approaches. The new sensor can become the starting point of a new class of microsensor. It measures volumetric properties of liquid analytes in a cavity, not interfacial properties to some artificial sensor surface as the majority of classical chemical and biochemical sensors.

Objective. The purpose of the work is to find solutions to overcome SAW-based liquid sensors limitations and the developing of a new sensor that uses acoustic measurements and includes a SAW device and acoustic metamaterial.

Materials and methods. A theoretical analysis of sensor structure was carried out on the basis of numerical simulation using COMSOL Multiphysics software. Lithium niobate (LiNbO3) 127.86° Y-cut with wave propagation in the X direction was chosen as a substrate material. Microfluidic structure was designed as a set of rectangular shape channels. A method for measuring volumetric properties of liquids, based on SAW based fluid sensor concept, comprising the steps of: (a) providing sensor structure with the key elements: a SAW resonator, a high-Q set of liquid-filled cavities and intermediate layer with artificial elastic properties between them; (b) measuring of resonance frequency shift, associated with the resonance in liquid-filled cavity, in the response of weakly coupled resonators of SAW resonator loaded by periodic microfluidic structure; (c) determination of volumetric properties of the fluid on the basis of a certain relationship between the speed of sound in liquid, the resonant frequency of the set of liquid-filled cavities, and the geometry design of the cavity.

Results. The new sensor approach is introduced. The eigenmodes of the sensor structure with a liquid analyte are carried out. The characteristic of sensor structure is determined. The key elements of introduced microfluidic sensor are a SAW structure, an acoustic metamaterial with a periodic set of microfluidic channels. The SAW device acts as electromechanical transducer. It excites surface waves propagating in the X direction lengthwise the periodic structure and detects the acoustic load generated by the microfluidic structure resonator. The origin of the sensor signal is a small frequency change caused by small variations of acoustic properties of the analyte within the set of microfluidic channels.

Conclusion. The principle of the new microacoustic sensor, which can become the basis for creating a new class of microfluidic sensors, is shown.

Introduction. Petroleum is a complex mixture of hydrocarbons. Sulphur is the most common heteroatom in pe-troleum and petroleum products. Its content in oil can reach 14 %. The determination of sulphur in oil and its removal is of great importance, since sulphur compounds adversely affect the quality of petroleum products and pollute the environment. Desulphurization of hydrocarbons is important in the processing of petroleum products, which needs in usage of accurate and simple methods for the sulphur-containing components determination. Most of developed methods are difficult to apply for flow online analysis, which can create difficulties in using them to monitor the content of sulphur-containing heteroatomic components in real time. Acoustic sensors are one of the possible solutions. In term of sensing of flammable liquids, the use of the acoustic methods is attractive since the analyte is not a part of an electrical measuring circuit and it is only acoustically coupled that prevents an occurrence of a spark.

Objective. The purpose of the work is to study the possibilities of online flow analysis of sulphur-containing heteroatomic components using acoustic measurements. The challenge is the development of a resonator system integrated with the pipe.

Materials and methods. Thiophene and oil fraction with the boundary boiling point of 100–140 oC were used to prepare the mixtures. Thiophene is a representative of sulphur-containing components, which may be included in the composition of petroleum and its derivatives. Experimental measuring equipment includes impedance analyzer, a developed sensor structure integrated with a liquid-filled pipe, a pump and a tank with a measured liquid. A theoretical analysis of sensor structure was carried out on the basis of numerical simulation using COMSOL Multiphysics software.

Results. The sensor structure was designed as a combination of 2D and 1D pipe periodic arrangements to achieve high Q-factor of acoustic resonance in the flow system. The eigenmodes of the sensor structure with a liquid analyte were carried out. The characteristic of sensor structure is determined. The sensor shows good sensitivity to the thiophene content with high resolution in-line analysis. This result is achieved by limiting the energy losses of acoustic resonance in radiation along the pipe by creating a periodic structure.

Conclusion. The study of acoustic properties of solutions prepared on the basis of thiophene and oil fraction with boundary boiling point 100–140 °C was performed. It shows that methods based on acoustic spectroscopy make it possible to accurately determine the concentration of heteroatomic components in gasoline mixtures, since the presence of heteroatomic components leads to a change in mechanical properties of liquid hydrocarbons mixtures. Possible applications for developed acoustic sensor are flow analysis for monitoring the quality of oil products.

