Antenna Diagram Research Articles

Modeling of Some Classes of Extended Oscillators: Simulations, Algorithms, Generating Chaos, and Open Problems

In this article, we propose some extended oscillator models. Various experiments are performed. The models are studied using the Melnikov approach. We show some integral units for researching the behavior of these hypothetical oscillators. These will be implemented as add-on sections of a thoughtful main web-based application for researching computations. One of the main goals of the study is to share the difficulties that researchers (who are not necessarily professional mathematicians) encounter in using contemporary computer algebraic systems (CASs) for scientific research to examine in detail the dynamics of modifications of classical and newer models that are emerging in the literature (for the large values of the parameters of the models). The present article is a natural continuation of the research in the direction that has been indicated and discussed in our previous investigations. One possible application that the Melnikov function may find in the modeling of a radiating antenna diagram is also discussed. Some probability-based constructions are also presented. We hope that some of these notes will be reflected in upcoming registered rectifications of the CAS. The aim of studying the design realization (scheme, manufacture, output, etc.) of the explored differential models can be viewed as not yet being met.

Analysis and modeling of radio propagation fading characteristics in tunnel construction

With the development of underground rail transit, the concept of intelligent tunnel construction has been proposed and promoted. High-quality networking during tunnel construction is a prerequisite for this, making it highly urgent to establish networking during tunnel construction. When studying intra-tunnel networking, it is necessary to consider the propagation characteristics of radio waves in the tunnel. In this paper, according to the actual needs of engineering in tunnel construction and the characteristics of tunnel scenes, an improved ray tracing method is proposed, which considers the type and installation position of antennas, transceiver frequency band and power in channel modeling, and proposes a field strength calculation method under different coordinate systems according to the characteristics of straight and curved segments during tunnel construction. In addition, the propagation characteristics of radio waves in dynamic tunnel construction scenarios are quantitatively analyzed. In this paper, by establishing antenna diagram, two-dimensional and three-dimensional models of tunnels, the computer simulation method is applied to compare with the improved algorithm, and the results have good consistency, in addition, the improved algorithm does not require a lot of modeling work in the early stage, and has high applicability and portability. Not only that, this paper also makes actual measurements of the subway under construction in Zhengzhou, China in different scenarios, and verifies the effectiveness of the method.

Satellite to buoy IoT communications in the Arctic Ocean

Internet of things (IoT), to Arctic Ocean areas using Low Earth Orbit (LEO) satellites for communication to and from sensor units on the sea, has become increasingly important. It is challenging to close the link budget from a buoy on sea to a LEO satellite due to restrictions on the availability of power in such installations. Phenomena as scattering from the sea surface and small-scale fading, ionospheric scintillations, diffraction loss at low elevation angles, and power availability in small LEO satellites and models for analysis are described. It is of great importance to have a radio wave propagation model that accurately predicts path loss between an installation on the sea and a LEO satellite taking all loss mechanisms into account. In this paper, a path-loss model for satellite to buoy communications over the sea is described. In this model, maritime propagation phenomena in the radio link include free space loss, scintillation loss caused by the ionosphere, diffraction loss at low elevation angle, and scattering at the sea surface depending on the wave height and small-scale fading. Furthermore, a buoy on the sea surface with strong angular movement will cause a varying receive signal level depending on the antenna diagram. These phenomena are assessed. A link budget for the frequencies 433, 868, and 3,400 MHz is calculated for a LEO satellite at a height of 800 km.

Design and Development of MIMO Antenna for Wireless Communications

A high-isolation eight-antenna multi-input multi- output (MIMO) array running in the 3.5 – 3.6 GHz band for future smartphones is proposed. Here, a novel balanced open-slot antenna is designed as an array antenna element, in which this antenna diagram can yield a balanced slot mode (with decreased ground effects) that can enhance the isolation between two adjoining enter ports. Furthermore, by means of meticulously arranging the positions of the eight antenna elements, proper polarization variety can additionally be correctly achieved, which similarly mitigates the coupling between antenna elements. A prototype used to be manufactured to validate the simulation. A excellent impedance matching (return loss >10 dB), excessive isolation(>17.5 dB), high complete effectivity (>63%), and low envelope correlation coefficient (ECC, <0.05) had been measured throughout the preferred operation bandwidth.

