Articles de revues : « Over The Horizon Radar Sky Wave »

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Saavedra, Zenon, Diego Zimmerman, Miguel A. Cabrera et Ana G. Elias. « Sky-wave over-the-horizon radar simulation tool ». IET Radar, Sonar & ; Navigation 14, n^o 11 (1 novembre 2020) : 1773–77. http://dx.doi.org/10.1049/iet-rsn.2020.0158.

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Ren, Fangyu, Huotao Gao et Lijuan Yang. « Distributed Multistatic Sky-Wave Over-The-Horizon Radar Based on the Doppler Frequency for Marine Target Positioning ». Electronics 10, n^o 12 (18 juin 2021) : 1472. http://dx.doi.org/10.3390/electronics10121472.

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Maritime safety issues have aroused great attention, and it has become a difficult problem to use the sky-wave over-the-horizon radar system to locate foreign targets or perform emergency rescue quickly and timely. In this paper, a distributed multi-point sky-wave over-the-horizon radar system is used to locate marine targets. A positioning algorithm based on the Doppler frequency is proposed, namely, the two-step weighted least squares (2WLS) method. This algorithm first converts the WGS-48 geodetic coordinates of the transceiver station to spatial rectangular coordinates; then, introduces intermediate variables to convert the nonlinear optimization problem into a linear problem. In the 2WLS method, four mobile transmitters and four mobile receivers are set up, and the Doppler frequency is calculated by transmitting and receiving signals at regular intervals; it is proven that the 2WLS algorithm has always maintained a better positioning accuracy than the WLS algorithm as the error continues to increase with a certain ionospheric height measurement error and the Doppler frequency measurement error. This paper provides an effective method for the sky-wave over-the-horizon radar to locate maritime targets.

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Su, H. T., H. Liu, P. Shui et Z. Bao. « Adaptive HF interference cancellation for sky wave over-the-horizon radar ». Electronics Letters 47, n^o 1 (2011) : 50. http://dx.doi.org/10.1049/el.2010.2821.

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Guo, Xin, Jin-Lin Ni et Guo-Sui Liu. « Architecture and signal processing of sky wave over-the-horizon radar ». Radio Science 38, n^o 5 (octobre 2003) : n/a. http://dx.doi.org/10.1029/2002rs002789.

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Hu, Jinfeng, Cao Jian, Chen Zhuo, Huiyong Li et Julan Xie. « Knowledge-Aided Ocean Clutter Suppression Method for Sky-Wave Over-the-Horizon Radar ». IEEE Geoscience and Remote Sensing Letters 15, n^o 3 (mars 2018) : 355–58. http://dx.doi.org/10.1109/lgrs.2017.2787693.

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Thayaparan, Thayananthan, Justin Marchioni, Alison Kelsall et Ryan Riddolls. « Improved Frequency Monitoring System for Sky-Wave Over-the-Horizon Radar in Canada ». IEEE Geoscience and Remote Sensing Letters 17, n^o 4 (avril 2020) : 606–10. http://dx.doi.org/10.1109/lgrs.2019.2928172.

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He, Huan, Yi Chun Pan et Fang Zhi Geng. « Research on Backscattering of Sky Wave from Sea Surface ». Applied Mechanics and Materials 602-605 (août 2014) : 2709–12. http://dx.doi.org/10.4028/www.scientific.net/amm.602-605.2709.

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For a long period, the sky-wave over-the-horizon radar (OTHR) has difficulty in detecting ship under the background of sea clutter, and it is difficult to apply the existing sea clutter model established in surface wave propagation mode to the sky-wave OTHR sea clutter suppression. Therefore, the difference between surface wave and sky wave propagation mode is analyzed firstly, then the scope of grazing angle about sky wave beam is calculated, finally the backscattering coefficients of sky wave from sea surface are derived by perturbation method and the backscattering mechanisms of sky wave from sea surface are analyzed. Results show that the mechanisms observe Bragg scattering mechanism. The backscattering coefficients of sky wave from sea surface which are given in this paper for the first time are significant for sky-wave OTHR sea clutter suppression.

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Chengyu, Hou, Ke Guo, Shi Tiange et Wang Yuxin. « Study on the Detectability of the Sky-Surface Wave Hybrid Radar ». Journal of Applied Mathematics 2014 (2014) : 1–10. http://dx.doi.org/10.1155/2014/602075.

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Working in the HF (high-frequency) band and the transmitter and receiver locating separately, the sky-surface wave hybrid radar both has the capabilities of the OTHR (over-the-horizon radar) and the advantage of the bistatic radar. As the electromagnetic wave will be disturbed by the ionosphere, interfered by the sea clutter and attenuated by the sea surface, the detectability of this radar system is more complex. So, in this paper, we will discuss the problem detailedly. First of all, the radar equation is deduced based on the propagation of the electromagnetic wave. Then, how to calculate the effect of the ionosphere and the propagation loss is discussed. And an example based on the radar equation is given. At last, the ambiguity function is used to analyze the range and velocity resolution. From the result, we find that the resolution has relation with the location of the target and the height of reflection point of the ionosphere. But compared with the location, the effect of the ionospheric height can be ignored.

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Lin, Zhi Rong, Jin Feng Hu, Ya Xuan Zhang, Wan Ge Li et Hui Ai. « Modified Ocean Clutter Cancellation Algorithm in Sky-Wave Radar ». Applied Mechanics and Materials 644-650 (septembre 2014) : 4249–52. http://dx.doi.org/10.4028/www.scientific.net/amm.644-650.4249.

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In sky-wave over-the-horizon radar system, it is difficult to detect ship because the Doppler shift of the ship is very close to the strong ocean clutter. Traditional clutter cancellation algorithms suppress ocean clutter by estimating clutter parameters and removing the clutter signal in time domain. However, they estimate the clutter parameters by the maximum value of the post DFT spectrum and thus lead to the low accuracy. In this paper, a modified clutter cancellation algorithm is proposed, which corrects estimated frequency by utilizing the three maximum spectrum values and overcomes the poor cancellation performance caused by inaccurate estimation of clutter parameters. Compared with traditional clutter cancellation algorithm, the proposed algorithm can get more accurate clutter parameters and reduce the energy and expansion of the remaining clutter. Simulation demonstrated that the proposed algorithm had a better clutter cancellation performance compared to the traditional ones.

