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whether to use coherent or non-coherent integration. Keep in mind the issues
discussed in the beginning of this section when deciding whether to use coher-
ent or non-coherent integration.
Second, determine the minimum required or required for
adequate detection and track. Typically, for ground based surveillance radars
that can be on the order of 13 to 15 dB. The third step is to determine how
many pulses should be integrated. The choice of is affected by the radar
scan rate, the radar PRF, the azimuth antenna beamwidth, and of course by the
target dynamics (remember that range walk should be avoided or compensated
for, so that proper integration is feasible). Once and the required SNR are
known one can compute the single pulse SNR (i.e., the reduction in SNR). For
this purpose use Eq. (1.82) in the case of coherent integration. In the non-
coherent integration case, Curry presents an attractive formula for this calcula-
tion, as follows
(
SNR
)
CI
(
SNR
)
NCI
n
P
n
P
2
(
SNR
)
NCI
2
n
P
(
SNR
)
NCI
(
SNR
)
NCI
n
P
(
SNR
)
1
=
------------------------
+
------------------------
+
------------------------
(1.87)
4
n
2
Finally, use from Eq. (1.87) in the radar equation to calculate the
radar detection range. Observe that due to the integration reduction in SNR the
radar detection range is now larger than that for the single pulse when the same
SNR value is used. This is illustrated using the following mini design case
study.
(
SNR
)
1
1.7.4. Mini Design Case Study 1.2
Problem Statement:
A MMW radar has the following specifications: Center frequency
, pulsewidth
9
, peak power
, azimuth cov-
f
=
94
GHz
τ
=
50
×
10
sec
P
t
=
4
W
erage
, Pulse repetition frequency
, noise figure
∆α
=
±
120°
PRF
=
10
KHz
; antenna diameter
; antenna gain
; radar cross
F
=
7
dB
D
=
12
in
G
=
47
dB
20
m
2
section of target is ; system losses ; radar scan time
. Calculate: The wavelength ; range resolution ; bandwidth
; antenna half power beamwidth; antenna scan rate; time on target. Com-
pute the range that corresponds to 10 dB SNR. Plot the SNR as a function of
range. Finally, compute the number of pulses on the target that can be used for
integration and the corresponding new detection range when pulse integration
is used, assuming that the SNR stays unchanged (i.e., the same as in the case of
a single pulse). Assume
σ
=
L
=
10
dB
T
sc
=
3sec
λ
∆
R
B
.
T
e
=
290
Kelvin
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