System clock recovery apparatus

A system clock and unified technology, applied in television, electrical components, image communication, etc., can solve the problems of unable to recover the system time reference PCR value and low clock accuracy, and achieve real-time tracking of system frequency, high phase accuracy, and ensure accuracy Effect

Inactive Publication Date: 2008-07-23
航天投资控股有限公司
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Problems solved by technology

[0004] Domestic literature mainly reports the application of digital TV and image communication through PCR correction of local clock. Among them, the clock synchronization method proposed by the patent "Video Signal Compression Device" (CN1182722C) uses difference comparison, but the clock accuracy recovered by this method Not high, and the system time reference PCR value cannot be recovered

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  • System clock recovery apparatus

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Embodiment Construction

[0020] As shown in Figure 1, the embodiment of the present invention consists of a PCR value extraction module, a loading control module, a dichotomy frequency capture module, a PID frequency tracking module, a local PCR generation module, a voltage-controlled crystal oscillator and a DA frequency control word output module.

[0021] The PCR value extraction module is mainly responsible for detecting from the TS stream and extracting the PCR value. The front end receives the MPEG-2 standard data stream. In the MPEG-2 system layer standard, the unit of the transmission data stream is a TS packet, which is fixed at 188 bytes. The header has a fixed 4-byte header and an optional variable-length The adaptive area is used to identify the type of the packet, as shown in FIG. 2 . The PCR value extraction module extracts the type identifier value, the adaptive field control bit, and the PCR flag bit according to the PCR message format. When the type identifier value is the required ty...

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Abstract

A system clock recover device comprises a PCR value extracting module, a loading control module, a dichotomy frequency capturing module, a PID frequency tracing module, a local PCR generating module and a DA frequency control word outputting module, and detecting a reference PCR value of the system clock from a TS flow and sending to the dichotomy frequency capturing module, simultaneity loading the control module and ensconcing the PCR value which is extracted from the PCR value extracting module into the local generating module, wherein the dichotomy frequency capturing module rapidly captures frequency points of the system clock according to the PCR of the TS flow and the local PCR value, and the frequency points are traced by the PID frequency tracing module, wherein the PID frequency tracing module adopts a PID algorithm by using the PCR value of the TS flow and the local PCR, the DA frequency control word outputting module outputs a control voltage according to the obtained frequency control words, a voltage control crystal outputs local clock frequency according to the outputting voltage of the DA frequency control word outputting module and sends to the local PCR generating module. The invention has the advantages of rapid frequency capturing and high phase accuracy.

Description

technical field [0001] A system clock PCR recovery device proposed by the invention is mainly applied in the DVB-RCS system. Background technique [0002] Based on the full understanding of the VSAT system, my country's VSAT system will be mainly used in satellite distance education, satellite interactive TV services, satellite broadband multimedia and Internet in the future. The prominent feature of these services is asymmetric data transmission. Therefore, according to the reality of our country, we choose to develop a satellite-based asymmetric data transmission system, that is, a satellite-based DVB application system. In the top-level design of the system, the forward link will use the DVB-S standard, and the return link will use the standard DVB-RCS standard. The DVB-RCS system is composed of a system master station and several remote stations. The system master station packages the data, video and IP voice to be sent to the satellite in TDM broadcasting system, and e...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04N7/62H04N7/50
Inventor 汪雪松程子敬邹光南刘大禹
Owner 航天投资控股有限公司
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