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Jiang, Wei, Wei-bo Deng et Qiang Yang. « Analyse of Sea Clutter for HF over the Horizon Hybrid Sky-surface Wave Radar ». Journal of Electronics & ; Information Technology 33, n^o 8 (9 septembre 2011) : 1786–91. http://dx.doi.org/10.3724/sp.j.1146.2010.01339.

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Zhang, Baiqiang, et Junhao Xie. « Array self-calibration for sky-wave over-the-horizon radar with gain-phase errors ». Journal of Engineering 2019, n^o 19 (1 octobre 2019) : 6192–95. http://dx.doi.org/10.1049/joe.2019.0228.

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Ren, Fangyu, Huotao Gao, Lijuan Yang et Sang Zhou. « Distributed Multistatic Sky-Wave Over-the-Horizon Radar’s Positioning Algorithm for the Marine Target ». International Journal of Antennas and Propagation 2021 (27 octobre 2021) : 1–7. http://dx.doi.org/10.1155/2021/1028784.

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This paper establishes a distributed multistatic sky-wave over-the-horizon radar (DMOTHR) model and proposes a semidefinite relaxation positioning (SDP) algorithm to locate marine ship targets. In the DMOTHR, it is difficult to locate the target due to the complexity of the signal path propagation. Therefore, this paper uses the ionosphere as the reflector to convert the propagation path from a polyline to a straight line for establishing the model, and then the SDP algorithm will be used to transform a highly nonlinear positioning optimization problem into a convex optimization problem. Finally, it is concluded through the simulations that the SDP algorithm can obtain better positioning accuracy under a certain Doppler frequency error and ionospheric measurement error.

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Song Ping, 宋萍, et 刘以安 Liu Yian. « Multi-Static Sky-Wave Over-the-Horizon Radar Location Model Based on Improved Dragonfly Algorithm ». Laser & ; Optoelectronics Progress 55, n^o 11 (2018) : 112001. http://dx.doi.org/10.3788/lop55.112001.

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Wang, Kai, Li Cheng, Xin Yu Wang et Cong Yi Fu. « Simulation and Analysis of Stealth Fighter RCS in High-Frequency Band ». Advanced Materials Research 571 (septembre 2012) : 547–50. http://dx.doi.org/10.4028/www.scientific.net/amr.571.547.

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The sky wave over-the-horizon radar (OTHR) works in high-frequency (HF) band, in which the stealth fighter RCS feature is largely different from that in microwave band. According to 3ds-Max model of F-22 fighter, RCS in HF band is computed by XFDTD software with different frequency, polarizations and angles. The simulation provides worthy preference on researching the ability of anti-stealth fighter of OTHR.

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Jin, Shu-ling, Yan Liang, Quan Pan et Yong-mei Cheng. « A Two-hierarchy Hough Transform Based Track Initiation Method for Sky-wave Over-the-Horizon Radar ». Journal of Electronics & ; Information Technology 30, n^o 8 (28 mars 2011) : 1968–72. http://dx.doi.org/10.3724/sp.j.1146.2006.02033.

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Luo, Zhongtao, Zishu He, Xuyuan Chen et Kun Lu. « Target location and height estimation via multipath signal and 2D array for sky-wave over-the-horizon radar ». IEEE Transactions on Aerospace and Electronic Systems 52, n^o 2 (avril 2016) : 617–31. http://dx.doi.org/10.1109/taes.2015.140046.

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Zhang, Jiazhi, Xin Zhang, Weibo Deng, Liang Guo et Qiang Yang. « A Novel Main-Lobe Cancellation Method Based on a Single Notch Space Filter and Optimized Correlation Analysis Strategy ». International Journal of Antennas and Propagation 2019 (7 mars 2019) : 1–11. http://dx.doi.org/10.1155/2019/1495097.

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The high-frequency hybrid sky-surface wave radar (HFSSWR) is a new kind of over-the-horizon radar system. Combining the advantages of both the sky wave radar and the surface wave radar, HFSSWR has drawn much attention in recent years. But the new system also brings new challenges. One of the most severe problems is that the heterogeneous environment makes a big challenge for the sea clutter suppression processing. Due to the nonstationary properties of the ionosphere, the first-order sea clutter statistics change significantly among range bins. So the new efficient sea clutter suppression method is required, and the clutter characteristics analyses are also in urgent need of research in order to guide the design of the algorithm in the background of HFSSWR. In this paper, utilizing the measured data set, we first analyse the range and spatial characteristics of the nonhomogeneous first-order sea clutter in HFSSWR. Then, an improved main-lobe cancellation (IMLC) method based on single notch space filter and correlation analysis is proposed to get training data which contains precise clutter information. A main-lobe clutter canceller based on the single notch space filter has been developed to block the target component, and an optimized correlation analysis (OCA) strategy is presented to choose the efficient training data. Finally, the method is examined by measured data and the results indicate that the method has a good performance for broadening first-order sea clutter suppression than the traditional method.

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Jia, Jing, et Wen Sheng. « Simulation on Detection Probability Loss of OTHR under Oppressive Active Jamming ». Applied Mechanics and Materials 701-702 (décembre 2014) : 544–48. http://dx.doi.org/10.4028/www.scientific.net/amm.701-702.544.

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Aim to quantificational evaluation of capability of countering oppressive active jamming for Sky-wave Over-The-Horizon Radar (SWOTHR), main oppressive jamming types for SWOTHR and measures of countering oppressive jamming of SWOTHR are analyzed minutely. Based on idea of power countermeasure, evaluation index of detection probability loss is put forward. Based on signal-to-interference ratio equation including the main measures of anti-jamming, simulation models of detection probability loss are established. Simulation results show that SWOTHR has strong capability of countering oppressive active jamming and capability of countering main lobe interference stronger than side lobe interference. And simulation results also confirm feasibility and validity of evaluation index and models.

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Ai, Hui, Jin Feng Hu, Wan Ge Li, Zhi Rong Lin et Ya Xuan Zhang. « A New Algorithm to Compensate Ionosphere Phase Contamination ». Applied Mechanics and Materials 644-650 (septembre 2014) : 4551–54. http://dx.doi.org/10.4028/www.scientific.net/amm.644-650.4551.