A Combined Antijamming and Antispoofing Algorithm for GPS Arrays

The Global Positioning System (GPS), with its accurate positioning and timing information, has become a commonly used navigation instrument for many applications. However, it is susceptible to intentional interference such as jamming and spoofing. The conventional antijamming GPS receiver fails to work in a combined jamming and spoofing attack scenario. To solve the problem, a combined antijamming and antispoofing algorithm for a GPS receiver based on an antenna array is proposed. In this method, the jamming is eliminated by subspace projection, and then a compressed sensing framework is adopted to obtain the direction of arrival (DOA) of the despreading satellite navigation signal and detect the spoofing signal. According to the DOA of the authentic and spoofing signals, the receiver uses adaptive multibeamforming to concurrently achieve the undistorted reception of the authentic satellite signal and the suppression of the spoofing. We analyse three aspects of algorithmic performance: the antenna array direction diagram, the spoofing detection and the acquisition results. The simulation results and their analysis preliminarily show that the proposed method can detect and suppress GPS jamming and spoofing effectively.

Refraction and Faraday rotation in the incoherent scatter radar technique

AbstractIn this paper we consider the radiolocation equation for the incoherent scatter radar (ISR) method; the equation accounts for refraction effect and Faraday rotation in the VHF frequency domain. Our research shows that we cannot ignore refraction in processing the incoherent scatter data when lag‐product is used to obtain the ionospheric characteristics. Effect of refraction can explain some uncertainties that arise during processing and interpretation of the ISR data. This effect shows that together with the “ion line” of incoherent scatter spectrum, a relatively small “electron line” also plays a significant role in forming the ionosphere response. The “electron line” behaves as an additional “radar induced” wideband radiolocation signal affected by refraction and Faraday rotation; it depends on the ionosphere temperature and ion composition. The presence of a wideband “electron line” produces specific distortions of the ISR spectrum during 3D‐forming of the ionosphere response inside the ISR antenna diagram pattern. During testing, we found that the signal from the ISR “electron line” can be measured at much higher altitudes comparing to the “ion line.” Hence, to improve the incoherent scatter technique, we can take the “electron line” and refraction into account.

Investigating the ionosphere response to exhaust products of “Progress” cargo spacecraft engines on the basis of Irkutsk Incoherent Scatter Radar data

The FSUE Central Research Institute of Machine Building (TsNIIMash), Rocket and Space Corporation “Energia”, and Institute of Solar-Terrestrial Physics of Siberian Branch of Russian Academy of Sciences (ISTP SB RAS) jointly conducted the active space experiment “Radar-Progress” in 2007–2015. During this experiment, we used the Irkutsk Incoherent Scatter Ra-dar to study space-time characteristics of ionospheric disturbances generated by exhaust products of “Pro-gress” cargo spacecraft engines. As the basic effect dur-ing exhaust product injection we consider the formation of new centers for recombination of ambient iono-spheric ions O+ on molecules of water and carbon diox-ide. This produces an ionization “hole” in the region of injection. In nighttime conditions when the majority of experiments were performed, this hole was filled by hydrogen ions from the plasmasphere, thus the ion composition in the vicinity of the hole and incoherent scatter spectra were changed. For successful obser-vation of the ionization hole dynamics, the critical fac-tors are the degree of radar antenna diagram filling by exhaust products and the velocity of the thermospheric neutral wind, which makes exhaust gases move from the antenna diagram. These two factors lead to poor repeatability of successful experiments. Successful experiments recorded a decrease in electron density up to 35 % in the hole that existed for 30 min. The lifetime of the region with high concentration of H+ ions can be as long as one hour.

