This is something what a photonic radar sees, the world around it.
In a race of making fifth generation combat aircrafts nations have realised that stealth capability is a major game changer in both wartimes and peace times. The rumoured destruction of Syrian S-300 battery by Israeli F 35s and the claimed uncontested flight of American F 22 Raptor at engagement ranges of the glorious S 400 prompts the Russians ( and everyone else) to think out an effective counter to this low observability technology. They seem to have found solution in an old abandoned concept where detection happens with the help of light and not radio waves. It works in similar way as that radar but uses infrared light beams instead of radio waves. If stated capabilities are to be believed then this new system would be able to detect stealth aircrafts at long ranges. The stealth aircrafts have measures taken to reduce the reflection of X band radio waves. The Radio Optic Phased Array Radar makers claim that since it uses light and not radio waves the optimisation of reduced radio waves reflections is not going to work. In this article we have attempted to dig out weather the claim is true or just another bragging. How exactly this thing works, what are its specific capabilities and whom are working in this field. Do give your opinion at the end.
WHAT IS PHOTONICS ???
Photonics is the science of generating, managing, and detecting photons (elementary particles and electromagnetic radiation quanta that can exist in a vacuum but move at the speed of light), as well as the physics and technology related to the use of photons. Photons, unlike electrons, have neither mass nor charge. Therefore, photonic systems are not affected by external electromagnetic fields and have a much greater transmission distance and signal bandwidth.
In other words, photonics deals with the control and conversion of optical signals, from transmitting information through optical fibers to creating new sensors that modulate light signals. Some sources say that the terms "optics" and "electronics" will gradually be replaced by the generalized name of "photonics". The first important technical device using photons was the laser, invented in 1960. After the fiber-optic transmissions began to be widely used worldwide in the 1980s, the term “photonics” became more common. Through the end of the twentieth century, photonics was largely focused on telecommunications. In particular, it became the basis for the development of the Internet. Currently, radio-photonics have started to replace "telecommunications" photonics. This new direction has emerged at the intersection of radionics, wave optics, microwave optoelectronics, and other branches of science and industry.
Radio-photonics are used in the transmission of information using electromagnetic waves of microwave and photonic devices and systems that can create radio-frequency waves with parameters unattainable with conventional electronics
NEED OF A PHOTONIC RADAR !
The next generation of radar (radio detection and ranging) systems needs to be based on software-defined radio to adapt to variable environments, with higher carrier frequencies for smaller antennas and broadened bandwidth for increased resolution. Today's digital microwave components (synthesizers and analogue-to-digital converters) suffer from limited bandwidth with high noise at increasing frequencies, so that fully digital radar systems can work up to only a few gigahertz, and noisy analogue up- and downconversions are necessary for higher frequencies. In contrast, photonics provide high precision and ultrawide bandwidth, allowing both the flexible generation of extremely stable radio-frequency signals with arbitrary waveforms up to millimetre waves, and the detection of such signals and their precise direct digitization without downconversion.
DEVELOPMENT OF RADIO PHOTONICS
The Russian school of photonics is considered one of the best in the world. Suffice it to recall the Nobel Prize in Physics awarded in 1964 to Alexander Prokhorov and Nikolai Basov for research leading to the creation of the laser and again in 2000 to Zhores Alferov for the development of optoelectronics.
Having yielded leadership in the field of microelectronics to western countries, Russia plans to beat the competition in another area, namely radio-photonics and defense technologies based on it. Domestic scientists believe that it is possible to completely give up electrons in favor of photons. Because photons have no mass and fly faster, the size of devices operating on the principles of photonics can be hundreds of times smaller than the usual modern servers. At the same time, data speed is ten times higher.
In Russia, KRET is developing radio photonic technology. Today, the concern and the Foundation for Advanced Studies are working on a promising project called “Development of an active phased array based on radio photons.” The project includes the creation of a special laboratory at concern enterprises, as well as the development of universal technology that will serve as the foundation for next-generation radar and electronic warfare systems.
According to the KRET CEO Nikolai Kolesov, the latest technology will make it possible to create effective and advanced next-generation receiver-transmitters, radar systems, electronic intelligence and electronic countermeasures by 2020. One of the main areas of work will be the creation of a next-generation active phased array antenna, whose basic elements will be created using the principles of radio photonics. This will reduce the weight of the apparatus 1.5-3 times, increase its reliability and efficiency up to 2-3 times, and raise the scanning speed and resolution dozens of times.
photonics based radar functioning explained by Finmeccanica
~ In US
The DARPA has developed a wide variety of technologies that would support development of such a system. Since a long time numerous research has been going on and the technology each time was termed unfeasible.