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The echo signals of sky-wave over-the-horizon radar involve ionospheric phase contamination with spectrum expansion. The bragg peaks expand and cover the frequency spectrum of low speed target. So ionospheric phase decontamination is necessary before coherent integration. The traditional Hankel Rank Reduction (HRR) phase decontamination method constructs the Hankel matrix by folding the echo signal, estimating instantaneous frequency through singular value decomposition. But HRR method requires the prior information of signal components. The estimation is invalid without priori information. The algorithm presented in this paper does not require the priori information. The algorithm based on matched fourier transform can accurately estimate the phase contamination function for the clutter noise ratio is high. Simulation shows that the proposed algorithm has better performance in phase decontamination.

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He, Tao, Guangjun Sun et Shujuan Ding. « Main lobe interference suppression method of Skywave OTHR based on fast-time STAP ». Journal of Physics : Conference Series 2414, n^o 1 (1 décembre 2022) : 012012. http://dx.doi.org/10.1088/1742-6596/2414/1/012012.

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Abstract For the sky-wave over-the-horizon radar (OTHR), how to effectively suppress the radio frequency interference (RFI)from the main-lobe direction is a problem. To solve this problem, this paper proposes a new space-fast time adaptive processing (fast-time STAP) which merges the matched filter coefficients used for pulse compression and the time steering vector of fast-time STAP. To compare with conventional methods, the method improves the match between the space-time steering vector of fast-time STAP and the real target signal, while the RFI and the noise from RFI are effectively suppressed by the interference-plus-noise covariance matrix which is composed of raw data. At the same time, the signal-to-noise ratio is improved. Compared with the traditional method, this method can be better applied to practical engineering. The results of computer simulation and experiments with real radar data verify the effectiveness of the proposed method.

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Li, Yang, Longshan Wu, Ning Zhang et Xinyang Wang. « Constant false alarm rate detection based on estimating statistical distribution of non‐homogeneous sea clutter in sky‐wave over‐the‐horizon radar ». IET Radar, Sonar & ; Navigation 14, n^o 1 (janvier 2020) : 48–60. http://dx.doi.org/10.1049/iet-rsn.2019.0193.

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Cuccoli, Fabrizio, Luca Facheris et Francesco Sermi. « Coordinate Registration Method based on Sea/Land Transitions Identification for Over-the-Horizon Sky-Wave Radar : Numerical Model and Basic Performance Requirements ». IEEE Transactions on Aerospace and Electronic Systems 47, n^o 4 (2011) : 2974–85. http://dx.doi.org/10.1109/taes.2011.6034678.

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Gao, Huotao, Geyang Li, Yongxu Li, Zijie Yang et Xiongbin Wu. « Ionospheric effect of HF surface wave over-the-horizon radar ». Radio Science 41, n^o 6 (3 novembre 2006) : n/a. http://dx.doi.org/10.1029/2005rs003323.

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Gorobets, V., V. Sinits’kiy et S. Khomenko. « A study of microwave over-sea propagation with high-potential x-band doppler radar ». RADIOFIZIKA I ELEKTRONIKA 26, n^o 1 (2021) : 12–19. http://dx.doi.org/10.15407/rej2021.01.012.

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Subject and Purpose. The paper is devoted to the microwave propagation over the sea in the nearshore region. Emphasis is on microwave attenuation measurements in the semi-shade and deep-shade areas with a view to study conditions of the microwave propagation on a beyond-the-horizon path in the nearshore area using a radar method. Methods and Methodology. A radar technique, developed and tested, provides measuring a microwave attenuation coefficient along a 60 km long beyond-the-horizon path in the tropospheric surface layer. High-grade radar and Doppler radar beacons (racons) are employed. Of interest are experimentally obtained temporal dependences of signals from racons situated at different heights and, also, spatial field distribution curves from a steadily moving racon running a height 1 to 27 m for 25 minutes. Results. A prototype of high-grade X-band coherent continuous-wave (Doppler) radar has been designed and fabricated. A radar technique has been developed and tested for the analysis of microwave beyond-the-horizon propagation conditions in the shadow region, which involves continuous-wave (Doppler) radar and Doppler racons with a radar cross section (RCS) of about 60 m2. Conclusions. The technique proposed enables reliable tracking of racon responses up to a double radiohorizon range on over-sea paths. This technique can be used for radar calibrations when dealing with various location problems in the nearshore area, including detection and tracking small-size and low-flying targets and their radar identification.

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Fabrizio, G. A., A. B. Gershman et M. D. Turley. « Robust adaptive beamforming for HF surface wave over-the-horizon radar ». IEEE Transactions on Aerospace and Electronic Systems 40, n^o 2 (avril 2004) : 510–25. http://dx.doi.org/10.1109/taes.2004.1310001.

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Guo, Qiang, Yu Kui Li, Bao Ning Gao, Ran Tao et Si Yong Zhou. « An Analysis for Ground Diffraction about Detecting beyond the Horizon Using Television-Based Bistatic Detection System ». Key Engineering Materials 428-429 (janvier 2010) : 505–10. http://dx.doi.org/10.4028/www.scientific.net/kem.428-429.505.

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Analysing the characteristics of a television transmitter carefully, the paper compares the television-based bistatic radar with the conventional monostatic and bistatic radar on targets detecting beyond the horizon in some given direction. In the light of the effect of ground diffraction produced by electromagnetic wave propagation on different radar ranges, it is shown that television-based bistatic radar has a potential advantage over conventional radar in targets detecting beyond the horizon because of its particular advantages in height gain and diffracting efficiency. At the same time, we have an in-depth study which is the decisive factor on radar ranging, height gain or diffraction effect, conduct an effective method of how determine the optimal wavelength so as to get the maximum radar detecting range.

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Protopapadakis, Eftychios, Athanasios Voulodimos, Anastasios Doulamis, Nikolaos Doulamis, Dimitrios Dres et Matthaios Bimpas. « Stacked Autoencoders for Outlier Detection in Over-the-Horizon Radar Signals ». Computational Intelligence and Neuroscience 2017 (2017) : 1–11. http://dx.doi.org/10.1155/2017/5891417.

