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20 pages, 2240 KiB

Open AccessArticle

Vessel Tracking Using Bistatic Compact HFSWR

by Weifeng Sun, Mengjie Ji, Weimin Huang, Yonggang Ji and Yongshou Dai

Remote Sens. 2020, 12(8), 1266; https://doi.org/10.3390/rs12081266 - 16 Apr 2020

Cited by 18 | Viewed by 4019

Abstract

Bistatic and multi-static high-frequency surface wave radar (HFSWR) is becoming a prospective development trend for sea surface surveillance due to its potential in extending the coverage area, improving the detection accuracy, etc. In this paper, the vessel detection and tracking performance of a [...] Read more.

Bistatic and multi-static high-frequency surface wave radar (HFSWR) is becoming a prospective development trend for sea surface surveillance due to its potential in extending the coverage area, improving the detection accuracy, etc. In this paper, the vessel detection and tracking performance of a newly developed bistatic compact HFSWR system whose transmitting and receiving antennas are not co-located was investigated. Firstly, the representation of the target range and Doppler velocity concerning a bistatic HFSWR was derived and compared with that of a monostatic system. Next, taking the characteristics of target kinematic parameters into account, a target tracking method applicable to a bistatic HFSWR is proposed. The simultaneous target tracking results from both monostatic and bistatic HFSWR field data are presented and compared. The experimental results demonstrate the good performance in target tracking of the bistatic HFSWR and also show that an HFSWR system combining monostatic and bistatic modes has the potential to enhance the target track continuity and improve the detection accuracy. Full article

(This article belongs to the Special Issue Bistatic HF Radar)

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28 pages, 9474 KiB

Open AccessFeature PaperArticle

Bistatic and Stereoscopic Configurations for HF Radar

by Stuart Anderson

Remote Sens. 2020, 12(4), 689; https://doi.org/10.3390/rs12040689 - 20 Feb 2020

Cited by 7 | Viewed by 4033

Abstract

Most HF radars operate in a monostatic or quasi-monostatic configuration. The collocation of transmit and receive facilities simplifies testing and maintenance, reduces demands on communications networks, and enables the use of established and relatively straightforward signal processing and data interpretation techniques. Radars of [...] Read more.

Most HF radars operate in a monostatic or quasi-monostatic configuration. The collocation of transmit and receive facilities simplifies testing and maintenance, reduces demands on communications networks, and enables the use of established and relatively straightforward signal processing and data interpretation techniques. Radars of this type are well-suited to missions such as current mapping, waveheight measurement, and the detection of ships and aircraft. The high scientific, defense, and economic value of the radar products is evident from the fact that hundreds of HF radars are presently in operation, the great majority of them relying on the surface wave mode of propagation, though some systems employ line-of-sight or skywave modalities. Yet, notwithstanding the versatility and proven capabilities of monostatic HF radars, there are some types of observations for which the monostatic geometry renders them less effective. In these cases, one must turn to more general radar configurations, including those that employ a multiplicity of propagation modalities to achieve the desired illumination, scattering selectivity, and echo reception. In this paper, we survey some of the considerations that arise with bistatic HF radar configurations, explore some of the missions for which they are optimal, and describe some practical techniques that can guide their design and deployment. Full article

(This article belongs to the Special Issue Bistatic HF Radar)

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12 pages, 522 KiB

Open AccessCommunication

Bistatic High-Frequency Radar Cross-Section of the Ocean Surface with Arbitrary Wave Heights

by Murilo Teixeira Silva, Weimin Huang and Eric W. Gill

Remote Sens. 2020, 12(4), 667; https://doi.org/10.3390/rs12040667 - 18 Feb 2020

Cited by 6 | Viewed by 2876

Abstract

The scattering theory developed in the past decades for high-frequency radio oceanography has been restricted to surfaces with small heights and small slopes. In the present work, the scattering theory for bistatic high-frequency radars is extended to ocean surfaces with arbitrary wave heights. [...] Read more.

