Graphics Programs Reference
In-Depth Information
quencies equal to are severely attenuated. Since Doppler is proportional to
target velocity ( ), target speeds that produce Doppler frequencies
equal to integer multiples of
nf
r
f
d
=
2
v
λ
⁄
f
r
are known as blind speeds. More precisely,
λ
f
r
2
v
blind
=
-------
;
n
≥
0
(7.3)
Radar systems can minimize the occurrence of blind speeds by either
employing multiple PRF schemes (PRF staggering) or by using high PRFs
where in this case the radar may become range ambiguous. The main differ-
ence between PRF staggering and PRF agility is that the pulse repetition inter-
val (within an integration interval) can be changed between consecutive pulses
for the case of PRF staggering.
input to
MTI filter
clutter returns
(a)
no
is
e l
e
ve
l
target
return
frequency
f
r
f
=
0
f
r
MTI filter
response
(b)
f
=
0
f
r
f
r
frequency
MTI filter
output
(c)
frequency
f
r
f
=
0
f
r
Figure 7.2. (a) Typical radar return PSD when clutter and target are
present. (b) MTI filter frequency response. (c) Output from an
MTI filter.
Search WWH ::
Custom Search