Re: Will LPI radar be used to guide SAMs?

[Chad Irby]

In article >,
Hobo > wrote:

> This NG loves to talk about whether or not stealth aircraft can be
> detected. What about the issue of detecting SAM radar? If LPI, or Quiet
> Radar techniques are used on the ground radars guiding SAMs this will
> make it difficult to find and destroy the radars.

The problem with LPI is that most of them are just very low power,
continuous-wave radars with a huge chunk of signal processing gear
tacked on. Smaller output, harder detection, right?

Except that defensive measures are getting better, too, for the same
reasons, and with that low power, jamming becomes much easier. And if
you get the power low enough, a cheap, disposable white-noise jammer
takes the whole thing out of the equation (most LPI sets are pretty
darned close to the noise threshold to begin with, which is what makes
them hard to detect).

Even with frequency hopping or broadband techniques, you're still
broadcasting a signal of *some* sort, and the smarter ECM systems will
still find you.

--
cirby at cfl.rr.com

Remember: Objects in rearview mirror may be hallucinations.
Slam on brakes accordingly.

[The Enlightenment]

"Hobo" > wrote in message
...
>
> I tried asking this question before and got zero responses;(
>
>
> This NG loves to talk about whether or not stealth aircraft can be
> detected. What about the issue of detecting SAM radar? If LPI, or
Quiet
> Radar techniques are used on the ground radars guiding SAMs this
will
> make it difficult to find and destroy the radars. Similarly, if the
same
> pseudo-random noise techniques are used for the datalink the SAMs
> guidance will be harder to jam.
>
> If one cannot bomb SAM radar or jam the datalink than flying in
enemy
> airspace becomes vastly more difficult. The basic ideas behind LPI
radar
> seem to come from the same information theory behind much of the
cell
> phone industry so the knowledge base is widespread.


Most modern SAM guidance techniques are heading towards an active
homing system. The French have a common active hommer on the AAM
mica and the SAM aster. The SAM is launched preloaded with the
co-ordinates and velocity of the target and the missile guides itself
using an inertial guidance system to the vicinity of the target at
which point the radar lights up. Usually a data link is also
available for midcourse corrections. In the case of AMRAAM there is I
believe only 1 midcourse update provided if at all.

In this way:
1 The command link can be of low bandwidth and is easily given the
characteristics of security and LPI. It is not neccesary to provide
feedback to the missile since it has an inertial guidance system.
2 Little warning is given since there is no tracking and illuminating
radar 'spiking' the target.
3 Jamming and stealth against the missile is less effective as the
radar's illuminating power increases as the missile active radar
approaches.
4 Multiple missiles can be launched.

The next stage of radar appears to be impulse radar. This AFAIKS
requires cryogenics. It consists of sequences of impulses of around 1
wavelength that contain broad spectrums of frequencies that can excite
any resonance's within a stealth structure. It also is extremely
capable of resolving chaff or terrain like ocean waves and ripples.

[Denyav]

>The problem with LPI is that most of them are just very low power,
>continuous-wave radars with a huge chunk of signal processing gear
>tacked on. Smaller output, harder detection, right?

As long as you use radar,or any kind of EM energy as a binary detection
method,right.
But if you start processing,for example, polarimetric data,you can easily
seperate signals reflected by man made objects from the others.

[Chad Irby]

In article >,
(Denyav) wrote:

> >The problem with LPI is that most of them are just very low power,
> >continuous-wave radars with a huge chunk of signal processing gear
> >tacked on. Smaller output, harder detection, right?
>
> As long as you use radar,or any kind of EM energy as a binary
> detection method,right. But if you start processing,for example,
> polarimetric data,you can easily seperate signals reflected by man
> made objects from the others.

You can't get polarization if you don't have a signal to polarize.

And signals of any polarization are easy enough to generate with jamming
equipment, so if you're relying on that, you've got to worry about being
spoofed.

--
cirby at cfl.rr.com

Remember: Objects in rearview mirror may be hallucinations.
Slam on brakes accordingly.

[Denyav]

>And signals of any polarization are easy enough to generate with jamming
>equipment, so if you're relying on that, you've got to worry about being
>spoofed.
>

So,ECM,predicted to be dead after arrival of stealth platforms are "in" again.

[Chad Irby]

In article >,
(Denyav) wrote:

> >And signals of any polarization are easy enough to generate with jamming
> >equipment, so if you're relying on that, you've got to worry about being
> >spoofed.
>
> So,ECM,predicted to be dead after arrival of stealth platforms are "in"
> again.

Funny - I don't ever remember hearing *anyone* except you make that sort
of comment.

I *do* remember saying - quite often - that ECM was a *lot* easier with
a stealth airframe. I'm sure some other folks have mentioned this to
you in recent months, too.

I guess it just sorta stealthed by you, there...

--
cirby at cfl.rr.com

Remember: Objects in rearview mirror may be hallucinations.
Slam on brakes accordingly.

[Chad Irby]

In article >,
Hobo > wrote:

> Great. Now what if the SAM radar is undetectable?

No such thing.

If it emits, it's detectable.

--
cirby at cfl.rr.com

Remember: Objects in rearview mirror may be hallucinations.
Slam on brakes accordingly.