Directivity Pattern Of Antenna Research Articles

METHOD OF REDUCING THE LEVEL OF BACK RADIATION OF ELECTROMAGNETIC WAVES OF APERTURE ANTENNAS

A method has been proposed and developed that allows you to significantly reduce the level of back radiation of electromagnetic waves of aperture-type antennas of any design. The essence of the method is the excitation of slowed surface waves on the outer side of the edge of the antenna aperture, which are in antiphase with electromagnetic waves of back radiation. Slowed surface waves are formed by an impedance metal comb, which performs the function of a retarding system, placed on the outer side of the opening edge of the antenna. The dependence of the formed characteristics of the electromagnetic field on the design parameters of the impedance comb is shown. The method was tested on the horn-slot ship antenna of the “Mius” type navigation radar station. The results of modeling and calculation of the directional pattern (DP) of the antenna confirm that the proposed method allows to reduce the level of the rear lobe of the directional pattern of the horn-slit antenna with an impedance comb by approximately 1.4 times.

Antenna Directional Pattern Testing System Based on Multirotor Unmanned Aerial Vehicles

Obtaining azimuth data of antennas after installation on actual platforms (such as large aircraft, ships, etc.) is crucial for effectively analyzing the platform's impact on the antennas and facilitating optimization and improvement. Traditional testing methods are unable to accurately and efficiently acquire azimuth data due to significant differences between measurements in a dark room and the actual conditions. With the rapid development of drone technology, unmanned aerial platforms have been widely utilized in various engineering fields. Utilizing the flexibility of drones in three-dimensional space and their ability to be precisely controlled through RTK technology, it is possible to use drones equipped with test antennas to measure the azimuth pattern by receiving spectrum signals transmitted by antennas on real platforms. In order to achieve precise angle control, a gimbal system is designed to control the angle of the test antenna. The effectiveness of the entire testing system is verified through experimental results.

ОСОБЕННОСТИ ПОСТРОЕНИЯ МОДЕЛИ ЗЕРКАЛЬНОЙ АНТЕННЫ С УЧЕТОМ ВЛИЯНИЯ МЕТЕОРОЛОГИЧЕСКИХ ФАКТОРОВ

An electrodynamic model of a millimeter-range single-mirror antenna with a puddle in the reflector is given. As a justification for the need for a model, the influence of rainfall on the design of millimeter-range mirror antennas was assessed. The aim of the study was to create a model of the parabolic reflector of a mirror antenna with an aqueous precipitation layer, with parameters chosen for the climatic region in which the antenna is located. An analysis of known models of single mirror antennas with a layer of precipitation has been carried out. It has been shown that the known models do not describe the operation of a millimeter-range mirror antenna with a reflector in which a puddle of water has formed. It is suggested that the influence of this layer on the directional characteristics of the antenna be assessed with the aperture method used for mirror antennas with reflector profile defects. The results of the modelling of the directivity pattern of a mirror antenna with a puddle of water in the reflector are presented. It is shown that the appearance of a puddle leads to an asymmetric change in the height of the first side lobes of the directivity pattern in the vertical plane. In the horizontal plane, changes are observed in the growth level of each side lobe, except for the first one. The lobes' symmetry is not affected. Research focus: The process of emitting a millimeter electromagnetic wave using a single mirror antenna with a layer of water in the reflector. Subject of the study: "Mirror antenna reflector with water precipitation layer - millimeter wavelength electromagnetic wave" system. Methods: Electromagnetic meteorological method, modified aperture method, modified Ruze method, statistical meteorological method. Main result: A wireless communication system using the magnetic component of the electromagnetic field has been developed. Practical relevance: The results of this research may be useful in the design of millimeter-range mirror antennas to assess the influence of meteorological precipitation on the directivity characteristics. The work was presented at the VIII All-Russian Microwave Conference "Microwave week 2022" in Moscow.

