Anti-ARM decoy emitters

I mentioned the possibility of decoying anti-radiation missiles with fake emitters in December, as one of many possible countermeasures against anti-radiation missiles.

This aspect - like gazillions of other countermeasures in military affairs - seems to rarely get attention in public discussions.

Therefore I'd like to present two examples of anti-ARM decoy emitters:

This is a U.S. system designed to protect Patriot battery radars
by luring OPFOR ARMs away from the real radar.

This is a Russian system against Western ARMs like HARM or Alarm
(the photo shows one component).

The principle of operation is quite easy to understand. Anti-radiation missiles exploit the target radar's electromagnetic emissions to find the correct direction to the radar.
Radars emit a main beam to the direction they have to scan and side lobes of secondary emissions that are unwanted and very small in advanced radar antenna designs (often claimed for electronically scanned antennas).
Anti-radiation missiles rarely receive the main beam of radars, but most of the time only undesired side lobes.
Any decoy needs to begin to emulate this main lobe/side lobe pattern realistically and can decoy the ARM in a moment when the real radar is temporarily shut down. The radar doesn't necessarily need to be shut down till the ARM's impact if the ARM seems to be locked on the decoy emitter.

It's really quite simple, although I wonder why the decoy emitters don't seem to be armoured to withstand an ARM hit.

Many decoys are part of the realm of electronic warfare (EW), and it's quite tough to get modern information about this from unclassified sources.
Most public discussions about areas that are under the influence of EW fail to appreciate EW's impact.

NATO's ARM stocks were quite thinned out by the 1999 Kosovo Air War, destroying rather few radars in the process. Yugoslavia had only a fraction as many air defence radars as the Warsaw Pact had in 1990.

Add in more advanced countermeasures than the mere tactics and camouflage used by the Yugoslavians and it becomes obvious that our success against OPFOR air defences is not guaranteed.


edit 2016: More about decoy techniques including earlier 1980's systems and  the use of reflectors to create additional false targets by reflecting the real radar's emissions is here: http://peters-ada.de/taktik_i.htm (mostly in German)

edit 2017: http://www.ncsist.org.tw/eng/csistdup/products/product.aspx?product_Id=260&catalog=10

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