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Radar (radio detection and ranging) is a detection system that uses radio waves to determine the distance (ranging), angle, and radial velocity of objects relative to the site. A radar system consists of a transmitter producing electromagnetic waves in the radio or microwave domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine the properties of the object(s). Radio waves (pulsed or continuous) from the transmitter reflect off the object and return to the receiver, giving information about the object’s location and speed.
Modern radar has many applications that impact our daily lives in ways. The weather forecasts that we rely on could not exist without specific ground and space-based radars. Doppler weather radar technology helps meteorologists locate and track incoming weather, like rain, snow, and hail. Law enforcement agencies like state (and some local) police utilize radar speed guns to detect speeding vehicles on the road. Most often, they are used in a stationary vehicle pointed toward oncoming traffic. They can detect speed from over a mile away, given the right angle and circumstances. Radar imaging could provide a non-invasive alternative to exploratory surgeries and other procedures. It can also track respiration, heart rate, and other vital signs, eliminating the need for uncomfortable on-body monitors and providing patients with more mobility and independence.
Advanced driver-assistance systems (ADAS) and autonomous technologies are providing cars with sensing capabilities that exceed human abilities, such as identifying unseen objects and triggering automatic emergency braking (AEB) potentially faster than a human driver can. Radar can perceive beyond human visual capabilities. It can sense range and velocity, and it can do so through rain, snow and fog, conditions under which human eyes, cameras and lidar are far more limited.
Radar originally was developed to meet the needs of military services, and it continues to have critical applications for national defense purposes. Radar is one of the primary ways to keep warfighters safe on the battlefield, whether on land, at sea, or in the air. Radars are used by armed forces for surveillance, to find targets and track their movements, and direct other weapons or countermeasures against them. For instance, radars are used to detect aircraft, missiles, artillery and mortar projectiles, ships, land vehicles, and satellites.
Military radars are also used for navigation and as weather radars. Radars are used by the Navy (coastal radars, ship-based radars), Air Force (weather navigation radar, airborne radar, precision approach radar), Army (perimeter surveillance radars, long-range surveillance radars, fixed and movable land radars), and in space applications.
In addition, radar controls and guides weapons; allows one class of target to be distinguished from another; aids in the navigation of aircraft and ships; and assists in reconnaissance and damage assessment.
Modern radar systems often have imaging capability, can yield digitized signals quickly and easily for use with graphical overlays, can be networked together so the total system is greater than the sum of its parts, and can serve several different functions—such as wide-area search, target tracking, fire control, and weather monitoring—where previous generations of radar technology required separate systems to do the same jobs.
Designers of next-gen military radar systems are under constant pressure to deliver enhanced capability to track and counter increasingly sophisticated threats, all at the lowest cost possible, while also factoring in ease of installation and upgrades.
Radar systems must overcome unwanted signals in order to focus on the targets of interest. These unwanted signals may originate from internal and external sources, both passive and active. High-tech radar systems are associated with digital signal processing, and machine learning and are capable of extracting useful information from very high noise levels.
Radar trends
Today, radar is used in systems with goals beyond object detection or position measurements. Chirped radar is used for the simultaneous position and velocity measurements, with some signal processing techniques used to extract accurate targets and track their positions. Today’s automobiles currently use chirped radar modules with a relatively small footprint, with modules operating in the K band for short-range target tracking (~24 GHz) or in the W band for long-range target tracking (~76-81 GHz).
The convergence between radar and telecommunications – one example being the use of electronically scanned antennas for 5G and 6G transmissions – points to another area of technological development with significant civilian and defence implications: multi-mission antennas. With the right waveforms and suitable hardware and software, the same antenna can be used for radar, as a communication system, as a receiver for different signals, and as a transmitter for jamming and electronic warfare.
- 3D Radar Systems
Many companies and military organizations globally are investing in 3D radar systems to increase the performance and efficiency of weather monitoring, military and surveillance systems. In a 3D radar system, measurements of all three space coordinates are made within a radar system. 3D radars have pencil beams which are rotated for scanning purposes. After each scanning rotation, the antenna elevation is shifted to the next sound. This process is further repeated on many angles to scan the entire volume of air around the radar within its maximum range. 3D radars are now replacing 2D radars mostly in the defense and meteorological industries.
- Rising Use of Passive Radars
Passive radars are gaining traction in the market as they are less expensive and more efficient. These types of radars comprise of a class of radar systems that detect and track objects by processing reflections from non-cooperative sources of illumination, such as commercial and communication signals. They use existing electromagnetic signals from the atmosphere to support imaging and tracking capabilities compared to the regular/active radar that sends out electromagnetic signals to the target and receives reflected signals from the target. Passive radars use ambient radio signals for tracking and surveillance and are less expensive to operate.
- Increasing Demand in Phased-array radars and Active Electronically Scanned Array (AESA)
Radar requirements and design adjust to meet the mission needs and the constraints of the operating platform. Airborne systems typically seek the best performance possible in a constrained size, weight and power (SWAP) envelope operating in a severe environment, so they tend to use the most advanced technology.