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Detection of outliers in radar signals is a considerable challenge in maritime surveillance applications. High-Frequency Surface-Wave (HFSW) radars have attracted significant interest as potential tools for long-range target identification and outlier detection at over-the-horizon (OTH) distances. However, a number of disadvantages, such as their low spatial resolution and presence of clutter, have a negative impact on their accuracy. In this paper, we explore the applicability of deep learning techniques for detecting deviations from the norm in behavioral patterns of vessels (outliers) as they are tracked from an OTH radar. The proposed methodology exploits the nonlinear mapping capabilities of deep stacked autoencoders in combination with density-based clustering. A comparative experimental evaluation of the approach shows promising results in terms of the proposed methodology’s performance.

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Nikolic, Dejan, Nikola Stojkovic, Zdravko Popovic, Nikola Tosic, Nikola Lekic, Zoran Stankovic et Nebojsa Doncov. « Maritime Over the Horizon Sensor Integration : HFSWR Data Fusion Algorithm ». Remote Sensing 11, n^o 7 (9 avril 2019) : 852. http://dx.doi.org/10.3390/rs11070852.

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In order to provide a constant and complete operational picture of the maritime situation in the Exclusive Economic Zone (EEZ) at over the horizon (OTH) distances, a network of high frequency surface-wave-radars (HFSWR) slowly becomes a necessity. Since each HFSWR in the network tracks all the targets it detects independently of other radars in the network, there will be situations where multiple tracks are formed for a single vessel. The algorithm proposed in this paper utilizes radar tracks obtained from individual HFSWRs which are already processed by the multi-target tracking algorithm at the single radar level, and fuses them into a unique data stream. In this way, the data obtained from multiple HFSWRs originating from the very same target are weighted and combined into a single track. Moreover, the weighting approach significantly reduces inaccuracy. The algorithm is designed, implemented, and tested in a real working environment. The testing environment is located in the Gulf of Guinea and includes a network of two HFSWRs. In order to validate the algorithm outputs, the position of the vessels was calculated by the algorithm and compared with the positions obtained from several coastal sites, with LAIS receivers and SAIS data provided by a SAIS provider.

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Bageston, J. V., C. M. Wrasse, R. E. Hibbins, P. P. Batista, D. Gobbi, H. Takahashi, V. F. Andrioli, J. Fechine et C. M. Denardini. « Case study of a mesospheric wall event over Ferraz station, Antarctica (62° S) ». Annales Geophysicae 29, n^o 1 (28 janvier 2011) : 209–19. http://dx.doi.org/10.5194/angeo-29-209-2011.

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Abstract. On 16–17 July 2007 during an observational campaign at Comandante Ferraz Antarctic Station (62° S, 58° W), a mesospheric wall was observed with an airglow all-sky imager. The wave appeared like an extensive dark region in the all-sky airglow images, with a large depletion in the OH emission. Simultaneous mesospheric winds measured with a MF radar at Rothera station and temperature profiles from SABER instrument, on board of TIMED satellite, were used to obtain the propagation condition of the wave. Wind measurements during four days, around the time of observation of the wave, are presented in order to discuss the type and consistence of the duct in which this wave was propagating. By using wavelet analysis and tidal amplitude components we found that 12 and 8 h components were the most important periodicities around the time interval of the wave observation. A collocated imaging spectrometer, for mesospheric temperature measurements, has been operated simultaneously with the all-sky imager. Direct effects of the mesospheric front have been seen in the spectrometric measurements, showing an abrupt decrease in both OH intensity and rotational temperature when the wave front passes overhead. The main contribution of the present work is the investigation of the type of duct in which the wall event was propagating. We found evidences for a thermal duct structure to support the mesospheric wall propagation. This result was obtained by two types of analysis: (a) the tidal components analysis and winds filtering (harmonic analysis), and (b) comparison between the terms of the m2 dispersion relation.

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Ravan, M., R. J. Riddolls et R. S. Adve. « Ionospheric and auroral clutter models for HF surface wave and over-the-horizon radar systems ». Radio Science 47, n^o 3 (juin 2012) : n/a. http://dx.doi.org/10.1029/2011rs004944.

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Feng, Mengyan, Hanxian Fang, Weihua Ai, Xiongbin Wu, Xianchang Yue, Lan Zhang, Chaogang Guo, Qing Zhou et Xiaoyan Li. « Research on a Simulation Model of a Skywave Over-the-Horizon Radar Sea Echo Spectrum ». Remote Sensing 14, n^o 6 (18 mars 2022) : 1461. http://dx.doi.org/10.3390/rs14061461.

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The capability of a skywave over-the-horizon radar (SWR) to achieve the continuous observation of a wide range of ocean dynamics parameters via a single ionospheric reflection has been demonstrated by many scholars. In order to expand the method of SWR detection of ocean dynamics parameters, a simulation model of an SWR sea echo spectrum based on the Barrick sea surface scattering cross-section model (Barrick model) and 3D ray-tracing method, suitable for a narrow-beam, frequency-modulated continuous-wave radar system (FMCW), was established. Based on this model, we simulated ideal and contaminated SWR sea echo spectra, respectively with the 3D electron density data output by the International Reference Ionosphere (IRI) model. Then, we further analyzed the effects of the grazing incidence angle, scattering angle, scattering azimuth angle and fetch length on the sea surface scattering cross-sections, the retrieval precision of the sea surface wind direction, and the root-mean-square (RMS) wave height, using the simulation data calculated by the Barrick model. The results show that these angles and fetch length cause a small expansion and contraction of the scattering cross-section, and have no influence on the retrieval precision of the sea surface wind direction, but will affect the retrieval precision of the RMS wave height; the influence of the grazing incidence angle and scattering angle is ~2.5 times that of the scattering azimuth angle. The ideal SWR sea echo spectrum has small broadening, but the ionosphere phase contamination will cause serious broadening and shifting of the SWR sea echo spectrum, and the higher order nonlinear term has greater contamination.

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Jati, Ahmad Nugroho, Ahmad Fauzi Haqqoni, Iswandi Iswandi et Risanuri Hidayat. « A High-Frequency Surface Wave Radar Simulation Using FMCW Technique for Ship Detection ». IJITEE (International Journal of Information Technology and Electrical Engineering) 4, n^o 1 (9 septembre 2020) : 19. http://dx.doi.org/10.22146/ijitee.56344.

