Calculated Radiation Patterns Research Articles

Planar slotted waveguide antenna array for monopulse radar

In monopulse radar, along with mirror and lens antennas, slotted waveguide antenna arrays (SWA) are often used, especially in those cases when it is required to have a flat non-protruding shape and compact dimensions. The design and manufacturing of such antennas have specialties associated with the use of non-standard feeding systems of radiating waveguides, which are considered in this paper as the example of creation of a flat SWA intended for use in a monopulse search and tracking radar. The aim of the article is calculating and modeling a slotted waveguide antenna array based on a hollow metal waveguide with a given level of side lobes and main lobe width of the radiation pattern. The developed SWA contains a radiating and feeding part. The radiating part, with 24 linear resonant waveguide-slot antennas with longitudinal slots on the wide wall of the waveguide, is divided into two subarrays to realize the monopulse mode. Each subarray is fed from the feeding waveguide through slanted slots cut in the wide wall of the waveguide. The antenna design calculation has been carried out in the MathCad, and the modeling has been performed in CAD Ansys HFSS. The energy method has been used to calculate the coordinates of the longitudinal slots on the wide wall of the radiating waveguide as well as the inclined slots on the wide wall of the feeding one. The calculated radiation patterns of the developed antenna array in the E- and H-planes in sum and difference modes have been shown. The paper outlines the methodology for designing a monopulse antenna system using a SWA. The system forms a beam directed perpendicular to the antenna plane. During the design process, the slotted waveguide antenna array based on a hollow waveguide has been modeled and researched to obtain the required characteristics specified in the technical requirements. The proposed approach can be applied to practical antenna design for monopulse radars.

Designing of a multi-frequency vibrator antenna on meander line with resonant loads and fragmented “floating ground”

Problem definition. Many VHF communication devices include multi-frequency vibrator antennas, among which a special place is occupied by the vibrator antennas with reactive loads as the most compact and simplest to produce. However, inductive loads usually used in practice don’t provide current cut-off at higher operating frequencies, which results in deformations of radiation patterns, and resonant circuits loads don’t provide sufficient shortening of the vibrator antenna due to appearance of shunt inductances. There is a need to formulate the new idea of the designing the multi-frequency vibrator antenna, which has absolutely another mechanism of work, is needed. Purpose. The purposes of this article are: to suggest the idea of the design the multi-frequency vibrator antennas, based on hybrid of meander line with parallel LC-circuits and fragmented “floating ground”; to form an equivalent scheme for calculating characteristics; to develop a methodology for calculating this type of antennas characteristics (input impedance, VSWR, current distributions over the vibrator and far-field radiation patterns); to do the calculation of characteristics of the monopole antenna on meander line with loads and to make an experimental check of the theoretical results. Results. A design of the multi-frequency vibrator antenna on meander line with parallel LC-circuits loads and fragmented “floating ground” is shown. An equivalent scheme for calculating antenna characteristics is given, an algorithm of calculation of input characteristics and current distributions over the antenna (both meander and “floating ground”) is described. The calculation of input impedance, VSWR, current distributions and radiation patterns of the vibrator antenna with two LC-circuits loads in meander line is done. An experimental check of the theoretical results in VSWR and far-field radiation patterns is made. Applicability of the proposed idea and methodology for the design the multi-frequency vibrator antennas on meander line is shown by analyzing calculated and experimental data. Practical significance. The results of this work can be used to design the multi-frequency VHF vibrator antennas with resonant loads, which have the identical radiation patterns at all operating frequencies.

A Novel Unit Classification Method for Fast and Accurate Calculation of Radiation Patterns

This paper proposes a novel unit classification technique to enhance the accuracy of the conventional pattern multiplication method by taking the mutual coupling effect and edge effect into consideration. The proposed technique classifies antenna elements into different groups based on their positions in arrays, specifically corner, edge, and inner groups. By simulating the radiation patterns of antenna elements with different boundary conditions, the pattern multiplication method is then used to calculate the radiation pattern of the antenna array based on the simulated results. Several numerical examples, including a square array, a hexagonal array, and a phased array, are provided to validate the effectiveness of the proposed method. The numerical results demonstrate that the proposed method not only reduces the computational time and memory usage but also significantly improves the accuracy. The proposed method provides a powerful tool for synthesizing and predicting the radiation pattern of array antennas and offers new avenues for optimizing array antennas and phased array antennas.

