Expendable Active Decoys (EAD)
Expendable Actie Decoys (EAD) are designed to lure the tracking gates of an enemy’s radar away from the aircraft.
EADs enhance the Self-Protection capability of naal and airborne platforms by proiding them the capability of being able to counter radar-based threats.
Based on miniaturized DRFM, EADs are small, actie jamming systems designed to be launched by a standard Chaff and Flares Counter-Measure Dispenser System (CMDS) such as the AN/ALE-40 or the AN/ALE-47 making it possible to include an effectie RF protection also for legacy platforms.
EADs are capable to draw threats away from the host platform, generating large miss distances.
Differently from an adanced on-board jammer, an EAD, during falling, proides the angular separation from the platform, which is particularly effectie in countering the terminal guidance mechanism of the threat, by proiding them a more attractie target to lock on.
Decoy ejection typically is initiated by the RWR of the self-protection suite upon detection of the presence of an approaching missile or can be actiated directly by the aircraft pilot following a missile alarm.
The Decoy typically begins to radiate the jamming signal to the ictim seeker immediately upon ejection and continues to radiate throughout the flight.
Once launched, the Decoy orients itself towards the aircraft’s wake by deploying small aerodynamic driers to keep it in stable ballistic flight.
The Decoy slowly deiates from the direction of the launcher’s elocity ector by natural deceleration because of friction and graity.
The dispensing altitude and rate of fall determine the period of effectie coerage.
Small parachutes can be employed to slow the rate of fall and increase the time of effectie
Figure 1 shows the concept of operation of an EAD:
-
The on board Radar Warning Receier (RWR) detects the presence of an approaching missile and designates the EAD that is released;
-
The flight of the decoy settles and the EAD finalizes its starting up procedure in few tens of milliseconds;
-
When the system becomes operational, it starts scanning for the designated threat.
-
As soon as the threat is lock, the EAD starts executing the countermeasure programmed in its library.
The whole process lasts less than 1 second.
Figure 1: EAD concept of operations
Expendable decoys can employ noise or deception jamming with noise jamming being the most common.
Deception jamming techniques can be employed to enhance the effectieness against pulse Doppler radars.
Multiple decoys are sometimes released at a predetermined rate to increase the chances of engaging the missile and, consequently, the aircraft’s chance of surial.
The primary components of an expendable decoy are the transmitting and the receiing antennas, technique generator, amplifier and power supply.
Some factors limit the effectieness of an ED and are major challenges in terms of its implementation:
-
The small size limits the quantity and type of jammer components that can be packaged in the cartridge.
Therefore the power and frequency coerage of the jammer are limited and the amount of time the jammer is effectie is limited as well. -
The geometry of the scenario and of the engagement is not predictable, so a wide antenna beam is required to be sure of the disturbing effect.
The reduction of the antenna directiity and the emitted power means a reduction of the ERP.
Figure 2 shows the components of an EAD, similarly to the ones of a standard flare. Among them, the main parts of an EAD are as follows
-
The flying body, which includes all the electronics of the countermeasure system.
-
The cartridge, which may include some electronics for allowing the communication between the flying body and the dispenser.
-
The ignition squib, which is the pyrotechnic element that explodes the EAD out of the dispenser during ejection.
Figure 2: EAD main components.
The key part of an EAD is the flying body.
It encloses all the components of the countermeasure system.
Figure 3 presents the block diagram of the flying body of an EAD with details of a possible implementation of a DRFM specifically designed for an EAD.
Figure 3: Block Diagram of the flying body of an EAD
The GEN-X Decoy is a small, one shot, and expendable terminal, RF threat programmable
Figure 4: RT-1489/ALE (GEN-X)
countermeasure that receies an RF signal from a recognized threat, such as airborne or land-based semi-actie radar guided missiles, and then transmits RF power to counter that threat.
The GEN-X Decoy can be launched from the AN/ALE-39 or AN/ALE-47 Countermeasure Dispensers using a CCU-63/B or CCU-136/A Impulse Cartridge.
Figure 5: Brite Cloud
Brite-Cloud is “a self-contained Digital RF Memory (DRFM) jammer for fast jet aircraft”, aiming at proiding “an off-board capability to decoy RF-guided missiles and fire control radars”.
More in general, the Brite-Cloud has been tuned to be effectie against surface-to-air and air-to-air threat systems.
ELT/590 (nickname: SPARK) is an adanced EAD system, which features hi-end DRFM performance in a
Figure 6: SPARK
form factor of a standard aerodynamic flare, presering its flight stability and compatibility with standard 812 flare dispensers.
SPARK is compatible with the NATO DAS standard by design.
The standard proides the definition of the interface between the so-called smart dispensers and smart stores.
SPARK is an example of smart store: by means of the communication with the dispenser, it allows the aionics to receie the logistic information of the decoy and can receie details about the threat to counter to improe the countermeasure effect.
