EW4 - Electronic Attack - Deception

Question 1

Define Deception jamming.

Answer 1

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.

Question 2

Describe Range Gate Stealing.
(Range Gate Pull Off)

Answer 2

• 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.

Question 3

Describe Velocity Gate Stealing.

Answer 3

• 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.

Question 4

Describe Flare employment

Answer 4

• 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.

Question 5

Describe Flare limitations.

Answer 5

• 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.

Question 6

What are the three main types of deception jammers

Answer 6

3 Main devices:
* Repeater.
* Transponder.
* Digital Radar Frequency Memory (DRFM).

Question 7

Describe Repeater Jammer

Answer 7

• Receives, stores, delays & repeats after amplifying.
• Only responds to pulses & therefore;
• Only produce false targets at greater distances than true
  target.

Question 8

Describe Transponder Jammer

Answer 8

• 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.

Question 9

Describe Digital Radar Frequency Memory (DRFM)

Answer 9

• Intercepts and analyses the incoming pulse.
• Adds:
  – Delays &,
  – Varying Doppler shifts.
• Therefore can jam coherent Doppler radars.

Question 10

What is False Target Generation

Answer 10

• 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).