DRDO creates radar absorbers & FSS Radomes for stealth aircraft's

[sayareakd]

DRDO creates radar absorbers & FSS Radomes for stealth aircraft's
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[Payeng]

Not sure what have I understood but it seems like a good news.

 

[W.G.Ewald]

Not sure what have I understood but it seems like a good news.

Me neither. :-(

The resistive FSS is able to absorb electromagnetic waves. ADE has developed several FSS radome panels like double square loop, circular loop, gridded square loop, four legged loaded loop, tripole loop and others.

How can you use your radar if it is enclosed in EM-resistive structure?

 

[santosh_g]

DRDO is currently working on technologies to create the upcoming Next generation Fighter Aircraft (NFGA) and UCAV AURA programs.

NFGA ?????? probably it's AMCA..

 

[sayareakd]

This will help you guys in understanding what we have made

ACAB Appointed by LIG Nex1 to Develop KFX Fighter Radome Prototype - Militer Review

 

[The Last Stand]

Not sure what have I understood but it seems like a good news.

I understood nothing except that DRDO gained experience for AMCA.

 

[santosh_g]

Me neither. :-(

we all know that DRDO use RAM coating to reduce radar cross section which will absorb the incident radar energy. This is also almost same.. They developed a new type of RAM coating i.e FSS type RAM coating.This type of RAM coating is thinner, lighter and braodband i.e it can absorb wide range of incident EM wave frequencies compared to normal RAM.

How can you use your radar if it is enclosed in EM-resistive structure?

Basic propert propert of RAM oating is it's unidirectional and this RFSS RAM coating works in same way.

 

[santosh_g]

The crucial resistive layer of Sailsbury Screen, also known as Jaumann Absorber (JA)

Wiki explained this concept in a simple manner. I just copied follwing thing from there:
Salisbury screens operate on the same principle as optical antireflection coatings used on the surface of camera lenses and glasses to prevent them from reflecting light. The easiest to understand Salisbury screen design consists of three layers: a ground plane which is the metallic surface that needs to be concealed, a lossless dielectric of a precise thickness (a quarter of the wavelength of the radar wave to be absorbed), and a thin glossy screen.
When the radar wave strikes the front surface of the dielectric, it is split into two waves.
One wave is reflected from the glossy surface screen. The second wave passes into the dielectric layer, is reflected from the metal surface, and passes back out of the dielectric into the air.
The extra distance the second wave travels causes it to be 180° out of phase with the first wave by the time it emerges from the dielectric surface
When the second wave reaches the surface, the two waves combine and cancel each other out due to the phenomenon of interference. Therefore there is no wave energy reflected back to the radar receiver.

 

[sayareakd]

I understood nothing except that DRDO gained experience for AMCA.

The radome (radar dome) is the streamlined structural part in the nose of the aircraft which protects the radar antenna from wind and weather. It is carefully designed to withstand the mechanical loads without compromising the radar performance. In addition, it increases the survivability of the aircraft due to its sophisticated stealth features.

this is basic, now what happens is that radar dome which house radar has to send the pulse out, in this processes when the enemy radar waves hit the aircraft dome, it goes pass radome and hit radar and rest of the aircraft and go back to the enemy radar, in this process it goes way aircaft's position to enemy radar. Now with the tech developed by us, what happens is that material allow the radar pulse to go out but didnt allow the enemy radar pulse to get pass radome. This is what my understanding is.

 

[santosh_g]

this is basic, now what happens is that radar dome which house radar has to send the pulse out, in this processes when the enemy radar waves hit the aircraft dome, it goes pass radome and hit radar and rest of the aircraft and go back to the enemy radar, in this process it goes way aircaft's position to enemy radar. Now with the tech developed by us, what happens is that material allow the radar pulse to go out but didnt allow the enemy radar pulse to get pass radome. This is what my understanding is.

yes abslutely.. but small corrections usually aircraft surface is the one whcih refelcts the waves coming from enemy radar back to it. The RCS (Radar cross section ) is a function of energy of waves refelcted by aicraft. Now the RAM coating absorbs some energy of enemy radar waves and refelcts them back makin RCS less. This Specialized FSS RAM is much more efficient than normal RAM what DRDO is using for present aircrafts.

