L64704 LSI Logic Corporation, L64704 Datasheet - Page 119

• Manufacturer Part Number: L64704
• Description: Satellite Decoder Technical Manual 5/97
• Manufacturer: LSI Logic Corporation

Equation 5.9
Equation 5.10
5.6.1.3 Frequency Sweep Without Prescaled Frequency Signal
The frequency sweep generator can also operate without using the pres-
caled frequency. This can be very convenient if the analog front end does
not provide for a prescaler function.
In this case, both the CAR_USWL (Group 4, APR 29:30) and
CAR_LSWL (Group 4, APR 31:32) registers must be set to zero. The
state of the CAR_SWP_SWP (Group 4, APR 33) bit controls the sweep
direction. Even though the Carrier Synchronizer controls the frequency
sweep rate based on the value in the CAR_SWR register (Group 4, APR
28), the microcontroller must monitor the sweep direction itself.
5.6.1.4 Frequency Sweep Rate
The Carrier Synchronizer determines the frequency sweep rate based on
the value in the CAR_SWR register. Set the value in the 8-bit CAR_SWR
register based on
K
power reference value (the value in the PWR_REF register, Group 4,
APR 19, is 84), K
(4 dB) for both the DDML and the NDAML phase error detectors (see
Section 5.6.2, “Carrier Phase
(10 dB), K
K
error during acquisition. It should always remain lower than 5 degrees.
During the tracking phase, the loop drives the residual steady state error
to 0.
Equation 5.10
For example, if
Assuming the analog components verify
(Group 4, APR 25) = 50, we get df/dt = 32.6 MHz per second.
Carrier Synchronizer
CAR_SWR
f ˙
D
D
=
is the gain of the carrier phase error detector. Assuming a standard
grows linearly with
CAR_SWR
D
is around 26 for the DDML and around 42 for the NDAML.
=
gives the sweep rate in Hertz per second.
64 K
K
D
------------ -
128
D
Equation
3.3
=
D
has a typical value of 10 for low Eb/No conditions
10
------------------------------------------------------------ -
R
PWR_REF
and
CAR
5.9.
Tracking”). For larger Eb/No conditions
C
CAR
=
K
3
VCO
.
CAR_KP
=
0.052 rad
is the phase loop steady state
Equation
, then CAR_SWR = 33.
5.11, and CAR_KP
5-15