L64724 LSI Logic Corporation, L64724 Datasheet - Page 253

• Manufacturer Part Number: L64724
• Description: Satellite Receiver
• Manufacturer: LSI Logic Corporation

Group 4, APR 42 – Set to 0x99.
This register defines the loop bandwidths for a particular baud rate. A
good approximation to the equivalent noise bandwidth is given in
tion
Equation B.54
For a baud rate of 21.3 Mbaud we can choose B
therefore
The loop equations are calculated as shown in
Equation
Equation B.55
Equation B.56
The damping factor (
values we get L
We can now calculate
B.58.
Equation B.57
Equation B.58
QPSK Demodulator and FEC Configuration Example: Low Data Rates
B
B
b
b
a
a
B.54.
L
L
=
=
=
=
=
=
---------------------- -
K
2 1 10
---------------------------------------------------------- -
---------------------- -
K
-----------------------------------------------------------
0.0003125 BaudRate
--------- - 1
2
1 10
B.56.
tim
2
tim
n
2
n
n
0.0388 3.75
T
0.0388 3.75
L
L
n
= 1 Krad/s.
tim
tim
T
2
3 2
+
tim
-------- -
4
3
1
= Fs x decimation_ratio/Fb = 60e6 *(0.25)/2.0e6 = 3.75.
----------------------- -
2.0 10
2
----------------------- -
2.0 10
1
is chosen as 1.0, and K
a
1
and
6
6
2
=
=
b
68.6 10
0.171 10
as shown in
–
4
–
5
Equation B.57
tim
Equation B.55
L
= 0.0388. Using these
= .625 Krad/s and
and
and
Equation
Equa-
B-39