Module 1 Flashcards
What is EW?
“Any military action whose objective is to exploit the EM spectrum.”
Roles of EW in military theatre?
- Improving situational awareness
- Reducing attrition
- Defeating enemy EW
What is Electronic Attack (EA)?
Use of EM, directed energy or anti-radiation weapons to attack facilities/equipment with intent of degrading, neutralising or destroying enemy combat capability.
What is Electronic Protection (EP)?
Protecting personnel, facilities and equipment from EW employment which may degrade, neutralise or destroy friendly combat capability.
What is Electronic Support (ES)?
Search for, intercept or locate sources of radiated EM energy for purpose of threat recognition and intelligence collection.
Five kinds of electronic threats?
- Radars
- Radar guided missiles
- Radar directed guns
- IR homing missiles
- Laser guided missiles
Missile EW systems/actions that can protect ADF assets?
- Missile approach warning system (MAWS)
- RF jammers
- Chaff
- Flares
- IR jammers
- Laser warning receivers
- Anti-radiation missiles
- Signature management
- Manoeuvre, tactics and planning
What is EM radiation?
A seld-propagating wave in space travelling at the speed of light, with electric and magnetic components. Can carry energy and information used in everyday equipment, such as TVs, radios, X-rays, IR/visible/UV, long-distance comms and radar.
Frequency ranges: Radio, radar, IR, visible, UV, X-ray?
- Radio: 1 Hz - 300GHz
- Radar: C - K band range (1GHz - 30GHz)
- IR: 300 GHz - 375 THz
- Visible Light: 375 THz - 430 THz
- UV: 430 THz - 100 PHz
- X-ray/Gamma/Cosmic: >100 PHz
EM Wave Properties?
- Electronic & Magnetic Component: EM waves propagate as travelling pair of electric and magnetic fields, two waves travelling perpendicular.
- Frequency (f): # cycles with respect to time that take place during propagation of EM wave, meased in Hz.
- Wavelength (λ): Measurement distance between point on one cycle and same point on next cycle, usually in micron meters (µm) or nanometers (nm). Amplitude of EM wave determines amount of energy withing - high amplitude = more energy.
- Polarisation: Orientation EM wave determined by direction of electric component.
-Travel: Speed of light when propagating in free space.
Factors affecting EM propagation:
- Spreading: EM waves travel in straight line tending to radiate spherically from transmission source; EM losses not linear.
- Interaction with materials: Occur when EM waves comes in contact with material where it is absorbed/reflected/transmitted. Harder for EM to pass through electrically conductive/dense materials.
- Attenuation in atmospheric conditions: Attribute to absorption and scattering of EM waves, increasing at high frequency = reduced range, affecting radar operation.
- Diffraction: Wave bends around corners of larger obstacles of same size/greater signal wavelength, or through aperture upon interactions.
- Scattering: EM wave hits smaller material directly related to signal wavelength, EM scatters in various directions.
- Reflection: Critical to radar operation, occurs when radar wave encounters flat surface. Better reflection returns = easier radar system detects and processes reflected signal.
- Radar horizon: Defined by distance radar beam rises enough above Earth’s surface to make detection of target at low level impossible. OTHR principle utilises charge particles in ionosphere to refract EM signal to reach desired location. Transmission in HF range. If frequency, power settings and angle of incident correctly balanced = transmission range increases.
- Signal interference: Source transmits EM signal which propagates and takes alternate paths to eventuate at intended target. Arriving signals take form of:
- Constructive interference - doubling signal strength; or,
- Destructive interference - decreasing signal to nothing.
EW Terminology: Signal Bandwidth?
Definition: Difference between upper and lower frequency limits of band containing useful components of signal.
Radar Application: BW related to pulsewidth with inverse proportionality. BW increases = PW decreases.
Data Transmission: BW dictates maximum amount information able to be sent.
EW Terminology: Noise?
Definition: Any unwanted signal.
Effects: Masks weak signals, degrades sensitivity, can result in false targets.
Types: In RF bands - major effect is internal noise.
- Thermal agitation noise - Produced by molecular agitation, proportional to temp & BW, random.
Signal to noise ratio (SNR): S / N
Sensitivity: Minimum detectable signal level.
EW Terminology: Gain?
Gain = Output / Input (usually in dB)
- Circuits - Ratio of output to input power
- Antennas - Directional field strength over isotropic field strength
- Signal processor: Increase in signal to noise ratio.
Attenuation (negative gain): Reduction signal amplitude from passing through atmosphere, wires, connectors.
Automatic Gain Control (AGC): Receiver sets gain to “best” see returns. Constant fals alarm rate.
What is an RF Antenna used for?
Efficiently convert electricity to RF energy and propagate through ait for transmission and intercept RF energy from air and convert to electricity.
- Can transmit or receive, cannot do both at same time
- Design allows alternating between transmit and receive quickly.
