Graphics Programs Reference
In-Depth Information
order to keep the number of false alarms under control in a changing and
unknown background of interference. CFAR processing can cause a loss in the
SNR level on the order of 1 dB.
Three different types of CFAR processors are primarily used. They are adap-
tive threshold CFAR, nonparametric CFAR, and nonlinear receiver techniques.
Adaptive CFAR assumes that the interference distribution is known and
approximates the unknown parameters associated with these distributions.
Nonparametric CFAR processors tend to accommodate unknown interference
distributions. Nonlinear receiver techniques attempt to normalize the root
mean square amplitude of the interference.
c. Quantization Loss:
Finite word length (number of bits) and quantization noise cause an increase
in the noise power density at the output of the Analog to Digital (A/D) con-
verter. The A/D noise level is
q
2
, where
is the quantization level.
⁄
12
q
on target sample
echo envelope
early sample
late sample
range gates
on target range
bin
(a) Target on the center of a range gate.
echo envelope
on target sample
late sample
early sample
range gates
on target range
bin
(b) Target on the boundary between two range gates.
Figure 1.25. Illustration of range gate straddling.
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