Active electronically scanned arrays (AESA) are revolutionizing the performance of modern radar systems, enabling an unprecedented degree of operational flexibility. AESA technology is particularly advantageous in fighter radars due to the overall superiority in terms of performance, reliability and life cycle cost.
Active Electronically Scanned Array (AESA) technology is gaining traction as it has advance tracking and detection capabilities. AESA has controlled array antenna in which the beam of radio waves can be electronically steered to point in different directions without moving the antenna. New AESA technologies have enabled an evolution to higher (millimeter wave) frequencies providing greater resolution with smaller phased-array antennas. These radars have much more efficient detection, targeting, tracking and self-protection capabilities compared to traditional mechanically scanned radar systems.
In the latest breed, the transmit/receive (TR) modules can be configured to operate either independently or in clusters. This enables the generation of multiple beams operating at different frequencies in order to devote scanning resources dynamically and intelligently. This highly adaptable configuration helps to reduce the probability of intercept compared with passive array radars. Additionally, directional reception and frequency agility reduce susceptibility to jamming, particularly if wideband.
Phased-array radars, based on electronically scanning antennas populated with transmit/receive (T/R) modules that employ GaAs MMIC chips, are on the cutting edge of military radar technology. They provide numerous advantages over conventional radars, particularly for fighter aircraft, including lower radar cross-section (greater stealthiness), simultaneous multiple-target engagement capabilities, extended target-detection range, higher survivability, greater reliability, and reduced weight and size. All the original T/R module and electronically scanned array technologies were developed by military contractors using government money.
4. MIMO Radars
In order to reduce the size, weight, power and cost (SWAP-C) of AESA radars and increase scalability, researchers are developing sophisticated techniques that leverage sparsely populated arrays that are combined to form larger virtual arrays using multiple-input multiple-output (MIMO) technology similar to techniques being developed for 5G wireless communications.
In a MIMO system, you have an array of Tx antennas that broadcast orthogonal signals. The reason to use MIMO is not focused on increasing the number of tracked targets, but on the resolution of target tracking, specifically in angular resolution within the field of view.
MIMO radar leverages spatial diversity with multiple separate transmit and receive antennas that use computational algorithms to calculate radar reflections and achieve compound resolution. These antenna systems can also operate at several frequencies, or over a wideband set of frequencies simultaneously without interfering, to further enhance the discrimination of legitimate targets over radar clutter.
5. Counter UAV Radars
Rise of the number of commercial UAVs as well as employment of UAVs by terrorists and military are leading to the search of counter UAV solutions. Drone detection radar is an integral part of any drone detection system that can be used to detect and counter potentially harmful UAVs within your airspace. Airport authorities and the military are looking to improve their ability to detect low, slow, and small targets, such as unmanned aerial vehicles (UAVs).
Being able to detect and classify a small, lightweight UAV at a distance of several kilometers – and then quickly analyze its velocity and course – can make the difference between normal operations and a complete flight shutdown.
Modern Doppler radar technology is one of the most effective means of achieving this. But it’s not enough alone. It is the combination with supporting technologies, including 3D digital array and data capture systems, that provides operators with comprehensive tracking and analysis capabilities that are needed in today’s cluttered air traffic environments.
6. Ultrawideband Millimeter-wave radars
To avoid the spectrum congestion at lower microwave frequencies, and to achieve high-precision and high-resolution capabilities many applications have moved beyond 20 GHz. Fortunately, at millimeter-wave frequencies, there are several frequency bands that are designated with 0.5 GHz, 1 GHz and even 4 GHz of available bandwidth. Radiation at millimeter-wave frequencies tends to suffer higher atmospheric losses but is more directional than at sub-6 GHz microwave frequencies. Millimeter-wave radars benefit from reduced noise, greater resolution due to ultra wide bandwidths, and reduced size.
Many of the latest automobile radars leverage the 79 GHz millimeter wave frequency band that can penetrate sufficiently in adverse conditions, such as fog, dust and rain that are impenetrable by optical sensors. Operation in this band also enables increased resolution and better hazard detection features.
The benefits of millimeter wave radar translate to other applications as well, including detection and surveillance of UAS/drones and even medical monitoring. For example, multi-channel radar for perimeter surveillance (MCRPS) and scanning surveillance radar systems (SSRS) using FMCW principals, with 1 GHz of bandwidth and 100 mW at 94 GHz, have been used to achieve 15 cm range resolution and classification of UAS/drones based on their rotor typologies. Also, 24 GHz band radar has been used in remote heart rate monitors able to discriminate and characterize a heartbeat accurately and efficiently with less than 7.17 ms of RMS error
7. Quantum Radars
Quantum Sensing exploit high sensitivity of quantum systems to external disturbances to develop highly sensitive sensors. They can measure Quantities such as time, magnetic and electrical fields, inertial forces, temperature, and many others. They employ quantum systems such as NV centers, atomic vapors, Rydberg atoms, and trapped ions. Quantum sensors will outperform current sensors with dramatically improved performance for critical Defense missions.