UTD-PO Solution for E-Plane Radiation Pattern Calculation of Rectangular Horn Antennas With Rectangular-Shaped Corrugations

Proposing a novel hybrid uniform theory of diffraction-physical optics (UTD-PO) formulation, we develop a method to calculate the E-plane radiation pattern of corrugated E-plane rectangular horn antennas with rectangular corrugations. We derive the technique from the estimation of the total field that reaches the emitting source (a magnetic current line), thereby assuming the impingement of a plane wave above the horn (reciprocity is applied). To validate our method, we compare the performance of the UTD-PO analysis with that of the electric field integral equation (EFIE) solved using the method of moments (MoM). Our method shows improved computational efficiency over EFIE and other numerical techniques that fully discretize the geometry.

Photonics-based modular multistate digital coherent system

Objectives. The study aimed to develop interspecies and interclass methods for constructing coherent radio engineering systems based on a modular complementary structure.Methods. A set of modules and submodules having no narrow specialization and together constituting a flexible broadband hardware-reconfigurable software-defined radio engineering structure is considered as the basic set for constructing a digital radio photonic system path. Due to their broadbandness and complementary structure, modules and submodules have many applications both as self-sustained devices and as part of more complex systems.Results. Functional diagrams of modern digital receiver-shapers, as well as modules for amplifying radio frequency signals and converting radio frequency signals into an optical signal are presented along with a radio photonic synchronization network for generating clock signals. Calculations of the introduced phase error of a quartz singlemode fiber and graphs of the dependence of the change in the signal phase on external influencing factors are given. A concept for integrating the presented modules into the construction of a modular transceiver multiposition wideband coherent digital radio photonic system is proposed. The results of calculating radiation patterns and mathematical modeling the beam deflection of a broadband antenna array are presented along with antenna systems based thereon.Conclusions. The proposed circuit design solutions allow the time required for developing new types of systems to be significantly reduced due to the range of ready-made technical solutions. Not only are the parameters of the developed devices comparable to the best world analogues, but they also surpass existing solutions in terms of system integration. The developments have been tested under R&D project at the Kaluga Scientific Research Institute of Radio Technology and Hardware Solution Technologies (TAR). The proposed solutions are integrated at the subsystem level into advanced developments of products for civil and special purpose. Further development of the concept of building ultra-wideband devices allows reaching a new level in the technology of constructing modular multiposition coherent digital radio photonic systems.

Enhancement of the Unidirectional Radiation Pattern of Shear Horizontal Ultrasonic Waves Generated by Side-Shifted Periodic Permanent Magnets Electromagnetic Acoustic Transducers With Multiple Rows of Magnets

Shear horizontal (SH) guided waves are widely used in non-destructive evaluation and can be generated by permanent magnet electromagnetic acoustic transducer (PPM EMATs). PPM EMATs generate SH waves that propagate both forwards and backwards. This is often an undesirable characteristic. Unidirectional generation can be achieved by the interference mechanism produced by two independent sources. This, however, is non-feasible for the conventional PPM EMATs due to the arrangement of PPM array and racetrack coil. Recently, we presented a design of an SH EMAT with side-shifted PPM arrays that generates SH waves nominally in a single direction. Due to the shift of the produced wavefronts from each array, that design produced side-lobes in the backward semi-plane. In this paper, we enhance the unidirectional generation of SH waves with side-shifted PPM EMATs by evaluating the effect of the separation between individual arrays as well as the number of rows of magnets in each array. An analytical model is used to calculate the radiation pattern. The amplitude of the backward side-lobes decreases either with increasing the number of magnets rows or decreasing the lateral gap between rows. This behaviour is explained by the amount of wavefront misalignment introduced by each design. Increasing the number of magnets rows also increases the directivity and the energy of the forward generated waves. Twelve different configurations were fabricated, with a reasonably short wavelength of 12 mm, and experimentally evaluated, agreeing with the theoretically calculated radiation pattern. The magnitude of the backward side-lobes was roughly halved when compared with the original design.

Asymptotic solution for the electromagnetic scattering of a vertical dipole over plasmonic and non‐plasmonic half‐spaces

A new asymptotic solution for the scattered electromagnetic fields of a vertical Hertzian dipole antenna in the presence of an imperfectly conducting half-plane for ordinary and plasmonic media is proposed. The scattered electric and magnetic field components are calculated from the intermediate Hertz potential expressed in terms of the Fourier-Bessel transforms associated with the Sommerfeld-type integral, which is difficult to evaluate due to the singularities of the integrand near the integration path and its oscillatory and slowly decaying integrand. Using the modified saddle point method, an approximate closed-form solution of the far-zone scattered electromagnetic fields including surface waves is presented. The new formulations are applied to calculate radiation patterns of different impedance half-planes for both ordinary and plasmonic media, that is, seawater, silty clay soil, silty loam soil and lake water as ordinary, and silver and gold as plasmonic media. Furthermore, a numerical evaluation of the proposed solution at various frequencies and comparisons with two alternative state of the art solutions shows that the proposed solution has higher accuracy in terms of the normalised root-mean-square error and the normalised maximum absolute error for plasmonic and non-plasmonic structures.

