izwest (izwest) wrote,

Ultra-wideband radars: yesterday or tomorrow?

Ultra-wideband radars: yesterday or tomorrow?

Ultra-wideband radars: yesterday or tomorrow?

Сверхширокополосные РЛС: вчера или завтра?

Modern local conflicts, even in the countries of the lowest level of development of the armed forces (Syria, Ukraine), show how great the role of electronic means of intelligence and detection is. And what advantages can be obtained by a party using, for example, counter-battery warfare systems against a party that does not have such systems.

Currently, the development of all radio-electronic systems is going in two directions: on the one hand, to maximize their control and communication systems, intelligence collection systems, high-precision weapons control systems in conjunction with all the previously listed systems and complexes.

The second line is the development of systems that will be able to complicate the work of all the above-mentioned means from the enemy with the simplest goal-not to allow the enemy to cause damage and harm to their troops.

Here it is also worth noting the work on the possibilities and methods of masking objects by reducing their radar visibility through the use of the latest radio-absorbing materials and coatings with changing reflective properties.

It is probably worth translating: we will not be able to make a tank invisible in the radio spectrum, but we can minimize its visibility as much as possible, for example, by covering it with materials that will give such a distorted signal that identification will be very difficult.

And yes, we still proceed from the fact that there are simply no absolutely invisible planes, ships and tanks. At least for now. If the goals are inconspicuous and difficult to distinguish.

But, as they say, each target has its own radar. The question of the frequency and power of the signal. But here lies the problem.

New materials, especially radar-absorbing coatings, new forms of calculating reflective surfaces, all this makes the background contrast levels of protected objects minimal. That is, the level of difference between the electrophysical properties of the object of control or defects in it from the properties of the environment becomes difficult to distinguish, the object actually merges with the environment, which makes its detection problematic.

Nowadays, the minimum levels of background contrast are actually close to the limit values. Hence, it is clear that for radars (especially circular viewing), which work precisely on contrast, it is simply necessary to ensure an increase, first of all, in the quality of the information received. And it is not quite possible to do this through the usual increase in the volume of information.

More precisely, it is possible to increase the efficiency/quality of radar reconnaissance, the only question is at what price.

If you take a hypothetical radar, no matter what purpose, just a circular-view radar with a range of, for example, 300 km (of the "Sky-SV" type) and set the task of doubling its range, then you will have to solve very difficult tasks. I will not give calculation formulas here, this is pure physics, not secret.

So, to increase the radar detection range twice, it is required:
- increase the radiation energy by 10-12 times. But again, no one has canceled physics, it is possible to increase the radiation so much only by increasing the energy consumed. And this entails the appearance of additional equipment for generating electricity in the station. And then there are a variety of problems with the same disguise.

- increase the sensitivity of the receiving device by 16 times. Less expensive. But is it even feasible? This is already a question of technologies and developments. But the more sensitive the receiver is, the more problems with natural interference that inevitably arise during operation. It is worth talking about interference from the actions of the enemy's electronic warfare separately.

- increase the linear size of the antenna by 4 times. It's the easiest, but it also adds difficulties. Harder to transport, more noticeable…

Although, frankly, the more powerful the radar, the easier it is to detect, classify, generate a personally calculated interference with the most rational characteristics for it and send it. And the increase in the size of the radar antenna plays into the hands of those who need to detect it in time.

In principle, it turns out such a vicious circle. Where developers have to balance on a knife edge, taking into account dozens, if not hundreds of nuances.

Our potential opponents from across the ocean are no less concerned about this problem than we are. There is such a department in the structure of the US Department of Defense as the DARPA - Defense Advanced Research Project Agency, which is engaged in just promising research. Recently, DARPA specialists have been directing their efforts to develop radars that use ultra-wideband signals (UWB).

