Surface and Volume Clutter - MATLAB Simulations for Radar Systems Design - page 272

8 h r r e
3

R h = -------------

(6.23)

where is the EarthÓs radius equal to . The denominator in Eq.
(6.22) is put in that format in order to account for refraction and for round
(spherical) Earth effects.

r e 6371 Km

The radar SNR due to a target at range R is

P t G 2 λ 2 σ t
4( 3 R 4 kT o BFL

SNR = ----------------------------------------

(6.24)

where, as usual, P t is the peak transmitted power, G is the antenna gain, λ is

the wavelength, σ t is the target RCS, k is BoltzmanÓs constant, T 0 is the

effective noise temperature, B is the radar operating bandwidth, F is the

receiver noise figure, and L is the total radar losses. Similarly, the Clutter-to-

Noise (CNR) at the radar is

P t G 2 λ 2 σ c
4( 3 R 4 kT o BFL

CNR = ---------------------------------------- (6.25)

where the σ c is calculated using Eq. (6.21).

When the clutter statistic is Gaussian, the clutter signal return and the noise
return can be combined, and a new value for determining the radar measure-
ment accuracy is derived from the Signal-to-Clutter+Noise-Ratio, denoted by
SIR. It is given by

1

SIR = -----------------------------

(6.26)

1
SNR

1
SCR

----------- + -----------

Note that the SCR is computed by dividing Eq.(6.24) by Eq. (6.25).

MATLAB Function Ðclutter_rcs.mÑ

The function Ðclutter_rcs.mÑ implements Eq. (6.22); it is given in Listing
6.1 in Section 6.6. It also generates plots of the clutter RCS and the CNR ver-
sus the radar slant range. Its outputs include the clutter RCS in dBsm and the
CNR in dB. The syntax is as follows:

[sigmaC,CNR] = clutter_rcs(sigma0, thetaE, thetaA, SL, range, hr, ht, pt, f0, b,
t0, f, l, ant_id)

where