Acceleration of FDTD radiation pattern calculation using two-dimensional ARMA

Acceleration of FDTD radiation pattern calculation using two-dimensional ARMA

Determining the Minimum Scan Step of an Electronically Scanned Antenna

Introduction. Electronically scanned antennas (ESA) appeared about a century ago. Although the methods of their design and production have been sufficiently studied, some individual parameters are yet to be revealed. One of such parameters is the minimum step of movement, along with a related parameter – the accuracy of beam alignment in a given direction. From the electrodynamic problem of radiation, it is obvious that the step is associated with the number of radiators and the accuracy of phase adjustment in analogue phase shifters, or with the quantization step in the case of using phase shifters with a discrete step.Aim. To discover a connection between the design parameters of ESA and the step of beam steering; to investigate the dependence between the step and the parameters of the phase shifter and types of beam forming phased array circuits; to create a mathematical apparatus for calculating the minimum step of beam movement for the sum and difference radiation patterns.Materials and methods. Analytical relations were determined for calculating the step depending on the geometric dimensions and location of the radiators. A software application was developed for calculating radiation patterns. A software and hardware complex was designed for beam control of an experimental C-band ESA.Results. A method was developed for calculating the minimum step of ESA scanning. Mathematical relations for calculating the minimum step and accuracy of the ESA beam setting were obtained. A comparison of the experimental and theoretical data on the minimum step of movement of the sum and difference beams of a C-band ESA with the ratio D/λ=10 in the X coordinate and D/λ=5 in the Y coordinate showed good agreement.Conclusion. The created mathematical apparatus makes it possible to calculate the minimum step of electron beam scanning with sufficient accuracy. The experimentally measured steps of the beam movement for an array of 144 elements confirmed the obtained analytical relationships. In an ESA with a small number of elements (N < 10), the minimum step of movement can be variable. The theoretically achievable minimum step of beam movement is determined by the phase shift of the least significant bit of the phase shifter and the electrical length of the antenna aperture.

Airborne Ground Penetrating Radar, Field Test

Deployment of a ground penetrating radar (GPR) on a flying machine allows one to substantially extend the application area of this geophysical method and to simplify carrying out large surveys of dangerous and hard-to-reach terrain, where usual ground-based methods are hardly applied. There is a necessity to promote investigations in this direction by modifying hardware characteristics and developing specific proceeding algorithms. For this purpose, we upgraded commercial ground-based subsurface sounding hardware and performed corresponding computer simulation and real experiments. Finally, the first experimental flights were done with the constructed GPR prototype mounted on a helicopter. Using our experience in the development of ground-based GPR and the results of numerical simulations, an appropriate configuration of antennas and their placing on the flying machine were chosen. Computer modeling allowed us to select an optimal resistive loading of transmitter and receiver dipoles; calculate radiation patterns on fixed frequencies; analyze the efficiency of different conductor diameters in antenna circuit; calculate cross-coupling of transmitting and receiving antennas with the helicopter. Preliminary laboratory experiments to check the efficiency of the designed system were performed on an urban building site, using a tower crane with the horizontal jib to operate the measuring system in the air above the ground area to be sounded. Both signals from the surface and subsurface objects were recorded. To interpret the results, numerical modeling was carried out. A two-dimensional model of our experiment was simulated, it matches well the experimental data. Laboratory experiments provided an opportunity to estimate the level of spurious reflections from the external objects, which helps to recognize weak signals from subsurface objects in GPR surveys under live conditions.

Analysis of Transmission Loss and Boresight Error of a Curved FSS Radome-Enclosed Antenna

In this paper, we numerically study a curved frequency selective surface (FSS) radome, which encloses a waveguide slot array antenna operating at 10GHz, using the ray tracing technique and flat model. The transmission loss (TL) and boresight error (BSE) are calculated for various degrees of freedom, such as elevation and azimuth angular scanning or gimbal systems of array antennas to examine the electromagnetic properties of the curved FSS radome. Our calculations of radiation patterns, TL, and BSE for a multi-layered dielectric radome are compared with those of a commercial EM solver for validation. Importantly, we quantify phase distortions, incurred by the curved FSS radome, using the insertion phase delay (IPD) of transmitted fields on the radome surface. Thereby, we demonstrate that the BSEs strongly depend on (1) the spatial distribution of phase distortions on the radome surface and (2) their average level. The present method is highly suited for analyzing radomes with arbitrary surface patterns inserted.

