Receiving Antenna Pattern Research Articles

Оценка влияния непреднамеренных помех на линию вверх канала управления беспилотного летательного аппарата

Modern unmanned aerial vehicles (UAVs) are becoming increasingly important in solving many problems, for example, when delivering goods, video recording, conducting aerial monito¬ring of the condition of remote and hard-to-reach objects, etc. When solving these problems, UAVs may experience unintentional interference from other radio-electronic equipment (RES). Currently, virtually no attention is paid to issues related to the analysis of the quality of operation of civilian UAVs in the presence of unintentional interference from other civil electronic distribution systems. The proposed method is intended to somewhat fill this gap. It is based on the assumption that a decrease in the quality of reception of useful signals in the radio control channel below a certain value due to the low signal-to-noise ratio at the input of the UAV receiver in its bandwidth will lead to errors in the UAV flight control commands and the wrong starting of on-board specialized equipment. The level of the interfering signal delivered to the UAV receiver from a stationary land-based transmitter depends on interaction areas between transmitter and receiver antenna patterns. A method for determining these areas, consisting of main and side lobes of antenna patterns, is proposed. This method can be used to solve the more general problem of analyzing the electromagnetic compatibility of UAV radio stations, control panels and ground-based electronic devices, as it is an integral part of solving this problem.

Improving GNSS-R Ocean Wind Speed Retrieval for the BF-1 Mission Using Satellite Platform Attitude Measurements

The receive antenna gain is needed to accurately calibrate the normalized bi-statistic radar cross section (NBRCS) measured by the BF-1 mission, which is a global navigation satellite system reflectometry (GNSS-R) constellation of two microsatellites and the first Chinese GNSS-R satellite mission. The instability of the satellite platform is the main cause of receive antenna gain errors. To obtain a high precision gain value, a calibration method that remaps the ocean surface detection location to the receive antenna pattern using satellite platform attitude measurements is proposed in this paper. Thirty-two orbits of Delay Doppler maps (DDMs) data, which were greatly disturbed by the attitude, are selected to test the effectiveness of the proposed algorithm. The accuracy of wind speed retrieval is analyzed, and results show that the data calibration algorithm is effective in reducing the wind speed retrieval error. Compared with the un-calibrated data, the data subjected to the calibration algorithm show a significant improvement of 19.33% in correlation coefficient and average decreases of 30.91% and 42.57% in root mean square error (RMSE) and mean bias error (MBE), respectively. Moreover, the comparison highlights that the influence of the satellite platform attitude disturbance on wind speed retrieval is abated significantly. The proposed approach can effectively improve the quality of GNSS-R measurements, allowing for a better understanding of global weather abnormalities and generally improving weather forecasting.

Моделирование процесса приема собственного радиотеплового излучения земной поверхности

The receiving model of the own soil radiothermal radiation by a bipolarized microwave radiometer when remote sensing the soil moisture from an unmanned aerial vehicle on low altitude is considered. The simulation is carried out taking into account the receiving antenna pattern with side lobes. The height, speed of the carrier and the main lobe axis angle are taken into account. The main parameters of the microwave radiometer for remote determination of portraits of moistened soils are given. The Earth's surface is modeled by a two-dimensional distribution function of the soil permittivity on the thickness of the near-surface layer and a deeper layer with a different permittivity value. The two-dimensional permittivity distribution function represents as "checkerboard" with a periodic change in the permittivity of the soil by "cells". Both the proper radiothermal radiation of the soil and the relict sky radiation of the celestial sphere, re-reflected by the earth's surface, are taken into account. The perspective of using the simulation results to optimize the parameters of the radiometer and remote sensing system according to the criterion of maximum sensitivity of the system to variations in soil moisture content is analyzed.

Large Intelligent Surface-Based Generalized Index Modulation

Novel communication technology based on large intelligent surface (LIS), which manipulates the phase of the incident waves to enhance the communication quality, has been proposed as a promising candidate for future wireless communication systems and standards. In order to improve the spectral efficiency, the concept of LIS assisted communications has been introduced into the realm of index modulation (IM) recently. In this letter, a practical LIS based generalized spatial modulation (LIS-GSM) scheme is proposed by modulating the transmit signals through both transmitter and LIS jointly while designing the pattern of receive antennas in a more flexible way. Furthermore, a unified framework for the derivation of the theoretical average bit error rate (ABER) based on the maximum likelihood detector is also presented. Simulation results demonstrate that LIS-GSM is more robust in terms of ABER as well as receive antenna pattern compared with conventional LIS-SM.

