Graphics Programs Reference
In-Depth Information
Radar line of sight
σ
ref
R
ref
Figure 1.14. Definition of radar line of sight and radar reference range.
P
t
G
2
λ
2
σ
ref
τ
ref
4(
3
kT
e
FL SNR
14
⁄
-----------------------------------------------------
R
ref
=
(1.58)
(
)
ref
The radar equation at any other detection range for any other combination of
SNR, RCS, and pulsewidth can be given as
SNR
ref
SNR
14
⁄
τ
τ
ref
σ
σ
ref
1
L
p
R
=
--------
---------
-----------------
-----
(1.59)
ref
where the additional loss term is introduced to account for the possibility
that the non-reference target may not be on the radar line of sight, and to
account for other losses associated with the specific scenario. Other forms of
Eq. (1.59) can be in terms of the SNR. More precisely,
L
p
R
ref
R
4
τ
τ
ref
1
L
p
σ
σ
ref
SNR
=
SNR
ref
--------
-----
---------
---------
(1.60)
As an example, consider the radar described in the previous section, in this
case, define , , and . The reference
pulsewidth is . Using Eq. (1.60) we compute the SNR at
for a target whose RCS is . Assume that to
be equal to . For this purpose, the MATLAB program
Ðref_snr.mÑ
has been developed; it is given in Listing 1.4 in Section 1.10.
0.1
m
2
σ
ref
=
R
ref
=
86
Km
SNR
ref
=
20
dB
τ
ref
=
0.1µsec
0.2
m
2
R
=
120
Km
σ
=
L
p
=
2
dB
(
SNR
)
120
Km
=
15.2
dB
1.6. Search (Surveillance)
The first task a certain radar system has to accomplish is to continuously
scan a specified volume in space searching for targets of interest. Once detec-
tion is established, target information such as range, angular position, and pos-
sibly target velocity are extracted by the radar signal and data processors.
Depending on the radar design and antenna, different search patterns can be
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