The scattering theory developed in the past decades for high-frequency radio oceanography has been restricted to surfaces with small heights and small slopes. In the present work, the scattering theory for bistatic high-frequency radars is extended to ocean surfaces with arbitrary wave heights. Based on recent theoretical developments in the scattering theory for ocean surfaces with arbitrary heights for monostatic radars, the electric field equations for bistatic high-frequency radars in high sea states are developed. This results in an additional term related to the first-order electric field, which is only present when the small-height approximation is removed. Then, the radar cross-section for the additional term is derived and simulated, and its impact on the total radar cross-section at different radar configurations, dominant wave directions, and sea states is assessed. The proposed term is shown to impact the total radar cross-section at high sea states, dependent on radar configuration and dominant wave direction. The present work can contribute to the remote sensing of targets on the ocean surface, as well as the determination of the dominant wave direction of the ocean surface at high sea states. Full article

(This article belongs to the Special Issue Bistatic HF Radar)

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20 pages, 14214 KiB

Open AccessArticle

Coast–Ship Bistatic HF Surface Wave Radar: Simulation Analysis and Experimental Verification

by Yonggang Ji, Jie Zhang, Yiming Wang, Chao Yue, Weichun Gong, Junwei Liu, Hao Sun, Changjun Yu and Ming Li

Remote Sens. 2020, 12(3), 470; https://doi.org/10.3390/rs12030470 - 2 Feb 2020

Cited by 13 | Viewed by 3553

Abstract

The coast–ship bistatic high-frequency surface wave radar (HFSWR) not only has the anti-interference advantages of the coast-based bistatic HFSWR, but also has the advantages of maneuverability and an extended detection area of the shipborne HFSWR. In this paper, theoretical formulas were derived for [...] Read more.

The coast–ship bistatic high-frequency surface wave radar (HFSWR) not only has the anti-interference advantages of the coast-based bistatic HFSWR, but also has the advantages of maneuverability and an extended detection area of the shipborne HFSWR. In this paper, theoretical formulas were derived for the coast–ship bistatic radar, including the first-order sea clutter scattering cross-section and the Doppler frequency shift of moving targets. Then, simulation results of the first-order sea clutter spectrum under different operating conditions were given, and the range of broadening of the first-order sea clutter spectrum and its influence on target detection were investigated. The simulation results show the broadening ranges of the right sea clutter spectrum and left sea clutter spectrum were symmetric when the shipborne platform was anchored, whereas they were asymmetric when the shipborne platform was underway. This asymmetry is primarily a function of platform velocity and radar frequency. Based on experimental data of the coast–ship bistatic HFSWR conducted in 2019, the broadening range of the sea clutter and the target frequency shift were analyzed and compared with simulation results based on the same parameter configuration. The agreement of the measured results with the simulation results verifies the theoretical formulas. Full article

(This article belongs to the Special Issue Bistatic HF Radar)

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28 pages, 7018 KiB

Open AccessArticle

Measuring the Directional Ocean Spectrum from Simulated Bistatic HF Radar Data

by Rachael L. Hardman, Lucy R. Wyatt and Charles C. Engleback

Remote Sens. 2020, 12(2), 313; https://doi.org/10.3390/rs12020313 - 18 Jan 2020

Cited by 6 | Viewed by 3946

Abstract

HF radars are becoming important components of coastal operational monitoring systems particularly for currents and mostly using monostatic radar systems where the transmit and receive antennas are colocated. A bistatic configuration, where the transmit antenna is separated from the receive antennas, offers some [...] Read more.

HF radars are becoming important components of coastal operational monitoring systems particularly for currents and mostly using monostatic radar systems where the transmit and receive antennas are colocated. A bistatic configuration, where the transmit antenna is separated from the receive antennas, offers some advantages and has been used for current measurement. Currents are measured using the Doppler shift from ocean waves which are Bragg-matched to the radio signal. Obtaining a wave measurement is more complicated. In this paper, the theoretical basis for bistatic wave measurement with a phased-array HF radar is reviewed and clarified. Simulations of monostatic and bistatic radar data have been made using wave models and wave spectral data. The Seaview monostatic inversion method for waves, currents and winds has been modified to allow for a bistatic configuration and has been applied to the simulated data for two receive sites. Comparisons of current and wave parameters and of wave spectra are presented. The results are encouraging, although the monostatic results are more accurate. Large bistatic angles seem to reduce the accuracy of the derived oceanographic measurements, although directional spectra match well over most of the frequency range. Full article