One of the recent developments in the related field is LiDAR or LADAR
The LiDAR is a Light Detection and Ranging and works much same as that a radar. Radar systems work by shooting out radio frequency waves that essentially bounce off targets and return to the equipment with that information. The farther away an object is, the longer it takes for radar to figure out it’s there. However, coupled with phased arrays which enable radar systems to shoot out a beam in a specific direction without the help of mechanical movement radar was able to keep up with the technological times, so to speak. Rather than radio waves, ladar uses lasers to scan a given area. It shoots out optical beams and returns information that is more detailed than radar. However, choosing a direction in which to shoot the beams or steering hasn’t been efficient enough to help ladar overtake its more popular brother. Now, though, DARPA has created a new form of 2D laser phased array that is so tiny and scalable, that ladar could move into the limelight.
Sanjay Raman, program manager for DARPA’s DAHI program, noted that stuffing all of the components of an optical phased array into a tiny 2D chip could “lead to new capabilities for sensing and imaging.” He believes the new tech could create high-resolution beam patterns, something previously difficult for optical phased arrays. Aside from giving ladar a much-needed upgrade, it’s theorized that the new system could help not only aid in biomedical imaging, but could be used in 3D holographic displays.
The new array is around the size of the head of a pin 576µm x 576µm and all of the required pieces, such as 4,096 nanoantennas arranged in a 64×64 fashion, are stuffed onto a single silicon chip. The goal of the design is to be scalable so the number of nanoantennas can greatly increase if necessary. DARPA has also demonstrated that dynamic beam steering can be achieved by an 8 x 8 array.
For knowing more details about the Nano-Photonic Antenna click on the button below from the university of Massachusetts.
~ In Italy
A team of researchers in Italy has developed the first fully photonics-based coherent radar system. In their paper published in the journal Nature, the team describes how they built their new radar system and what it might mean for the future of radar systems. The radar system, part of a project known as PHODIR (Photonics-based fully digital radar) is an effort to improve the tracking and speed calculation abilities of current electronic signal based systems. It's well understood that making improvements in such a system will require higher frequency signals, something that can't be done with current systems due to an increase in noise that creates more uncertainty in the signals received. For that reason, scientists have been looking to use lasers—such signals are much more stable.
Building a radar system using a laser requires an optical mode of oscillation that is able to maintain a highly stable phase relationship—that's the hurdle the researchers had to overcome. They used a mode-locked laser, it allowed for establishing a periodic sequence of laser pulses that exhibited low timing jitter. Using it, in conjunction with a computer running software they wrote, they were able to produce an RF signal with low phase noise by adding an optical filter located past the laser, which was sent to a photo diode, allowing for two optical modes to be selected.
The radar system the team built is still just a prototype, though it does appear feasible. The team tested its abilities by monitoring real aircraft taking off at a nearby airport and then comparing what they observed with data from traditional electronic signal based systems. They report that the systems matched very closely. Another area of concern is range, which could impact jitter, and thus the accuracy of the system. The proposed architecture exploits a single pulsed laser for generating tunable radar signals and receiving their echoes, avoiding radio-frequency up- and downconversion and guaranteeing both the software-defined approach and high resolution. Its performance exceeds state-of-the-art electronics at carrier frequencies above two gigahertz, and the detection of non-cooperating aeroplanes confirms the effectiveness and expected precision of the system.
Except this there are many attempts being made in the field of photonics but these above ones and most others are related to telecommunication.
For that we need to understand what is Phased Array Optics.
Phased array optics is the technology of controlling the phase of light waves transmitting or reflecting from a two-dimensional surface by means of adjustable surface elements. This thing is exactly what we call as Optical Phased Array Radar. By dynamically controlling the optical properties of a surface on a microscopic scale, it is possible to steer the direction of light beams, or the view direction of sensors, without any moving parts. Phased array optics refers to arrays of lasers or SLMs with addressable phase and amplitude elements smaller than a wavelength of light. While still theoretical, such high resolution arrays would permit extremely realistic three-dimensional image display by dynamic holography with no unwanted orders of diffraction.
