Methodological Approach to Reducing the Radar Cross Section of Local Scatterer under Given Frequency-Angular Observation Conditions

This paper focuses on application of spectral estimation methods for scattering center’s radar cross section estimation and reduction under given frequency-angular observation conditions. A methodological approach has been developed to reduce the local center’s radar cross section with given object overall dimensions. The developed methodological approach is based on parametric optimization of object geometry, firstly, to reduce the local scatterer radar cross section and, secondly, to maximize object payload. The problem overview is presented in the introduction. The first section is devoted to mathematical formulation of the problem. The following section includes the comparison analysis of the different types of geometrical shapes. As a result, the object with exponential profile is chosen as the best one due to the ability to manage rear vertex local scatterer amplitude by changing the curvature parameter. In the third section the optimal curvature parameter value of the exponential profile is justified for the given object overall dimensions and frequency-angular observation conditions. It is demonstrated that the main characteristic to analysis is two-dimension functional dependence of the local scatterer mean radar cross section from geometrical parameter and angle of observation. It is proved that this mentioned dependence may be received by the implementation such well-known spectral estimation method as CLEAN to the object sinogram. The recognition range is calculated for two different hypothetical radars to assert the efficiency. It is offered in the conclusion to complicate the developed approach with radio absorption materials implementation as the direction of the future investigations.

Application of aerological radar to determine the wind profile in the lower troposphere

Currently, radar and radionavigation systems for aerological sounding of the atmosphere with the help of aerological radiosondes launched into the atmosphere are widely used to provide operational weather and climate forecasts. Meteorological radar systems for various purposes have been developed to obtain operational data on the free atmosphere. The systems are operated, providing measurement of meteorological parameters by noncontact methods. One of the most important meteorological parameters is the vertical wind profile. Specialized radars have been created to determine the distribution of wind direction and speed by altitude. They allow measuring the dynamic parameters of the wind in real time. The article considers the possibility of creating a radar for the wind parameters measuring the lower troposphere based on the modernization of a serial domestic aerological radar. Technical characteristics of the radar such as the pulse transmitting power, the sensitivity of the receiver, the ability to control the antenna radiation pattern accurately by angular coordinates make it possible to provide fundamental wind measurement in the lower troposphere. The main issues of modernization are related to the need of implementation of the coherent operation mode into the radar receiver and transmitter and ensuring the coherent energy storage of the reflected signal during the interval of statistical stability of the atmosphere. The information about the wind at the measured altitude is estimated from the Doppler spectrum of the signal reflected from meteorological inhomogeneities. The ability to accurately point the antenna during the sounding session allows determination of the vertical wind profile in the altitude range, even in clear sky conditions.

Terahertz Scanning Reflectometer for Structure Visualization of Polymer Constructions in Additive Manufacturing

The results of the development and practical application of a quasi-optical system for reflectometry of objects in the terahertz frequency range for analyzing the structure in additive manufacturing of objects are presented. A backward-wave oscillator is used for continuous generation of electromagnetic radiation; an acousto-optic converter (Golay cell) is applied as a detector. The reflectometer is controlled by personal computer through the L-card E 154 input-output module and the standard digital-to-analog converter of the STD-21 spectrometer. The system is tested at the frequency of 874 GHz on the 3D-printed composite structure sample. Our paper is terahertz reflectometer with a source of continuous monochromatic electromagnetic radiation based on a backward wave oscillator is presented. The purpose of this work in creating a scanning THz reflectometer is considered to have been achieved. At the same time, the following tasks are solved: a quasi-optical scheme of the reflectometer is selected and assembled; the hardware part of the system (all mechanisms and components) is implemented; a program for controlling the radiation intensity registration system is adapted for this task; the test sample is manufactured using 3D printing technology, the THz reflectometer is tested. The obtained practical results of registration of the two-dimensional distribution of the reflection coefficient show that the use of THz radiation is promising for visualizing the structure of structures obtained by additive technology. Further development of the project is planned by changing the construction of the positioning mechanism, which will provide micrometric calibration of the sample holder relative to the diaphragm. The use of the quasi-optical scheme of the two-beam interferometer for recording the phase distribution and amplitude of reflected THz radiation will allow obtaining information about the spatial location of defects (inhomogeneities) of products obtained by additive technology.

