EW3 - Electronic Attack - Jamming

Question 1

State the three sub-divisions of Electronic Attack

Answer 1

3 sub-divisions:
– Jam.
– Deceive.
– Neutralise.

Question 2

List the four main EA equipment types

Answer 2

• Radar Jammers:
  – Electronic noise jamming &,
  – Electronic deception jamming.
• IR Jammers:
  – Directed IR countermeasures (DIRCM).
• Countermeasure dispensing systems (CMDS):
  – Chaff & flares.
• Decoys.

Question 3

Describe jamming.

Answer 3

The use of mechanical devices or electromagnetic transmissions to interfere with adversary electronic devices, equipment or systems.

Question 4

State the two forms of jamming.

Answer 4

2 Forms:
– Electronic jamming;
* Friendly transmission to render an adversary transmission unusable.

– Mechanical Jamming;
* Chaff or decoys to clutter a sensor.

Question 5

Describe Spot jamming.

Answer 5

• Continuous jamming of one radar on one specific freq.
• Requires precise knowledge of victim parameters.
• Ineffective against multiple radars on diff. freq.

Question 6

Describe Barrage jamming.

Answer 6

• Transmit noise across a given bandwidth.
• Allows jamming of several transmitters on diff. freq. (incl. frequency agile) simultaneously.
• Disadvantage:
  – Power is spread = less power on any given freq.
  – Wasted power on freq. not being used.
  – Need as high a power output as possible.

Question 7

Describe Swept Spot jamming.

Answer 7

• Required when there are not enough spot jammers to counter multiple radars or when the radar is spread over a wide bandwidth.
• Continuous movement of a ‘spot’ frequency of noise across a selected bandwidth.
• Sweep should be fast enough to re-saturate the receiver before it recovers.
• Advantages of both spot and barrage jamming.

Question 8

State the limitations of Chaff.

Answer 8

• May negate noise jamming.
• May alert unaware enemy
• Only effective against radar guided missiles.
• Enemy radars characteristics must be known for appropriate chaff packages.
• Chaff cloud characteristics (fall rates) must be known for optimal employment.
• Limited effectiveness against advanced radars.

Question 9

Explain Power Centroid Tracking

Answer 9

• Radar adjust its aim point to maximise total return.
• Radar will ‘break-lock’ on the aircraft if:
  – Separation between aircraft & countermeasure increases to > 1 RRC.

Question 10

What are the Jamming applications

Answer 10

** Jamming Against Surveillance Radars.

– To avoid detection;
– Electronic jamming (induce noise/confusion).

** Jamming Against Weapon Radars.

– If detected, induce error so the weapon misses.
– Jam so that the system cannot counter your attack.

Question 11

How is noise jamming achieved

Answer 11

• Achieved by:
  – Generating random noise energy.
  – Amplifying it.
  – Radiating it towards threat.
• If receiver SNR < 1, noise
  jamming is taking place