Исследование реакции ионосферы на продукты горения топлива при работе двигателей транспортных грузовых кораблей серии «Прогресс» по данным Иркутского радара некогерентного рассеяния

The FSUE Central Research Institute of Machine Building (TsNIIMash), Rocket and Space Corporation “Energia”, and Institute of Solar-Terrestrial Physics of Siberian Branch of Russian Academy of Sciences (ISTP SB RAS) jointly conducted the active space experiment “Radar-Progress” in 2007–2015. During this experiment, we used the Irkutsk Incoherent Scatter Radar to study space-time characteristics of ionospheric disturbances generated by exhaust products of “Progress” cargo spacecraft engines. As the basic effect during exhaust product injection we consider the formation of new centers for recombination of ambient ionospheric ions O+ on molecules of water and carbon dioxide. This produces an ionization “hole” in the region of injection. In nighttime conditions when the majority of experiments were performed, this hole was filled by hydrogen ions from the plasmasphere, thus the ion composition in the vicinity of the hole and incoherent scatter spectra were changed. For successful observation of the ionization hole dynamics, the critical factors are the degree of radar antenna diagram filling by exhaust products and the velocity of the thermospheric neutral wind, which makes exhaust gases move from the antenna diagram. These two factors lead to poor repeatability of successful experiments. Successful experiments recorded a decrease in electron density up to 35 % in the hole that existed for 30 min. The lifetime of the region with high concentration of H+ ions can be as long as one hour.

Near- and Far-Field Characterization of Planar mm-Wave Antenna Arrays with Waveguide-to-Microstrip Transition

We present the design and characterization of planar mm-wave patch antenna arrays with waveguide-to-microstrip transition using both near- and far-field methods. The arrays were designed for metrological assessment of error sources in antenna measurement. One antenna was designed for the automotive radar frequency range at 77 GHz, while another was designed for the frequency of 94 GHz, which is used, e.g., for imaging radar applications. In addition to the antennas, a simple transition from rectangular waveguide WR-10 to planar microstrip line on Rogers 3003™ substrate has been designed based on probe coupling. For determination of the far-field radiation pattern of the antennas, we compare results from two different measurement methods to simulations. Both a far-field antenna measurement system and a planar near-field scanner with near-to-far-field transformation were used to determine the antenna diagrams. The fabricated antennas achieve a good matching and a good agreement between measured and simulated antenna diagrams. The results also show that the far-field scanner achieves more accurate measurement results with regard to simulations than the near-field scanner. The far-field antenna scanning system is built for metrological assessment and antenna calibration. The antennas are the first which were designed to be tested with the measurement system.

The indirect self-tuning method for constructing radio environment map using omnidirectional or directional transmitter antenna

In this paper, we propose a new indirect method for constructing the radio frequency layer of radio environment map (RF-REM) called self-tuning method (STM). The proposed STM takes into account the characteristics of the operating environment and performs estimation of the transmitter parameters, i.e. its location, antenna diagram, antenna azimuth, transmit power, as well the parameters of the propagation model to obtain the best match between the available measurements and the predicted signal levels. We compare STM to several most often considered existing methods using different numbers of randomly distributed measurements, which could in practice be obtained in a participatory-like manner. The performance evaluation of the methods is performed in terms of averaged root mean square error ( $\overline {\text {{RMSE}}}$ ) and 95% confidence interval (CI) calculated between the constructed RF-REMs and the reference RF-REM, as well as in terms of false alarm zone ratio (FAZR) and correct detection zone ratio (CDZR 1). The analysis shows the robustness of the STM to various spatial distributions of measurements and its fast convergence and low residual root mean square error compared to the inverse distance weighted (IDW) method, the inverse distance square weighted method (IDW2), the Kriging method, and the location estimation-based method (LIvE).

Research and Analysis about Array Antennas in Mobile Communications

Because the direction of a single antenna is limited, and for strengthening the direct radiant ability of the antenna, we will put the weaker direction antennas together in some way to constitute an antenna array system. The antenna array is also called the array antenna or a disperse antenna array. The antenna cell can be the symmetry center-fed dipole, the aperture antenna, the circle antenna or other forms of the antennas whose direction are limited. In practice, the antenna array is almost constituted of similar antenna cells. I have mainly completed the antenna array direction diagram in conditions of some kinds of parameters. And at last, I get the useful results for practice. This also provides theories basis for the analysis of smart antenna.