System for wireless power transfer

The issues of wireless power transfer over short distances are considered. The approach may be used for wireless charging of batteries in unmanned vehicles. It is proposed to use the technique of microstrip structures for power transfer. The microstrip structures form a directional coupler on symmetrical strip lines when approaching by front parts. The length of the interaction lines is chosen several times longer than a quarter of the wavelength. Ballast resistors are excluded from the circuit. This approach leads to small losses of power transfer when the distance between microstrip structures changes over a wide range. Modeling of the operation of the power transfer system has been carried out, an experimental sample has been made and experimental studies have been carried out. The simulation and experiment are well accorded.

Method for increasing noise resistance of radar sensors with frequency selection

The description of a new method of signal generation and processing which provides an increase in the noise immunity of radar sensors (RS) with frequency switching (FS) radiation is presented. The principle of method is in the use of a set of time intervals when measuring the phase difference of signals at different radiation frequencies and, accordingly, a set of the Doppler frequency values in the signal spectrum when determining the average value of the Doppler frequency, as well as the use of forward and reverse IF sequences. This method allows averaging the results of calculating individual implementations and, thereby, increase the accuracy of determining the target speed and distance to it. At the same time, the stability of the RS with FS also increases to the effects of signals from third-party radio sources and interference from the underlying surface. The results of experimental studies of the method are obtained on the example of the autodyne RS with the 8-mm frequency range, made on the basis of the Gann diode generator with frequency control by varicap. The method may be used in on-board (for example, automotive) radar sensors designed to detect moving targets, measure the distance to them, as well as determine the speed and direction of movement.

Specific Features of Volume-modular Technology Application in the Design of Microwave Electronic Devices

State of problem. Today a significant part of passive microwave electronic devices is implemented in the form of single-layer structures. In some cases, such approach leads to an increase in the overall dimension’s characteristics of electronic equipment. Moreover, the application of single-layer microwave boards leads to the complexity of replacing individual functional units. Therefore, the replacement of the entire microwave board is required to improve any of its functional part. It is nonprofit economically and inefficient technologically. Significant progress in eliminating the above-mentioned disadvantages may be achieved by the application of volume-modular technology of design microwave electronic devices. Purpose. The purpose of the research is to present a brief overview of the features of the application of volume-modular technology in the design of microwave electronic devices of modern radio-electronic equipment. The volume-modular way of implementing microwave devices is described. It allows improving their weight and overall dimension characteristics and at the same time maintaining and increasing their functionality. The basic principles of design of volume modular microwave electronic devices are formulated. The results of numerical simulation of the electrodynamics characteristics of a strip-slot transition are presented. The method for quantitative assessment of the influence of volume-modular technology on the weight and dimensions characteristics of microwave electronic devices is considered. The main advantages and disadvantages of volume-modular technology are listed. Results. We demonstrate a possibility of reducing the overall dimensions characteristics of passive microwave electronic devices by more than 10 times while maintaining their electrical parameters. Each component is presented in the form of a structurally separate and complete board with unified overall and connecting dimensions. The standard electromagnetic coupling between functional parts makes it possible to assemble microwave electronic devices with specified electrodynamics characteristics from the base elements.

Detecting Cycle Slips in Carrier-Phase Measurements of Single Frequency Navigation Receivers with Different Instabilities of Reference Oscillators

The use of carrier-phase measurements significantly increases the accuracy of solutions when using the measurements of navigation receivers. One of the problems in carrier-phase measurements is discontinuities (cycle slips) in the measurements. The existing algorithms of detection and compensation of cycle slips in carrier-phase measurements of a singlefrequency navigation receiver either require additional information (for example, Doppler measurements), or operate only in differential mode, or can only detect large cycle slips. The purpose of the research is the development of algorithms for detecting small cycle slips in carrier-phase measurements of single-frequency receivers without using additional information. We use methods of filtering of the trend in the carrier-phase measurements using polynomial or adaptive bases, as well as modified sparse recovery algorithms to estimate cycle slips in the difference between code and carrier-phase measurements. The algorithm which is used to search cycle slips in carrier-phase measurements depends on the quality of the reference oscillator of the navigation receiver. For receivers with high-stability reference oscillators (e.g. active hydrogen maser), one can use polynomial filtering of the trend, the filtering result directly detects discontinuities in carrier-phase measurements with a probability close to unity. For navigation receivers with low-stability reference oscillators (quartz reference oscillators), a modified algorithm for minimization of the total variation with filtering of the trend applied to the difference between the code and carrier-phase single-frequency measurements detects discontinuities in 1 cycle slip against the background of the noise component of comparable magnitude with a probability of 0.8. The results may be applied in navigation systems with single-frequency receivers with low stability reference oscillators, as well as in a posteriori processing of receivers’ measurements to correct carrier-phase measurements on the preprocessing stage.

