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In the realm of defense and surveillance, the evolution of radar technology has been a silent yet transformative journey. Traditional radar systems, with their colocated transmitters and receivers, have long been the stalwarts of air defense and maritime surveillance. However, a new contender has emerged on the horizon – passive radars.
The Rise of Passive Radars
In an ever-evolving landscape of defense technology, passive radars have emerged as a silent but powerful force, revolutionizing air defense and maritime surveillance. Unlike traditional radar systems that emit radio waves and then detect their reflections, passive radars capitalize on existing signals, such as television and radio broadcasts, to detect targets.
This allows the bistatic range of the object to be determined. In addition to bistatic range, a passive radar will typically also measure the bistatic Doppler shift of the echo and also its direction of arrival. These allow the location, heading and speed of the object to be calculated. In some cases, multiple transmitters and/or receivers can be employed to make several independent measurements of bistatic range, Doppler and bearing and hence significantly improve the final track accuracy. It is a specific case of bistatic radar, the latter also including the exploitation of cooperative and non-cooperative radar transmitters.
Among the various types of passive radars, Passive Coherent Location (PCL) stands out for its utilization of commercial signals, such as FM and AM radio, TV broadcasts, and satellite communications, to detect and track targets with precision.
The concept of passive radar is not new, but recent advancements in signal processing and computing power have propelled its adoption on a global scale. For the first time, these allowed designers to apply digital signal processing techniques to exploit a variety of broadcast signals and to use cross-correlation techniques to achieve sufficient signal processing gain to detect targets and estimate their bistatic range and Doppler shift. With the ability to operate covertly and detect targets with precision, passive radars have become indispensable tools for military and civilian applications alike.
The Advantages of Passive Radars
Conventional radar systems rely on emitting radio waves and detecting their reflections to determine the range and location of objects. In contrast, passive radars operate without a dedicated transmitter. Instead, they utilize third-party transmitters in the environment, measuring the time difference of arrival between direct signals and reflections to pinpoint targets. This innovative approach, also known as passive coherent location, harnesses non-cooperative sources of illumination such as commercial broadcasts and communications signals. This innovative approach offers numerous advantages, from enhanced stealth capabilities to cost-effectiveness, making passive radars a cornerstone of modern defense strategies.
- Stealth and Covert Operations: One of the most significant advantages of passive radars lies in their stealth capabilities. By operating silently and without emitting signals, they are extremely difficult to detect or jam by adversaries, enhancing operational security.
- Cost-Effectiveness: Passive radars offer a cost-effective alternative to traditional radar systems, requiring fewer resources to operate and maintain. Their reliance on existing signals in the environment eliminates the need for dedicated transmitters, resulting in significant cost savings.
- Wide Coverage and Precision: With their ability to detect and track targets using reflections from ambient signals, passive radars provide wide coverage and precise location data. They can measure bistatic range, Doppler shift, and direction of arrival, offering comprehensive situational awareness.
Applications in Air Defense and Maritime Surveillance
Passive radars play a crucial role in both air defense and maritime surveillance. In air defense, they offer a silent yet powerful means of detecting stealth aircraft and low-flying targets. Their covert operation and wide coverage make them indispensable tools for safeguarding airspace. Similarly, in maritime surveillance, passive radars provide unparalleled capabilities for tracking ships and vessels, enhancing border security and maritime law enforcement efforts.
In air defense, passive radars provide a critical layer of surveillance, complementing traditional radar systems. By leveraging ambient signals, these radars can detect stealth aircraft that evade conventional radar detection. Moreover, their ability to operate without emitting signals minimizes the risk of detection by enemy forces, enhancing operational security.
Beyond the skies, passive radars extend their reach to the seas, offering unparalleled capabilities in maritime surveillance. With a vast coverage area and the ability to detect ships and vessels using their radio emissions, passive radars provide crucial intelligence for naval operations, border security, and maritime law enforcement.
Advantages of Passive Radars
- Stealthy Operations: By relying on ambient signals, passive radars operate silently, making them difficult to detect or jam by adversaries.
- Cost-Effectiveness: Compared to traditional radar systems, passive radars require fewer resources to operate and maintain, resulting in significant cost savings.
- Wide Coverage Area: Passive radars can cover large geographic areas without the need for extensive infrastructure, making them ideal for monitoring vast stretches of airspace and maritime territory.
