§10.2 The three parts of Electronic Warfare

The three pillars of EW interlock in a continuous cycle: ESM provides the knowledge, ECM carries out the attack, EPM keeps your own systems standing against the opponent's ECM. None of the three works without the other two.

Electronic Counter Measures

Electronic Counter Measures (ECM) — in modern doctrine Electronic Attack — is the offensive part of EW: the use of electromagnetic energy (or energy-absorbing/reflecting means) to degrade, neutralise or destroy enemy sensors, links and weapons.

The main forms, which Electronic Counter Measures works out one by one:

• Jamming: actively transmitting interference signals — as raw noise (noise jamming, Noise jamming) or as intelligent false echoes (deceptive jamming, Deceptive jamming).
• Decoys: false targets that lure weapons and sensors away from the real target (Decoys).
• Expendables: chaff against radar (Chaff) and flares against IR seekers (Flares).
• DIRCM and counter-IR: directed energy and tactics against heat-seeking threats (Directional Infrared countermeasures to Counter-IR tactics).
• Signature reduction (stealth): strictly speaking passive, but functionally ECM before the term existed — the sensor simply gets too little energy back (Stealth).
• In the extreme case hard kill: anti-radiation missiles (Passive homing) that physically destroy the emitter.

The unifying principle: every ECM technique attacks a specific link of the chain from Radar/Executing the fire control sequence using the EMS — the SNR (noise), the tracker's gates (deception), the seeker's selection logic (decoys/expendables) or the energy balance itself (stealth).

Electronic Protective Measures

Electronic Protective Measures (EPM) — modern Electronic Protection — is the defensive part: all measures that ensure that your own systems keep functioning when the opponent employs ECM. Note the direction: EPM does not protect the platform against missiles, but the sensor or link against interference.

EPM lies partly in technology and partly in behaviour:

• Technical measures (often called "ECCM" — Electronic Counter-CounterMeasures): frequency agility, PRI jitter (PRI modulation), pulse compression with matched filtering (Pulse compression and pulse integration), monopulse tracking (Techniques of the target tracking radar), side-lobe blanking and adaptive nulling (Main lobes, side lobes and back lobes), CFAR (Threshold, Constant False Alarm Rate and Automatic Gain Control), home-on-jam modes and burn-through (Introduction).
• Procedural measures: emission discipline (EMCON — only transmit when you have to), frequency planning, alternating sensors, and trained operators who recognise jamming and work around it.

Electronic Protective Measures works out the most important EPM principles. The core in advance: every ECM technique needs an assumption about how the radar works — EPM is breaking those assumptions.

Electronic Support Measures

Electronic Support Measures (ESM) — modern Electronic Support — is the listening part: searching for, intercepting, locating and identifying enemy electromagnetic emissions for immediate operational decisions: threat warning, target location, and steering your own ECM.

ESM exploits the fundamental asymmetry of Peak power and average power of the pulse radar: a radar has to send its signal out and back (1/R⁴), but the ESM receiver picks it up directly (1/R²) — and so hears the radar at a (much) greater distance than the one at which that radar can see. Listening almost always beats transmitting.

What an ESM system extracts from an intercepted signal (compare the radar parameters of Pulse radar):

Together these parameters form the electronic fingerprint that is checked against a threat library: "X-band, PRF 1,200 Hz, conical scan = fire control radar type Y, belonging to weapon system Z". EW: Electronic Support Measures covers the most important on-board ESM applications: the Radar Warning Receiver and the Missile Approach Warning System.