Statistical Estimation and Tracking of Refractivity from Radar Clutter

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becomes large at high altitudes making the narrow-angle scheme inaccurate at
more than a few kilometers. However, the form given in (1.29) totally satisfies all
accuracy needs of the lower atmospheric narrow-angle ducted propagation environments
simulated in this work.
1.3.2 Radar Sea Clutter Calculation Under Non-Standard Propagation
Conditions
Using the classical radar equation, received radar clutter power can be
written as
P c
= P tG 2 t λ2 F 4 σ
(4π) 3 R 4 , (1.32)
where P t is the transmitter power, G t is the transmit antenna gain, λ is the wavelength,
σ is the sea surface radar cross section (RCS), R is the range, and F is the
propagation factor (ratio of the electric field at a point to that which would have
been created by the same system operating in free space with the on-axis gain of
the antenna) [15]. After F is calculated at the effective scattering height given as
0.6 times the mean wave height [16], the one-way propagation loss L then can be
written as
L fs
L = L fs /F 2 (1.33)
= (4πR)2
λ 2 , (1.34)
where L fs is the free space loss. Sea surface RCS can be written as σ = A c σ o ,
where A c is the illuminated area (proportional to R at small grazing angles) and
σ o is the normalized sea surface radar cross section (RCS). Then the clutter power
can be written as
P c
= P tG 2 t 4πA cσ o
L 2 λ 2 (1.35)
P c = Cσo R
L 2 (1.36)
P c,dB = −2L dB + σ o (R) dB + 10 log 10 (R) + C dB , (1.37)