Radar equation review 11910 Radar eq Rayleigh scatter

Radar equation review 1/19/10

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:

Radar equation, Mie scatter

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

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

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

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

Radial profile of Zmin for WSR-88 D Range (km) r = 2 km At 50 km: Z = 58. 4 d. B + (-107 d. Bm) +20 log 10(50) = -20. 6 d. BZ. At 10 km: Z = 58. 4 +(-107) + 20 log 10(10) = -28. 6 d. BZ. end