Amplitude-phase Distribution Research Articles

Probe correction of measurements of the amplitude-phase distribution in the near field

Probe correction of measurements of the amplitude-phase distribution in the near field

Features of excitation reconstruction in flat multielement phased antenna array face using dynamic directional patterns

The study focuses on reconstructing the amplitude-phase distribution of flat multielement passive and active phased antenna arrays with the use of dynamic radiation patterns, measured with electronical scanning without mechanical rotations and antenna movements. The paper describes the measurement settings of dynamic radiation patterns, necessary for reconstructing the amplitude-phase distribution. Findings of the research show that to reconstruct the amplitude-phase distribution according to dynamic radiation diagrams, there is no need for increased computational resources due to the use of Fourier transformation algorithms. After the method was experimentally verified on the specific samples of active phased antenna arrays, its high efficiency was established. The paper gives the examples of reconstructing the amplitude-phase distribution from dynamic radiation patterns in the presence of malfunctions in active phased array antennas.

TRANSFORMATION OF SURFACE WAVES OF COUPLED DIELECTRIC WAVEGUIDES INTO VOLUME WAVES USING DIFFRACTION GRATINGS

Development and improvement of operational characteristics of communication lines, radiolocation and navigation, surface overview, remote control and warning systems at the airports and at the railway stations is provided due to development of shorter-wave electromagnetic ranges. Designing new millimeter and submillimeter wave band radio complexes requires not only upgrading of existing antennas but also creation of new antenna classes – diffraction radiation antennas, for example. One of the basic problems in antenna engineering is the formation of required amplitude-phase distribution (APD) of the electromagnetic field on antenna aperture that provides for the given operational characteristics. The known techniques of APD forming at the aperture of diffraction radiation antennas are acceptable for the apertures, which are not less than 50 wavelengths. The possibility of forming the amplitude distribution with symmetrically falling edges at the 10...50 wavelength aperture by supplementing an additional segment of dielectric waveguide is investigated in this paper. The additional segment of dielectric waveguide changes the serial system of radiating elements feeding into a serial-parallel one. The efficiency of energy and APD transformation in the antenna aperture for different values of dielectric waveguide – dielectric waveguide and dielectric waveguide – grating coupling factor is evaluated. The results can be applied in the design of millimeter range antenna systems and functional units based on open transmission lines.

DEVELOPMENT OF CONCEPT OF HARDWARE-SOFTWARE COMPLEX OF MODULAR DESIGN FOR DETERMINATION OF ANTENNA SYSTEMS׳ CHARACTERISTICS BASED ON MEASUREMENTS IN THE NEAR FIELD

Measuring the amplitude-phase distribution of the radiation field of complex antenna systems on a certain surface close to the radiating aperture allows solving the problem of reconstructing the free-space diagram in the far field and also helps in determining the influence of various structural elements and defects of radiating surfaces on formation of directional diagram. The purpose of this work was to develop a universal hardware-software complex of a modular design aimed for determining the characteristics of wide range of antenna systems in respect of measurements of the amplitude-phase distribution of the radiation field in the near zone.The equations that connect the structure of radiation fields of the antenna system at various distances from it in planar, cylindrical and spherical coordinate systems as well as structural diagrams of the hardware part of measuring complexes have been analyzed.As a result, the concept of constructing a universal hardware-software complex for measuring the radiation field of various types of antenna systems with any type of measurement surface for solving a wide range of applied problems has been developed. A modular structure of hardware and software has been proposed; it allows reconfiguring the complex rapidly in order to measure the characteristics of any particular antenna system at all stages of product development and testing, and also makes the complex economically accessible even for small enterprises and organizations.

Spatial suppression of interference in hybrid reflector antennas*

The article describes a 7-beam hybrid reflector antenna with a 19-element feed element which forms a radiation pattern in the form of a cluster. During the research the synthesis of the amplitude-phase distribution of the antenna feed element has been conducted. A radiation pattern for three situations of interference: along the first side lobe, along the ramp of the main lobe, along the main lobe.

Methods for restoring the amplitude-phase distribution in the aperture in the spherical near-field scanning

The methods of restoration of amplitude-phase distribution in the antenna aperture by a transition to a plane wave on the basis of the asymptotic behavior of the Hankel functions at infinity and by direct calculation of the intensity of the components of the vector in a spherical coordinate system and transfer to a Cartesian plane on a uniform grid. Powered by comparing them to the data computing and natural experiments.

Focusing of a field in a hydroacoustic waveguide into a given depth interval

We propose and test in a field experiment a method that uses an emitting vertical array to focus a field to a given depth interval in a vertical section of an underwater sound channel at the observation distance. The amplitude-phase distribution of signals at the array elements is found by solving the variational problem of maximizing the ratio of mean sound field intensities inside and outside the chosen area of the section. The introduction of an additional restriction on the range of allowable grazing angles of excited waves has made it possible to obtain a solution in the form of a wave beam propagating without bottom reflections. Such solutions can be used for field focusing without information on the bottom parameters.