What is UWB? These are ultrashort pulses, lasting from a nanosecond or less, with a spectrum width of at least 500 MHz, that is, much more than that of a conventional radar. The power of the emitted signal according to the Fourier transforms (of course, not Charles, a utopian, who is taught in history at school, but Jean-Baptiste Joseph Fourier, the creator of the Fourier series, after whom the principles of signal conversion are named) is distributed over the entire width of the spectrum used. This leads to a decrease in the radiation power on a particular part of the spectrum.

A radar operating on the UWB is much more difficult to detect during operation than a conventional one precisely because of this: it works as if not one powerful beam-signal, but as if a lot of weaker ones, deployed in the likeness of a brush. Yes, experts will forgive me for such a simplification, but this is solely for "translation" to a simpler level of perception.

That is, the radar "shoots" not with a single pulse, but with a so-called "bundle of ultrashort signals". This gives additional advantages, which will be discussed below.

UWB signal processing, in contrast to narrow-band signals, is based on the principles of detector-free reception, so that the number of packets in the signal is not limited at all. Accordingly, there are practically no restrictions on the frequency band width of the signal.

Here a long-overdue question arises: what does all this physics give, what advantages?

They are, of course, there. UWB radars are being developed and developed precisely because the UWB signal allows much more than a conventional signal.

UWB-signal radars have the best capabilities for detecting, recognizing, determining coordinates and tracking the trajectories of objects. This is especially true for objects that are equipped with means of anti-radar masking and reducing radar visibility.

That is, the UWB signal does not care whether the observed object belongs to the so-called "stealth objects" or not. Coatings against radar also become conditional, since they are not able to reflect/absorb the entire signal, some part of the package will "hook" the object.

Radars on the UWB identify targets more efficiently, both single and group. More accurately determine the linear dimensions of goals. It is easier for them to work with small-sized targets that can fly at low and ultra-low altitudes, that is, UAVs. These radars will have significantly higher noise immunity.

Separately, it is believed that the UWB will allow better recognition of false targets. This is a very useful option when working, for example, with the warheads of intercontinental ballistic missiles.

But do not get hung up on the air surveillance radar, there are other options for using the radar on the UWB, no less, and perhaps even more effective.

It may seem that an ultra-wideband signal is a panacea for everything. From drones, from stealth planes and ships, from cruise missiles.

In fact, of course not. The UWB technology has obvious disadvantages, but there are also enough advantages.

The strength of the UWB radar is a higher accuracy and speed of detection and recognition of targets, determination of coordinates due to the fact that the operation of the radar is based on a variety of frequencies of the operating range.

The "highlight" of the UWB is generally hidden here. And it is precisely in the fact that the operating range of such a radar has many frequencies. And this wide range allows you to select those sub-bands at the frequencies of which the reflective abilities of the objects of observation are shown as well as possible. Or-as an option-this can negate, for example, anti-radar coatings, which also cannot work on the entire frequency range due to the fact that coatings for aircraft have weight restrictions.

Yes, today means of reducing radar visibility are used very widely, but here the key word is "reduction". No coating, no most cunning form of the case will be able to protect against radar. Reduce visibility, give a chance-yes. No more than that. Fairy tales about "invisible planes" were debunked in Yugoslavia in the last century.

The calculation of the UWB radar will be able to pick up (and, quickly, from a database of similar data) the package of sub-frequencies that will "highlight" the object of observation in all its glory as clearly as possible. Here we will not be talking about the clock, modern digital technology allows you to do with minutes.

And, of course, the analysis. Such a radar should have a good analytical complex that will allow processing the data obtained from the irradiation of an object at a variety of frequencies and comparing them with reference values in the database. Compare with them and give the final result, what kind of object came into the radar field of view.

The fact that the object will be irradiated at a variety of frequencies will play a positive role, in that the error in recognition will decrease, and there is less probability of failure of observation or counteraction by means of the object.

Increasing the noise immunity of such radars is achieved by identifying and selecting radiation that can interfere with the clear operation of the radar. And, accordingly,the restructuring of the receiving complexes to other frequencies to ensure minimal interference.

Everything is very beautiful. Of course, there are also disadvantages. For example, the mass and dimensions of such a radar are significantly superior to conventional stations. This still greatly complicates the development of the UWB radar. About the same as the price. It is more than sky-high for prototypes.

