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CXD1968AR 参数 Datasheet PDF下载

CXD1968AR图片预览
型号: CXD1968AR
PDF下载: 下载PDF文件 查看货源
内容描述: DVB -T解调器 [DVB-T Demodulator]
分类和应用:
文件页数/大小: 97 页 / 746 K
品牌: SONY [ SONY CORPORATION ]
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CXD1968AR  
Symbol Resampling (ITP)  
This block resamples the complex baseband data to compensate for errors between the transmitter clock  
and ADC sampling clock frequency thus ensuring the FFT block receives the correct number of samples  
per OFDM symbol. An all-digital resampling technique is used which eliminates the cost and stability issues  
associated with internal or external VCXOs. The timing offset can be read from an I2C register allowing  
external monitoring or control.  
Frequency Synchronization Loop (CRL)  
The frequency synchronization loop compensates for intentional transmitter carrier frequency offsets and  
tuner local oscillator frequency error inherent in the RF to IF conversion process. An all-digital AFC  
technique estimates the frequency shift using the pilots in the OFDM signal and derotates the I/Q  
constellation before the FFT process. Frequency offset information can be read from an I2C register.  
This information may be extracted during a channel scan and subsequently applied to the tuning when  
pre-selecting (zapping) a channel. The offset range can be programed to allow faster acquisition to  
broadcast channels even beyond 3 × ±166kHz transmitter offset. Scanning under software control is  
simplified using the extended acquisition range.  
ACI and CCI Rejection and Digital AGC (CSF + CAS)  
These blocks filter any residual adjacent channel interference such as NICAM energy leaking through the  
edges of the SAW filter. The CCI filter can optionally cancel co-channel interference such as vision carrier  
of an analog TV signal. Digital AGC is also performed to restore a consistent signal after filtering. The CCI  
filter is automatically applied in the presence of analog co-channel interference, resulting in optimum  
performance for the received channel. The CSF block provides extra adjacent channel rejection,  
particularly in ZIF mode where there is reduced folding in-band of ACI signals.  
COFDM Symbol Synchronization Block (SYR)  
This block acquires and tracks the position of the FFT sampling window within the OFDM symbol, to allow  
the FFT to recover the useful carriers including pilot tones with minimal ISI. This block can be programed  
to perform a fast detection of the guard time interval and mode without using TPS, reducing acquisition  
time. Alternatively a specific mode and guard configuration can be programed also reducing acquisition  
times for known channels.  
The CXD1968AR utilizes a new tracking algorithm which improves symbol tracking in multipath channels,  
particularly beneficial for reception of SFN broadcasts where there can be echoes outside the guard  
interval. The algorithm permits acquisition and tracking of pre-cursive and post-cursive echo delays inside  
and outside the guard interval, and also automatically tracks the “birth” and “death” of echoes occurring at  
different delays, even if the delay of the main echo path changes. The tracker contains automatic CCI  
detection and filter selection further optimizing channel reception.  
FFT Processor  
This block performs a 2048 or 8192 point FFT on the derotated I/Q samples.  
Pilot Processing and Common Phase Error (CPE) Correction (SCR and PPM)  
This block corrects for the phase slope and common phase error present on the carriers due to the FFT  
trigger point being chosen to minimize ISI. A fast acquisition mode can be programed to allow the device  
to start outputting transport stream data before a full superframe has been received.  
Channel Estimation  
This block estimates a time varying channel frequency response using the pilot carriers embedded in every  
COFDM symbol. This estimate is then interpolated in the frequency domain and used to correct each of  
the individual OFDM carriers in the CHC block. This block also estimates the signal and noise power for  
each carrier, which is used as a reliability estimate to weight the soft decisions of each bit fed to the Viterbi  
decoder. This feature helps to improve PAL CCI performance where vision and sound carriers can distort  
nearby COFDM carriers.  
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