Monochromatic ultrasonic transmission tomography

This paper presents a method of monochromatic diffraction ultrasonic transmission tomography that takes into account the amplitude-phase distribution of the field diffracted on the object. The depth resolution of objects is achieved by multi-angle measurements. The the results of numerical modeling and experimental studies at a frequency of 40 kHz in air confirm the applicability of the method.

Конструкция антенной системы с рефлектором сложной формы

The design of the antenna system with complex shape reflector is developed. The antenna system is a linear phased array of the eight broadband radiators. The design of a broadband radiator with a reflector is considered. Inclusion of the quarter-emitter short-circuited loop on the symmetrical transmission line in the feed point provides a power balancing. Coordination of the radiator in a wide frequency band is achieved by placing of the passive short dipole near the radiator current elements. The shape of the dipole and its position are determined experimentally. Reflector is specially shaped to provide the electrical properties of the radiator. The design of the beam-forming circuit for implementing a given amplitude-phase distribution of array excitation is offered. Previously calculated lengths of connecting cables participate in the formation of the phase distribution of antenna array. Application of the flat sheet and fiberglass fairing is provided by the design for protection of the antenna system against climatic factors. The experimental results for radiator and prototype antenna system in general are presented. Aluminum alloy sheet with cutting, bending, welding and applying a conductive protective coating are used in the manufacture of the antenna system. This provides low cost of the antenna system, good mass-size parameters and high manufacturability of the design.

Опыт разработки высокочастотных трактов пассивной фазированной антенной решетки в виде гибридных интегральных модулей СВЧ

The article specifies the design challenges associated with the construction of phased antenna array high-frequency paths with a given amplitude-phase distribution of an average power level microwave signal. The authors propose several variants of the microstrip-based implementation of these paths. The design description for two microwave modules shows the possibility of using the integrated technology to build VHF and UHF wavelength band beam-forming antenna systems in order to reduce their mass, dimensions, production and setup costs. The article proposes what component parts could be used to build integrated phased antenna arrays. As a basic set of components used directional coupler with the right connections, providing amplitude and phase distribution of the signal by a given law. And as the substrate for the stripline is proposed to use a dielectric material with a dielectric constant greater than 10. The authors demonstrate the possibilities for the usage of state-of-the-art software to design, conduct accurate numerical simulation for and setup microwave antenna modules. The paper described in detail the calculation method of amplitude – phase characteristics of subgroups using Microwave Office software company Applied Wave Research (AWR). The calculated and experimental radiation pattern of antenna systems performed based on the developed and manufactured by the described integrated microwave modules.

Алгоритм синтеза линейных антенных решеток c требуемой диаграммой направленности и целочисленными ампли­тудными коэффициентами

Ahe problem of technical implementation of phased array antennas (PAR) with the required radiation pattern (RP) is the complexity of the construction of the beamforming device that consists of a set of controlled attenuators and phase shifters. It is possible to simplify the technical implementation of PAR, if complex representation of coefficients of amplitude-phase distribution of the field along the lattice is approximated by real values in the synthesis stage. It is known that the amplitude distribution of the field in the aperture of the antenna array and the radiation pattern are associated with Fourier transform. Thus, the amplitude and phase coefficients are first calculated using the Fourier transform, and then processed according to the selected type of circuit realization of attenuators and phase shifters. The calculation of the inverse Fourier transform of the modified coefficients allows calculating the synthesized orientation function. This study aims to develop a search algorithm for amplitude and phase coefficients, taking into account the fact that integer-valued amplitudes and phases are technically easier to implement than real ones. Synthesis algorithm for equidistant linear array with a half-wavelength irradiators pitch (&l;/2) is as follows. From a given directivity function the discrete Fourier transform (DFT) in the form of an array of complex numbers is found, the resulting array is then transformed into a set of attenuations for attenuators and phase shifts for phase shifters, while the amplitude coefficients are rounded off to integers, and phases are binarizated (0, ?). The practical value of this algorithm is particularly high when using controlled phase shifters and attenuators integrally. The work confirms the possibility of a thermoelectric converter of human body application for an electronic medical thermometer power supply.

