The algorithm for calculating CCOR depends on whether the optional R
2
autocorrelation lag
is computed.
7.4.7.1 R0, R1 Clutter Correction
In this case CCOR is estimated from,
= 10log
0
0
= 10log
+
+ +
= 10log
1 +
1
+ 1 +
1
Here, the expression is strictly valid only when the signal-to-noise ratio (SNR=S/N) is large.
When the 2-lag approach is used, the clutter corrections are not as accurate for weak
weather signals. However, the error is typically less than 3 dB.
7.4.7.2 R0, R1 Clutter Correction Using Clutter Signal and Noise Power
Calculations
In this case there is enough information to compute the clutter signal and noise power
independently. The algorithm for CCOR is:
= 10log
+
= 10log
1
+ 1
The clutter power is computed from:
=
0
0
= + + +
The signal power S is then computed from:
=
1
exp
2
2
2
W is the width that has been previously calculated. This approach yields more accurate
results for the clutter correction in the case of a low SNR.
7.4.8
Weather Signal Power (SIG Threshold)
The SIG parameter provides an estimate of the weather signal-to-noise ratio in dB for
thresholding.
The SIG calculation is dierent depending on the whether the optional R
2
autocorrelation is
computed.
Table 53 SIG Calculation
Autocorrelation Equation Description
R
0
, R
1
= 10log
0
+
Represents the SNR after the
removal of clutter.
The CCOR value is that described
for R
0
, R
1
in 7.4.7 Clutter
Correction (CCOR threshold)
(page 205).
RVP900 User Guide M211322EN-J
206
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