Improving CyGNSS-Based Land Remote Sensing: Track-Wise Data Calibration Schemes

Cyclone Global Navigation Satellite System (CyGNSS) data have been used for generating several intermediate products, such as surface reflectivity (Γ), to facilitate a wide variety of land remote sensing applications. The accuracy of Γ relies on precise knowledge of the effective instantaneous radiative power (EIRP) of the transmitted GNSS signals in the direction of the specular reflection point, the precise knowledge of zenith antenna patterns which in turn affects estimates of EIRP, the good knowledge of receive antenna patterns etc. However, obtaining accurate estimates on these parameters completely is still a challenge. To solve this problem, in this paper, an effective method is proposed for calibrating the CyGNSS Γ product in a track-wise manner. Here, two different criteria for selecting data to calibrate and three reference options as targets of the calibrating data are examined. Accordingly, six calibration schemes corresponding to six different combinations are implemented and the resulting Γ products are assessed by (1) visual inspection and (2) evaluation of their associated soil moisture retrieval results. Both visual inspection and retrieval validation demonstrate the effectiveness of the proposed schemes, which are respectively demonstrated by the immediate removal/fix of track-wisely noisy data and obvious enhancement of retrieval accuracy with the calibrated Γ. Moreover, the schemes are tested using all the available CyGNSS level 1 version 3.0 data and the good results obtained from such a large volume of data further illustrate their robustness. This work provides an effective and robust way to calibrate the CyGNSS Γ result, which will further improve relevant remote sensing applications in the future.

Passive Bistatic Radar Detection Performance Prediction Considering Antenna Patterns and Propagation Effects

This article deals with the problem of detection performance prediction for passive bistatic radars that use illuminators of opportunity, such as radio or television transmitters. First, a simplistic free-space propagation model is introduced. Next, the effects of the transmitter and receiver antenna patterns are analyzed. Then, the influence of the pattern-propagation factor is investigated, considering the elevation patterns, multipath, and diffraction. The performance prediction of the free-space model and a more realistic model with antenna patterns and propagation effects are compared. The variation of the echo power level caused by the propagation effects predicted in the simulations is verified with real data acquired with an FM-based passive radar. The presented approach allows for a more realistic prediction of the passive radar performance to be achieved in comparison with a simple free-space propagation assumption. Some examples of passive radar performance optimization using the introduced methodology are presented.

능동위상배열안테나의 부엽제거기 적용 시 모노펄스 왜곡 보정

The sidelobe canceler is used to remove the received sidelobe jamming signal on the receive antenna pattern. The sidelobe canceler does not use the main antenna but is constructed using an auxiliary antenna. The sidelobe canceler generates a sidelobe cancel beam of the auxiliary antenna using the received signal of the main and auxiliary antennas. The main beam pattern that cancels the jamming signal is generated by combining the main antenna beam and sidelobe cancel beam pattern. However, in the case of a jamming signal received near the main lobe of the main antenna, distortion occurs in the main antenna pattern by applying a sidelobe canceler. Owing to this distortion, the monopulse slope characteristic for the angle estimation of the target is also distorted. This paper proposes a simple and effective method using antenna measurement data (e.g., near-field chamber measured data) to compensate for the monopulse slope distortion that occurs when the sidelobe canceler is applied. The proposed method was verified using simulations wherein the improvement in the distorted monopulse slope characteristics was confirmed.

Добова залежність ослаблення радіосигналу Х-діапазону на трасі «геостаціонарний штучний супутник Землі – Земля»

Subject and Purpose. Statistical data on how the satellite signal level varies with changes in the characteristics of tropospheric layers and lower-troposphere hydrometeors serve designers a useful guide in the development of systems for diagnosing weather conditions and hydrometeor characteristics. The aim of the work is to generalize results from the long-term research into daily dependences of X-band radio signal attenuation between the geostationary satellite and Earth terminals. On this basis it is possible to find relationship between signal level changes at the point of reception and geophysical atmospheric agents. Methods and methodology. A receiving measuring and recording complex developed by the authors is employed for the purpose of establishing relationship between geostationary satellite signal level at the receiving point and geophysical atmospheric agents. Results. A block-diagram of the receiving measuring and recording complex is presented, its operation described. Geometric parameters of the radio signal path of propagation have been considered. Signal level measuring results obtained using a Hot Bird geostationary satellite in the period from 03 to 17 January 2019 have been generalized and interpreted. Conclusions. X-band radio signal attenuation on the path from a geostationary satellite to the Earth has a daily dependence. The radio signal level variations are not connected with alterations in spatial and technical parameters of the geostationary satellite or receiving equipment. The day and night changes in radio signal level are attributed to different daytime durations and different angles of sunbeam (including twilight) incidence on tropospheric areas associated with the receiving antenna pattern in the propagation direction, which entails changeable temperature regime and moisture content in these areas. Geophysical agents in the highest tropospheric layers insolated from far beyond the horizon can also be interpreted for long-distance tropospheric radio wave propagation in these tropospheric regions.

