Electronic countermeasure

Germany and United Kingdom interfered with enemy communications along the western front during World War I while the Royal Navy tried to intercept German naval radio transmissions.

[2] World War II ECM expanded to include dropping chaff (originally called Window), jamming and spoofing radar and navigation signals.

Cold War developments included anti-radiation missiles designed to home in on enemy radar transmitters.

Jamming is accomplished by a friendly platform transmitting signals on the radar frequency to produce a noise level sufficient to hide echos.

[1] Transponders may alternatively increase return echo strength to make a small decoy appear to be a larger target.

[1] Dispersal of small aluminium strips called chaff is a common method of changing the electromagnetic properties of air to provide confusing radar echos.

Planned for adoption around 2020, it will use a small AESA antenna divided into quadrants[5] for all around coverage and retain the capability of highly directional jamming.

DARPA's Precision Electronic Warfare (PREW) project aims to develop a low-cost system capable of synchronizing several simple airborne jamming pods with enough precision to replicate the directionality of an electronically scanned antenna, avoiding collateral jamming of non-targeted receivers.

[6] An expendable active decoy that uses DRFM technology to jam RF based threats has already been developed by Selex ES[7] (merged into Leonardo new name of Finmeccanica since 2017).

The 55 mm format of the system has undergone flight trials with the Gripen aircraft and the development of a 218 variant is at an advanced stage.

[9] The Raytheon SLQ-32 shipboard ECM package came in three versions providing warning, identification and bearing information about radar-guided cruise missiles.