A Review of Over-the-Horizon Radar Systems: Global Perspectives on Design, Operational Principles, and Performance

Ajay Prudhvi Raj; Sahebgowda Patil; Anthonysamy Arockia Bazil Raj; Kamla Prasan Ray

doi:doi:10.11648/j.ajea.20261401.11

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A Review of Over-the-Horizon Radar Systems: Global Perspectives on Design, Operational Principles, and Performance

Ajay Prudhvi Raj^*

, Sahebgowda Patil, Anthonysamy Arockia Bazil Raj, Kamla Prasan Ray

Published in American Journal of Electromagnetics and Applications (Volume 14, Issue 1)

Received: 28 November 2025 Accepted: 31 January 2026 Published: 16 March 2026

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Abstract

This paper presents a comprehensive global review of over-the-horizon radar (OTHR) systems, spanning both skywave and surface-wave designs across operational, research, and historical contexts. The review integrates technical descriptions of system architectures, operating frequency ranges, waveform designs, signal processing methods, and performance characteristics, supported by corrected historical attributions and consolidated references. Major operational systems-including JORN, ROTHR, Nostradamus, the Russian 29B6 ”Container,” and Iran’s Sepehr-are examined alongside research networks such as SuperDARN and large-scale high-frequency surface-wave radar arrays used for oceanographic monitoring. Historical and retired systems, including the Soviet Duga, Cobra Mist, and the U.S. OTH-B network, are analyzed for the technical lessons they provide regarding antenna siting and noise suppression. A comparative table summarizes key parameters across all systems, offering a unified reference framework. Applications in defense surveillance, maritime domain awareness, environmental monitoring, and ionospheric research are outlined. Furthermore, this survey highlights emerging trends critical to the next generation of OTHR, such as multi-frequency agility for ionospheric resilience, machine learning-based clutter suppression, and the integration of spaceborne or UAV-borne sensors for enhanced data fusion. By linking historical technical challenges with modern adaptive signal processing and compact deployable architectures, this survey serves as both a strategic technical reference and a forward-looking roadmap for the continued evolution of high-frequency radar technology.

Published in	American Journal of Electromagnetics and Applications (Volume 14, Issue 1)
DOI	10.11648/j.ajea.20261401.11
Page(s)	1-16
Creative Commons	This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.
Copyright	Copyright © The Author(s), 2026. Published by Science Publishing Group

Keywords

HF Propagation, IONOSPHERE, Over the Horizon Radar, Radio Wave Propagation, Surveillance, Target Detection

References

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Raj, A. P., Patil, S., Raj, A. A. B., Ray, K. P. (2026). A Review of Over-the-Horizon Radar Systems: Global Perspectives on Design, Operational Principles, and Performance. American Journal of Electromagnetics and Applications, 14(1), 1-16. https://doi.org/10.11648/j.ajea.20261401.11

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ACS Style

Raj, A. P.; Patil, S.; Raj, A. A. B.; Ray, K. P. A Review of Over-the-Horizon Radar Systems: Global Perspectives on Design, Operational Principles, and Performance. Am. J. Electromagn. Appl. 2026, 14(1), 1-16. doi: 10.11648/j.ajea.20261401.11

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AMA Style

Raj AP, Patil S, Raj AAB, Ray KP. A Review of Over-the-Horizon Radar Systems: Global Perspectives on Design, Operational Principles, and Performance. Am J Electromagn Appl. 2026;14(1):1-16. doi: 10.11648/j.ajea.20261401.11

