L64724 LSI Logic Corporation, L64724 Datasheet - Page 143

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

5.6.1.2 Timing Loop Sweep Equations and Timing Loop Bias
Figure 5.4
Upper
Sweep
Limit
The equations for the sweep rate and sweep limit are given below in
Equation 5.9
rate in Hz/sec and DF_RATIO is the decimation filter down sampling
ratio, which can be 1, 2, 4, 8 or 16. T is the symbol time and Fs is the
sampling (A/D) frequency.
Equation 5.9
Choose CLK_USWL or CLK_LSWL as given in
Sweeplimit indicates the upper desired sweep limit in Hz for CLK_USWL
and it indicates the lower limit for CLK_LSWL.
Equation 5.10
Note that X stands for either U or L. Also, you must set the appropriate
sweeplimit.
Choose CLK_BIAS according to
Equation 5.11
where Fs = sampling frequency, and Fb = baud rate.
Timing Clock Recovery
Lower
Sweep
Limit
Sweep
Start
Point
CLK_BIAS
frequency
CLK_SWR
CLK_XSWL
and
=
Timing Loop Sweep Operation
=
2
CLK_SWR
CLK_USWL
CLK_BIAS
27
2
----------------------------------------------------------- -
Equation
42
=
F s
2
----------------------------------------------
Fs
------ -
Fb
24
F s
sweeprat e Tb
---------------------------- -
DF_RATIO
------------------------ -
DF_Ratio
sweeplimit
------------------------ -
DF_Ratio
5.10. Sweeprate indicates the desired sweep
time
1
1
1
Equation
5.11.
Equation
5.10.
5-11