(This article belongs to the Special Issue Bistatic HF Radar)

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27 pages, 3932 KiB

Open AccessArticle

Passive Detection of Moving Aerial Target Based on Multiple Collaborative GPS Satellites

by Mingqian Liu, Zhiyang Gao, Yunfei Chen, Hao Song, Yuting Li and Fengkui Gong

Remote Sens. 2020, 12(2), 263; https://doi.org/10.3390/rs12020263 - 12 Jan 2020

Cited by 9 | Viewed by 3773

Abstract

Passive localization is an important part of intelligent surveillance in security and emergency applications. Nowadays, Global Navigation Satellite Systems (GNSSs) have been widely deployed. As a result, the satellite signal receiver may receive multiple GPS signals simultaneously, incurring echo signal detection failure. Therefore, [...] Read more.

Passive localization is an important part of intelligent surveillance in security and emergency applications. Nowadays, Global Navigation Satellite Systems (GNSSs) have been widely deployed. As a result, the satellite signal receiver may receive multiple GPS signals simultaneously, incurring echo signal detection failure. Therefore, in this paper, a passive method leveraging signals from multiple GPS satellites is proposed for moving aerial target detection. In passive detection, the first challenge is the interference caused by multiple GPS signals transmitted upon the same spectrum resources. To address this issue, successive interference cancellation (SIC) is utilized to separate and reconstruct multiple GPS signals on the reference channel. Moreover, on the monitoring channel, direct wave and multi-path interference are eliminated by extensive cancellation algorithm (ECA). After interference from multiple GPS signals is suppressed, the cycle cross ambiguity function (CCAF) of the signal on the monitoring channel is calculated and coordinate transformation method is adopted to map multiple groups of different time delay-Doppler spectrum into the distance–velocity spectrum. The detection statistics are calculated by the superposition of multiple groups of distance-velocity spectrum. Finally, the echo signal is detected based on a properly defined adaptive detection threshold. Simulation results demonstrate the effectiveness of our proposed method. They show that the detection probability of our proposed method can reach 99%, when the echo signal signal-to-noise ratio (SNR) is only −64 dB. Moreover, our proposed method can achieve 5 dB improvement over the detection method using a single GPS satellite. Full article

(This article belongs to the Special Issue Bistatic HF Radar)

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17 pages, 2592 KiB

Open AccessArticle

The Scattering Coefficient for Shore-to-Air Bistatic High Frequency (HF) Radar Configurations as Applied to Ocean Observations

by Zezong Chen, Jian Li, Chen Zhao, Fan Ding and Xi Chen

Remote Sens. 2019, 11(24), 2978; https://doi.org/10.3390/rs11242978 - 11 Dec 2019

Cited by 4 | Viewed by 2747

Abstract

To extend the scope of high frequency (HF) radio oceanography, a new HF radar model, named shore-to-air bistatic HF radar, has been proposed for ocean observations. To explore this model, the first-order scattering coefficient and the second-order electromagnetic scattering coefficient for shore-to-air bistatic [...] Read more.

To extend the scope of high frequency (HF) radio oceanography, a new HF radar model, named shore-to-air bistatic HF radar, has been proposed for ocean observations. To explore this model, the first-order scattering coefficient and the second-order electromagnetic scattering coefficient for shore-to-air bistatic HF radar are derived using the perturbation method. In conjunction with the contribution of the hydrodynamic component, the second-order scattering coefficient is derived. Based on the derived scattering coefficients, we analyzed the simulated echo Doppler spectra for various scattering angles and azimuthal angles, operation frequencies, wind speeds, and directions of wind, which may provide the guideline on the extraction of sea state information for shore-to-air bistatic HF radar. The singularities in the simulated echo Doppler spectra are discussed using the normalized constant Doppler frequency contours. In addition, the scattering coefficients of shore-to-air bistatic HF radar are compared with that of monostatic HF radar and land-based bistatic HF radar. The results verify the correctness of the proposed scattering coefficients. The model of shore-to-air bistatic HF radar is effective for ocean observations. Full article