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Indonesia is an archipelagic country with a vast sea area. This vast sea area becomes a challenge in conducting regional surveillance to maintain maritime conditions. The use of buoys and satellites still has shortcomings in carrying out surveillance despite its excellent surveillance capabilities. A high-frequency radar technology with 3-30 MHz frequency and surface wave propagation are very suitable because it has a radar range that can cross the horizon or commonly refer to as Over the Horizon (OTH). The Frequency Modulated Continuous Wave (FMCW) technique on this radar obtains distance and velocity information by a continuously transmitted frequency modulation. The use of radar in Indonesia for marine surveillance is still infrequent. Therefore, it is relatively difficult to conduct testing and obtain data. In addition, the direct examination requires extended time, so a simulation program is needed. This paper discusses the design of a High-Frequency Surface Wave Radar (HFSWR) simulation program using FMCW modulation technique. The simulation program detected two objects based on time delays due to the distance and velocity of the object with a maximum range of 350 km. It displayed the results in an informative manner. The object detection was based on the results of the Fast Fourier Transform (FFT) from the mixed signals. The mixed signal is a combination of transmitted signal and reflected signal in which there are time delay components due to the object. The simulation program had been tested with input values of distance and velocity that vary, both for one object and two objects, in the radial direction. It generated output that was close to the input value with a level of accuracy of ± 2 km.

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Vlasov, Yu M., I. A. Glinkin et S. V. Litvinov. « APPLICATION OF OBLIQUE IONOSPHERIC SOUNDING TO INCREASE THE ACCURACY CHARACTERISTICS OF THE OVER-THE-HORIZON RADAR ». Issues of radio electronics, n^o 3 (20 mars 2018) : 11–18. http://dx.doi.org/10.21778/2218-5453-2018-3-11-18.

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The over-the-horizon radar stations of the space wave are sensitive to changes in the ionosphere. For the accurate operation of such radars, it is necessary to have up-to-date information on the ionosphere at the reflection point of radio waves. The article gives an example of the implementation of a network of ionospheric stations working in the interests of the FG of the radar station with the example of the Australian system JORN. It is proposed to use the Russian vertical ionosondes Parus-A for ionospheric support of the radar. These ionosondes are also capable of performing oblique sounding at distances up to 2000 km. The results of oblique sounding by these ionosondes are shown on various routes on the territory of Russia: in the European part of the country, in Siberia and in the Far East. The features are explained and the analysis of the data is carried out. It is concluded that the problem is topical and that it can be solved. The potential is shown in the ionosonde Parus-A at the development stage and implemented later.

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Yang, Xuguang, Changjun Yu, Aijun Liu, Linwei Wang et Taifan Quan. « The Vertical Ionosphere Parameters Inversion for High Frequency Surface Wave Radar ». International Journal of Antennas and Propagation 2016 (2016) : 1–8. http://dx.doi.org/10.1155/2016/8609372.

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High Frequency Surface Wave Radar (HFSWR), which is currently applied in over-the-horizon detection of targets and sea states remote sensing, can receive a huge mass of ionospheric echoes, making it possible for the ionospheric clutter suppression to become a hot spot in research area. In this paper, from another perspective, we take the ionospheric echoes as the signal source rather than clutters, which provides the possibility of extracting information regarding the ionosphere region and explores a new application field for HFSWR. Primarily, pretreatment of threshold segmentation as well as connected region generation is used in the Range-Doppler (R-D) Spectrum to extract the ionospheric echoes. Then, electron density and plasma frequency of field aligned irregularities (FAIs) caused by plasma instabilities in the F region are obtained by the coherent backscattered radar equation. The plasma drift velocity of FAIs can also be estimated from Doppler shift. Ultimately, the effectiveness of inversion is verified by comparing with IRI2012.

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Fu, Tian Jiao, Li Guo Zhang et Jian Yue Ren. « Bi-Station Multi-Target Tracking Using Range and Doppler Measurements ». Applied Mechanics and Materials 329 (juin 2013) : 338–43. http://dx.doi.org/10.4028/www.scientific.net/amm.329.338.

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The azimuthal measurements of the high frequency ground wave radar are poor in an actual environment, which can cause the plots highly decentralized and damage the formation of the over-the-horizon tracks. To solve the problem, a new radar system is proposed to triangulate target tracks using range and Doppler measurements only. On the basis of the analysis of the characteristics of the range-finding location, a multi-target tracking algorithm under non-clutter condition is given in this paper, which further improves the tracking algorithm of this system. Simulation results show the effectiveness of this method.

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Anderson, Stuart. « Societal Applications of HF Skywave Radar ». Remote Sensing 14, n^o 24 (12 décembre 2022) : 6287. http://dx.doi.org/10.3390/rs14246287.

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After exploratory research in the 1950s, HF skywave ‘over-the-horizon’ radars (OTHR) were developed as operating systems in the 1960s for defence missions, notably the long-range detection of ballistic missiles, aircraft, and ships. The potential for a variety of non-defence applications soon became apparent, but the size, cost, siting requirements, and tasking priority hindered the implementation of these societal roles. A sister technology—HF surface wave radar (HFSWR)—evolved during the same period but, in this more compact form, the non-defence applications dominated, with hundreds of such radars presently deployed around the world, used primarily for ocean current mapping and wave measurements. In this paper, we examine the ocean monitoring capabilities of the latest generation of HF skywave radars, some shared with HFSWR, some unique to the skywave modality, and explore some new possibilities, along with selected technical details for their implementation. We apply state-of-the-art modelling and experimental data to illustrate the kinds of information that can be generated and exploited for civil, commercial, and scientific purposes. The examples treated confirm the relevance and value of this information to such diverse activities as shipping, fishing, offshore resource extraction, agriculture, communications, weather forecasting, and climate change studies.

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Fechine, J., C. M. Wrasse, H. Takahashi, A. F. Medeiros, P. P. Batista, B. R. Clemesha, L. M. Lima et al. « First observation of an undular mesospheric bore in a Doppler duct ». Annales Geophysicae 27, n^o 4 (1 avril 2009) : 1399–406. http://dx.doi.org/10.5194/angeo-27-1399-2009.

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Abstract. On 1 October 2005, during the SpreadFEx campaign, a distinct mesospheric bore was observed over São João do Cariri (7.4° S, 36.5° W), Brazil by using airglow all-sky imagers. The event appeared both in the OI5577 and OH emissions, forming a well extended wave front which was followed by short waves from behind. Simultaneous wind and temperature data obtained by the meteor radar and the TIMED/SABER satellite instrument revealed that the bore event occurred during the Doppler ducting condition in the emission layers.