GNSS scale determination using calibrated receiver and Galileo satellite antenna patterns

The reference frame of a global terrestrial network is defined by the origin, the orientation and the scale. The origin of the ITRF2014 is defined by the ILRS long-term solution, the orientation by no-net rotation conditions w.r.t. the previous reference frame (ITRF2008), and the scale by the mean values from global VLBI and SLR solution series (Altamimi et al. in J Geophys Res Solid Earth 121:6109–6131, 2016). With the release of the Galileo satellite antenna phase center offsets (PCO) w.r.t. the satellites center of mass (GSA in Galileo IOV and FOC satellite metadata, 2019) and the availability of new ground antenna calibrations for GNSS receivers, based on anechoic chamber measurements or on robot calibrations, GNSS global network solutions qualify to contribute to the scale determination of terrestrial networks, as well. Our analysis is based on global multi-GNSS solutions of the years 2017 and 2018 and may be seen as “proof of concept” for the contribution of GNSS data to the scale determination of the terrestrial reference frame. In a first step, the currently used Galileo PCO estimations (Steigenberger et al. in J Geod 90:773–785, 2016) are compared to the released PCO values, which show discrepancies on the decimeter-level. Eventually, the published Galileo PCOs are used in an experimental solution as known values. GNSS-specific PCOs are estimated, as well, for GPS and GLONASS, together with the “standard” parameters set up in global GNSS solutions. From the estimated network coordinates, a time series of daily scale parameters of the terrestrial network is extracted, which shows an offset of the order of 1 ppb (parts per billion, corresponding to a height difference of 6.4 mm on the Earth’s surface) w.r.t. to the ITRF2014 network and an annual variation with an amplitude of about 0.3 ppb.

On Over-the-Air Testing for Devices With Directional Antennas

This paper investigates the impact of devices under test (DUTs) with directional antennas on the recreated channel in the over-the-air (OTA) testing for massive multiple-input multiple-output (MIMO) devices using prefaded signal synthesis (PFS) technique. Assuming the uplink in real radio environments, the directional receiver (Rx) antenna patterns would affect the gains in different incoming directions, thereby affecting the spatial characteristics of the target channel. A typical multi-probe anechoic chamber (MPAC) setup for massive MIMO base stations (BSs) is studied, where a limited number of probe antennas are distributed over the probe wall to emulate the target channel by proper probe weighting. The directional antenna patterns would have nonnegligible effects on the emulated spatial characteristics which may become inaccurate for DUTs with directional antennas and thus need to be re-examined. Therefore, the reconstructed channel with the PFS technique will be investigated under the MPAC setup in this paper, with particular focus on the DUTs with directional antennas. The deviations between the covariance matrix of the Rx antennas under the target channel and the covariance matrix under the reconstructed channel are used as the metric to evaluate the performance of the reconstructed channel, and the optimal probe weights are also re-determined. Furthermore, given beamforming capability of massive MIMO BSs, the impact of the BS antenna patterns on angular spectrum is investigated as well. In addition, since the reconstructed channel needs to not only reflect the spatial characteristics of Rx antennas but also reflect the spatial characteristics of transmitter antennas and propagation environment, the end-to-end channel capacities are evaluated. Simulation results under various scenarios show that the accuracies of the reconstructed channel in terms of spatial correlation, angular spectrum and channel capacity can be improved by using the re-optimized probe weights when directional antenna patterns of the DUTs are taken into account.

Characterizing Background Signals and Noise in Spaceborne GNSS Reflection Ocean Observations

This letter analyzes the background signals and thermal noise received over ocean scenes in spaceborne global navigation satellite system (GNSS)-reflectometry (GNSS-R) remote sensing using observations from the cyclone GNSS (CYGNSS) constellation. The measured noise floor contains a stable and predictable radiometric thermal noise component and a more variable background signal component from unintended specular reflections within the CYGNSS receive antenna pattern from all GNSS satellite constellations (GPS, Galileo, GLONASS, Beidou, and all SBAS). The presence of SBAS reflections, in particular, is evident in the noise floor measurements, especially the U.S. wide area augmentation system (WAAS) satellites. The results show that the impact is negligible, since background signal contributions by other GNSS transmitters affect both the “signal” and “noise” portions of CYGNSS’s delay Doppler map measurements, and therefore cancel when the measured noise floor is subtracted from the desired signal. The potential increase in measurement uncertainty introduced by any residual background signal to the CYGNSS calibration is analyzed.