One by one we will anaylise the claims made by KRET to know what it exactly means.
1 The weight of KRET's photonic radar would be reduced to more than half and the resolution increased ten fold times.
- Normally AESA radars have arrays made of numerous Transmit / Receive or T/R modules. It is simple thermodynamics that when metal is heated it expands and heating affects flow of current. Hence their is a cooling system in these radars that keep tempreture in control. Their are coolant carrying pipes that pass through arrays that take away heat. This entire assembly increases the weight. In a photonic radar their won't be any metallic T/R modules. So need of a cooling system. This contributes in reduction of weight.
The degree of resolution depends on the width of the transmitted pulse, the types and sizes of targets, and the efficiency of the receiver and indicator. The smaller the width of pulse the better is the resolution. As the pulse will strike two different targets even if they are close to each other they can be differentiated. The frequency of radio waves lie in centimertic or millimetric zone see diagram below.
The photons lie mostly in visible spectrum and some what the right side of visible spectrum but left side of those meant as radio waves. This 'infrared' area is where the waves of ROFAR work. Since these waves are smaller in size they can differentiate between targets better.
2 ROFAR allows you to get TV picture in radar range. It would open up new opportunities for improvement in smart skin.
- Here we need to understand what picture does the radar sees and what exactly is displayed. The radar generally gets in return various waves emitted by itself and those have slightly different frequencies.
Those are a collective representation of Voltage spikes that is exactly what a radar sees. (see pics below) So why not the radar displays this on screen why just a dot?? It is because the pilot simply don't want to waste time studying those spikes and guess what it is, it does not look like an aircraft. If their is a threat around better display it with just a Dot and show its distance, speed and various physical characteristics.
The radar cannot see the exact shape of the aircraft. It is because the EM Radio waves are of the wavelengths of centimetric or millimetric size. Thus the resolution is less.
To know how, know the basics of resolution, click on the button below.
But what if we use nanometric waves. The resolution would be more. The voltage spikes would more look exactly like the object it is displaying. It would make a multispectral 3D image of the aircraft. It would display the target being seen as a very different 3D unusually coloured world.
The claim here is that ROFAR can create a near photographic level quality of image at longer ranges.
This is a bold claim.
It is bold in the sense that in radar detection, YOU are the owner of the detection medium. The detection medium is electromagnetic (EM) radiation. We are the owners in the sense that we generate EM radiation at will, then we focus in a particular direction, and whatever returns we process it.
That is NOT how vision works.
If you see a red ball, it is not your eyes that created the EM radiation that the ball reflected to the physical wavelength of the color red. Rather, the ball reflects light from other sources that give the human eye the color red. The Moon reflects light from the Sun and the Earth. You do not own the detection medium.
But now imagine your eyes, like Superman's x-ray vision, generating EM radiation in a very coherent manner, like a laser beam, then direct that beam anywhere you want and receives human-like vision. In this case, you own the detection medium.
The Russians have effectively claimed they created an electronic eye. Not a bionic eye because a bionic eye require organic matter.
3 The radar would be able to look 500 km away.
- The claim says that the radar would be able to look an aircraft 500 km away and the image be zoomed in manner that the aircraft may appear like it is just 50 m away. The claim also says that the signals can pass through walls and radar would be able to see inside an aircraft who is sitting and what appliances are used. Just like having an XRay vision.
Normally range of any radar is always against a target RCS. The lesser the RCS the lesser the range. Their is an exponential relation between range and RCS of target which has been nicely explained previously in one of our articles of Radar equations. But since speculations say that the design if it's antenna would be different. Although it will also be an array like a phased array radar but the individual modules would be of different construction. Thus it can't clearly be said that the same radar equations can be used to find out range against different RCS values.
The 500 KM detection range is against a standard size of an aircraft. It isn’t clear as to what size is considered standard.
THIS CLAIM HAS A PROBLEM.
It is so, that we are talking about waves of more than 100 Ghz frequency. This is W band, or Extremely high frequency. As per theory Compared to lower bands, radio waves in this band have high atmospheric attenuation they are absorbed by the gases in the atmosphere. Therefore, they have a short range and can only be used for terrestrial communication over about a kilometer. Absorption by humidity in the atmosphere is significant except in desert environments, and attenuation by rain is a serious problem even over short distances.
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