Performance Analysis of Uncoordinated Interference Mitigation for Automotive Radar

As a key sensor for Advanced Driving Assistance System (ADAS), millimeter automotive radar has been a promising candidate for fulfilling tasks including adaptive cruise control and collision avoidance. However, the widely deployment of millimeter automotive radars may cause serious mutual interference among vehicles, thus degrading radar ranging performance severely. In this article, we analyze the mutual interference among multiple Frequency Modulated Continuous Wave (FMCW) radars. On one hand, we model the interference precisely by employing Matern Hard-Core Process (MHCP) model to characterize the distribution of vehicle nodes in practical bidirectional two-lane and multi-lane scenarios. Besides, the interference is analyzed in terms of the channel fading, the directional antenna pattern and the fluctuation of the target Radar Cross-Section (RCS) in two-lane and multi-lane scenarios. Besides, we analyze the reflected interference in detail. On the other hand, we evaluate the interference mitigation performance of the Random Frequency Division Multiplexing (RFDM) and Frequency Hopping (FH) approaches in terms of the probability of false detection and miss detection, effective detectable density and maximum number of interference-free radar. Finally, a novel AFH-PM mitigation approach is proposed to further improve the interference mitigation performance, which combines the adaptive FH technology with the binary phase modulation. Simulation results verify the proposed framework for interference analysis by employing Monte Carlo method, and the performance improvement of RFDM, FH and AFH-PM is 6.7 dB, 7.6 dB and 8.2 dB, respectively.

Design of traveling wave slotted waveguide array antenna with high efficiency

<span lang="EN-US">The slotted waveguide antenna is one of the most important antennas used in high-frequency applications, in radars, navigation systems, remote sensing systems and communications because of its efficiency and high gains. In this paper, the slotted waveguide antenna was designed and simulated with suitable specifications with a working frequency range of 2-2.45 where this antenna was checked by plotting S parameters in the designed frequency band and we got a very good reflection coefficient for the designed antenna (S11) at the operating frequency, draw and illustrate the three-dimensional radiation pattern of the designed antenna that shows the gain and bandwidth at the operating frequency. The performance of a 9-element slotted waveguide array antenna with an operating frequency of up to 12 GHz was also investigated by plotting the S11 parameters and illustrating the designed antenna directivity diagram.We obtained the reflection coefficient of the designed array antenna (S11) below -23 dB at the operating frequency, and the SWG antenna directivity pattern with a maximum value of=13.2 dB and a minimum value of=-23 dB.</span>

Directional antennas modelling and coverage analysis for UAV networks with blockage effects in urban environment

AbstractIn recent years, the use of unmanned aerial vehicles (UAVs) as flying base stations (BSs) has attracted widespread attention in both academia and industry. Most of the existing research on UAV networks in dense urban environment focus on omnidirectional antenna patterns, which results in severe interference and overlapping between coverage area due to dominant line‐of‐sight (LOS) links. This paper proposed a directional antennas model with tunable beamwidth and blockage effects in urban UAV networks, and derive the coverage probability of UAV networks in dense urban environment by stochastic geometry tools, where UAVs and users are deployed according to independent Poisson point process (PPP). Specifically, a realistic and mathematically tractable directional antenna pattern is adopted and radiation gain is modelled by a continuous function of the elevation angle . In addition, the blockage effects of the buildings are considered by establishing a three‐dimensional blockage model where buildings are distributed according to PPP with heights followed by Rayleigh distribution. Numerical results match well with simulations and provide optimal deployment parameters for UAV deployments.

