What is the expendable decoy concept and how does it create a false target for a missile seeker?

The expendable decoy concept creates a false target for a missile seeker by deploying a small, inexpensive device that mimics the aircraft's radar or infrared signature, causing the missile to track the decoy instead of the real aircraft. RF (radar) decoys: a small device ejected from the aircraft that contains a radar repeater or augmentor. The decoy receives the threat radar's signal, amplifies it (or retransmits it with additional false information), and radiates it back toward the threat radar/missile seeker. The decoy's effective RCS appears larger than the aircraft's RCS, attracting the missile seeker. Types: passive corner reflector/Luneburg lens (a simple device that creates a large RCS at the decoy's location; effective against simple radars but: does not move convincingly (it decelerates quickly after ejection)), active repeater (a DRFM-based device that captures the radar signal, adds delay/Doppler modulation, and retransmits; creates a convincing moving target with controllable RCS), and chaff (millions of thin metallic strips cut to resonant length (lambda/2) that create a radar-reflective cloud; effective for obscuring the aircraft's location but: does not create a discrete false target; the chaff cloud quickly disperses and decelerates). IR (infrared) decoys: flares (magnesium/Teflon pyrotechnic flares that burn at 2000-3000 K, creating an intense IR source visible to IR-guided missiles; effective against older IR seekers; modern seekers discriminate flares from aircraft by: spectral differences (flare spectrum differs from jet exhaust), kinematic differences (flare decelerates; aircraft does not), and imaging (the flare does not look like an aircraft in an imaging seeker)).