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@article{10.11648/j.ajea.20261401.11,
  author = {Ajay Prudhvi Raj and Sahebgowda Patil and Anthonysamy Arockia Bazil Raj and Kamla Prasan Ray},
  title = {A Review of Over-the-Horizon Radar Systems: Global Perspectives on Design, Operational Principles, and Performance
},
  journal = {American Journal of Electromagnetics and Applications},
  volume = {14},
  number = {1},
  pages = {1-16},
  doi = {10.11648/j.ajea.20261401.11},
  url = {https://doi.org/10.11648/j.ajea.20261401.11},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ajea.20261401.11},
  abstract = {This paper presents a comprehensive global review of over-the-horizon radar (OTHR) systems, spanning both skywave and surface-wave designs across operational, research, and historical contexts. The review integrates technical descriptions of system architectures, operating frequency ranges, waveform designs, signal processing methods, and performance characteristics, supported by corrected historical attributions and consolidated references. Major operational systems-including JORN, ROTHR, Nostradamus, the Russian 29B6 ”Container,” and Iran’s Sepehr-are examined alongside research networks such as SuperDARN and large-scale high-frequency surface-wave radar arrays used for oceanographic monitoring. Historical and retired systems, including the Soviet Duga, Cobra Mist, and the U.S. OTH-B network, are analyzed for the technical lessons they provide regarding antenna siting and noise suppression. A comparative table summarizes key parameters across all systems, offering a unified reference framework. Applications in defense surveillance, maritime domain awareness, environmental monitoring, and ionospheric research are outlined. Furthermore, this survey highlights emerging trends critical to the next generation of OTHR, such as multi-frequency agility for ionospheric resilience, machine learning-based clutter suppression, and the integration of spaceborne or UAV-borne sensors for enhanced data fusion. By linking historical technical challenges with modern adaptive signal processing and compact deployable architectures, this survey serves as both a strategic technical reference and a forward-looking roadmap for the continued evolution of high-frequency radar technology.
},
 year = {2026}
}

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T1  - A Review of Over-the-Horizon Radar Systems: Global Perspectives on Design, Operational Principles, and Performance

AU  - Ajay Prudhvi Raj
AU  - Sahebgowda Patil
AU  - Anthonysamy Arockia Bazil Raj
AU  - Kamla Prasan Ray
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PY  - 2026
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DO  - 10.11648/j.ajea.20261401.11
T2  - American Journal of Electromagnetics and Applications
JF  - American Journal of Electromagnetics and Applications
JO  - American Journal of Electromagnetics and Applications
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PB  - Science Publishing Group
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AB  - This paper presents a comprehensive global review of over-the-horizon radar (OTHR) systems, spanning both skywave and surface-wave designs across operational, research, and historical contexts. The review integrates technical descriptions of system architectures, operating frequency ranges, waveform designs, signal processing methods, and performance characteristics, supported by corrected historical attributions and consolidated references. Major operational systems-including JORN, ROTHR, Nostradamus, the Russian 29B6 ”Container,” and Iran’s Sepehr-are examined alongside research networks such as SuperDARN and large-scale high-frequency surface-wave radar arrays used for oceanographic monitoring. Historical and retired systems, including the Soviet Duga, Cobra Mist, and the U.S. OTH-B network, are analyzed for the technical lessons they provide regarding antenna siting and noise suppression. A comparative table summarizes key parameters across all systems, offering a unified reference framework. Applications in defense surveillance, maritime domain awareness, environmental monitoring, and ionospheric research are outlined. Furthermore, this survey highlights emerging trends critical to the next generation of OTHR, such as multi-frequency agility for ionospheric resilience, machine learning-based clutter suppression, and the integration of spaceborne or UAV-borne sensors for enhanced data fusion. By linking historical technical challenges with modern adaptive signal processing and compact deployable architectures, this survey serves as both a strategic technical reference and a forward-looking roadmap for the continued evolution of high-frequency radar technology.

VL  - 14
IS  - 1
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Ajay Prudhvi Raj

Department of Electronics Engineering, Defence Institute of Advanced Technology (DIAT), Pune, India

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http://orcid.org/0009-0004-4666-3413
Sahebgowda Patil

Department of Electronics Engineering, Defence Institute of Advanced Technology (DIAT), Pune, India

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Anthonysamy Arockia Bazil Raj

Department of Electronics Engineering, Defence Institute of Advanced Technology (DIAT), Pune, India

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Kamla Prasan Ray

Department of Electronics Engineering, Defence Institute of Advanced Technology (DIAT), Pune, India

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http://orcid.org/0000-0002-8400-613X

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Raj, A. P., Patil, S., Raj, A. A. B., Ray, K. P. (2026). A Review of Over-the-Horizon Radar Systems: Global Perspectives on Design, Operational Principles, and Performance. American Journal of Electromagnetics and Applications, 14(1), 1-16. https://doi.org/10.11648/j.ajea.20261401.11

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ACS Style

Raj, A. P.; Patil, S.; Raj, A. A. B.; Ray, K. P. A Review of Over-the-Horizon Radar Systems: Global Perspectives on Design, Operational Principles, and Performance. Am. J. Electromagn. Appl. 2026, 14(1), 1-16. doi: 10.11648/j.ajea.20261401.11