A deep neural network based MU-MIMO beamforming training protocol for IEEE 802.11ay

IEEE 802.11ay supports a multi-user multiple-input-multiple-output (MU-MIMO) beamforming training (BFT); hence, an access point (AP) can perform data transmissions simultaneously with multiple stations (STAs). During MU-MIMO BFT, the AP sends a significant number of action frames to the STAs to determine appropriate directional antenna patterns. However, if transmit sectors (TSs) used in the transmission of action frames are selected inefficiently, the AP could perform redundant transmissions; this could eventually lead to the poor performance of the MU-MIMO BFT in terms of signaling and latency overhead. To select the appropriate TSs, the AP is required to accurately estimate the link qualities measured at the STAs when certain TSs are used simultaneously to transmit an action frame. Therefore, in this study, we propose a deep neural network (DNN)-based scheme that performs efficient MU-MIMO BFT. It achieves this by accurately estimating link qualities measured at the STAs when an action frame is transmitted through multiple TSs. Moreover, it performs this function without collecting any additional channel information that is not specified in the standard. For performance evaluation, we conducted extensive simulations with realistic mmWave channel and antenna array models in four indoor and outdoor propagation scenarios. The simulation results demonstrate that our scheme transmits fewer action frames and achieves a lower BFT time than existing schemes.

Effects of Receiver Beamforming for Vital Sign Measurements Using FMCW Radar at Various Distances and Angles.

Short-range millimeter wave radar sensors provide a reliable, continuous and non-contact solution for vital sign extraction. Off-The-Shelf (OTS) radars often have a directional antenna (beam) pattern. The transmitted wave has a conical main lobe, and power of the received target echoes deteriorate as we move away from the center point of the lobe. While measuring vital signs, the human subject is often located at the center of the antenna lobe. Since beamforming can increase signal quality at the side (azimuth) angles, this paper aims to provide an experimental comparison of vital sign extraction with and without beamforming. The experimental confirmation that beamforming can decrease the error in the vital sign extraction through radar has so far not been performed by researchers. A simple, yet effective receiver beamformer was designed and a concurrent measurement with and without beamforming was made for the comparative analysis. Measurements were made at three different distances and five different arrival angles, and the preliminary results suggest that as the observation angle increases, the effectiveness of beamforming increases. At an extreme angle of 40 degrees, the beamforming showed above 20% improvement in heart rate estimation. Heart rate measurement error was reduced significantly in comparison with the breathing rate.

РЕЗУЛЬТАТИ ЕКСПЕРИМЕНТАЛЬНИХ ДОСЛІДЖЕНЬ БАГАТОДІАПАЗОННОГО ІМІТАТОРА ПОСТАНОВНИКА АКТИВНИХ ШУМОВИХ ПЕРЕШКОД

The article provides information on the results of experimental studies of a multi-band hardware and software complex for simulating the action of an active noise jammer, which has been created for the training of operators of radar stations of radio engineering troops. One of the important elements of the professional training of the radar stations operators of the air defense radio engineering forces is their ability to work in difficult target and jamming conditions. The existing simulators for training operators do not fully meet the requirements of the quality of training, since they form only secondary bearing marks on the jammer manufacturer and do not reproduce the situation of deterioration of target detection conditions as a result of the simultaneous action of active and passive noise jammer, as well as the influence of the autocompensator of jammer on the quality of the radar, as it happens in real situation. The offered device for simulating the influence of active jammer has been built according to the modular principle and implemented using software-defined radio technology, which allows to quickly change both the type of signal and its parameters. Power amplifiers and antenna systems have been designed to operate in the 140–190 MHz, 470–900 MHz, and 2500–3500 MHz bands, and for experimental research radar stations in the meter, decimeter, and centimeter wave ranges have been involved. The method of using the simulator has been substantiated, and the conducted studies showed that for radar stations in which the angular beams of the directional pattern have different operating frequencies, there is an additional possibility of simulating the action of the active jammer by changing the frequency of the jammer in the case of operation of the complex directly near the suppression object, where the directional pattern of the radar station antenna has not yet been formed. The method of using the complex both for training sessions and during tactical exercises of the radio technical troops unit to simulate the action of an air-based jamming device or a dropped jamming transmitter has been substantiated. Keywords: active noise jammer; simulation; hardware and software complex; radar station; programmed radio.

