Radar Performance Flashcards
External Factors affecting Radar Performance
Clutter
target characteristics
External noise
Atmosphere attenuation
External Factors- Clutter
Terrain
buildings
Clouds
Sea
External Factors- Target characteristics
Size
Shape
Distance
type of material
External factors- External noise
Atmospheric
Cosmic
Deliberate jamming
Accidental jamming
External factors- Atmospheric attenuation
Absorption
-Oxygen
- water vapour
Scattering
-Water droplets
-Fog
Internal factors affecting radar performance
Transmitter peak power
Receiver sensitivity and noise factor
Frequency of operation
Shape of radar beam and scanning methods
Pulse repetition frequency
Pulse width or pulse duration
Internal factors- transmitter peak power
To double the range of a system, the power has to be increased by 16 times
Half range = 1/16th power
Half power 84% of range
Internal factors- receiver sensitivity and noise factor
Radar returns extremely small - high gain required
Internal- frequency of operation - 4 factors that govern choice of frequency
Size of target
Beam width
Max Detection range
Size of aerial and waveguides
Factors that affect PRF
Display definition
Max selected range
Aerial scanning speed
Transmitter mean power
Factors determining Pulse width
Receiver bandwidth
Target discrimination
Minimum detection range
Transmitter mean power
Internal factors- Size of target
Wavelength must be less than quarter of the size of the target
Internal factors- beam width
The higher the frequency of operation, the narrower the beam becomes
For good angular discrimination a narrow beam is required
Internal factors- Detection range
Internal factors- shape of beam
Pencil = narrown in azimuth and elevation
Fan beam = broad in elevation and narrow in azimuth
Cosec^2 Beam = broad in elevation and narrow in azimuth (used for ground mapping)
Internal factors- scanning methods
Continuous scan 360 degrees
Sector scan 120 degrees
Conical scan circles round in a cone shape
Bar scan = scans left to right top to bottom
Pulse spacing
1 over PRF
Long range - PS is increased - PRF is lower
Short range - PS is reduced - PRF is higher
Internal factors- PRF maximum required
2nd time around echoes
(When the pulse from the ambiguous zone arrives after the radar does its 2nd pulse)
Jittering the PRF will help individual radars to eliminate 2nd time around echoes
Internal Factors- PRF aerial scanning speed (3 factors governing rotation factor of the aerial)
PRF
Maximum range of system
Display definition
Higher scanning speed = high PRF, short range
Low Scanning speed = low PRF, Long range
Internal factors-PRF- Display definition
Internal factors-PRF-Transmitter mean power
Internal factor-Pulse width
Detecting targets close together is called target discrimination or range resolution