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AMA Style

Raj AP, Patil S, Raj AAB, Ray KP. A Review of Over-the-Horizon Radar Systems: Global Perspectives on Design, Operational Principles, and Performance. Am J Electromagn Appl. 2026;14(1):1-16. doi: 10.11648/j.ajea.20261401.11

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@article{10.11648/j.ajea.20261401.11,
  author = {Ajay Prudhvi Raj and Sahebgowda Patil and Anthonysamy Arockia Bazil Raj and Kamla Prasan Ray},
  title = {A Review of Over-the-Horizon Radar Systems: Global Perspectives on Design, Operational Principles, and Performance
},
  journal = {American Journal of Electromagnetics and Applications},
  volume = {14},
  number = {1},
  pages = {1-16},
  doi = {10.11648/j.ajea.20261401.11},
  url = {https://doi.org/10.11648/j.ajea.20261401.11},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ajea.20261401.11},
  abstract = {This paper presents a comprehensive global review of over-the-horizon radar (OTHR) systems, spanning both skywave and surface-wave designs across operational, research, and historical contexts. The review integrates technical descriptions of system architectures, operating frequency ranges, waveform designs, signal processing methods, and performance characteristics, supported by corrected historical attributions and consolidated references. Major operational systems-including JORN, ROTHR, Nostradamus, the Russian 29B6 ”Container,” and Iran’s Sepehr-are examined alongside research networks such as SuperDARN and large-scale high-frequency surface-wave radar arrays used for oceanographic monitoring. Historical and retired systems, including the Soviet Duga, Cobra Mist, and the U.S. OTH-B network, are analyzed for the technical lessons they provide regarding antenna siting and noise suppression. A comparative table summarizes key parameters across all systems, offering a unified reference framework. Applications in defense surveillance, maritime domain awareness, environmental monitoring, and ionospheric research are outlined. Furthermore, this survey highlights emerging trends critical to the next generation of OTHR, such as multi-frequency agility for ionospheric resilience, machine learning-based clutter suppression, and the integration of spaceborne or UAV-borne sensors for enhanced data fusion. By linking historical technical challenges with modern adaptive signal processing and compact deployable architectures, this survey serves as both a strategic technical reference and a forward-looking roadmap for the continued evolution of high-frequency radar technology.
},
 year = {2026}
}

Copy | Download

TY  - JOUR
T1  - A Review of Over-the-Horizon Radar Systems: Global Perspectives on Design, Operational Principles, and Performance

AU  - Ajay Prudhvi Raj
AU  - Sahebgowda Patil
AU  - Anthonysamy Arockia Bazil Raj
AU  - Kamla Prasan Ray
Y1  - 2026/03/16
PY  - 2026
N1  - https://doi.org/10.11648/j.ajea.20261401.11
DO  - 10.11648/j.ajea.20261401.11
T2  - American Journal of Electromagnetics and Applications
JF  - American Journal of Electromagnetics and Applications
JO  - American Journal of Electromagnetics and Applications
SP  - 1
EP  - 16
PB  - Science Publishing Group
SN  - 2376-5984
UR  - https://doi.org/10.11648/j.ajea.20261401.11
AB  - This paper presents a comprehensive global review of over-the-horizon radar (OTHR) systems, spanning both skywave and surface-wave designs across operational, research, and historical contexts. The review integrates technical descriptions of system architectures, operating frequency ranges, waveform designs, signal processing methods, and performance characteristics, supported by corrected historical attributions and consolidated references. Major operational systems-including JORN, ROTHR, Nostradamus, the Russian 29B6 ”Container,” and Iran’s Sepehr-are examined alongside research networks such as SuperDARN and large-scale high-frequency surface-wave radar arrays used for oceanographic monitoring. Historical and retired systems, including the Soviet Duga, Cobra Mist, and the U.S. OTH-B network, are analyzed for the technical lessons they provide regarding antenna siting and noise suppression. A comparative table summarizes key parameters across all systems, offering a unified reference framework. Applications in defense surveillance, maritime domain awareness, environmental monitoring, and ionospheric research are outlined. Furthermore, this survey highlights emerging trends critical to the next generation of OTHR, such as multi-frequency agility for ionospheric resilience, machine learning-based clutter suppression, and the integration of spaceborne or UAV-borne sensors for enhanced data fusion. By linking historical technical challenges with modern adaptive signal processing and compact deployable architectures, this survey serves as both a strategic technical reference and a forward-looking roadmap for the continued evolution of high-frequency radar technology.

VL  - 14
IS  - 1
ER  -

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