Analysis of a folded reflect-array antenna using particle swarm optimization

In this paper, a method for design and optimization of folded reflect-array antennas is proposed based on particleswarm optimization (PSO). In addition to such a powerful optimization algorithm, two further requirements have to be fulfilled. The first one is a good and fast algorithm for the exact prognosis of the far-field radiation diagram, resulting from a specific element configuration on the reflector. Additionally, a good choice of the fitness function for the evaluation of the resulting radiation diagrams is necessary. In both, reflect-array-related aspects such as phase truncation, reflection losses, and cell discontinuities have to be considered. Antenna optimization based on this technique is presented in this paper at the example of two 77 GHz folded reflect-array antennas. The efficiency of this approach is demonstrated with these examples, and the results are verified by measurement, showing an excellent agreement with the specifications of the diagram masks. The implemented tool, including a realistic antenna diagram preview, allows the investigation of the design parameters’ influence on the antenna performance, such as illumination amplitude, high substrate losses, and phase truncation.

Abnormal Radiation Pattern of Metamaterial Waveguide

The idea to inverse the radiation pattern of the microwave antenna due to appli- cation of the isotropic metamaterial screen with negative refractive index in S band is demon- strated at the flrst time in this investigation. The electromagnetic simulation of waveguide antenna patterns by moment's methods demonstrates an agreement modeling antenna patterns with measured antenna diagrams for values of metamaterial efiective parameters (permittivity and permeability) extracted from measured S-parameters of metamaterial sheet sample.

Investigations of short-scale fluctuations in a helicon plasma by cross-correlation enhanced scattering

Correlation enhanced scattering (CES) near the upper hybrid resonance has been applied for studying small-scale plasma density fluctuations excited by the rf fields in a helicon discharge. The turbulent fluctuations are diagnosed for conditions where the electron plasma frequency exceeds the electron cyclotron frequency considerably. The frequency and wave number spectra of the fluctuations are measured both in the plasma core as well as in outer region of the helicon discharge. The spectral measurements evidence the short-scale fluctuations to originate from a parametric decay instability. The low-frequency fluctuations obey the ion-sound dispersion relation while the lower sideband of the helicon wave frequency satisfies the Trivelpiece–Gould wave dispersion relation. In order to gain more insight in the experimental results and, in particular, to estimate the fluctuation level the backscattering process is analyzed both numerically and analytically for high-density plasma conditions. A fully electromagnetic model was developed that takes into account the radial density distribution of the plasma column as well as the antenna diagram of the rectangular emitting/receiving horn. Using this model the relative amplitude of ion-sound density fluctuations in the core of the helicon discharge is estimated as 11%. The role of nonlinear effects on formation of the scattering spectra due to the high fluctuation level in the plasma center is discussed. The findings also demonstrate that the CES diagnostic can be applied to diagnose fluctuations in spherical tokamak plasmas where the probing conditions resemble those of high-density helicon discharges.

Spatial and wavenumber resolution of Doppler reflectometry

Doppler reflectometry spatial and wavenumber resolution is analysed within the framework of the linear Born approximation in the slab plasma model. An explicit expression for its signal backscattering (BS) spectrum is obtained in terms of the wavenumber and frequency spectra of turbulence, which is assumed to be radially statistically inhomogeneous. The scattering efficiency for both back (BS) and forward scattering (FS) (in the radial direction) is introduced and shown to be inversely proportional to the square of the radial wavenumber of the probing wave at the fluctuation location, thus making the spatial resolution of diagnostics sensitive to the density profile. It is shown that in the case of FS additional localization can be provided by the antenna diagram. It is demonstrated that in the case of BS the spatial resolution can be better if the turbulence spectrum at high radial wavenumbers is suppressed. The improvement in Doppler reflectometry data localization by a probing beam focusing on the cut-off is proposed and described. It is shown that Doppler reflectometry data interpretation based on the obtained expressions is possible.

Comparison of Measurements With Prediction Methods for Propagation by Diffraction at 88–108 MHz

Three methods for predicting attenuation due to diffraction are tested against a large database of 115 614 measurement points, representing 115 614 different path profiles of 100-m horizontal resolution, and vertical root mean square error of about 6 m. The signal level at each geographic measurement point is calculated as the median of about 40 basic measurements, and the measurement database is thus reduced from about four million basic measurements. The mobile measurements are taken from main FM (88-108 MHz) broadcasting emitters located in southern Norway, and the corresponding broadcasting antenna diagrams have been measured by helicopter. Path profiles are categorized by number of terrain obstructions between emitter and receiver, in order to study their effect on each propagation loss method. The current ITU method and Picquenard's construction, with a variable number of included terrain obstructions, are compared with the measurements, and difference statistics are calculated. A particular version of Picquenard's construction is shown to be better than the current ITU method in terrain of Norwegian type. This new method is, in contrast to the ITU method, within the estimated expected errors resulting from using Norwegian digital terrain elevation data.

