Graphics Programs Reference
In-Depth Information
f
r
f
0
f
0
-2
2
-1
1
-2
-1
1
2
f
d
f
d
Doppler bank
f
0
f
0
-2
2
-1
1
-2
2
-1
1
(b)
(a)
Figure 1A.2
. S
pectra of transmitted and received waveforms, and Doppler
bank. (a) Doppler is resolved. (b) Spectral lines have moved
into the next Doppler filter. This results in an ambiguous Dop-
pler measurement.
We choose and such that they are relatively prime with respect to one
another. One choice is to select and for some
integer . Within one period of the desired PRI ( ) the two PRFs
and coincide only at one location, which is the true unambiguous target
position. The time delay establishes the desired unambiguous range. The
time delays and correspond to the time between the transmit of a pulse on
each PRF and receipt of a target return due to the same pulse.
f
r
1
f
r
2
f
r
1
=
Nf
rd
f
r
2
=
(
N
+
1
)
f
rd
N
T
d
=
1
⁄
f
rd
f
r
1
f
r
2
T
d
t
1
t
2
Let be the number of PRF1 intervals between transmit of a pulse and
receipt of the true target return. The quantity
M
1
is similar to
except it is
M
2
M
1
for PRF2. It follows that, over the interval
to
, the only possible results
0
T
d
are
or
. The radar needs only to measure
and
M
1
=
M
2
=
M
M
1
+
1
=
M
2
t
1
. First, consider the case when
. In this case,
t
2
t
1
<
t
2
M
f
r
1
M
f
r
2
t
1
+
------
=
t
2
+
------
(1A.2)
for which we get
t
2
t
1
M
=
-----------------
(1A.3)
T
1
T
2
where
and
. It follows that the round trip time to the
T
1
=
1
⁄
f
r
1
T
2
=
1
⁄
f
r
2
true target location is
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