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Andrioli, V. F., P. P. Batista, B. R. Clemesha, N. J. Schuch et R. A. Buriti. « Multi-year observations of gravity wave momentum fluxes at low and middle latitudes inferred by all-sky meteor radar ». Annales Geophysicae 33, n^o 9 (30 septembre 2015) : 1183–93. http://dx.doi.org/10.5194/angeo-33-1183-2015.

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Abstract. We have applied a modified composite day analysis to the Hocking (2005) technique to study gravity wave (GW) momentum fluxes in the mesosphere and lower thermosphere (MLT). Wind measurements from almost continuous meteor radar observations during June 2004–December 2008 over São João do Cariri (Cariri; 7° S, 36° W), April 1999–November 2008 over Cachoeira Paulista (CP; 23° S, 45° W), and February 2005–December 2009 over Santa Maria (SM; 30° S, 54° W) were used to estimate the GW momentum fluxes and variances in the MLT region. Our analysis can provide monthly mean altitude profiles of vertical fluxes of horizontal momentum for short-period (less than 2–3 h) GWs. The averages for each month throughout the entire data series have shown different behavior for the momentum fluxes depending on latitude and component. The meridional component has almost the same behavior at the three sites, being positive (northward), for most part of the year. On the other hand, the zonal component shows different behavior at each location: it is positive for almost half the year at Cariri and SM but predominantly negative over CP. Annual variation in the GW momentum fluxes is present at all sites in the zonal component and also in SM at 89 km in the meridional component. The seasonal analysis has also shown a 4-month oscillation at 92.5 km over SM in the zonal component and over CP at the same altitudes but for the meridional component.

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Lamer, K., A. Tatarevic, I. Jo et P. Kollias. « Evaluation of gridded scanning ARM cloud radar reflectivity observations and vertical doppler velocity retrievals ». Atmospheric Measurement Techniques 7, n^o 4 (29 avril 2014) : 1089–103. http://dx.doi.org/10.5194/amt-7-1089-2014.

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Abstract. The scanning Atmospheric Radiation Measurement (ARM) cloud radars (SACRs) provide continuous atmospheric observations aspiring to capture the 3-D cloud-scale structure. Sampling clouds in 3-D is challenging due to their temporal–spatial scales, the need to sample the sky at high elevations and cloud radar limitations. Thus, a suggested scan strategy is to repetitively slice the atmosphere from horizon to horizon as clouds advect over the radar (Cross-Wind Range-Height Indicator – CW-RHI). Here, the processing and gridding of the SACR CW-RHI scans are presented. First, the SACR sample observations from the ARM Southern Great Plains and Cape Cod sites are post-processed (detection mask, gaseous attenuation correction, insect filtering and velocity de-aliasing). The resulting radial Doppler moment fields are then mapped to Cartesian coordinates with time as one of the dimensions. Next the Cartesian-gridded Doppler velocity fields are decomposed into the horizontal wind velocity contribution and the vertical Doppler velocity component. For validation purposes, all gridded and retrieved fields are compared to collocated zenith-pointing ARM cloud radar measurements. We consider that the SACR sensitivity loss with range, the cloud type observed and the research purpose should be considered in determining the gridded domain size. Our results also demonstrate that the gridded SACR observations resolve the main features of low and high stratiform clouds. It is established that the CW-RHI observations complemented with processing techniques could lead to robust 3-D cloud dynamical representations up to 25–30 degrees off zenith. The proposed gridded products are expected to advance our understanding of 3-D cloud morphology, dynamics and anisotropy and lead to more realistic 3-D radiative transfer calculations.

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Lamer, K., A. Tatarevic, I. Jo et P. Kollias. « Evaluation of gridded Scanning ARM Cloud Radar reflectivity observations and vertical Doppler velocity retrievals ». Atmospheric Measurement Techniques Discussions 6, n^o 6 (8 novembre 2013) : 9579–621. http://dx.doi.org/10.5194/amtd-6-9579-2013.

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Abstract. The Scanning ARM Cloud Radars (SACR's) provide continuous atmospheric observations aspiring to capture the 3-D cloud-scale structure. Sampling clouds in 3-D is challenging due to their temporal-spatial scales, the need to sample the sky at high elevations and cloud radar limitations. Thus, a common scan strategy is to repetitively slice the atmosphere from horizon to horizon as clouds advect over the radar (Cross-Wind Range Height Indicator – CWRHI). Here, the processing and gridding of the SACR CW-RHI scans are presented. First, the SACR sample observations from the ARM Oklahoma (SGP) and Cape-Cod (PVC) sites are post-processed (detection mask, velocity de-aliasing and gaseous attenuation correction). The resulting radial Doppler moment fields are then mapped to Cartesian coordinates with time as one of the dimension. The Cartesian-gridded Doppler velocity fields are next decomposed into the horizontal wind velocity contribution and the vertical Doppler velocity component. For validation purposes, all gridded and retrieved fields are compared to collocated zenith pointing ARM cloud radar measurements. We consider that the SACR sensitivity loss with range, the cloud type observed and the research purpose should be considered in determining the gridded domain size. Our results also demonstrate that the gridded SACR observations resolve the main features of low and high stratiform clouds. It is established that the CW-RHI observations complemented with processing techniques could lead to robust 3-D clouds dynamical representations up to 25–30° off zenith. The proposed gridded products are expected to advance our understanding of 3-D cloud morphology, dynamics, anisotropy and lead to more realistic 3-D radiative transfer calculations.

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Guo, L., et G. Lehmacher. « First meteor radar observations of tidal oscillations over Jicamarca (11.95° S, 76.87° W) ». Annales Geophysicae 27, n^o 6 (26 juin 2009) : 2575–83. http://dx.doi.org/10.5194/angeo-27-2575-2009.