However, the developers of such systems are very optimistic about the future. On the one hand, when a product begins to be mass-produced, it always reduces the cost. And in terms of mass, engineers are counting on electronic components based on gallium nitride, which can significantly reduce both the mass and the size of such radars.

And, for sure, it will happen. For each of the directions. And as a result, the output will be a radar with powerful, ultrashort pulses in a wide frequency range, with a high repetition rate. And-very important – high-speed digital data processing, capable of" digesting " large amounts of information received from receivers.

Yes, technologies with a capital letter are very much needed here. Avalanche-span transistors, charge-accumulating diodes, gallium nitride semiconductors. Avalanche transistors in general are not that underestimated devices, they are devices that will still show themselves. In the light of modern technologies, they are the future.

Radars using ultrashort nanosecond pulses will have the following advantages in comparison with conventional radars:

- the ability to penetrate through obstacles and reflect off targets located outside the line of sight. For example, this can be used to detect people and equipment behind an obstacle or in the ground;
- high stealth due to the low spectral density of the UWB signal;
- the accuracy of determining the distance is up to several centimeters due to the small spatial extent of the signal;
- the ability to instantly recognize and classify the target by the reflected signal and high target detail;
- increased efficiency in terms of protection against all types of passive interference caused by natural phenomena: fog, rain, snow;

And this is not all the advantages that a UWB radar can have in comparison with a conventional radar. There are moments that only specialists and people who are well versed in these issues will be able to appreciate.

These properties make UWB radar promising, but there are a number of problems that are being addressed by research and development.

Now we should talk about the disadvantages.

In addition to the cost and size, the UWB radar is inferior to a conventional narrow-band radar. And it is significantly inferior. A conventional radar with a pulse power of 0.5 GW is able to detect a target at a distance of 550 km, while a UWB radar is capable of detecting a target at 260 km. With a pulse power of 1 GW, the narrow-band radar detects a target at a distance of 655 km, the UWB radar at a distance of 310 km. As you can see, almost twice.

But there is another problem. This is the unpredictability of the reflected signal shape. A narrow-band radar works with a signal in the form of a sine wave, which does not change when passing through space. The amplitude and phase change, but they change predictably and in accordance with the laws of physics. The UWB signal varies both in the spectrum, in its frequency domain, and in time.

Today, the recognized leaders in the development of the UWB radar are the United States, Germany and Israel.

In the United States, the army already has a portable mine detector AN/PSS-14 for detecting various kinds of mines and other metal objects in the soil.

The United States also offers this mine detector to its NATO allies. AN / PSS-14 allows you to see and view objects in detail through obstacles and ground.

The Germans are working on a project of the UWB Ka-band "Pamir" radar with a signal band width of 8 GHz.

The Israelis created on the principles of the UWB "stenovizor", a compact device" Haver-400", capable of" looking " through walls or soil.

The device was created for counter-terrorist units. This is generally a separate type of UWB radar, implemented by the Israelis very beautifully. The device is really able to study the operational and tactical situation through a variety of obstacles.

And further development, "Haver-800", which is distinguished by the presence of several separate locators with antennas, allows not only to study the space behind the barrier, but also to form a three-dimensional picture.

Summing up, I would like to say that the development of UWB radars of various directions (land, sea, air defense) will allow those countries that will be able to master the technology of designing and manufacturing such systems to significantly strengthen their intelligence capabilities.

After all, the number of captured, correctly recognized and taken for escort with the subsequent destruction of targets is the key to victory in any confrontation.

And if we take into account that the UWB radars are less susceptible to interference of various properties…

The use of UWB signals will significantly increase the efficiency of detecting and tracking aerodynamic and ballistic objects when monitoring the airspace, viewing and mapping the Earth's surface. The UWB radar can solve many problems of ensuring the flight and landing of aircraft.

The UWB radar is a real opportunity to look into tomorrow. It is not for nothing that the West is so closely engaged in developments in this direction.

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