https://itech.aorti.ru/upload/iblock/467/rti_ii_4_19_2017.pdf page 24.
Sintering approaches are also used layers of structure or combining through polyimide layers and selective epitaxial growth of active layers in areas formed topology on the plate. Here flexibility of technologies is combined with high technology and complexity, the need for precise control of material parameters and critical dimensions of topology elements. An increase in the performance, functionality, and reliability of radio-photonic circuits is possible only when switching from discrete elements to integral. Construction of complex radio-photonic systems in the frequency range more than 30–40 GHz on the basis of discrete components becomes problematic and ineffective; therefore, the increase in the frequency range is typical for the FIS. For instance, a combination of the А3В5 / Si heterogeneous integration technology and the use of micro ring resonators as part of a PIS modulator recently allowed to create by developers record superlinear modulator with free dynamic range in the USA 117 dB · Hz2 / 3 [3]. FROM THE CENTER OF COMPETENCE TO CLUSTER One of the most important active elements of the radio-photonic component base is a microwave modulator. When using radio-photonic schemes with external modulation, the laser emits in a continuous mode, and the modulation of the signal is carried out by the modulator. This is currently the approach made it possible to achieve maximum modulation frequencies of 100 GHz and data transmission rates up to 400 Gbit / s. The development of a component base for radiophotonics has begun in Russia. For example, a modulator based on lithium niobate was developed at the Physicotechnical Institute (FTI) named after A.F. Ioffe RAS. However, until now, there was practically no groundwork in the country integrated radio-photonics technologies for formation of FIS. As a result, NRNU MEPhI became one of the leading centers of excellence for creation of a cluster for integrated radio photonics. It has great scientific and technical potential for research and developments in this extremely important area. Firstly, NRNU MEPhI has an experienced technological line for the development of electronic and optoelectronic devices for microwave electronics based on non-silicon heterostructures А3В5. Most of the processes on the creation of integrated radio photonics components on the InP technological platform.
You should understand what is modulation: Modulation is a technique to put the information of the message signal (at frequency A) to a carrier signal (at frequency B), this is often done to reduce interference or to reduce antenna size in case the message signal frequency is too low. In continuous waveform, this is done by adjusting the amplitude, phase or frequency off the carrier signal
31:52(english subtitles) there is an interesting bit on photonic radar operating in the Terra hertz frequency range.
He didn't mean the radar will transmit THz wave because the nature of Terra hertz is that it will get absorbed almost 100% immediately once it travel into atmosphere.
Water vapor in the atmosphere will absorb THz frequency at much much greater than they even absorb Infrared or visible light. You get attenuation rate of over 100dB-1000 dB per km. 100 dB is equal to 10.000.000.000 reduction in signal power. There is pretty good reason why THz frequency only used in the lab instead of any actual radar.
To understand what he mean, you should understand how a radar work in the first place
In a coherent radar system, not only the amplitude but also the phase of the signal is considered to find range and velocity. Each cycle of magnetron oscillations starts with phase which is not related to the previous pulsed cycle, so RF oscillator is used to act as phase reference to find the phase of reflected signal.
In the transmit part, the oscillator generated a low frequency then this frequency go through the up-conversion process before being transmitted . Whereas, the receiver in a coherent radar working by frequency mixing with the local oscillator to convert a received signal to a lower intermediate frequency (IF) which can be more conveniently processed than the original carrier frequency that it transmitted (the process of mixing two frequency is called
heterodyning . ).Sometimes this conversion happen twice. The problem is that this up conversion, down conversion and mixing process is actually a main source of phase noise in radar; it adds the frequency fluctuations and hence leads to errors and in case of coherent radar the information is extracted from the change in the phase of the signal. So, in order to get good performance we need the phase of signal to be stable
In short, you need to get rid of the up/down conversion, so what they come up with, is using a mode locked laser to generate signal
The signal from the laser is split into two separate paths, where two different modes are
selected by filters. One mode on one path is modulated to shape the radar pulse while the other mode on second path is frequency shifted. Frequency shift is required to get RF signal at required high frequency as we are using one MLL for transmitter and receiver at sampling rate. The two processed modes are then combined and detected in photodiode => There will be negligible increase of phase noise compared to original mode locked laser.
In the current radar, the way the receiver down convert the signal is by mixing it with the local oscillator. But this affect phase stability of the signal. With a photonic radar the signal is directly converted to digital form by the mode locked laser to be analyzed, there is no phase instability because the mode locked laser can provide a stable train of pulse with low jittering.
