SI2109-D-FMR Silicon Laboratories Inc, SI2109-D-FMR Datasheet - Page 29

• Manufacturer Part Number: SI2109-D-FMR
• Manufacturer: Silicon Laboratories Inc

Specifications of SI2109-D-FMR

• Operating Temperature (min): 0C
• Operating Temperature (max): 70C
• Operating Temperature Classification: Commercial
• Lead Free Status / Rohs Status: Supplier Unconfirmed

Figure 15. Fade Recovery Sequence
Unlock
Unlock
Unlock
Unlock
Unlock
Fail
Carrier Frequency Loop
Symbol Timing Loop
Analog AGC Search
CFO Estimation
Receiver locked
Viterbi Search
Frame Search
Calibration
LO Tuning
(Limited)
lock
lock
lock
lock
Done
Done
Rev. 1.0
6.4.6. C/N Estimator
A carrier-to-noise estimator is provided to aid in satellite
antenna positioning. The C/N measurement mode bit,
CNM, controls whether the count is performed over a
fixed-length or infinite window. With a fixed-length
window, the window size is defined by register CNW.
Measurements are stored in a 16-bit saturating register,
CNL. Setting the C/N estimator start bit, CNS clears the
CNL register and initiates the C/N measurement. When
operating in the finite window mode, the CNS bit is
automatically cleared when the measurement is
complete. The CNS bit must be cleared manually in the
infinite mode to stop the count. An external lookup table
is used to translate the measurement into a C/N
estimate for a given setting of the C/N threshold, CNET,
and a given digital AGC setting.
6.5. Channel Decoder
6.5.1. Viterbi Decoder
The Viterbi decoder performs maximum likelihood
estimation of convolutional codes in compliance with
DVB-S and DSS standards. When lock is achieved, the
Viterbi lock indicator, VTL, is asserted. If Viterbi lock is
not achieved after exhausting the specified parameter
space, the device declares Viterbi search failure by
asserting the VTF bit. The Viterbi search commences
under the control of the acquisition sequencer.
The device can be programmed to attempt to
automatically acquire Viterbi lock using all, one, or a
subset of the supported code rates using the VTCS
register.
If lock is achieved, the status of the search, including
code rate, puncturing pattern phase, 90-degree phase
rotation, and I/Q swap, can be monitored in the Viterbi
search status registers, VTRS, VTPS, and VTIQS.
6.5.2. Viterbi BER Estimator
The Viterbi BER estimator measures the frequency of
bit errors at the input of the Viterbi decoder. The Viterbi
BER mode bit, VTERM, controls whether the count is to
be performed over a fixed length or infinite window. The
window size is defined by VTERW. The BER count is
stored in a 16-bit saturating register, VTERC. Setting
the Viterbi BER measurement start bit, VTERS, will
clear the VTERC register and initiate the measurement.
When operating in the finite window mode, the VTERS
bit will automatically be cleared when the measurement
is complete. The VTERS bit must be cleared manually
in the infinite mode to stop the count.
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