cxd2817r Sony Electronics, cxd2817r Datasheet - Page 2

• Manufacturer Part Number: cxd2817r
• Description: Cable And Terrestrial Tv Digital Broadcast Demodulator Ic Achieves The Industry?s Top Class Performance
• Manufacturer: Sony Electronics

Current Products (sampling frequency fs = 20.5 MHz)
According to the sampling theorem, frequencies
higher than fs/2 (10.24 MHz) are aliased to lower
frequencies and appear as interference in the
desired band.
MFN (Multi-Frequency Network) Scheme
Each broadcast tower broadcasts on a
different frequency. Although multipath is not a
problem, the frequency utilization efficiency is
poor.
Figure 1
Figure 2
Figure 3
IF/Low-IF
41 MHz
X'tal
RF
Ach
Block Diagram
Introduction to SFN and Comparison of Performance Outside the Guard Interval
A/D Converter Countermeasures for Adjacent Channel Interference
Reference clock
RF sense
RF_AGC
IF_AGC
I
Cch
2
C bus
IF
fs/2
Bch
DVB-T/C Demodulation IC
I
ADC
ADC
AGC
Tuner
2
Clock
C bus
PLL
SFN (Single-Frequency Network) Scheme
Each broadcast tower broadcasts on the same
frequency. Although the frequency utilization
efficiency is good, workarounds for multipath
interference are required.
CXD2817R (sampling frequency fs = 41 MHz)
Since fs/2 is 20.5 MHz, the adjacent waveforms
are sampled correctly by the A/D converter. As a
result, adjacent waveforms are not aliased into
the desired band. The adjacent waveforms are
excluded in the signal after conversion to a digital
signal.
demodulator
demodulator
(DVB-C)
COFDM
(DVB-T)
QAM
Ach
Ach
decoding
Viterbi
Ach
decoding
RS
fs/2
Status monitor
TASK_3_30 C/(N+I) Performance in Single Frequency
TS output
TASK_3_23 Immunity to "Analog" Signals in Other Channels
control
I
2
C bus
18
16
14
12
10
–300 –200 –100
8
6
4
2
0
Performance has been significantly improved for
multipath outside the guard interval, allowing this
IC to respond flexibly to changes in signal
specifications even after the transition to SFN.
666 MHz 64QAM CR = 2/3 GI = 1/8
–30
–35
–40
–45
–50
–55
Networks inside the guard interval
Compared to current methods, resistance to
adjacent channel interference is improved
significantly.
666 MHz 64QAM CR = 3/4 GI = 1/4
N–2
Desired signal/interfering signal ratio
Lock flag
TS output
TS error
I
2
C bus
Delay time [μs]
N–1
better
0
better
100
N+1
200
N+2
300
CXD2817R
CXD1981R
Spec (Nordig)
CXD2817R
CXD1981R
Spec (Nordig)