Troposcatter Deviation Losses Study for OTH Microwave Propagation

Microwave over-the-horizon propagation via troposcatter mechanism is a valuable candidate for passive sensing of remote radiation source applications, e.g., electronic reconnaissance. The result from the misalignment between target emitting and the system receiving antenna, the additional deviation losses in azimuthal and elevation angle are indispensable to model the receiving antenna pattern as well as the arrival scattering signal level. Based on the scatter transfer function, the deviation losses are derived assuming Gaussian antenna patterns and verified by existing measured data from the 1950s. Finally, potential application values of the deviation losses in electronic reconnaissance are provided.

First step toward a synthetic diagnostic for magnetic fluctuation measurements using cross-polarization scattering on DIII-D

Cross-polarization scattering (CPS) provides localized magnetic fluctuation ( ) measurements in fusion plasmas based on the process where scatters electromagnetic radiation into the orthogonal polarization. The CPS system on DIII-D utilizes the probe beam of a Doppler backscattering (DBS) diagnostic combined with a cross-view CPS receiver system, which allows simultaneous density and measurements with good spatial and wavenumber coverage. The interpretation of the signals is challenging due to the complex plasma propagation of the DBS probe beam and CPS receive beams. A synthetic diagnostic for CPS is therefore essential to interpret data and perform detailed validation tests of non-linear turbulence simulations. This work reports a first step toward a synthetic diagnostic for CPS utilizing GENRAY, a 3-D ray tracing code, to simulate the propagation of the probe and scattered rays. The local wavenumber is calculated from the local O- and X-mode wavenumbers using the wave vector matching scattering condition. The CPS wavenumber values and spatial locations are determined by a complex consideration that includes the local density and level, receive antenna pattern and orientation, scattering volume, wavenumber values detected at the various scattering centers, and alignment of the magnetic wave vector with the plane perpendicular to the magnetic field. The issue of a spurious CPS signal due to polarization mismatches for launch and receive is also discussed. It is suggested that simultaneous O- and X-mode DBS measurements should be utilized for better understanding of the CPS signal contamination when the cutoff locations for both polarizations are close.

Statistical Evaluation of the Azimuth and Elevation Angles Seen at the Output of the Receiving Antenna

A method to evaluate the statistical properties of the reception angle seen at the input receiver that considers the receiving antenna pattern is presented. In particular, the impact of the direction and beamwidth of the antenna pattern on distribution of the reception angle is shown on the basis of 3D simulation studies. The obtained results show significant differences between distributions of angle of arrival and angle of reception. This means that the presented new method allows assessing the impact of the receiving antenna pattern on the correlation and spectral characteristics at the receiver input in simulation studies of wireless channel. The use of this method also provides an opportunity for analysis of a co-existence between small cells and wireless backhaul, what is currently a significant problem in designing 5G networks.

Small-Scale, Local Area, and Transitional Millimeter Wave Propagation for 5G Communications

This paper studies radio propagation mechanisms that impact handoffs, air interface design, beam steering, and multiple-input multiple-output for 5G mobile communication systems. Knife-edge diffraction (KED) and a creeping wave linear model are shown to predict diffraction loss around typical building objects from 10 to 26 GHz, and human blockage measurements at 73 GHz are shown to fit a double KED model, which incorporates antenna gains. Small-scale spatial fading of millimeter wave (mmWave)-received signal voltage amplitude is generally Ricean-distributed for both omnidirectional and directional receive antenna patterns under both line-of-sight (LOS) and non-line-of-sight (NLOS) conditions in most cases, although the log-normal distribution fits measured data better for the omnidirectional receive antenna pattern in the NLOS environment. Small-scale spatial autocorrelations of received voltage amplitudes are shown to fit sinusoidal exponential and exponential functions for LOS and NLOS environments, respectively, with small decorrelation distances of 0.27-13.6 cm (smaller than the size of a handset) that are favorable for spatial multiplexing. Local area measurements using cluster and route scenarios show how the received signal changes as the mobile moves and transitions from LOS to NLOS locations, with reasonably stationary signal levels within clusters. Wideband mmWave power levels are shown to fade from 0.4 dB/ms to 40 dB/s, depending on travel speed and surroundings.

