Radar equation review

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Radar equation review

• 1/19/10

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Radar eq (Rayleigh scatter)
The only variable is h, the pulse length Most
radars have a range of h values.
Rewrite the radar eq as
Convert to log form
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Radar equation, Mie scatter
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Uses of the radar equation

• Convert Pr to Z
• Used for specifications, such as minimum
  detectable signal (minimum detectable
  reflectivity at some standard range)
• The general form of the radar equation also
  applies to sodars and lidars

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Important radar parameters

• Wavelength (cm vs mm)
• Peak transmit power
• Pulse vs. continuous wave (CW)
• Pulse length
• Pulse repetition frequency
• Beam width
• Minimum detectable signal
• Duty cycle PW/PRT or Pavg/Ppeak
• Receiver bandwidth
• Antenna size (gain)
• Scan rate

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Lidar equation

• But, additional terms representing absorption and
  extinction are important.

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Beam width estimate
For D 8 ft (2.44 m) if?? 3.2 cm, then ?
1.27(0.032)/2.44 57.3 0.95 deg if ? 8.6
mm, then ? 1.27(0.0086)/2.44 57.3 0.26
deg For D 2 ft (0.61 m) if ? 3.2 mm, then
? 1.27(.0032)/0.61 57.3 0.38 deg 3.2 cm
9.4 GHz 8.6 mm 35 GHz 3.2 mm 94 GHz
These are estimates need to conduct test on
antenna range to get actual value
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Radial profile of Zmin for WSR-88D
Range (km)
?r 2 km
At 50 km Z 58.4 dB (-107 dBm) 20 log10(50)
-20.6 dBZ. At 10 km Z 58.4 (-107)
20log10(10) -28.6 dBZ.
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