State the stages of the ES process.
(SIIL)
- Search
- Intercept
- Identify
- Locate
State the four ES receiver groups of a conventional system.
- ESM System (SIGINT)
- Radar Warning Receivers (RWR)
- Missile Approach Warning Systems (MAWS)
- Laser Warning Receivers (LWR)
Describe the function of the following ES components: Antennas
- Provide Gain & Directivity.
- Angular coverage, gain, polarisation, physical size & shape is application dependant.
- May be an array to provide required angular coverage, polarisation & frequency bandwidth.
Describe the function of the following ES components: Receivers
- Receiver - a device that intercepts transmitted electromagnetic energy and transforms it into useable intelligence.
Describe the function of the following ES components: Signal Processors
- Must deal with many signals (millions of pulses per second)
- Tasks performed by ES systems include:
– Deinterleaving Signals.
– Signal Processing
– LOB and Fix
Describe the function of the following ES components: Emitter Library
- Produced by EW Support units of platform such as JEWOSU
- Lists all known emitters in Area of Operations or a refined list to match the required Search Strategy based off the:
– Electronic Order of Battle (EOB). - The library is loaded into the PDS Host Processor via a drive.
– Also known as ‘Pre-Flight Message’ (PFM)
Describe the Heterodyne principle.
** Convert high frequency (GHz) signals into lower frequency (MHz) - Intermediate Frequency or IF.
– Referred as Heterodyning.
- 2 Signals are mixed in a non-linear device:
– Received RF input combined &,
– Oscillator RF input. - 2 New frequencies are produced:
– Sum & Difference of combined inputs. - ‘Difference’ frequency used in Superheterodyne Receiver:
– Lower frequency is normally used as the intermediate-frequency (IF).
– Other 3 frequencies are filtered out. - Multiple stage mixing referred as Super-heterodyning.
Describe the following ES receiver terminology - Frequency coverage
The frequency range through which the receiver is able to tune.
Describe the following ES receiver terminology - Selectivity
Ability to discriminate signals of close but different frequencies, and amplify only desired signal.
Describe the following ES receiver terminology - Dynamic range
The range of signal amplitudes that a device can process without
distortion of the output signal.
Describe the following ES receiver terminology - Sensitivity
The smallest detectable signal power a receiver needs to receive in order to distinguish the signal from the noise.
Describe the following ES receiver terminology - Signal to noise ratio
The ratio of signal voltage to noise voltage at receiver input or output.
Describe the following ES receiver terminology - Fidelity
Accurate
The accurate reproduction of the intelligence. A flat, neutral frequency response
WFHGRSHP
State the requirements of ES receivers.
- have a wide input bandwidth
- have fine frequency resolution (selectivity)
- be highly sensitive (able to detect very weak signals)
- have a good dynamic range (able to detect very strong and very weak signals).
- receive all polarity signals
- scan all directions
- be able to process simultaneous signals
- have a high POI.
Describe the operation of Scanning Superheterodyne receivers.
- Is a narrow bandwidth receiver.
- Is swept over frequency range of interest.
- Sweep stopped on detected signals for analysis.
- Limited by POI of emitters with scanning antennas
Describe the operation of Channelised Superheterodyne receivers.
**Channelised **
* Receiver divides frequency range to be covered into contiguous channels by filters
- Channel bandwidth determines frequency resolution:
– i.e., a measure of minimum amount two signals must be separated to resolve them in frequency.
Describe signal de-interleaving.
- Extraction of signal of interest from mix of all signals present.
- Applied in:
– Time, Frequency & AOA domains.
List the parameters that can be measured by ES Systems.
(ARTPPPPSI)
– Angle of Arrival (AOA),
– Radio Frequency (RF) and bandwidth (BW),
– Time of Arrival (TOA),
– Pulse Amplitude (PA),
– Pulse Repetition Interval (PRI) / Pulse Repetition Frequency (PRF),
– Pulse Width (PW),
– Polarisation,
– Scan Type and Scan Rate &,
– Intra Pulse and Inter Pulse modulation.
Describe Probability of Intercept (POI).
** the likelihood that a radar signal emitted by a radar system will intersect (or intercept) with a target object
Describe Probability of Report (POR).
** POR is the probability that a target signal once detected
will be processed, correctly identified & presented to the
operator within a specified time.
EEP
List the factors determining POR.
- Emitter library needs to ensure inclusion of emitter;
- Emitter library needs to minimise ambiguity &;
- Processing power in dense signal environments.
List the four main methods of direction finding.
- Enables avoidance, EA and engagement with weapons
4 main methods:
– Directional Antenna;
– Amplitude Comparison;
– Phase Comparison (Interferometry) &;
– Time Difference of Arrival (TDOA).
Explain the following direction finding methods: Amplitude Comparison
Detects the difference in signal amplitude (strength) between
antennas
- By comparing the Amplitude of the signal at multiple antennas
you can then calculate the DOA of the signal. - Used for both Pulsed & CW signals.
Explain the following direction finding methods: Phase Comparison (Interferometry)
- Measures phase difference of incoming signal in each
antenna;
– Caused by path distance difference between different antennas. - AOA calculated from phase difference.