- Resilience to Electronic Warfare: With no emissions to track or disrupt, passive radars are inherently resilient to electronic warfare tactics employed by hostile forces.
Passive multistatic radars (PMRs) Operational Performance and Capabilities
Passive multistatic radars (PMRs) represent a significant advancement in radar technology, especially in countering stealth threats. Unlike conventional radars that emit electromagnetic pulses for detection, PMRs rely on opportunistic signals from existing transmitters, such as communication networks and broadcast stations, making them inherently covert and difficult to detect. Among the various types of passive radars, Passive Coherent Location (PCL) stands out for its utilization of commercial signals, such as FM and AM radio, TV broadcasts, and satellite communications, to detect and track targets with precision.
The operational performance of PMRs is comparable to conventional radar systems, with detection ranges varying depending on the type of signals utilized. For instance, PMRs employing FM radio stations can achieve detection ranges of up to 150 km, while those using high-power TV broadcasts can extend their range beyond 300 km. Additionally, the accuracy of PMRs is influenced by deployment geometry, with height measurements becoming feasible in configurations with significant altitude variations among transmitters, receivers, and targets.
Research and Development Landscape
Research on PMRs is gaining momentum worldwide, with numerous institutions and organizations actively exploring their potential applications and technological advancements. From the United States to Europe and beyond, research efforts span academia, government agencies, and private enterprises. However, the complexity of PMR systems presents challenges in terms of synchronization, data fusion, and resource management, necessitating innovative solutions for coherent operation and signal processing.
Technological Innovations and Future Prospects
Recent advancements in radar technology, such as AESA (Active Electronically Scanned Array) and advanced signal processing, are poised to further enhance the capabilities of PMRs. Saab’s Giraffe 4A/8A S-band radars exemplify this trend, leveraging AESA technology and advanced processing to improve performance against small targets. New processing techniques, including multiple hypothesis tracking, enable PMRs to analyze weak returns over time, enhancing target detection and tracking capabilities.
The Growing Market and Technological Advancements
The global passive radar market is on a trajectory of steady growth, driven by technological advancements and increasing demand from defense and civilian sectors. With the rise of stealth-based threats and the need for advanced surveillance capabilities, passive radars are poised to become integral components of defense systems worldwide.
The passive radar market is poised for significant growth in the coming years, driven by advancements in technology, increasing adoption in defense and civilian sectors, and emerging threats necessitating innovative surveillance solutions. According to Visiongain research firm, the global passive radar market is projected to grow from US$ 2,324 million in 2020 to US$ 4,313 million by 2030, representing a Compound Annual Growth Rate (CAGR) of 6.38% during the forecast period.
Advantages and Market Dynamics
Passive radar, distinct from traditional radar systems, operates by utilizing reflections from existing electromagnetic signals in the atmosphere, rather than emitting its own electromagnetic radiation. This inherent covert nature offers several advantages, including reduced detectability, lower thermal signature, and enhanced operational security. As a result, passive radar systems are expected to capture a significant portion of the defense, civilian radar, and homeland security markets.
Technological Advancements and Market Trends
In response to evolving threats, research on counter-stealth technologies has gained momentum, leading to advancements in passive radar systems. Companies are developing advanced air defense systems with passive sensor capabilities, offering early warning and air situational awareness without the use of active radars. The emergence of stealth fighter jets from countries like China and Russia has spurred investments in passive radar technologies, particularly in the United States.
Regional Market Dynamics
The United States currently dominates the North American passive radar market, driven by investments in research and development from government agencies, such as the Air Force Research Labs, and leading defense contractors like Raytheon and Lockheed Martin. Ongoing research and technological opportunities are expected to fuel growth in the adoption of passive radar technologies across commercial and defense sectors in the region.
Competitive Landscape and Future Outlook
Key players in the passive radar market include Airbus SE, BAE Systems PLC, Raytheon Company, and Israel Aerospace Industries Ltd., among others. These companies are unveiling advanced passive radar models to tap into new markets and enhance their competitive edge. For instance, ELTA Systems unveiled a Passive Coherent Location Radar System that enables real-time tracking of multiple targets using reflections from FM or Digital Audio Broadcasting towers.