Statistical synthesis of radiometric imaging formation in scanning radiometers with signal weight processing by Kravchenko windows

Statistical optimization of the radiometric images (RMIs) algorithms formation in scanning radiometers with weight correction of the antenna amplitude-phase distribution and synchronous sliding strobing of the received noise-like signal by a function describing the antenna pattern corrected by temporal Kravchenko windows is performed for the first time. The ambiguity function (AF) of the scanning radiometer, which determines the RMI quality, is found. It is established that the AF shape substantially depends on the amplitude field distribution (AFD) in the antenna. It is shown that the use of the AFD in the antenna in the form of weight functions (classic and Kravchenko) makes it possible to correct the AF shape and to increase the RMI quality. A simulation of the RMI formation algorithm is performed. It follows from the analysis of simulation data that the use of the weight Kravchenko functions provides higher accuracy of the RMI restoration compared with classic weight functions.

Remote ultrasonic defectoscopy of sound radiating objects through the air

A method of obtaining ultrasonic images of objects radiating ultrasonic acoustic waves in the air is proposed. Object images are retrieved by spatially matched filtering of the amplitude-phase distribution of the ultrasonic field measured in a planar rectangular region at a distance from the radiating object under investigation. The field is measured at different frequencies in a wide band, which allows one to reduce the level of noise and artifacts in the retrieved images by processing in a wide frequency band.

Phased array with controlled directivity pattern

Amplitude-phase distribution of currents in the emitters that allows independent control of the main lobe and the blind spot on the directivity pattern of the antenna where the gain substantially decreases is analyzed. The problem is solved with the aid of controlled amplitudes and phases of the waves emitted by the antenna array. The main lobe and the blind spot on the directivity pattern are formed using the synthesis of the complex amplitudes of currents in the emitters.

Selection and generation of multipass modes in an open resonator

The original numerical wave model of the open resonator has been employed in the investigation of conditions for multipass mode generation. It is shown that for Fresnel numbers larger than unity, multiple reflections of radiation from the stable resonator mirrors lead to sustained quasi-stationary oscillations which are indicative of multipass mode generation. Various types of ray trajectories have been considered at the paraxial resonance conditions. Trajectory selecting techniques are suggested to provide the high quality output beams at large Fresnel numbers. The results of numerical experiments on amplitude-phase distribution of output radiation are presented for the suggested schemes.

Focusing of a sound beam in an underwater waveguide using a vertical antenna

We propose a method for calculating the amplitude-phase distributions of signals on the elements of an emitting antenna for generating narrow wave beams and field focusing at given points of the waveguide. The efficiency of the method is confirmed by the data of a field experiment conducted in Lake Ladoga.

Portable Acoustic-Electric Combined System for Partial Discharge Detection in GIS

A portable acoustic-electric detection system for GIS partial discharge is developed. This system integrates both high and low-speed data acquisition devices, and is capable of multichannel joint detection of ultra-high-frequency and high-frequency current as well as ultrasonic signal generated during the GIS partial discharge process. The software of this system is developed based on LabVIEW. It can successively capture, acquire and store the pulse waveform of partial discharge, calculate the phase of discharge pulse and realize time-frequency analysis and amplitude-phase distribution analysis of PD signals at the same time. By calculating the time difference of multi-channel ultra-high-frequency (UHF) signals and of PD ultrasonic signals or the time difference between the two, the system is able to locate the PD source. This system has been applied to on-site partial discharge detection of 220kV and 500kV GIS substations, and the test results have verified the performance of the system.

Influence of Mutual Coupling and Current Distribution Errors on Advanced Phased Antenna Array Nulling Synthesis

Phased antenna array synthesis procedures based on the amplitude-phase and only-phase distributions providing the side lobe cancellation in a required direction are presented. A receiving antenna array was considered. It is characterized by the direction of the main beam for receiving the useful signal and the additional nulling direction. The required amplitude—phase distribution along the array is provided by the phase shifters and controllable attenuators/amplifiers. Moreover the modified synthesis procedure that takes into account the mutual coupling influence in the antenna array was proposed. Finally the radiation pattern transformation under the influence of the current distribution errors connected with a quality of phase shifters and attenuators/amplifiers was investigated.

The field radiated by a single-mode optical waveguide excited by a field with a complex amplitude-phase spatial distribution

A single-mode optical waveguide excited by a field having a complex amplitude—phase spatial distribution is considered. The field formed at the output of the waveguide is investigated. It is shown that the field structure at the input of the waveguide is transformed at its output into a simple structure with a distribution close to the Gaussian one. It is found that higher order spatial maxima of the input field falling within the waveguide’s aperture also participate in the formation of the output field.

Synthesis of antenna arrays with shaped-beam patterns

A method for the synthesis of the amplitude-phase distribution of an antenna array, which uses embedded element patterns, is developed. In the general case, the method ensures formation of an arbitrary shaped-beam pattern. Features of the synthesis of shaped-beam patterns of antenna arrays with elliptical polarization and vector patterns are considered. The numerical analysis of the synthesis method, which is performed for an array of rectangular waveguides with vector patterns, confirms the efficiency of the proposed approach.