Особенности модифицированной модели спектральных и энергетических характеристик рассеянных волн с учетом диаграмм направленности приемной и излучающей антенн при бистатическом зондировании морской поверхности

Особенности модифицированной модели спектральных и энергетических характеристик рассеянных волн с учетом диаграмм направленности приемной и излучающей антенн при бистатическом зондировании морской поверхности

Two-Way Pattern Grating Lobe Control for Distributed Digital Subarray Antennas

An approach to controlling the two-way pattern (i.e., the product of the transmitting and receiving antenna patterns) for a distributed digital subarray antenna (DDSA) is presented. Collectively combining periodic widely separated subarrays results in grating lobes (GLs), and they are unwanted because of the ambiguities that accompany them. The approach to GL control presented here involves a combination of conventional suppression methods on the transmitting side and in the digital beamforming on the receiving side, filling the gaps between the subarrays with “virtual” elements, thus forming a contiguous array. Individually, the transmitting and receiving antenna patterns may not have adequate performance, but it is demonstrated that if designed to complement each other, the two-way pattern can achieve ultralow sidelobe performance. The effects of receiving element signal-to-noise ratio (SNR) and errors in calibration are also addressed.

On the Pulse Extension Loss in Digital Beamforming SAR

One of the benefits of synthetic aperture radar (SAR) systems utilizing digital beamforming is the ability to increase the receive power. The relevant SAR technique is known as SCan-On-REceive (SCORE), which steers the receive antenna beam such that it follows the radar pulse echo traversing the ground. This allows the use of a narrow receive beam in elevation, and therefore, the height of the receive antenna can be increased, resulting in a higher gain, which explains the higher receive power. Although advantageous, this technique has some pitfalls, which impose an upper limit on the antenna size and constrain the selection of SAR operation parameters. These limitations (which are often neglected in the system conception) are caused by the pulse extent on the ground and the way it is modulated by the receive antenna pattern. This letter addresses and quantifies the effects caused by the transmit pulse length (here denoted as pulse extension loss) through a rigorous analysis, with the purpose of introducing an important SAR performance figure. Closed expressions are derived for the simplified case of a uniform linear antenna array.

Technical overview of the millimeter-wave imaging reflectometer on the DIII-D tokamak (invited).

The two-dimensional mm-wave imaging reflectometer (MIR) on DIII-D is a multi-faceted device for diagnosing electron density fluctuations in fusion plasmas. Its multi-channel, multi-frequency capabilities and high sensitivity permit visualization and quantitative diagnosis of density perturbations, including correlation length, wavenumber, mode propagation velocity, and dispersion. The two-dimensional capabilities of MIR are made possible with 12 vertically separated sightlines and four-frequency operation (corresponding to four radial channels). The 48-channel DIII-D MIR system has a tunable source that can be stepped in 500 μs increments over a range of 56 to 74 GHz. An innovative optical design keeps both on-axis and off-axis channels focused at the cutoff surface, permitting imaging over an extended poloidal region. The integrity of the MIR optical design is confirmed by comparing Gaussian beam calculations to laboratory measurements of the transmitter beam pattern and receiver antenna patterns. Measurements are presented during the density ramp of a plasma discharge to demonstrate unfocused and focused MIR signals.

Measurements of In-Flight Cross-Track Antenna Patterns of Radar Depth Sounder/Imager

Antenna arrays with low sidelobes in the cross-track direction are needed for sounding and imaging ice-sheets margins including outlet glaciers. Weak radar signals from the ice-bed interface are often masked by off-vertical surface clutter from extremely rough crevassed surfaces in ice-sheet margins. Synthetic aperture radar (SAR) processing can be used to synthesize a large array for reducing clutter in the along-track direction. Low-side-lobe transmit- and receive-antenna patterns must be generated from a limited size array in the cross-track direction. Airborne antenna pattern measurements are critical to verifying pattern characteristics in the presence of a non-ideal ground plane and neighboring aircraft structures, as well as in-flight operational dynamics. In this paper, we describe a set of airborne measurements performed to determine and optimize antenna patterns for the very high frequency (VHF) array used to sound and image polar ice sheets. We measured antenna patterns by flying over a relatively smooth ice surface at an altitude of about 2700 m. The pattern data were obtained by processing the surface echoes with aircraft rolled from left to right over more than five cycles. We also simulated antenna patterns using a three-dimensional computer model of the entire airborne platform and compared with experimental results. The discrepancies between the measured and simulated results are less than 2.7 dB for 85% of the data samples. The measured pattern data will be used to optimize our array processing algorithms.