Special Issue "Bistatic HF Radar"

A special issue of Remote Sensing (ISSN 2072-4292).

Deadline for manuscript submissions: 31 January 2020.

Special Issue Editor

Prof. Dr. Stuart Anderson
E-Mail Website
Guest Editor
Physics Department, University of Adelaide, Adelaide SA 5007, Australia
Interests: radiowave propagation, electromagnetic scattering, oceanography and ionospheric physics, focusing on applications to HF radar

Special Issue Information

Dear Colleagues,

The proliferation of HF radar systems for ocean remote sensing and maritime surveillance continues apace, with hundreds of such radars now deployed around the world. The overwhelming majority of these radars operate in the conventional monostatic configuration, with the transmitting and receiving systems collocated or closely spaced (the term quasi-monostatic is often used in this case). This simple geometry has obvious advantages in terms of cost, siting requirements, communications, maintenance, signal processing, and echo interpretation and has been adopted by HF radars exploiting line-of-sight, surface wave, and skywave propagation modalities.

All these considerations notwithstanding, in some circumstances, there can be compelling reasons to implement bistatic configurations, defined as geometries in which the separation between transmitter and receiver is comparable with the range to the zones being interrogated. Factors which can drive this decision include energy budget, desire to exploit hybrid propagation modes, scattering characteristics of the targets of interest, properties of the clutter, survivability, and covertness.

While there continues to be a thriving literature on the design and application of monostatic HF radars, the same does not hold for bistatic configurations. Motivated by our desire to expand the palette of missions which can be addressed by HF radars, especially some that cannot be addressed by monostatic radars, we issue this invitation to authors to contribute articles that report state-of-the-art research on bistatic HF radar design, physics, signal processing, echo interpretation, and applications in the maritime domain.

Prof. Dr. Stuart Anderson
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Remote Sensing is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • HF radar
  • OTH radar
  • Bistatic radar
  • Radio oceanography
  • Radiowave propagation

Published Papers (5 papers)

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Open AccessArticle
Measuring the Directional Ocean Spectrum from Simulated Bistatic HF Radar Data
Remote Sens. 2020, 12(2), 313; https://doi.org/10.3390/rs12020313 (registering DOI) - 18 Jan 2020
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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Open AccessArticle
Passive Detection of Moving Aerial Target Based on Multiple Collaborative GPS Satellites
Remote Sens. 2020, 12(2), 263; https://doi.org/10.3390/rs12020263 - 12 Jan 2020
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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Open AccessArticle
The Scattering Coefficient for Shore-to-Air Bistatic High Frequency (HF) Radar Configurations as Applied to Ocean Observations
Remote Sens. 2019, 11(24), 2978; https://doi.org/10.3390/rs11242978 - 11 Dec 2019
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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Open AccessArticle
Ocean Surface Cross Section for Bistatic HF Radar Incorporating a Six DOF Oscillation Motion Model
Remote Sens. 2019, 11(23), 2738; https://doi.org/10.3390/rs11232738 - 21 Nov 2019
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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Open AccessLetter
Continuous Tracking of Targets for Stereoscopic HFSWR Based on IMM Filtering Combined with ELM
Remote Sens. 2020, 12(2), 272; https://doi.org/10.3390/rs12020272 - 14 Jan 2020
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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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Bistatic and stereoscopic configurations for HF radar

Stuart Anderson

    Physics Department, University of Adelaide, Adelaide SA 5007, Australia

Abstract: Remote sensing of our geophysical environment by means of radio waves in the HF band is now a truly global activity, with decametric radars operating in scores of countries, and on every continent. In a number of instances, international collaborations facilitate the integration of the outputs from individual radars to yield regional or even basin-scale products, thereby increasing the quality, diversity and utility of the derived information.

The overwhelming majority of these radars operate in the conventional monostatic configuration, with the transmitting and receiving systems collocated or closely spaced (the term quasi-monostatic is often used in this case). This simple geometry has obvious advantages in terms of cost, siting requirements, communications, maintenance, signal processing, and echo interpretation and has been adopted by HF radars exploiting line-of-sight, surface wave, and skywave propagation modalities.

All these considerations notwithstanding, in some circumstances there can be compelling reasons to implement bistatic configurations, defined as geometries in which the separation between transmitter and receiver is comparable with the range to the zones being interrogated. Factors which can drive this decision include energy budget, desire to exploit hybrid propagation modes, scattering characteristics of the targets of interest, properties of the clutter, survivability, and covertness. Bistatic HF radars with very specific missions have been deployed since the 1960’s, predominantly in defense applications, but the convenience of monostatic designs and the adequacy of their standard remote sensing products have tended to discourage wider adoption of bistatic configurations.

Once we allow for the separation of transmit and receive facilities, many possible configurations emerge. Each of these subsystems can be located on land, at sea, in the air or even in space, with a range of propagation mode combinations possible for the signal paths from transmitter to target and target to receiver. Of these, line-of-sight, surface wave and skywave modes are by far the most common, though more exotic propagation mechanisms have been explored. Table 1 presents a taxonomy of the main configurations; those which are understood to have been implemented, or at least reached the advanced design phase, are indicated by the colored dots.

This diverse array of system geometries offers many opportunities for remote sensing. In particular, the ability to extend the range of Bragg resonant scattering to lower wavenumbers opens the way to observing some environmental phenomena to which monostatic radars are insensitive, and to addressing others in ways that enable more precise measurements to be made.

In this paper we discuss the corresponding radar process models, including the underlying physics, and illustrate the application of bistatic configurations to specific remote sensing missions.

 

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