НАРУЖНАЯ ПЛАНАРНАЯ АНТЕННАЯ РЕШЕТКА МОБИЛЬНОГО ИНТЕРНЕТА 3G/4G

Internet antennas-busters are one of the most common antennas of suburban subscriber stations of broadband radio access systems. In many ways, the speed of information transmission in such systems limits the signal level provided by the base station in the entire operating band of the Internet signal. Since the antenna located on the wall of the house is stationary, it can be made relatively large, which allows you to implement a higher gain and accordingly increase the signal level on the router. At the same time, the market for such antennas is quite saturated with a wide variety of antenna designs, but due to the increase in the number of people working in remote mode and the expected transition to mobile communication systems 5G, it still continues to develop rapidly. The paper proposes a new design of the transceiver mobile Internet antenna-buster, whose main advantage is absolute imperceptibility when installed outdoors. We consider a planar in-phase 8-element antenna array installed on the window glass of a suburban building. As the individual emitters of the lattice are encouraged to use a planar wave dipoles. A feeding scheme for the antenna array on flat two-wire lines has been developed, which provides in-phase and almost equal amplitude excitation of all array elements of the array. Calculations of antenna radiation patterns in the range of 1700-2700 MHz are given. It is shown that the developed antenna has a gain of 8-9 dB in the range of 1700-2100 MHz and 10-12 dB in the range of 2400-2700 MHz. These values are practically not inferior to similar indicators of known collinear antenna arrays and in the upper part of the work range, they have a gain of 1-2 dB compared to their analogs. A planar array matching scheme has been developed that provides a VSWR of about 2.5 in the range of 1700-2100 MHz and no worse than 2 in the range of 2400-2700 MHz. Variants of constructing planar antenna arrays with broadband emitters that provide similar matching without the use of additional matching devices are presented.

COMPARISON OF HOGHORN ANALYSIS METHODS

The paper compares an aperture method and full-wave numerical simulations of hoghorn, which is used as a simple primary feed for reflector antennas or individually without reflector. The hoghorn consists of a sectoral horn flaring in only one plane and a parabolic cylinder. We briefly explain the calculations of hoghorn dimensions, aperture distributions and radiation patterns. This is suitable for numerical computations. We analyze the completely new simultaneous comparisons of the ample experiments with numerical results of both the aperture method and the numerical simulations. This enables to obtain innovative conclusions. Proposed improvements can diminish slight differences of one polarization between experiments and numerical simulations. We have used the described methods for the design of certain antennas for multilateration systems, such as Tamara and Vera passive radars, for civilian and military air traffic control, which greatly improve the accuracy of tracking aircrafts.

DESIGNING A DEPLOYABLE ENVIRONMENTAL SPIRAL CONICAL LOGARITHMIC GRAPHENE ANTENNA FOR SATELLITE COMMUNICATIONS

One of the main directions in the development of information technology is satellite communications (SС). Therefore, the elemental base of the SС is subject to increased requirements for weight and size characteristics and environmental friendliness. Research is needed on the use of new materials and technologies that will provide the required level of the above characteristics in order to achieve these requirements. One such promising technology is the printing of graphene inks on biodegradable substrates. Graphene inks do not corrode and are lighter than metal analogues. The possibility of using this technology allowed us to develop the direction of deployable antennas, which have the preferred weight and size characteristics, are easily transported and installed. The results of the development of an environmental spiral logarithmic graphene antenna for satellite communications, are presented. This antenna can be applied in the L-, S- and C-bands as well as GPS bands. A possible design and folding method is presented. The effect of the substrate's revolutions number on the S parameter is considered. The calculated radiation pattern in two planes is presented.

An Implementation of Interactive Application for the Synthesis of Communication Systems with Antenna Arrays

