Graphics Programs Reference
In-Depth Information
For an X-band radar, choose
f
o
=
9
GHz
, then
3 0
8
×
9 0
9
λ
=
-----------------
=
0 . 0 3 3 3
m
(8.90)
×
2.25
m
2
Assume an aperture size
A
e
=
; thus
4π
A
e
λ
2
4
×
0.0333
π 2.25
×
G
=
------------
=
-----------------------------
=
25451.991
⇒
G
=
44
dB
(8.91)
)
2
(
Assume square aperture. It follows that the aperture 3-dB beamwidth is cal-
culated from
π 180
2
4π
θ
3
db
×
25451.991
4
×
G
=
----------
⇒
θ
3
dB
=
-------------------------------------
=
. °
(8.92)
2
π
2
×
The number of beams required to fill the search volume is
Ω
n
b
=
k
p
-----------------------------------
⇒
n
b
=
399.5
⇒
choose n
b
=
400
(8.93)
)
2
(
1.3
⁄
57.296
k
p
=
1.5
Note that the packing factor is used to allow for beam overlap in order to
avoid gaps in the beam coverage. The search scan rate is 2 seconds. Thus, the
minimum PRF should correspond to 200 beams per second (i.e., ).
This PRF will allow the radar to visit each beam position only once during a
complete scan.
k
p
f
r
=
200
Hz
It was determined in
Chapter 2
that 4-pulse non-coherent integration along
with a cumulative detection scheme are required to achieve the desired proba-
bility of detection. It was also determined that the single pulse energy for the
missile and aircraft cases are respectively given by (see page 118)
E
m
=
0.1147
Joules
(8.94)
E
a
=
0.1029
Joules
(8.95)
However, these values were derived using and . The
new wavelength is and the new gain is . Thus,
the missile and aircraft single pulse energy, assuming the same single pulse
SNR as derived in Chapter 2 (i.e.,
λ
=
0.1
m
G
=
2827.4
λ
=
0.0333
m
G
=
25451.99
SNR
=
4
dB
) are
0.1
2
2827.4
2
×
0.0333
2
E
m
=
0.1147
×
------------------------------------------
=
0.012765
Joules
(8.96)
25452
2
×
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