L64724 LSI Logic Corporation, L64724 Datasheet - Page 146

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

5.7.1.3 Frequency Sweep Rate
5.7.1.4 CAR_SWR
5-14
If the CAR_AUTO_SWP (Group 4, APR 41) bit is used, the sweep
waveform is similar to that shown in
direction changes once the upper or lower limit is reached.
The Carrier Synchronizer determines the frequency sweep rate based on
the value in the CAR_SWR register. Set the value in the 16-bit
CAR_SWR register based on
Equation 5.12
The suggested value for CAR_SWR can be derived by calculating the
value for sweep_rate as shown in
Equation
Equation 5.13
Equation 5.14
Rs is the symbol rate and M and N are as shown in the following table.
To provide reliable acquisition at any signal-to-noise ratio, the
microcontroller uses two sweep rates. The fast rate pulls the loop out of
Demodulator Module Functional Description
CAR_SWR
Sweep_Rate
slow_sweep_rate[MHz/s]
fast_sweep_rate[MHz/s]
7.5 to 3.75
Rs (MS/s)
15 to 7.5
3.75 to 2
45 to 15
2 to 1
5.13.
=
=
2
----------------------------------------------------------
34
CAR_SWR
---------------------------------------- -
sweeprat e T b
T
˙
32
M
8
8
8
4
Fs
2
=
=
33
M x Rs MS/s
N x Rs MS/s
Fs
Equation
Equation 5.14
N
8
2
1
1
1
Figure
5.12.
5.6, where the sweep
and substituting it in