Sure =>
http://www.defence.pk/forums/military-forum/53000-what-wrong-rafale-2.html
But we can also take a look at the latest claim...As highlighted below...
Speaking of target resolution, there is a report that Chinese universities are testing a new "radar cloaking" device that can essentially make the enemy see what the radar operator wants them to see and to hide what needs to be hidden. For example, they can make a fighter jet appear as a bird on radar or simply make something disappear even when it's still there.
In radar detection, these are the basic items
INSIDE a single radar pulse
TRAIN that tell us that there is a valid target...
- Freq (wavelength)
- Amplitude
- Pulse width
- Pulse repetition freq (PRF)
- Pulse repetition interval (PRI)
Frequency and amplitude are self explanatory. Pulse width is the duration of a pulse inside a pulse train. A 'pulse train' mean exactly what the word 'train' imply: a series of <something> . You cannot ignore the 'train' as it is vital for any analysis of an incoming signal.
There is a crucial distinction between the PRF and the PRI in radar detection:
- The 'pulse repetition freq' (PRF) is how many pulses per time unit.
- The 'pulse repetition interval' (PRI) is that space between the
BEGINNING of one pulse to the
BEGINNING of the next pulse, regardless of the pulse width. Or between the
END of one pulse to the
END of the next pulse. In other words, the PRI is either leading-to-leading or trailing-to-trailing, but never trailing-to-leading or leading-to-trailing.
An incoming signal bounced off the aircraft. That deflected signal made the aircraft into an 'emitter' or 'illuminator' or several other words but they all describe the same thing: a transmitter. In other words, as long as a body produce a signal be it deliberate or accidental, that body is a transmitter.
If you can deliberately manipulate the above pulse train characteristics, in theory, you can create a radar echo of any size you want. But in order to present that impression, you must know the values of those characteristics before you can produce an echo with at least similar values. If you want to appear larger, you must add power to your transmission. If you want to appear smaller, you must somehow negate (cancel) some (or all) of the seeking signal.
Before you can produce a deception 'echo', which we know is not a true deflected signal, you must have a sample of that pulse train. Obvious enough, no? You cannot know the PRI if all you sampled was only two pulses. You cannot know the PRF unless you know the time gaps between pulse train
S (plural). The time gap between pulse trains is not the same as the time gaps between pulses inside a train. The analogy is the gaps between cars on a locomotive. We can see those gaps clearly enough. So the best sampling -- before you can produce a deception signal -- is to include several pulse trains.
But what if the seeking radar employ
'PRF jittering'? Internet keywords search here...
Pulse repetition freq (PRF) jittering is a technique where the seeking radar will alter the PRF inside a pulse train in order to compensate for certain background clutter situations and against signal analyses methods in ECM suites. The seeking radar will know the 'jittering' pattern inside said pulse train. The seeking radar will change that pattern from train to train. What if the seeking radar employ frequency agility from pulse to pulse inside said pulse train? How about amplitude agility?
The variations are quite literally endless and the burden of memory is upon
YOU, not the seeking radar. All the enemy has to do is remember the characteristics of the immediate train and be on the alert for an echo with similar characteristics, change those characteristics on the next train, and so on. On the other hand, you cannot afford the luxury of the chance that the enemy will not repeat those same characteristics at any time. You have to remember them after your samplings, assuming you were fortunate enough to have a valid sampling, to immediately produce a deception 'echo' of similar pulse train characteristics.
What is claimed by your pal sounds awfully similar to the SPECTRA active cancellation method. The SPECTRA will be effective against second and third tier air forces, not against US.
tongue:
