SinoDefence Forum

antimatter

I ran across the website and saw someone posted the F-22 RCS versus freuqency plot. I thought it's kind of interesting.

It reminds me of the diode plot. Able to clamp the voltage at 0.7V. After that
it starts to breakdown. It's law of physics.

The F-22 patterns after the spherical shape. But there's plenty of non-spherical areas like its vertical tail, it's inlet, . those little imperfections will get exposed if outside of its engineering spec.

to me, it's kind of make sense, every product has its limitation. it can only works for certain range of voltage and frequency. Outside of engineering spec, it won't work.

Law of physics.

FriedRiceNSpice

I wonder how credible the source is... one would think such information would be kept highly classified.

crobato

X band should be 8 to 12 GHz. This is the common range for fighter radar. 2 to 8 GHz is C and S band, which is the common range for AEW (S band, 2-4GHz) and SAM fire control radars (C band, 4 to 8 GHz). A few fire control radars, mainly short range gun control radars, use the Ku-K-Ka bands. The chart is based on the rather obvious information that you should be stealthy against AEW, SAM and fighter radars.

I think we have covered the frequency range vs. stealth topics before in this forum all in different threads.

__________________
"Lets do a thermal sweep."

antimatter

The actual number is not too important.
But do you think that's an actual breakdown point for the plane? maybe 14Ghz, maybe 20Ghz? 25Ghz?

but there got to be a breakdown point! law of physics. Can't be violated!

I think if a plane can carry an overkilled very high frequency radar maybe like a 30Ghz, which way out of normal tracking radar commonly used. I will not surprised if F-22's RCS will shot up dramatically.

Pointblank

But then such a radar would require a ton of power, so the aircraft would likely be bigger than a Boeing 747 in order to carry all the power generators and the fuel needed...

Edit: It would also be incredibly short ranged as well...

antimatter

isn't the AWACS has the size of 747? I heard even the jet fighter's AESA has the power to burn down other plane. The AWACS AESA should be pretty long range. I guess.

Pointblank

The power generation unit ALONE would take up a 747 or two for the radar to be of any practical use, let alone the fuel needed to power it. Radars of the 20-30GHz range are incredibly short-ranged; you would probably SEE the F-22 visually before you actually pick one up on such a radar...

AESA is not the cure all for radars; they offer better resolution, redundancy, and high ECM resistance. Not power.

antimatter

I am not sure about power it needed but the radar the astronomer used are incredibly far. They are into hundred of Ghz. So, I don't think 30 Ghz radar is too short range.

Observation Type: Galactic, extragalactic, spectral line, continuum
Frequency band(s):
250 GHz
350 GHz
450 GHz
650 GHz
850 GHz

Pointblank

Look at the power source. They are hooked up to a electrical grid which can supply tons of power with no size or weight constraint. An airborne radar is limited by the max size of the generator that can be carried by an airplane.

antimatter

Since those hundred of Ghz astronomoy ground based radar can go across intergalactic. maybe it can modified to be track F-22 and guide the missile.
I am sure F-22 will not be stealthy against a 200Ghz military modified astronomy radar.

Missile guided by Ground based asronomy radar against F-22. That's an idea!

Pointblank

These ultra high frequency radars are no good for search... such radars are designed to be astronomical interferometers, which are designed to probe objects at very high resolutions, and are only capable of a very limited range of observations. These radars are also VERY expensive, and that's why you don't see very many of them.

antimatter

I don't understand. If they used for intergalactic space probing, why you say it's very limited range? if it has very resolution, isn't it perfect for target locking/tracking?
I think it can used in conjunction with long range searching radar.

how about a ground based AESA astronomy radar?

crobato

If my understanding of radar is correct, even within the 2GHz to 12GHz range, the RCS isn't a constant. Some frequencies will be more effectively dealt than others, meaning there is a sweet spot in all of this. The F-22 is going to be more effective in dealing the 8 to 12GHz band, which is X-band, because that is the fighter radar most of all. The SAM and AEW radar bands will be less effective and so. In the B-2 its the reverse, the sweet spot should be more on the 2 to 8GHz bands, especially between the 2 to 4GHz range. That's because the mission priority of the B-2 is different.

Pointblank is correct in that the higher the frequency you go, the more energy loss you are faced with as the waves travel through the air, and the higher the energy requirement. S, C and X bands are chosen for their general efficiency and balance per mission requirement in the first place. The K bands are very inefficient for volume search. All this means is that the stealth fighters should not be stupid to get too low on the ground or get into range with something like a SPAAG or Otomatic, you know the AA tanks that carry radars on the turret. AA tanks, and for that matter, CIWS both land and naval often use K band radars for fire control. The Oto Melara gun with the 76mm guided projectile uses a Ka band illuminator. For that matter, the other significance of this is possibly using Ku, K or K bands for gun fire control, missile illuminators and seeker heads.

Anti-stealth radars are focused on low wavelengths, which is what you failed to see. That's the wavelengths lower than 2GHz. They have tremendous search volume and range for their power, but what they lack is resolution. The answer to that problem is the big volume search radar has to que a sharper resolution one, and that's where the answer is on the previous paragraph.

There is a certain limit to where shaping is a factor. If the wavelength is long enough, does not matter what the object is shaped like, it appears as an "object", though it may be difficult or impossible to determine its identity because there is no discriminating features. RAM or composites do not work against long wavelengths, because radar absorbency is size dependent, so the material thickness, honeycomb cell or sandwich, or ferrite particle has to be matched in direct physical size of the radar frequency.

PB, only with the current generation of AESAs, where an element appears limited up to 10 or 20 watts of power. However, elements with up to 40 watts, or maybe 50 watts of power is already in experimental stage. The problem is the tremendous heat, but Gallium Nitride as the semiconductor material might change all that, ushering a new generation of AESAs. According to the Russians, once the beam reaches 20kw, there is so much power you can't hide from it no matter what you do. That means for an array with 1000 elements you need 20w per element.

__________________
"Lets do a thermal sweep."

antimatter

crobato, what you think when a ground based long range 200Ghz astronomy phase array radar shine on the F-22? does it track the plane well? should be. It's ultra high resoluioned.

Pointblank

What I mean is that you are essentially looking for a jumping grasshopper in a large field using a telescope... I say less than 1 in a trillion chance of finding one...

And what I mean about limited range is that such a radar is only good for a certain number of applications... some of which may not be good for guiding weapons or tracking.