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Abstract. Tidal oscillations in the equatorial mesosphere and lower thermosphere (MLT) region over Jicamarca (11.95° S, 76.87° W) are studied using the observations from the newly installed Jicamarca All-sky Specular MEteor Radar (JASMET). The vertical structure and seasonal variability of diurnal and semidiurnal tides from 80–100 km are presented. The analyses show a strong diurnal tide over Jicamarca for both zonal and meridional components with the meridional amplitudes being larger than the zonal ones. Maximal diurnal amplitudes, 45 m/s for zonal and 55 m/s for meridional, are observed around equinox. The zonal diurnal amplitudes reach maxima at 90–96 km, while the meridional diurnal amplitudes grow with altitude for most months. Semidiurnal amplitudes vary not as strong as diurnal amplitudes. The vertical structures of the tidal components are compared with Global Scale Wave Model (GSWM02) prediction and the tidal wind analysis results from TIDI measurements onboard of the TIMED satellite. The data from JASMET and TIDI show similar amplitudes for both diurnal and semidiurnal tides. GSWM02 overestimates diurnal amplitudes, but underestimates semidiurnal amplitudes for both zonal and meridional components.

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Coleman, Timothy A., Kevin R. Knupp et Daryl E. Herzmann. « An Undular Bore and Gravity Waves Illustrated by Dramatic Time-Lapse Photography ». Journal of Atmospheric and Oceanic Technology 27, n^o 8 (1 août 2010) : 1355–61. http://dx.doi.org/10.1175/2010jtecha1472.1.

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Abstract On 6 May 2007, an intense atmospheric undular bore moved over eastern Iowa. A “Webcam” in Tama, Iowa, captured dramatic images of the effects of the bore and associated gravity waves on cloud features, because its viewing angle was almost normal to the propagation direction of the waves. The time lapse of these images has become a well-known illustration of atmospheric gravity waves. The environment was favorable for bore formation, with a wave-reflecting unstable layer above a low-level stable layer. Surface pressure and wind data are correlated for the waves in the bore, and horizontal wind oscillations are also shown by Doppler radar data. Quantitative analysis of the time-lapse photography shows that the sky brightens in wave troughs because of subsidence and darkens in wave ridges because of ascent.

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Bashkuev, Yu B., L. Kh Angarkhaeva et D. G. Buyanova. « THE SURFACE IMPEDANCE OF THE "THIN ICE - SEA" AND "THICK ICE - SEA" STRUCTURES IN VLF-VHF RADIO WAVE BANDS ». RADIO COMMUNICATION TECHNOLOGY, n^o 48 (16 juin 2021) : 24–33. http://dx.doi.org/10.33286/2075-8693-2021-48-24-33.

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To calculate the propagation of the electromagnetic field over the two-layer struc-ture "ice - sea", the areas of applicability of the impedance boundary conditions are determined depending on the thickness of the ice and the angle of incidence of the vertically polarized wave in the range of 0.01-420 MHz. The article examines the structures "thin ice - sea" and "thick ice - sea" (six models of ice cover). The ice thickness varied from 0.03 to 9 m. The results are needed to calculate the atten-uation function and the field level in the VLF, LF, MF, HF, VHF radio wave bands. It is shown that for the structure “ice - sea” it is important to take into account the dependence of the surface impedance on the angle of incidence for over-the-horizon radar systems in the HF radio wave range. In the VHF range the frequency bands are determined for ice 80 cm thick, in which the impedance boundary condi-tions are applicable.

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Alpatov, Viktor, Susanna Bekker, Stanislav Kozlov, Andrey Lyakhov, Valentin Yakim et Sergey Yakubovsky. « ANALYZING EXISTING APPLIED MODELS OF THE IONOSPHERE TO CALCULATE RADIO WAVE PROPAGATION AND A POSSIBILITY OF THEIR USE FOR RADAR-TRACKING SYSTEMS. II. DOMESTIC MODELS ». Solar-Terrestrial Physics 6, n^o 3 (22 septembre 2020) : 60–66. http://dx.doi.org/10.12737/stp-63202008.

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We consider the ionospheric models that are suitable for over-the-horizon HF and UHF band radars. Namely, there are three such models: the numerical model developed by IZMIRAN and Fedorov Institute of Applied Geophysics, the numerical model designed by ISTP SB RAS and IDG RAS, and the probabilistic model worked out by IDG RAS. We briefly describe these models and report the results of the analysis of their compliance with radar requirements. Probabilistic models are shown to be most promising; hence, they must be placed at the frontier of ionosphere simulation.

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Alpatov, Viktor, Susanna Bekker, Stanislav Kozlov, Andrey Lyakhov, Valentin Yakim et Sergey Yakubovsky. « ANALYZING EXISTING APPLIED MODELS OF THE IONOSPHERE TO CALCULATE RADIO WAVE PROPAGATION AND A POSSIBILITY OF THEIR USE FOR RADAR-TRACKING SYSTEMS. II. DOMESTIC MODELS ». Solnechno-Zemnaya Fizika 6, n^o 3 (22 septembre 2020) : 73–81. http://dx.doi.org/10.12737/szf-63202008.

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We consider the ionospheric models that are suitable for over-the-horizon HF and UHF band radars. Namely, there are three such models: the numerical model developed by IZMIRAN and Fedorov Institute of Applied Geophysics, the numerical model designed by ISTP SB RAS and IDG RAS, and the probabilistic model worked out by IDG RAS. We briefly describe these models and report the results of the analysis of their compliance with radar requirements. Probabilistic models are shown to be most promising; hence, they must be placed at the frontier of ionosphere simulation.

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Aksenov, Oleg, Stanislav Kozlov, Andrey Lyakhov, Vyacheslav Trekin, Yuriy Perunov et Sergey Yakubovsky. « ANALYZING EXISTING APPLIED MODELS OF THE IONOSPHERE FOR CALCULATING RADIO WAVE PROPAGATION AND POSSIBILITY OF THEIR USE FOR RADAR SYSTEMS. I. CLASSIFICATION OF APPLIED MODELS AND THE MAIN REQUIREMENTS IMPOSED ON THEM FOR RADAR AIDS ». Solar-Terrestrial Physics 6, n^o 1 (1 avril 2020) : 69–76. http://dx.doi.org/10.12737/stp-61202008.

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We review modern HF–X band radars covering over-the-horizon problems. The ionosphere significantly affects wave propagation in all the bands. We describe available correction techniques, which use additional evidence on the ionosphere, as well as models of different degrees of complexity. The fact that the field of view cannot be covered by ground-based instruments as well as the growing requirements to the precision and stability of the radars result in the impossibility of ionospheric correction with up-to-date models, hence the latter require further elaboration. We give a virtually full classification of the models. The article summarizes the requirements to the models for the radars depending on their function.