STUDY OF THE INFLUENCE OF INTENSIFYING ADDITIVES ON LOW-TEMPERATURE SYNTHESIS OF SLAVSONITE AND CELZIAN IN THE CREATION OF RADIOTRANSPARENT CERAMIC MATERIALS

The studies carried out concern the development of structural radiotransparent ceramic materials based on the four-component system BaO–SrO–Al2O3–SiO2. Due to the widespread use of radar equipment at modern aviation facilities, the development of radiotransparent fairings for them is a rather important and urgent task.The purpose of the fairings is to protect the antenna devices of radar stations from environmental influences during flight. Based on this, the fairings must meet a complex set of requirements for aerodynamic, thermal, radio engineering and mechanical properties. These requirements at supersonic flight speeds of modern objects increase significantly, since the improvement of the aerodynamic shape, the increase in the mechanical strength and thermal stability of the fairings contradicts the interests of radio engineering, leading to a significant deterioration in their radiotransparency and to distortions of antenna directional patterns. The consequence is a decrease in the range of radar stations and serious deterioration in their accuracy characteristics.The aim of the research was to obtain, on the basis of the BaO–SrO–Al2O3–SiO2 system, crystalline phases of slavsonit and celsian at low temperatures and times of synthesis, by introducing sintering intensifiers with fluxing and modifying action.The influence of a number of additives on the intensification of the low-temperature synthesis of slavsonit and celsian is investigated. The positive effect of the eutectic additive of the SnO2–Li2O system on the preparation of a densely sintered ceramic material based on solid solutions of slavsonit and monoclinic celsian is shown. It has been established that, according to its dielectric properties, the obtained ceramic material can be classified as structural radio-transparent materials.

The Dependence of the Antenna Directional Pattern on the Body Shape

The Dependence of the Antenna Directional Pattern on the Body Shape

Guest editorial: Smart communications and networking: architecture, applications, and future challenges

Guest editorial: Smart communications and networking: architecture, applications, and future challenges

A Comprehensive Comparison for Different Hybrid Based Localization Algorithms for Indoor Communications

The era of the wireless communication-based indoor environment has resulted in several challenges represented by signal reflection, diffraction, and attenuation. Thereby, it affects several wireless-based applications such as positioning, localization, monitoring different objects. With such challenges, estimation error would be increased significantly, and the accuracy will be reduced. To handle such challenges, several new approaches were proposed by many researchers. The most interesting approach for the localization purpose was the hybrid localization approach. A combination of several parameters would be utilized to propose methods that take advantage of these parameters. In this work, a comprehensive analysis was carried out for results obtained based on the proposition of two hybrid algorithms for localization in an indoor environment. The first algorithm utilized the Received Signal Strength (RSS) and Angle of Arrival (AoA) parameter to be tested for both Omni and Directional antenna type Access point (AP) device. While the second algorithm was based on the use of Time of Arrival (ToA) and RSS, which have been calculated via Wireless InSite (WI) software. The analyzing results indicate that using AoA/RSS method with the Omni AP antenna has achieved higher accuracy for the overall normal distribution scenario. However, ToA/RSS has shown higher accuracy estimation for far point distribution. Meanwhile, AoA/RSS with Directional antenna AP has an accuracy limited with distribution location. Due to the characteristics of the directional antenna pattern.