Recent Advancements
The realm of passive radars is undergoing a transformation driven by exciting advancements. One key area of progress is miniaturization and integration. This translates to compact and portable systems, making deployment in remote locations and on mobile platforms like drones or vehicles a breeze. Furthermore, multi-static and multi-frequency operations are on the rise. These systems utilize multiple receivers spread across a wider area and operate on different radio frequencies, leading to sharper target detection and tracking accuracy. Additionally, advancements in signal processing are yielding improved algorithms that can effectively filter out background noise and clutter. This translates to better target identification, even in challenging environments. The future holds even more promise with the integration of Artificial Intelligence (AI). AI can analyze complex radar data in real-time, automate target recognition, and predict potential threats, allowing for faster and more efficient decision-making. Finally, research is pushing the boundaries by exploring the use of new signal sources like satellite navigation signals or mobile phone networks. This expansion broadens the range of environments where passive radars can be effectively deployed.
Case Studies and Industry Developments
- Silentium Defence: The Maverick M-series passive radar system developed by Silentium Defence represents a significant milestone in portable, covert radar technology. Designed for air defense and maritime surveillance, it offers critical sovereign capability for the Australian Defence Force and its allies.
- ELTA Systems: ELTA Systems’ Passive Coherent Location Radar System exemplifies the latest advancements in passive radar technology. By detecting and tracking aerial threats based on reflections from FM or Digital Audio Broadcasting towers, it provides real-time tracking of multiple targets with unmatched precision.
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IAI’s Passive Radar System:
ELTA Systems, a subsidiary of IAI, unveiled a new system in 2020 that detects and tracks aerial threats using reflections from FM or DAB towers.
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Australian Army’s Passive Radars:
Silentium Defence is supplying its Maverick M-series passive radar system to the Australian Army for evaluation. These compact systems use existing environmental signals and offer covert operation.
Germany’s recent development of a passive radar system utilizing radiation from the Starlink satellite network marks a significant advancement in target detection and imaging technology. The system, known as the SABBIA 2.0 demonstrator, is designed by the Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR) and represents a promising leap forward in radar capabilities.The concept behind this innovative radar system lies in its opportunistic use of existing transmitters from the vast Starlink satellite network. Starlink, comprising more than 3000 satellites in low Earth orbit, provides global coverage and a robust bandwidth signal to its customers worldwide. Leveraging this network for radar applications offers several advantages, including enhanced coverage, resilience against jamming, and improved detection of stealth targets.
One of the key strengths of the Starlink-based passive radar system is its ability to exploit the sheer number of satellites in the constellation. With satellites positioned at varying angles and trajectories, the system can effectively illuminate objects from multiple directions. This multi-angle illumination increases the likelihood of detecting targets, even those obscured or difficult to detect using traditional radar systems.
The operational principle of the SABBIA 2.0 system involves two main components: a high-gain reference antenna and a surveillance antenna. The reference antenna tracks a selected Starlink satellite and captures its signal, while the surveillance antenna, positioned to observe a specific area of interest, receives echoes from potential targets within that area. By correlating the signals received from the reference and surveillance antennas, the system can accurately detect and track targets without emitting its own electromagnetic radiation.
This passive radar technology represents a significant step forward in radar innovation, offering military and civilian applications alike. In addition to its potential for covert operation and enhanced target detection, the system’s reliance on existing satellite infrastructure makes it a cost-effective and scalable solution for various surveillance needs.
The successful demonstration of the SABBIA 2.0 passive radar system underscores Germany’s commitment to advancing defense technology and leveraging cutting-edge innovations for national security. As research and development in passive radar technology continue to progress, we can expect further enhancements in target detection, imaging, and situational awareness capabilities, contributing to a safer and more secure future.
Future Outlook
As the demand for advanced surveillance capabilities continues to grow, the future of passive radars appears brighter than ever. Ongoing research and development efforts aim to further enhance the performance and versatility of these systems, paving the way for their widespread adoption across military and civilian sectors.
Conclusion
In a world where threats are constantly evolving, passive radars offer a beacon of hope, providing unmatched surveillance capabilities with stealth and precision. From safeguarding the skies to protecting maritime interests, these innovative systems are reshaping the landscape of defense technology, ensuring a safer and more secure future for nations around the globe. As we look to the horizon, it is clear that the era of passive radars has arrived, heralding a new era of surveillance excellence.
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