EW4 - Electronic Attack - Deception Flashcards
1
Q
Define Deception jamming.
A
The deliberate radiation, re-radiation, alteration, absorption, or
reflection of electromagnetic energy in a manner intended to
mislead the enemy in the interpretation or use of information
received by their electronic systems.
2
Q
Describe Range Gate Stealing.
(Range Gate Pull Off)
A
- Early & late tracking gates straddle target echo.
- AGC circuits set to the desired level for echo strength.
- Signal amplified & re-transmitted with minimum delay;
- Strong signal causes the AGC to adjust:
– Radar then starts to track the false target. - Repeated signal successively delayed or advanced on a pulse to-pulse basis away from the true target echo.
3
Q
Describe Velocity Gate Stealing.
A
- Works in relation to frequency (Doppler).
- To steal locking gate, deception signal is shifted in frequency.
- Captures Doppler filters through the AGC of victim.
- The false signal is successively increased or decreased in frequency away from the target frequency.
4
Q
Describe Flare employment
A
- Designed to decoy IR missiles in terminal phase.
- Composed of magnesium, teflon & viton (MTV).
- Composition determines characteristics:
– Rise time
– Burn time
– Energy output
– Spectral power distribution &;
– Peak temperature - Wavelengths produced must be close to A/C:
- Current generation flares maximised at 1-3 microns.
- Countermeasure is to sample the short & long bands;
– Discard targets with high radiance in lower band.
5
Q
Describe Flare limitations.
A
- Only limited number can be carried;
- Flare flight path & separation may not suit threat;
- Flare dispensing interval may allow target re-acquisition between flares;
- Weapons can discriminate against flares on basis of temporal and/or spectral characteristics;
- Once loaded, flare characteristics cannot be adjusted to match
aircraft power changes &, - Flares not intense enough to protect aircraft using afterburning.
6
Q
What are the three main types of deception jammers
A
3 Main devices:
* Repeater.
* Transponder.
* Digital Radar Frequency Memory (DRFM).
7
Q
Describe Repeater Jammer
A
- Receives, stores, delays & repeats after amplifying.
- Only responds to pulses & therefore;
- Only produce false targets at greater distances than true
target.
8
Q
Describe Transponder Jammer
A
- Receives, stores & processes to predict PRI & agility.
- Is able to pre-empt incoming pulses & therefore;
- Generate false targets at greater or smaller ranges than true target.
9
Q
Describe Digital Radar Frequency Memory (DRFM)
A
- Intercepts and analyses the incoming pulse.
- Adds:
– Delays &,
– Varying Doppler shifts. - Therefore can jam coherent Doppler radars.
10
Q
What is False Target Generation
A
- Appears on screen as a set of returns which look like targets.
- Re-transmits signal with slight
delay:
– Deceives in range & azimuth (if in side lobes). - Overcome by varying PRF (PRI).