CS3710 Amphion, CS3710 Datasheet - Page 4

• Manufacturer Part Number: CS3710
• Description: 32 Qam Modulator
• Manufacturer: Amphion

The insertion of unique word information for receiver frame
synchronization follows the scheme outlined in the Intelsat
standard IESS-308. The insertion of the unique word occurs
every 16 RS codewords which makes up a superframe. It is
assumed that the first frame input after reset is the first block
of a superframe. The unique word is a 4-byte value with 2
bytes over-writing the final 2 parity bytes in the first 2
successive Reed-Solomon codewords of a superframe. .
The interleaver follows the Intelsat IESS308 scheme, which
involves a block interleaver with a depth of 4 frames and an
offset between each frame of 60 bytes. That is, 4 consecutive
frames are written into the interleaver in row order, but with
successive frames offset from each other by 60 byte locations.
The data is then read out in column order.
The TCM encoder is based on a rate ½ convolutional encoder
with puncture rate 9/10 as shown in Figure 4. The punctured
TCM encoded symbols are then mapped to the 32 QAM
constellation. The TCM coding is performed directly on the
byte wide data that is input from the interleaver. The output
from the TCM encoder is in the form of 5 bit symbols which
are further coded to 3-bit words passed to the spectral shaping
filter.
4
CS3710
Unique Word Mnemonics
Unique word 3
Unique word 2
Unique word 1
Unique word 0
UNIQUE WORD INSERTION
TCM ENCODER
INTERLEAVER
32 QAM Modulator
Value in Hex
0xBE
0x5A
0x66
0x0F
Figure 4: Encoder for Rate 9/10 Trellis Code for 32-QAM
(with puncturing)
The puncture patterns for 9/10 puncture rates are defined
below.
The SSBMap sub-block performs the following functions:
•
•
•
The output from the TCM encoder is pushed into the FIFO
when it is valid. The symbols from the FIFO are further coded
to 3-bit I-output and Q-output according to the 32-QAM.
When SSB is enabled, the SSB pattern, a sine wave in the
I-channel and a cosine in the Q-channel, replaces the symbol
from the FIFO and is fed to the transmit filter. This drives the
filter full scale, and hence the SSB stream is re-scaled to the
maximal amplitude of the 32 QAM constellation.
9/10
Bit 4
Bit 8
Bit 3
Bit 7
Bit 6
Bit 5
Bit 2
Bit 1
Bit 0
Code
Rate
Inserts TCM coded symbols into a transmit FIFO for
resampling
Codes re-sampled TCM symbols to 3-bit I-Q samples for
RRC filter input
Replaces I-Q samples with SSB pattern when SSB is
enabled
1 1
1 X X 1 Applied to bit 4 and bit 3 of a 9-bit input
Rate 3/4 punctured
Puncture Pattern (X marks a punctured bit)
SSB AND MAPPER
encoder
Applied to the MSB (bit 8) of a 9-bit input
symbol
symbol
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
First TCM symbol
(unpunctured)
Second TCM symbol
(punctured)