Introduction. When operating high-precision measurement setups, the reliability of measurements needs to be guaranteed. The displacement of elements from the measurement path can lead to a distortion of measurement results, especially in measurement setups operating in the microwave range. In order to ensure measurement reliability, the positions of elements in the measurement setup needs to be monitored. The monitoring should be performed during the measurement. The control device, which should be connected to the automatic control system of the measurement setup, should neither mechanically affect the setup elements nor introduce any interference. Currently used control systems for the technical characteristics do not meet the necessary requirements.

Objective. To design a control system which allows for the monitoring of displacements of elements in a high precision measuring setup with an accuracy of 1.0 · 10 4 mm and digital signal processing. The control system thus designed should neither mechanically affect the controlled elements nor introduce electrical and electromagnetic interferences.

Materials and methods. The system thus designed utilises optical methods for displacement monitoring based on the principles of geometric optics. Mathematical modelling (Mathcad) methods were used to determine the reaction of the system to changes in the beam trajectory and to estimate the sensitivity of the optical control system. Charge-coupled devices (CCD) were used to record the system response to optical path changes.

Results. The study presents two designs of a control system for the displacement monitoring of high precision measurement setup elements. The first system design allows for the detection of the occurrence of displacement, while the second system design allows for the identification of the displaced element. The system is capable of registering displacements of elements up to an accuracy of 1.0 · 10 4 mm and monitoring the position of elements while exposed to vibration. The system does not mechanically or electromagnetically affect the controlled elements. All system elements are resistant to microwave radiation and increased background radiation, excluding the CCD which needs to be placed outside the active zone. The monitoring system for movements of elements in the high-precision measuring setup allows for digital signal processing. The study proposes a method to increase system accuracy.

Conclusion. The system can be used in setups with increased microwave, x-ray and radiation emission. In comparison with systems based on other physical principles (inductive, capacitive and rheostat), the system thus developed is much easier to implement.

Introduction. The developmental direction of information-measuring systems used to record, pre-process and analyse excess low-frequency noise (flicker noise) in modern experimental technology is well known. Every measuring channel is presented in the form of a multistage circuit with specified parameters at each stage. This creates difficulties in adapting a measuring system to specific experimental conditions. While the solution may be to unify all the components of the channel, the problem lies in estimating the intrinsic noise of the electronic elements which provide a change in amplifier parameters.

Objective. To analyse the intrinsic noise of electronic potentiometers. To develop a low-noise unified DC amplifier with the possibility of external digital control parameters. To study the characteristics of a DC amplifier thus developed.

Materials and methods. The superposition method was used to perform theoretical calculation of noise gain for each component of a non-inverting amplifier. Experimental studies were based on a system consisting of a low-noise amplifying path and spectroanalyser using the data acquisition module E14-440. Software "Power-Graph" was used.

Results. The results of the theoretical analysis of noise amplification for metal-film resistors and experimental studies of the characteristics of electronic potentiometers indicated that their noise voltages specific values are almost identical. The use of a digital potentiometer as a feedback element and a low-noise bipolar-powered bias source (AD8400) permitted the implementation of a unified module with cascading capability. External digital control was based on a single-chip microcontroller PIC18F2550, using the "Master-Slave" channel level protocol and ASCII-command-line interface based on RS-485 network. This control enabled adaptation for measuring electronic component noise, low currents and voltages, flicker noise and the construction of systems for information collecting and processing.

Conclusion. The theoretical and practical results achieved herein enable the design of multichannel distributed DC measuring systems. The systems will offer adaptability for measuring channels to the tasks required, and the possibility of correction of real time characteristics.

Introduction. Increasing demands of precise geometry measurements by science and industry cause the necessity of improvement in an associated branch of legal and practical metrology. One of the most significant fields is the measurement of internal dimensions and so the issues with the unit of meter transfer. Now we face the situation when the current accuracies of National standards of different levels in corresponding traceability chain (reference rings measurements) get close to each other. This means that we have to make the standard of upper level more precise. One of the obvious ways is to apply the latest ultra-stable laser locked to a frequency comb.

Objective. The objective is to propose possibilities for improvement of the National secondary standard of the unit of length by researching its measuring capabilities to minimize measurement uncertainty.

Materials and methods. The calculation of expanded uncertainty of internal diameter measurements by the National secondary standard of the unit of length is performed according to the international document «Guide to the Expression of Uncertainty in Measurement» JCGM 100:2008 approved by BIPM. The secondary standard research results represented in previous reports and publications are also taken into consideration.

Results. Detailed uncertainty budget for the proposed measuring system is given as well as graphical data representing the accuracy improvement.

Conclusion. Actions for minimization of measurement uncertainty components of the National secondary standard of the unit of length in the field of reference ring internal diameter measurements in combination with state-of-the-art laser interferometer system improve it to the next frontiers of accuracy and precision.