You have a knack for explaining technical things in simple English, would you be kind enough to explain how this particular system works.
Thanks!
https://www.raytheon.com/capabilities/products/ale50
Sure...
The operative part of the Raytheon source is this...
...towed decoy acts as a preferential target that lures enemy missiles away by providing a much larger radar cross section than the aircraft.
Using the AIM-120 as example, the missile's radar operating freq is in the X band, a common region that is the best compromise for range and target resolutions.
- Airspeed
- Altitude
- Heading
- Aspect angle
The AMRAAM -- in all of its versions -- employs sophisticated proportional navigation (PN) algorithms to pursue and calculate a collision course to the target.
https://en.wikipedia.org/wiki/Proportional_navigation
If you drive and have to negotiate a traffic circle (roundabout) you have just performed one such PN algorithm.
Radar detection provides comprehensive target resolutions. The more complex those algorithms, the better the quality of the missile, and the higher the lethality. Radar guided artillery uses PN guidance against moving targets or to delay multiple shells on the same target. Deployed PN navigation laws in weapons systems are top secret, as in felony class.
The corollary is that the lower the quality of those target resolutions, such as provided by a passive sensor like IR, the less the need for sophisticated algorithms, or that more sophisticated algorithms are simply wasted. This is why IR sensors are accompanied by the simpler variants of 'pursuit' or tail chase navigation laws.
https://en.wikipedia.org/wiki/Pursuit_guidance
However, in radar detection, there is an inverse relationship between array size and beamwidth: The smaller the array the wider the beamwidth, and the larger the array, the smaller the beamwidth.
A large beamwidth is good for volume search. A small beamwidth is good for individual objects.
http://meteorologytraining.tpub.com/14271/css/14271_60.htm
Beam width varies directly with wavelength and inversely with
antenna size. Radar systems that produce relatively small beam widths generally provide greater target resolution.
Here is one effect of beamwidth in relation to target...
Depending how many objects are in side the beam and how they are arrayed, lateral or linear, the radar will see one object and multiple ghosts.
The cause is the resolution cell.
https://www.its.bldrdoc.gov/fs-1037/dir-029/_4335.htm
The volume of space that is occupied by a
radar pulse and that is determined by the
pulse duration and the horizontal and vertical beamwidths of the transmitting radar.
Note: The radar
cannot distinguish between two separate objects that lie within the same resolution cell.
What the towed decoy does is exploit this antenna size vs beamwidth weakness that is inherent in all radars. The towed decoy is active, meaning it transmit RF signals to create that larger radar cross section (RCS).
We tow the decoy in order to preserve that ghosting effect for as long as possible. Discarding the the decoy, no matter how EM 'loud' it maybe, the aircraft and the decoy will quickly separate so that the missile will reacquire the aircraft.
Towing distance. Too close to the aircraft and it would be pointless because the missile will see both as one object anyway. Too far from the aircraft and the decoy may momentarily escape the beam and allow the missile's radar to reacquire the aircraft.
Signal discrimination. The missile's radar knows what kind of signals it transmits, everything from base frequency to pulse repetition (PRF). It takes any echo and compares to what was transmitted. The threat could be from a larger ground based SAM to the smaller air-air missile. The decoy must be responsive to that variable which means the decoy will have a threat library.
Multiple threats. The decoy must be able to distinguish different radar threat parameters. All radars are considered 'threats'. A friendly source does not negate that status. The decoy must be able to target specific threats and to focus its countermeasures to ignore friendly sources.
The technical details of these characters are secret, of course, but the general operational ideas should be enough for the interested laymen.