ADVANCED GRAM-SCHMIDT METHOD FOR RADAR SIGNAL PROCESSING

Context. When protecting radar stations from active noise interference acting along the side lobes of the antenna directional pattern, spatial filtering of signals is used, which is realized by using antennas that are spaced apart in space. In this case, the difference in the directions of reception of the useful signal and the interference makes it possible to form the optimal value of the weighting coefficients of the adaptive spatial filters to suppress the interference. However, if the interfering source moves into the main beam region, then the spatial differences between the wanted signal and the interference are reduced. This leads to significant distortion of the main antenna radiation pattern. As a result, the accuracy of measuring the angular coordinates deteriorates, as well as the sensitivity of the radar receiver. The article proposes a structural-parametric method for adapting a spatial filter, which ensures effective operation of the radar when exposed to the active noise interference both from the direction of the side lobes and from the direction of the main beam.
 Goal. Improving the efficiency of the radar when the active noise interference source is shifted from the direction to the side lobes to the direction of the main beam.
 Method. The proposed method makes it possible, due to the structural adaptation of the multichannel spatial filter, to exclude the distortion of the main beam of the radiation pattern of the radar antenna and to ensure its operation under conditions of possible interference from the main beam. Structural adaptation of the spatial filter is realized by the current analysis of the weighting coefficients of the compensation blocks.
 Results. The structural diagram of the multichannel spatial filter by the Gram-Schmidt method with structural-parametric adaptation, as well as the structural diagram of the compensation block, has been improved. As a result of the simulation, the possibility of eliminating distortions of the radiation pattern of the main antenna of the radar in conditions of the possible impact of the active noise interference along the main beam of the radiation pattern of the radar has been confirmed.
 Conclusions. The scientific novelty of the work consists in the improvement of the signal-processing algorithm at spatial filtering both when exposed to the active noise interference from the direction of the side lobes, and when the interference source is shifted to the direction of the main beam of radar. The practical novelty of the work lies in the development of a structural diagram and a mathematical model of an improved spatial filter with structural-parametric adaptation.

Influence of the radius of a perfectly conducting cylinder on the radiation pattern of a patch antenna

In this paper, we consider the change in the directional pattern of a microstrip patch antenna located on a perfectly conducting plane and a cylinder covered with a dielectric layer. The mathematical apparatus of the Green’s tensor functions for flat and cylindrical layered metaldielectric structures is used to calculate field characteristics. The obtained results are of special interest in the design of conformal single radiators and antenna arrays located on curved surfaces that can be approximated by a cylinder, for example, the fuselage of small-sized aircraft or supports for the installation of antenna systems. It is demonstrated that the curvature of the base surface for a single element has little effect on the radiation pattern within the width of the main lobe; nevertheless, the increase in the radius of the used cylinder influences the level of the back lobe significantly.

Performance Evaluation of Uplink Multiuser MIMO-OFDM System With Single RF Chain Receiver

In response to the recent increase in wireless-traffic demand in various wireless communication networks, the number of spatial multiplexings, represented by multiple input multiple output (MIMO) systems, has been increasing. Assuming a realistic hardware configuration achieving an increase in the number of spatial multiplexings depends on increasing the amount of hardware, such as analog/digital (A/D) and D/A converters, and radio frequency (RF) chains. Simplifying the hardware configuration while maintaining large channel capacity was the challenging issue to further improve the channel capacity in Beyond-5G and 6G. This paper proposes a novel system configuration based on an uplink multiuser MIMO - orthogonal frequency division multiplexing (OFDM) system with a single RF chain receiver. By oversampling OFDM signals with a single RF chain receiver, our approach provides an additional spatial multiplexing by switching the antenna directivity pattern in synchronization with the received sampling frequency. Oversampled OFDM signals are typically used for noise reduction, in the proposed configuration, they are used for adding spatial multiplexings. We clarify the potential of the proposed configuration for improving the channel capacity by applying it to the uplink multiuser MIMO-OFDM system. To demonstrate its feasibility, we developed a testbed and analyzed its effectiveness in experiment in an actual indoor office environment.

OBSERVATION CONTROL DEVICE FOR THE URAN-4 DECAMETER RADIO TELESCOPE

The URAN-4 radio telescope has been operating at the Odessa Radio Astronomy Observatory of the Radio Institute of the National Academy of Sciences of Ukraine since 1986. The telescope is an element of a decameter long-base interferometer – the radio telescopes which are located across the territory of Ukraine from west to east. The URAN-4 consists of antenna and upgraded radiometer. Antenna consists of 128–element with phased array with dimensions of 232.5 x 22.5 m. The telescope operates in the 10 – 30 MHz range. Its receiving equipment is capable of separating two polarization components of the received signal. The radiation pattern of the radio telescope is 2,7x22 degrees at 25 MHz. The resolution of 2 seconds is realized in the interferometer mode. The instrumental complex of the radio telescope includes the upgraded device for controlling its operation. This device is made in the form of a separate unit. The ATMEL AT90S8515 microcontroller with registers and a communication circuit between the unit and the computer are mounted in it. The discrete movement in space of the antenna's directional pattern and sets the required attenuation in the attenuator during calibration are carried out with the upgraded controlling device at a given time during the observation period. The controlling device also allows adjust the current time of the computer using GPS.

Low pilot overhead channel estimation for CP‐OFDM‐based massive MIMO OTFS system

In high-speed mobile scenarios, due to the high-speed relative motion between transmitter and receiver, the high Doppler frequency shift interferes with the inter-subcarrier orthogonality in orthogonal frequency-division multiplexing (OFDM) systems. Therefore its performance is significantly degraded. Recently, orthogonal time–frequency space (OTFS) is considered as an effective alternative scheme to OFDM for time-varying channels. As with OFDM-massive multiple input multiple output (MIMO) systems, downlink channel estimation is necessary for OTFS-massive MIMO systems to improve the spectral efficiency in frequency-division duplex (FDD) mode without channel reciprocity. Here, first the cyclic prefix -OFDM-based massive MIMO OTFS system channel with antenna directivity pattern is analyzed, and transform the burst sparsity in the angle domain into block sparsity by using non-uniform Fourier transform (NUFT). Furthermore, to solve the problem that the pilot overhead grows linearly with the number of antennas, we propose a three-dimensional (3D) dynamic support detect (DSD) algorithm. Compared with the traditional OMP algorithm, and the 3D-structured orthogonal matching pursuit algorithm, simulation results demonstrate the proposed DSD algorithm has higher channel estimation accuracy, and lower pilot overhead.

Investigation of the Directional Characteristics of the Antenna of the Satellite Earth Station Using the Spiral Scanning Method

Results of earth station antenna experimental studies of satellite communication were shown. This antenna looks like two-mirror construction designed by Cassegrain circuit with parabolic reflector, which diameter is 1.2 m. This results made with help of spherical scanner by spiral scanning method. Antenna directional patterns were constructed. Deviation reasons of the measured directional characteristics from the calculated ones were analyzed

A Link Quality Estimation-Based Beamforming Training Protocol for IEEE 802.11ay MU-MIMO Communications

The multi-user multiple-input-multiple-output (MU-MIMO) beamforming training (BFT) enables an access point (AP) and multiple stations (STAs) to determine appropriate directional antenna patterns; to this end, the AP transmits multiple action frames to the STAs during the MU-MIMO BFT. However, if the antenna weight vectors (AWVs) are determined to transmit the action frames inefficiently, this could lead to unnecessary transmissions, which could increase the BFT time. To mitigate the signaling overhead, the schemes used in our previous work employed AWVs, which use multiple beams simultaneously to transmit the action frames. Nevertheless, these existing schemes are still adversely affected by redundant transmissions because these schemes overlook the transmit diversity gain obtained from multi-beam concurrent transmission. Therefore, in this study, we propose a novel transmit antenna configuration scheme that mitigates the signaling overhead by considering the transmit diversity of the inter-symbol interference (ISI) channel incurred when multiple beams are used simultaneously. Our proposed scheme determines each candidate antenna weight vector (AWV) using multiple beams and efficiently identifies the STAs within reach of the corresponding multi-beam concurrent transmission. The numerical and simulation results demonstrate that our proposed scheme shortens the BFT time in comparison with existing schemes.