Introduction. Modern radar and communications systems contain phased array antennas. One of the synthesis problems of such systems is the formulation of requirements for components, modules and units which are comprised in it. To solve this problem, one needs to build a coverage area and to analyze an impact of characteristics of its parts. The quality of analysis and synthesis of such complex systems can be enhanced by use of interactive data visualization, which requires a fairly quick calculation of characteristics.Aim. Development of an interactive application for increasing the synthesis capabilities of communication systems containing antenna arrays and for improving the characteristics of systems of interest.Materials and methods. To accelerate the calculation of radiation patterns, the antenna array pattern in a form suitable for the fast Fourier transform algorithm was used. To find the required amplitude-phase distributions, Kotelnikov series expansion and genetic algorithm were used.Results. In the developed application, amplitude-phase distribution, directivity pattern of a linear equidistant array and coverage area were displayed. An interactive change of the amplitude-phase distribution at radiation elements and synthesized radiation patterns in given directions were possible. With introduction of changes to the radiation pattern, the amplitude-phase distribution and the array radiation pattern itself changed in directions other than the specified one. The coverage area was rebuilt when any of the characteristics changes. If necessary, the coverage area display could be turned off. The paper provides an example of using the application in the synthesis of a communication system with an aircraft.Conclusion. The use of the developed application allows one to extend the capabilities and significantly reduce the analysis and synthesis time of the communication secondary radar systems with antenna arrays too. Besides, the application is used for training specialists for industry enterprises.

Proof of the density tapering concept of an unequally spaced array by electric field distributions of electromagnetic simulations

ABSTRACTThe design method of an unequally spaced array was based on the density tapering in the textbook “Antenna theory” in 1969. The effects on grating lobe reductions were shown by radiation pattern calculations. However, no proof for the achievement of density tapering was shown. In this paper, through direct comparisons of the objective amplitude distribution with electric field distributions by electromagnetic simulation, density tapering is examined. A log-periodic dipole antenna operating from 900MHz to 2500MHz is designed for the array element. The unequally spaced 31-element array antenna is used for calculation. At many kinds of density tapering and many frequencies, calculated electric field distributions in a near-field region of the array antenna agree with the given density tapering distributions. The paper results show that the density tapering is achieved from 900MHz to 2000MHz and the effects of grating lobe reductions are ensured from 900MHz to 2500MHz.

Synthesis of a Radiator in the Frequency Range of 0.9…5.8 GHz

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.

Study of Integrated Antennas-Filters on Dielectric Resonators

New structures of dielectric resonators, simultaneously performing the functions of antennas and input filters of transceiver-transmitting devices of communication in the microwave wavelength range, are proposed. The new structures have the form of coupled systems of dielectric resonators, some of which are located in the segment of the evanescent waveguide and perform the functions of a band-pass filter, and the other part of the resonators are located in open space and perform the functions of an antenna system. A part of the resonators of the antenna subsystem has the form of dielectric semi-cylinders glued onto a metallic conductive screen and plays the role of directors forming the radiation characteristic. Two cases of the same and different in shape and material dielectric resonators are considered. For the case of dielectric resonators of different types, using the perturbation theory, a system of equations was obtained for the coefficients of the expansion of the scattering field from the known coupled oscillations of the system. Using the developed theory, the frequency dependence of the reflection coefficient of the proposed antenna-filters was calculated. It is shown that the proposed structures are characterized by much more rectangular amplitude-frequency characteristics, which allows to effectively solve the problems of electromagnetic compatibility of several communication systems using adjacent bandwidths. An additional advantage of the considered antenna filters are smaller dissipative losses, which is important for reducing bit errors. Calculated radiation patterns of antennas in the far zone. It is also shown that the radiation characteristics of the antennas do not change, or change only slightly compared with antennas made only with the help of similar structures of dielectric resonators. The obtained simulation results can significantly reduce computation time and optimize complex communication systems that simultaneously perform channel separation and radiation functions.

Improved Cylindrical HIE-FDTD Method and Its Application to a Metal Disk-Type Surface Wave Splitter

The cylindrical hybrid implicit–explicit finite-difference time-domain method, in which the implicit scheme is adopted only in the circumferential direction, is improved in order to treat general electromagnetic problems. The connection of the field in a specific plane gives the problem with a cyclic matrix, the solution of which is performed with the Sherman–Morrison formula. The convolutional perfectly matched layer is also introduced in cylindrical coordinates. The present method is used to analyze a metal disk-type surface wave splitter. The computational time is reduced to less than 20% of the explicit method, yielding almost the same numerical results. Calculated radiation patterns are compared with experimental results.

Double effects between reflection and edge-diffraction in NURBS-UTD method

ABSTRACTSecond-order ray types in uniform geometrical theory of diffraction method are studied in this paper where non-uniform rational B-spline technique is introduced to construct targets. Reflection-edge diffraction ray type and edge diffraction-reflection ray type which are always appeared in multi-scatterer environments are investigated. Ray paths are found through numerical optimization based on Fermat’s principle. Ray fields carried by these kinds of rays are calculated based on single effected ray fields to discuss their contribution to the total ray fields. It can be seen that the consideration of reflection-edge diffraction effect and edge diffraction-reflection effect can improve the computational precision slightly in calculation of radiation patterns. Numerical results show the validation and the improvement.