Frequency-tunable device based on a multilayer strip-slot transition and its application for measuring the dielectric properties of materials

The paper presents the results of theoretical and experimental researches of a frequency-tunable device based on the multilayer strip-slot transition with the U-shaped slot resonator of the variable length. The application of the presented device makes it possible to implement a resonant method for measuring the dielectric properties of materials in the microwave frequency range. The numerical simulation in the rigorous formulation of the electrodynamics problem is performed for the theoretical research. The aim of the theoretical research is to determine the electrical characteristics of the multilayer strip-slot transition with the U-shaped slot resonator of the variable length. The results of numerical simulation prove the possibility of applying the multilayer stripslot transition with the U-shaped slot resonator of the variable length to implement the resonant method for measuring the dielectric properties of materials in the microwave frequency range. The experimental research is performed on the sample of the multilayer strip-slot transition with the U-shaped slot resonator of the variable length in the frequency range (850–1250) MHz. Measurements of S-parameters of the multilayer strip-slot transition with the U-shaped slot resonator of the variable length are accomplished using the vector network analyzer. The material under research is BaFe10Ti2O19. The results of theoretical and experimental researches are in good qualitative and quantitative agreement.

Investigation and modification of the inversed vortex phase field method for phase unwrapping

The paper focuses on the problem of the phase unwrapping in spaceborne remote-sensing interferometric synthesized aperture radar (InSAR) systems. Major unwrapping methods and techniques are considered and the modification of the inversed vortex phase field method of phase unwrapping for interferometric data processing of space-borne synthesized aperture radars is proposed. The modification includes the separation and unwrapping of the low-frequency phase only, and obtaining of the residual phase interferogram, which phase range does not exceed 1-2 ambiguity height values. This approach significantly reduces the number of phase residues and increases the processing speed. The other modification implies filter processing of the residual phase without phase unwrapping, which includes iterative separation of the low-frequency using the Gaussian filter and phase subtraction. This approach moves phase fringes to the relief inflection areas, and is similar to the minimum-cost flow unwrapping results. The computational complexity of the algorithm is proportional to the interferogram size and the number of the phase residues of the low-frequency phase interferogram. The accuracy of digital elevation models obtained by the algorithm was estimated using the ALOS PALSAR radar data and the reference altitude data. The results show, that the accuracy is compared with the minimum-cost flow method, but has the less computational complexity.

Miniaturized bandpass filter based on double spiral stripline resonators

A new miniature monolithic bandpass filter, which can be manufactured using multilayer standard all-PCB technology, is presented. Each resonator in the filter is formed by metal spirals of the left and right wist inserted into each other, in which one pair of adjacent ends is grounded, and the other is free. Spiral inductors have the form of identical rectangular frames and are designed on dielectric substrates, located on a multilayer structure strictly under each other with alternating turns of the left and right spirals. The design of the filter based on such multilayer double-spiral resonators is both small in size, and highly selective, which is proved by the measured characteristics of the fourth order filter fabricated at seven dielectric layers of RO4350B material. The filter has the central frequency of the passband f0 = 60 MHz, and the fractional bandwidth Δf / f0 = 18%, while the size of the device is of the device are only 34 × 16.5 × 4.3 mm3 (0.007λ0 × 0.003λ0 × 0.001λ0, where λ0 is the wavelength at the center frequency f0). The filter has a wide stopband, which extends up to the frequency of 16f0 at a level of –38 dB.