Global Positioning System Reference
In-Depth Information
10
−5
Galileo BOC(1,1)
GPS C/A
10
−6
10
−7
10
−8
10
−9
10
−10
−6
−4
−2
0
2
4
6
Frequency [MHz]
FIGURE 3.4. GPS C/A and Galileo BOC(1,1) sharing L1 spectrum. Center frequency is
1575
.
42 MHz.
If one of the output values of these so-called very early and very late correlators
is higher than the punctual correlation, the channel is tracking a side peak and
corrective action is taken.
According to Nunes & Sousa & Leitão (2004), the ACF for BOC(
pn
,
n
) with
=
2
p
|
τ
|
T
c
is given as
p
=
1, 2,
...
and
k
(
−
1
p
(
−
T
c
,
)
|
τ
|
k
+
k
2
1
)
+
2
kp
+
k
−
p
)
−
(
4
p
−
2
k
+
1
for
|
τ
|≤
T
c
,
r
(τ )
=
0
,
otherwise.
(3.10)
This ACF is plotted in Figure 3.5. For
p
=
1thisis
(
−
1
−
T
c
,
)
|
τ
|
k
+
k
2
1
)
+
3
k
−
1
−
(
5
−
2
k
for
|
τ
|≤
T
c
,
r
(τ )
=
0
,
otherwise.
The ACF for the BOC
(
n
,
n
)
signal with bandwidth
b
is given as [see Winkel
(2000), Equation (2.68)]
2
r
BL
(τ/
n
−
1
r
BOC
(τ )
=
(
n
−|
k
|
)
T
c
−
2
k
)
−
r
BL
(τ/
T
c
−
2
k
−
1
)
−
r
BL
(τ/
T
c
−
2
k
+
1
)
,
k
=−
n
+
(3.11)
where
Si
2
)
+
2
b
cos
2
)
1
1
r
BL
(
t
)
=
π
(
t
+
1
)
π
b
(
t
+
1
π
b
(
t
+
1
2
π
Si
2
)
+
cos
2
)
1
1
+
π
(
−
)
π
(
−
π
(
−
t
1
b
t
1
b
t
1
2
b
2
π
Si
2
bt
−
cos
2
bt
(3.12)
2
t
π
1
−
π
π
2
b
π
Search WWH ::
Custom Search