EW Flashcards
Define EW
Use of EM energy to determine, exploit, reduce or prevent hostile use of the EM spectrum, which retains friendly use
Define ESM / EP
Electronic Support Measures / Electronic Protection
Actions taken to search for, intercept, identify and locate sources of radiated EM energy for the purpose of threat recognition.
Define ECM / EA
Electronic Countermeasures / Electronic Attack
Action taken to prevent or reduce the enemies effective use of the EM spectrum
Define EPM / ED
Electronic Protective Measures / Electronic Defence
Actions taken to retain effective friendly use of the EM spectrum.
What are the three major classes of EW receivers, and give an example of each?
Radar Warning Receiver (RWR)
o Function: Platform protection.
o Example: Detects weapon radars
Electronic Support Measures (ESM)
o Function: Gathers information about signal sources for immediate and short-term actions.
o Example: Intercepting and analysing EM emissions
Electronic Intelligence (ELINT)
o Function: Collects detailed information over longer periods, often for strategic purposes.
o Example: Gathers intelligence from electronic signals
A scanning directional antenna is used to provide DF when space is limited. What is used to overcome POI and sensitivity problems?
Direction Finding (DF)
A complimentary omnidirectional antenna is included to overcome POI and sensitivity problems.
What is range advantage?
The ability of an ESM system to detect, classify, and identify a contact passively before its active sensors can detect the ESM system.
What are the principal requirements of a RWR, ESM, and ELINT system?
Radar Warning Receiver (RWR):
o Detect weapon radar
o Provide warning
o Detect the main beam
o Low to medium sensitivity
o Wide spatial coverage
o Direction information
o Real-time operation
Electronic Support Measures (ESM):
o Obtain maximum information
o Wide frequency and spatial coverage
o High sensitivity
o Direction information for signal sorting
o Good parameter resolution
o Near real-time operation
Electronic Intelligence (ELINT):
o Low instantaneous bandwidth
o Wide frequency coverage
o Detect the main beam
o High sensitivity and resolution
o Detailed analysis
o Non-real-time operation.
In deinterleaving signals or pulses intercepted by the ESM system’s receiver are sorted to aid emitter identification. To accomplish this common parameters are generally used. Which are the common parameters generally used?
Angle of Arrival (AOA)
Frequency
Pulse Width (PW)
Time of Arrival (TOA)
Amplitude.
How does a Scanning Antenna derive DF information?
By continuously rotating in azimuth, tracing the emitter’s antenna pattern.
To achieve greater accuracy in phase comparison AOA measurements, which technique is used?
Lower Spacing – Gives coarse but unambiguous measurement of AOA
Higher Spacing - more precise but ambiguous results, resolved by the coarser measurement.
How are sidelobes countered in Q12?
using a complimentary omnidirectional antenna
What is the major limitation of IFM?
Its difficulty in dealing with simultaneous pulses and continuous wave (CW) signals
How is Time-Share Channelised superior to Band-Folded?
Because they avoid increased noise problems by only processing one band at a time
Explain at which point during a missile engagement that a ship would employ distraction and seduction chaff. Provide a description of how each works.
Distraction chaff: Deployed early to create multiple false targets and confuse the incoming missile’s targeting system.
Seduction chaff: Released later, closer to the ship, to draw the missile away from the target and towards the chaff cloud. This provides a more immediate countermeasure as the missile approaches.
Confusion Chaff: Shown randomly around the unit to increase the number of targets seen by enemy radar. Forces the enemy to interrogate each return to determine which are real or chaff.
Which of the following diagrams adequately describes the response of a PPI to Inverse Gain Jamming, Noise jamming and frequency agility?
• (D) Inverse Gain Jamming would create a whited-out sector on the PPI display.
• Noise Jamming would create a cluttered or blacked-out area on the PPI.
• (C) Frequency Agility would result in a clearer display as it counters the jamming.
• (A) Main Beam and Side lobe jamming
Inverse Gain Jamming – The jammer senses the beam pattern of the transmitter radar. It transmits a constant equivalent radiated power at the receiver. This swamps the reliever and whites out of a sector of the PPI.