Rydberg atoms, have extreme sensitivity to electric fields, including microwave fields ranging from 100 MHz to over 1 THz will lead to Micrometer size Quantum antennas for communications, radar and electronic warfare systems for full range of frequencies.
Quantum radars will be able to detect stealth aircrafts. Quantum radars use quantum entanglement of two photons, one of the photons is sent towards target while keeping the second captive for observation. As the transmitted particle will bounces off targets its behavior that can be observed in the captive particle. The result is much more detailed information about the target than seen in previous radars. Another benefit of quantum radars: they emit very little energy and are thus difficult to detect.
A Chinese company, Electronic Technology Group Corporation, claims to have developed quantum radar will be able to detect US stealth aircraft such as F-22 Raptor, and F-35. It is also claimed to be able to determine the type of aircraft or the weapons the plane is carrying.
Radar technology trends
Modern radar systems are combining advanced materials, solid-state modules, digital signal processors, ultrafast analog-to-digital (A-D) and digital-to-analog (D-A) converters, fast commercial off-the-shelf (COTS) microprocessors to give a better performance in small, compact, and efficient packages.
Advanced DSP and digital waveform generation technology enhances programmability and flexibility to provide next-generation radar waveforms. Commercial FPGAs have become extremely powerful—with over 20 TMACs of fixed-point performance and 10 tera floating point operations per second (TFLOPS) of single-precision floating point performance; and unlike CPUs and GPUs, FPGAs can be reconfigured as requirements change. In a military scenario, this facilitates and enables flexible adaptation to evolving threats, especially considering their capabilities with respect to latency, parallelism, input/output (I/O) speed and computational intensity.
The development of analog-to-digital converters (ADC) and digital-to-analog converters (DAC) has been to increase the speed of ADC/DAC components to enable direct RF sampling/synthesis at gigahertz frequencies. Higher frequency digital synthesis and sampling eliminate stages of up-conversion and down-conversion, avoiding the performance limitations associated with mixers in the signal chain for high microwave and millimeter-wave frequency radar while increasing bandwidth.
With the increasing demand for FPGAs, general-purpose processors (GPP), and ADC/DACs, associated components and technologies are also needed. This includes high-speed RAM, longer-term memory storage, such as solid-state drives (SSD), embedded computers, and data acquisition control systems.
A contributing factor to enhanced capabilities and decreased costs is the development of new antenna and radar fabrication technologies. New semiconductor materials, such as gallium arsenide (GaAs) and gallium nitride (GaN) are helping systems designers improve efficiency and shrink overall system size. Among these, GaN power transistors, low noise amplifiers (LNA) and active electronically steered array (AESA) antennas have been central to recent radar and radar jammer system deployments around the globe.
Radars employing these technologies outperform conventional radar systems and have spurred a flood of new and innovative radar design and fabrication approaches. New AESA technologies have enabled an evolution to higher (millimeter wave) frequencies providing greater resolution with smaller phased-array antennas, while modular design approaches enable rapid adoption of new digital processing
With the development of device and packaging technology such as GaN MMICs, conformal radar, digital array radar, MIMO architecture and integrated RF systems are anticipated trendsetters for future advancement.
RF/microwave and digital technologies, such as OpenVPX and OpenRFM will also enhance the modular design and development of high performance military electronics that rely on tightly coupled digital and RF/microwave systems.
3D Printed Radar Components, Modular Radar Design and Magnetic Material Enhancements
To further reduce radar component SWAP-C, advances in 3D printing of electronics, modular RF/microwave component design techniques and the use of magnetic material enhancements are being investigated by research institutions, industry and the DoD. Smaller, more efficient, scalable and flexibly manufactured radar components, including antennas and RF/microwave passive components, will lead to more sophisticated manpack, UAS and commercial radar systems. Such techniques must be able to print the antenna, phase-shifters, filters and transmission lines on a low-cost substrate.
Metamaterials: Bringing radar sophistication up while driving costs way down
Metamaterials (materials engineered to have properties that have not yet been found in nature) may be the next big leap in conventional radar technology. Research and development from a company called Echodyne is using the enhanced materials to drastically reduce the size, weight, and ultimately price of radar devices. With these physical, material, and financial shifts, metamaterial-based radar systems may find applications outside their target military markets, such as in cars and personal drones. Military radar system costs begin at $100,000, but metamaterial-based radar systems are aiming for a price point in the low thousands or even hundreds of dollars, which could make defense-level radar technology available to the mass market. In addition to revolutionary metamaterials, this new radar technology uses standard printed circuit boards and copper wire tracing for its electronic components. By using common electronic parts, this radar technology can take advantage of the existing methods of electronic circuit board repair for maintenance.
References and Resources also include:
https://www.pasternack.com/t-Radar-Technology-Advancements-and-New-Applications.aspx