 

[sayareakd]

yes abslutely.. but small corrections usually aircraft surface is the one whcih refelcts the waves coming from enemy radar back to it. The RCS (Radar cross section ) is a function of energy of waves refelcted by aicraft. Now the RAM coating absorbs some energy of enemy radar waves and refelcts them back makin RCS less. This Specialized FSS RAM is much more efficient than normal RAM what DRDO is using for present aircrafts.

One thing i dont understand is when the our aircraft send radio pulse same radome which absorb or reflect to other direction enemy radio pulse will also do the same to our radar pluse which is coming back, so how the radar works if pulse does not come back ?

 

[sayareakd]

hope this will be used in LCA, then it will further reduce its radar signature.

 

[santosh_g]

One thing i dont understand is when the our aircraft send radio pulse same radome which absorb or reflect to other direction enemy radio pulse will also do the same to our radar pluse which is coming back, so how the radar works if pulse does not come back ?

That's the interesting part. all types of RAM coating are unidirectional and frequency selective. so it wont absorb specifi frequency EM wave and it wont absorb an EM wave incident in specific direction.

 

[one]

Which language is that????

 

[santosh_g]

One thing i dont understand is when the our aircraft send radio pulse same radome which absorb or reflect to other direction enemy radio pulse will also do the same to our radar pluse which is coming back, so how the radar works if pulse does not come back ?

And most importantly while characterizing the RCS of an aircraft, engineers usually identify hotspots which are causing more RCS and they might apply RAM coating particularly to those parts. They might skip applying RAM coating at NOSE CONE where actually radar sits, so that it wont be a problem.

 

[natarajan]

As we progress we should develop cyber tech too as china may steal it

 

[p2prada]

A radome is a complex bit of surface. It is coated with dielectrics and other materials which allow only your own radar beams to leave the nose cone while preventing unknown beams from reflecting off the radar array.

Sure, this is only an ideal system. In a real system, the radome will also eat up some of the energy that your own radar emits. The problem comes when miniscule levels of energy that is reflected back from the target at near the maximum detectable range of the radar might get lost in this complex spider web.

It is a decent achievement. It won't help just AMCA, but also LCA Mk2.
@santosh_g

NFGA is a misspelling. It is NGFA or Next Generation Fighter Aircraft. AMCA is the other name whereas the Sukhoi-HAL program is called Fifth Generation Fighter Aircraft or FGFA. They are not being very creative with project names.

 

[cloud]

A radome is a complex bit of surface. It is coated with dielectrics and other materials which allow only your own radar beams to leave the nose cone while preventing unknown beams from reflecting off the radar array.
.

Radar has to receive the reflected beam from enemy fighter right? then wouldn't this unidirectional or absorbing coating will prevent it? making radar useless if applied on radar dome.

 

[p2prada]

Radar has to receive the reflected beam from enemy fighter right? then wouldn't this unidirectional or absorbing coating will prevent it? making radar useless if applied on radar dome.

The dielectric is frequency sensitive. So it is designed to allow your own radar beams to travel between the membrane.

Patent US7006052 - Passive magnetic radome - Google Patents

Radome induced wave perturbations are a principal consideration in radome construction. An ideal radome is electromagnetically transparent to a large number of radio frequencies, through a wide range of incident angles. However, in practice, conventional radomes are inherently lossy and are narrowbanded. Moreover, loss generally increases with angle of incidence. Radomes are generally designed to have a lower loss at a specific angle of incidence and a larger loss at the remaining angles. Often, the angle at normal incidence is chosen as the angle of lower loss in a radome design.

Traditionally, the RF loss in radomes is minimized by adjusting the phase factor of the radome at a single radio frequency. For instance, the thickness of a dielectric radome having a given permittivity can be a multiple of half a wavelength at a given frequency. When so formed, a very small reflection coefficient will result at that frequency. Unfortunately, such a radome transmits electromagnetic waves with minimal loss only over a narrow frequency band about a center frequency. In order to overcome this limitation, some radomes are made of several layers of dielectric slabs, so that a broader group of frequencies can be transmitted with low loss.

 

[W.G.Ewald]

we all know that DRDO use RAM coating to reduce radar cross section which will absorb the incident radar energy. This is also almost same.. They developed a new type of RAM coating i.e FSS type RAM coating.This type of RAM coating is thinner, lighter and braodband i.e it can absorb wide range of incident EM wave frequencies compared to normal RAM.


Basic propert propert of RAM coating is it's unidirectional and this RFSS RAM coating works in same way.

Ok, thanks for explanation.