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Aksenov, Oleg, Stanislav Kozlov, Andrey Lyakhov, Vyacheslav Trekin, Yuriy Perunov et Sergey Yakubovsky. « ANALYZING EXISTING APPLIED MODELS OF THE IONOSPHERE FOR CALCULATING RADIO WAVE PROPAGATION AND POSSIBILITY OF THEIR USE FOR RADAR SYSTEMS. I. CLASSIFICATION OF APPLIED MODELS AND THE MAIN REQUIREMENTS IMPOSED ON THEM FOR RADAR AIDS ». Solnechno-Zemnaya Fizika 6, n^o 1 (30 mars 2020) : 86–96. http://dx.doi.org/10.12737/szf-61202008.

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We review modern HF–X band radars covering over-the-horizon problems. The ionosphere significantly affects wave propagation in all the bands. We describe available correction techniques, which use additional evidence on the ionosphere, as well as models of different degrees of complexity. The fact that the field of view cannot be covered by ground-based instruments as well as the growing requirements to the precision and stability of the radars result in the impossibility of ionospheric correction with up-to-date models, hence the latter require further elaboration. We give a virtually full classification of the models. The article summarizes the requirements to the models for the radars depending on their function.

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Sarkhel, Sumanta, Gunter Stober, Jorge L. Chau, Steven M. Smith, Christoph Jacobi, Subarna Mondal, Martin G. Mlynczak et James M. Russell III. « A case study of a ducted gravity wave event over northern Germany using simultaneous airglow imaging and wind-field observations ». Annales Geophysicae 40, n^o 2 (22 mars 2022) : 179–90. http://dx.doi.org/10.5194/angeo-40-179-2022.

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Abstract. An intriguing and rare gravity wave event was recorded on the night of 25 April 2017 using a multiwavelength all-sky airglow imager over northern Germany. The airglow imaging observations at multiple altitudes in the mesosphere and lower thermosphere region reveal that a prominent upward-propagating wave structure appeared in O(1S) and O2 airglow images. However, the same wave structure was observed to be very faint in OH airglow images, despite OH being usually one of the brightest airglow emissions. In order to investigate this rare phenomenon, the altitude profile of the vertical wavenumber was derived based on colocated meteor radar wind-field and SABER temperature profiles close to the event location. The results indicate the presence of a thermal duct layer in the altitude range of 85–91 km in the southwest region of Kühlungsborn, Germany. Utilizing these instrumental data sets, we present evidence to show how a leaky duct layer partially inhibited the wave progression in the OH airglow emission layer. The coincidental appearance of this duct layer is responsible for the observed faint wave front in the OH airglow images compared O(1S) and O2 airglow images during the course of the night over northern Germany.

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Ilcev, Dimov Stojce. « Introduction to Coastal HF Maritime Surveillance Radars ». Polish Maritime Research 26, n^o 3 (1 septembre 2019) : 153–62. http://dx.doi.org/10.2478/pomr-2019-0056.

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Abstract This paper presents the main technical characteristics and working performances of coastal maritime surveillance radars, such as low-power High-Frequency Surface Wave Radars (HFSWR) and Over the Horizon Radars (OTHR). These radars have demonstrated to be a cost-effective long-range early-warning sensor for ship detection and tracking in coastal waters, sea channels and passages. In this work, multi-target tracking and data fusion techniques are applied to live-recorded data from a network of oceanographic HFSWR stations installed in Jindalee Operational Radar Network (JORN), Wellen Radar (WERA) in Ligurian Sea (Mediterranean Sea), CODAR Ocean Sebsorsin and in the German Bight (North Sea). The coastal Imaging Sciences Research (ISR) HFSWR system, Multi-static ISR HF Radar, Ship Classification using Multi-Frequency HF Radar, Coastal HF radar surveillance of pirate boats and Different projects of coastal HF radars for vessels detecting are described. Ship reports from the Automatic Identification System (AIS), recorded from both coastal and satellite Land Earth Stations (LES) are exploited as ground truth information and a methodology is applied to classify the fused tracks and to estimate system performances. Experimental results for all above solutions are presented and discussed, together with an outline for future integration and infrastructures.

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Bageston, J. V., C. M. Wrasse, P. P. Batista, R. E. Hibbins, D. C. Fritts, D. Gobbi et V. F. Andrioli. « Observation of a mesospheric front in a dual duct over King George Island, Antarctica ». Atmospheric Chemistry and Physics Discussions 11, n^o 5 (31 mai 2011) : 16185–206. http://dx.doi.org/10.5194/acpd-11-16185-2011.

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Abstract. A mesospheric bore was observed with an all-sky airglow imager on the night of 9–10 July 2007 at Ferraz Station (62° S, 58° W), located on King George island on the Antarctic Peninsula. The observed bore propagated from southwest to northeast with a well defined wave front and a series of crests behind the main front. There was no evidence of dissipation during its propagation within the field of view. The wave parameters were obtained via a 2-D Fourier transform of the imager data providing a horizontal wavelength of 33 km, an observed period of 6 min, and a horizontal phase speed of 92 m s−1. Simultaneous mesospheric winds were measured with a medium frequency (MF) radar at Rothera Station (68° S, 68° W) and temperature profiles were obtained from the SABER instrument on the TIMED satellite. These wind and temperature profiles were used to estimate the propagation environment of the bore. A wavelet technique was applied to the wind in the plane of bore propagation at the OH emission height spanning three days centered on the bore event to define the dominant periodicities. Results revealed a dominance of near-inertial periods, and semi-diurnal and terdiurnal tides suggesting that the ducting structure enabling bore propagation occurred on large spatial scales. The observed tidal motions were used to reconstruct the winds employing a least-squares method, which were then compared to the observed ducting environment. Results suggest an important contribution of large-scale winds to the ducting structure, but with buoyancy frequency variations in the vertical also expected to be important. These results allow us to conclude that the bore was supported by a duct including contributions from both winds and temperature (or stability). A co-located airglow temperature imager operated simultaneously with the all-sky imager confirmed that the bore event was the dominant small-scale wave event during the analysis interval.

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