3 Electronic Attack Flashcards
Disruptive EA: How does Noise Jamming work?
We can increase the ambient noise in the receiver bandwidth so that the SNR becomes too low to allow detection.
Active vs Passive EA
Active: Emission of energy
Passive: No emission of energy
What is Disruptive EA
Increasing ambient noise to blind enemy radar
What are two requirements for joise jamming to work?
Directed at the enemy receiver’s antenna
Cover the enemy receiver frequency bandwidth
What is Burnthrough Range?
Range where radar echo becomes visible over the Jamming.
Below the Burnthrough Range, the (enemy) radar echo is visible.
After the Burnthrough range, the jamming signal is stronger than the radar return.
What are the components of the Jamming Equation?
Signal Strength S
Jammer Strength J (note that it is only one way propagation)
Signal to Jamming Ratio
Spot Jamming
Barrage Jamming
Swept Spot Jamming
What is the tradeoff relevant to Jamming?
Power vs. Bandwidth
You need to spread your power accross the bandwidth to be effective over that frequency range.
Jamming Tactics: Self-Screening
A single aircraft must both jam and attack. Power must be distributed between the two.
Jamming Techniques: Escort
A more specialized aircraft may be used which is equipped specifically for jamming. More power can be used for jamming.
The Jammer is with the group for a balance between Stand-ff and Forward Deployed.
Jamming Tactics: Stand-Off
Jammer is behind the attack aircraft to remain safe. But it has less jamming signal strength.
Jamming TacticsL Forward Deployed
The Jammer aircraft is forward to increase the jamming power. But the aircraft is more vulnerable.
What is Deceptive EA? What are 3 methods?
Multiple Target Generation
Range Deception
Angle Deception
What are Repeater Jammers?
Incident signal is repeated and amplified appropriately to create false echo’s IOT change the range perceived by enemy radar.
What is a Responsive Repeater Jammer?
Received signal parameters are stored to be used long after the pulse has ceased.
What is a False Target Generator?
Creates mutliple images on radar display, difficult to matinain over a number of pusles
Range Gate Pull-Off (RGPO) with diagram.
Inverse Gain
Sends out jamming pusles in-between incoming pulses, which cause a constant gain at the enemy receiver. This makes it appear as though it is on target.
How is Inverse Gain Jamming overcome?
Monopulse.
Cross-polarization jamming
The jammer take the incoming pulse, flips the polarization, and sends it back out. The cross-polarized pulses appear as false lobes, making it appear at a different angle.
Downside is it requires a lot of power at the transmitter to appear the same power level at the receiver due to the cross-polarization.
Cross-Eye
Sends two signals which are phase shifted IOT create a null in the direction of own self and constructive signal in another angle from the receiver.
Requires two separate antennas
What is Passive EA / ECM?
Signature Reduction
Decoys
How do we reduce visual signature?
Paint colour
How do we reduce infrared signature?
Insulation
Light coloured paint
Exhaust cooling
Pre-wet
How do we reduce radar signature reduction
Less corner reflectors
Smaller superstructure
RAM
Obtuse angle design
Less deck fittings
What are the three ways Decoys are deployed?
Confusion
Distraction
Seduction
Decoys: Confusion
Employed during the search phase.
Used to deny accurate bearing and range information
Decoys: Destraction
Used when missile is in-flight but not locked on
Provides an alternative for the missile to lock-on to.
Decoys: Seduction: Dump
(Chaff + Decoy)
Aim is to break missile lock
Used with RGPO
Decoys: Seduction: Centroid
Chaff deployed all around the ship to create a much larger target.
By the time the missile intercepts, the ship will have moved away and the missile will track the largest RCS which is the chaff cloud.
How does Chaff work?
Resonant Dipoles act as radar reflectors. There are many sizes of ribbon because the greatest re-radiation is when the length is half a wavelength.
What is a limitation of Chaff?
Difficult to manufacture with width < 0.2 mm
Launching
Dispersal
Polarization - chaff clouds often devide into two clouds because the horizontally polarized ribbons fall slower than vertivally polarized
Name two broad categories of EA
Active and Passive
Name two categories of active EA
Disruptive and deceptive
What is an objective of jamming?
To conceal your location
Name 4 hamming tactics
Self-screening
Escort
Stand-off
Forward deployed
Name EA techniques for creating angular errors in searching/tracking radars
Inverse Gain
Cross-polarization
Cross-eye jamming