Definition of a parameter for a typical specific absorption rate under real boundary conditions of cellular phones in a GSM networkd

Abstract. Using cellular phones the specific absorption rate (SAR) as a physical value must observe established and internationally defined levels to guarantee human protection. To assess human protection it is necessary to guarantee safety under worst-case conditions (especially maximum transmitting power) using cellular phones. To evaluate the exposure to electromagnetic fields under normal terms of use of cellular phones the limitations of the specific absorption rate must be pointed out. In a mobile radio network normal terms of use of cellular phones, i.e. in interconnection with a fixed radio transmitter of a mobile radio network, power control of the cellular phone as well as the antenna diagram regarding a head phantom are also significant for the real exposure. Based on the specific absorption rate, the antenna diagram regarding a head phantom and taking into consideration the power control a new parameter, the typical absorption rate (SARtyp), is defined in this contribution. This parameter indicates the specific absorption rate under average normal conditions of use. Constant radio link attenuation between a cellular phone and a fixed radio transmitter for all mobile models tested was assumed in order to achieve constant field strength at the receiving antenna of the fixed radio transmitter as a result of power control. The typical specific absorption rate is a characteristic physical value of every mobile model. The typical absorption rate was calculated for 16 different mobile models and compared with the absorption rate at maximum transmitting power. The results confirm the relevance of the definition of this parameter (SARtyp) as opposed to the specific absorption rate as a competent and applicable method to establish the real mean exposure from a cellular phone in a mobile radio network. The typical absorption rate provides a parameter to assess electromagnetic fields of a cellular phone that is more relevant to the consumer.

Influence of the antenna diagram on a stellar interferometer that is suffering from telescope-pointing errors.

We report our experimental investigations of the influence of differential telescope-pointing errors on data corruption in an optical stellar interferometer. This effect was investigated theoretically as a function of the telescope antenna diagram, which depends on the aperture diameter. Using a laboratory breadboard consisting of a three-telescope array, we carried out the experiments with various aperture diameters and complex objects. The results matched the simulation and demonstrate that, when there is no error in pointing, a large aperture size induces correctible error but that, with a pointing error, data corruption becomes critical. In both cases, the larger the apertures, the more corrupt the data.

Soil Moisture (Water-Content) Assessment by an Airborne Scatterometer: The Chernobyl Disaster Area and the Negev Desert

Soil water content is an important component that influences meso- and microscale processes. The agricultural capacity of a site is directly affected by soil water content and it is especially important in arid regions. In temperate and humid regions, soil water content is important in determining flood risks. Environmentally, soil water content will influence the risk of carrying pollutants through the soil. For these reasons, a scatterometer was developed as a remote sensor for mapping soil water content. The scatterometer is frequency modulated using a continuous wave. This scatterometer operates at nadir with a wide antenna diagram of 10°. Measurements were conducted in two environments with different implications. The first was in the Chernobyl nuclear disaster area and the second in the Negev desert. Results show a good correlation between soil water content and the amplitude of the returned signal measured by the scatterometer. Thus, the scatterometer provides an efficient tool for mapping soil water content. The long wavelength (P-band) of λ=68 cm makes this scatterometer more sensitive to soil water content and less affected by surface roughness than scatterometers operating at shorter wavelengths.

Spectrum Utilization in a Digital Radio-Relay Network

Digital radio-relay networks in urban areas have been proposed to connect telephone switching centers and to develop new broad-band services. This paper describes a methodology for evaluating the "amount" of radio spectrum "used" by a node in the network, on the basis of general criteria and definitions for spectrum use and efficiency. Several factors influencing the spectral efficiency of the system (antenna diagrams, propagation characteristics, network density, modulation techniques) are taken into account in the proposed approach. Some examples of application, allowing the assessment of trends and possible tradeoffs in spectrum utilization are given. Extensions and other applications of this approach are suggested.