Electronic countermeasure

Electronic countermeasures are broadly classified into jamming (noise or deceptive) and deception techniques, which can be active (transmitting energy) or passive (reflecting or absorbing energy). Active ECM includes barrage jamming, which floods a frequency band with noise, and spot jamming, which targets a specific frequency. Deceptive ECM, such as range-gate pull-off and angle deception, manipulates the victim radar's processing to create false targets or mislead tracking. Passive ECM includes chaff (metallic strips that create false echoes), decoys, and radar-absorbent materials. Modern systems integrate multiple techniques, often controlled by software-defined radios and digital RF memory (DRFM) to replicate and retransmit signals.²

The first ECM was radio jamming during World War I, when both sides attempted to disrupt enemy communications. In World War II, the British developed 'Window' (chaff) to blind German radar, and the Allies used 'Carpet' jammers to counter anti-aircraft fire.³ The Cold War saw the rise of dedicated ECM aircraft like the EF-111A Raven and the development of anti-radiation missiles that home on enemy radar emissions. The Vietnam War highlighted the importance of ECM in suppressing surface-to-air missile threats, leading to the development of more sophisticated jamming pods. Modern ECM is increasingly software-based, with systems like the AN/ALQ-99 and the F-35's AN/ASQ-239 offering integrated, adaptive countermeasures.

ECM is employed across all military domains: airborne, naval, ground, and space. Aircraft use self-protection jammers, towed decoys, and expendable active decoys to defeat radar-guided missiles. Naval vessels deploy electronic attack systems like the AN/SLQ-32 to jam anti-ship missiles and radar. Ground forces use vehicle-mounted and man-portable jammers to disrupt IED triggers and enemy communications. Space-based ECM is emerging, with satellites capable of jamming adversary communications and radar. The proliferation of low-cost drones has also led to the development of counter-drone ECM, which disrupts the drone's control links and GPS.

Beyond the headline systems, ECM includes niche techniques like 'cross-eye' jamming, which creates a false angle error in monopulse radars, and 'inverse gain' jamming that exploits antenna sidelobes. The use of 'buddy' jamming, where one aircraft jams for another, is a lesser-known tactic. In the 1970s, the US Navy's 'Have Quick' frequency-hopping radios were developed to resist jamming, but early ECM also included 'burn-through' jamming, which overwhelms a radar's receiver. A notable historical oddity is the 'Battle of the Beams' in WWII, where British ECM 'bent' German navigation beams to misdirect bombers. Additionally, ECM has civilian applications in countering piracy and protecting critical infrastructure from drone attacks.

Chaff

Thin strips of metal or fiber that reflect radar signals, creating false echoes to confuse enemy radar.

DRFM

Digital Radio Frequency Memory; a technique that captures and retransmits radar signals to create deceptive false targets.

Jamming

The deliberate transmission of radio frequency signals to interfere with enemy radar or communications.

Electronic warfare

Military action involving the use of electromagnetic spectrum to control the spectrum and attack the enemy.