Basically what do he mean when he talk about the THz?. A microwave or mm-wave signal can be
generated in the optical domain based on optical
heterodyning (I explained this earlier in case you forget), in which two optical waves of different wavelengths beat at a photodetector. An electrical beat
note is then generated at the output of the photodetector with a frequency corresponding to the
wavelength spacing of the two optical waves. This technique is capable of generating an electrical signal with a frequency up to the THz band, limited only by the bandwidth of the photodetector. But like I said before, generating an electrical signal at a certain frequency is one thing while transmitting it and use its in radar detection is an entirely different thing all together. The problem with THz is that it will get attenuated immediately by the atmosphere , whereas the problem with Hz band is that it basically turn your radar into an omi directional transmitter, so you can't really know where your target come from.
https://rg.ru/2018/04/08/revoliuciia-v-tehnike-lokacii-v-rossii-sozdaetsia-radiofotonnaia-rls.html "A team of specialists on the basis of the Research Institute of long-range radar is developing a fundamentally new X-band radar station, operating on the basis of radiophoton technologies
For example, the basis of radar systems for missile defense and tracking of space objects are huge radar systems. The rooms in which the equipment is located are multi-storey buildings. The use of photonic technology will fit all the control and processing systems in much smaller dimensions - literally in several rooms. At the same time, the technical capabilities of radars to detect even small objects at a distance of thousands of kilometers will only increase. Moreover, due to the use of photonic technologies on the radar screen will appear not a mark of the target, and its image, which is unattainable by classical radar. That is, the operator instead of the usual glowing point will see that it is really flying - a plane, a rocket, a flock of birds or a meteorite, it is worth repeating, even thousands of kilometers from the radar.
Now all radar systems - military and civilian - operate in a strictly defined range of frequencies, which complicates technical design and leads to a variety of radar range. Photon radars will achieve the highest degree of unification. They are able to instantly adjust in a very wide range of working frequencies - from meter values to millimeters."
Nope, no they don't , I'm pretty sure the writter of this click bait article doesn't even understand normal radar, let alone a photonic one.
Ее обзор составит 270 градусов
tass.ru
TASS, January 4. The newest radar station "Yakhroma", the construction of which in Crimea was announced by the Minister of Defense of the Russian Federation Sergei Shoigu at the annual board of the Ministry of Defense, will operate in four ranges with a view of 270 degrees. A source in the military-industrial complex told TASS about it.
"This station has no analogues, it will operate in four bands: meter, centimeter, decimeter and millimeter," the agency's interlocutor said, specifying that the station's view would be 270 degrees
In December 2020, during the final collegium of the military department, Russian Defense Minister General of the Army Sergei Shoigu announced that the construction of the newest Yakhroma radar station in Sevastopol would begin in 2021.
The station will enter the missile attack warning system. The main purpose of the system is to detect and escort ballistic missiles fired at the territory of the Russian Federation or its allies as soon as possible.
The technology will be converted into a product within five years, according to the producer
tass.com
.
You are confusing between a radar station and an individual radar. A station can easily have multiple type of radars, with vastly different aperture and radiating elements. So actually, it isn't surprise at all that it can operate at different frequencies
MOSCOW, January 22. /TASS/. The RTI Joint Stock Company, a developer and producer of high-tech products, will create new radars that operate in terahertz frequency range and are capable of pinpointing the smallest drone, RTI CEO Pavel Laptayev told TASS.
"The terahertz technology [featuring radio wave length below one millimeter] will be converted into a product within five years. These radars can detect small drones, and function in space," Laptayev explained.
Nope, as I have explained earlier, unless you can literally modify the earth atmosphere so that it no longer absorb THz wave, then no, you will not have a THz radar
I am 110% sure that I think I remember seeing your username browse the photonic radar thread when a user posted this source.
https://fpi.gov.ru/press/news/razra...antenna-voshla-v-top-10-izobreteniy-2020-goda
An antenna of low profile height, capable of operating with a wide frequency band, developed within the framework of a project of the Foundation for Advanced Study, was included in the Top 10 of the best inventions of 2020 according to Rospatent.
On the basis of the invention, dummies of antennas were created, an antenna array of the first in the world practice of a working demonstration model of a radio-optical phased active antenna array was built. The technology makes it possible to create antennas and antenna arrays, which can be made in the form of active casing of various carriers with a thickness slightly more than the thickness of the paint-and-lacquer coating.
The main executor of the project is Concern Vega JSC, the head enterprise of the intelligence information systems division of the Ruselectronics holding company of the Rostec State Corporation, specializing in the development and production of an extensive range of modern radio-electronic products and systems for military and civil purposes. The concern's management includes more than 20 organizations. The author of the invention is Dmitry Zaitsev, Deputy General Designer for Radiophotonics of JSC Concern Vega.
I think yours and another users complaint is frequencies like VHF and UHF need huger antennas. Well the antennas of the photonic radar they demonstrated look stackable and in terms of thickness will have no issues spreading all over the body of an aircraft. Oh well but the fun does not stop there.
I think you miss understand the point when I said UHF, VHF need huge antenna.
Firstly, you don't need huge antenna to simply transmit VHF or UHF wave, you can transmit these wave with small antenna. The problem is that, if you want to make a useful radar, then the gain (directivity) of that radar must be adequate, in short, the beamwidth must be narrow. An to get a narrow beam width at low frequency, you Must have a big antenna, otherwise, your beamwidth would be omi direction or simply too wide, which make your so called "radar" useless
Secondly, they can even put a VHF antenna on the vertical tail fin of F-18 and F-35, and patch antenna generally can be very thin.
But the problem with your proposed Photonic radar which according to internet tabloid "
can work in the frequency range from Hz to Thz" is not the thickness of the antenna, the problem is with the spacing between the radiating elements because electronic scanned array steer their beam by wave interference. In short, you can make the radiating elements very thin, but the big issue is the spacing between them on the surface they are on, even if you can make the individual element as thin as paper, it still doesn't solve the problem that I mentioned at all.