(This article belongs to the Special Issue Bistatic HF Radar)

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21 pages, 3003 KiB

Open AccessArticle

Ocean Surface Cross Section for Bistatic HF Radar Incorporating a Six DOF Oscillation Motion Model

by Guowei Yao, Junhao Xie and Weimin Huang

Remote Sens. 2019, 11(23), 2738; https://doi.org/10.3390/rs11232738 - 21 Nov 2019

Cited by 14 | Viewed by 3063

Abstract

To investigate the characteristics of sea clutter, based on ocean surface electromagnetic scattering theory, the first- and second-order ocean surface scattering cross sections for bistatic high-frequency (HF) radar incorporating a multi-frequency six degree-of-freedom (DOF) oscillation motion model are mathematically derived. The derived radar [...] Read more.

To investigate the characteristics of sea clutter, based on ocean surface electromagnetic scattering theory, the first- and second-order ocean surface scattering cross sections for bistatic high-frequency (HF) radar incorporating a multi-frequency six degree-of-freedom (DOF) oscillation motion model are mathematically derived. The derived radar cross sections (RCSs) can be reduced to the floating platform based monostatic case or onshore bistatic case for corresponding geometry setting. Simulation results show that the six DOF oscillation motion will result in more additional peaks in the radar Doppler spectra and the amplitudes and frequencies of these motion-induced peaks are decided by the amplitudes and frequencies of the oscillation motion. The effect of the platform motion on the first-order radar spectrum is greater than that of the second-order, and the motion-induced peaks in the first-order spectrum may overlap with the second-order spectrum. Furthermore, yaw is the dominant factor affecting the radar spectra, especially the second-order. Moreover, the effect of platform motion on radar spectra and the amplitudes of the second-order spectrum decreases as the bistatic angle increases. In addition, it should be noted that the amplitudes of the Bragg peaks may be lower than those of the motion-induced peaks due to the low frequency (LF) oscillation motion of the floating platform, which is an important finding for the applications of the floating platform based bistatic HF radar in moving target detection and ocean surface dynamics parameter estimation. Full article

(This article belongs to the Special Issue Bistatic HF Radar)

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13 pages, 1671 KiB

Open AccessLetter

Continuous Tracking of Targets for Stereoscopic HFSWR Based on IMM Filtering Combined with ELM

by Ling Zhang, Dongwei Mao, Jiong Niu, Q. M. Jonathan Wu and Yonggang Ji

Remote Sens. 2020, 12(2), 272; https://doi.org/10.3390/rs12020272 - 14 Jan 2020

Cited by 16 | Viewed by 2761

Abstract

High frequency surface wave radar (HFSWR) plays an important role in marine surveillance on account of its ability to provide wide-range early warning detection. However, vessel target track breakages are common in large-scale marine monitoring, which limits the continuous tracking ability of HFSWR. [...] Read more.

High frequency surface wave radar (HFSWR) plays an important role in marine surveillance on account of its ability to provide wide-range early warning detection. However, vessel target track breakages are common in large-scale marine monitoring, which limits the continuous tracking ability of HFSWR. The following are the possible reasons for track fracture: highly maneuverable vessels, dense channels, target occlusion, strong clutter/interference, long sampling intervals, and low detection probabilities. To solve this problem, we propose a long-term continuous tracking method for multiple targets with stereoscopic HFSWR based on an interacting multiple model extended Kalman filter (IMMEKF) combined with an extreme learning machine (ELM). When the trajectory obtained by IMMEKF breaks, a new section of the track will start on the basis of the observation data. For multiple-target tracking, a number of broken tracks can be obtained by IMMEKF tracking. Then the ELM classifies the segments from the same vessel by extracting different features including average velocity, average curvature, ratio of the arc length to the chord length, and wavelet coefficient. Both the simulation and the field experiment results validate the method presented here, showing that this method can achieve long-term continuous tracking for multiple vessels, with an average correct track segment association rate of over 91.2%, which is better than the tracking performance of conventional algorithms, especially when the vessels are in dense channels and strong clutter/interference area. Full article

(This article belongs to the Special Issue Bistatic HF Radar)

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