JP2007013752A - Receiver for digital cable broadcasting responding to u.s. open capable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein a signal with another transfer rate different from one set by the receiving side is erroneously judged as carrier wave lock even when the signal is received, resulting from likelihood when any of three kinds of symbol rate is determined to be transmitted such as in an FDC system which is the cable system in the U.S. when Θ for judging lock/unlock of QPSK carrier waves is provided with the likelihood so as to make it strong against noise and jamming. <P>SOLUTION: The lock/unlock of a Carrier lock Status of a Status of FDC is judged by whether information (such as packet acquisition information, billing information, user information and channel information) transmitted by Out of Band from the transmitting side is acquired by a POD (Point of Device) located in a rear stage of a QPSK demodulation part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a receiver for digital cable broadcasting and a television set corresponding to the OpenCable standard / specification in the United States.

  In the US cable industry, the OpenCable standard was established in 1997 for the purpose of revitalizing the cable industry by the proposal of a group that determines the standard for North American cable called Cable Lab. One of the OpenCable standards is OpenCableHostDevice1.0CoreFunctionalRequirement related to a receiver that receives broadcasts corresponding to OpenCable.

  Among the specifications, there is a specification regarding the contents for displaying the cable reception status (STATUS) of the receiver called OPENCABLE HOST DEVICE DIAGNOSTICS. Among the STATUS items, there is an item indicating the signal state of the FDC called Status of FDC.

  In the Status of FDC, the standard is set to display the center frequency of the FDC and the carrier lock state of the FDC (described on page 50 of Non-Patent Document 1).

  When a cable broadcasting receiver is installed in the customer's house, the status of the cable broadcasting to be distributed is determined by looking at these statuses.

  Next, the configuration of a conventional receiver is shown in FIG.

  Select a desired channel from the IN_BAND band QAM modulation signal sent from the cable company, QAM demodulation and error correction, decode the transport stream signal, and OUT_OF_BAND band FDC signal sent from the cable company (A modulation scheme is QPSK modulation) selects a desired frequency, performs QPSK demodulation and error correction, and decodes billing information, user information, channel information, etc. in the POD unit, and a transport stream A back-end unit 402 that restores MPEG images and digital audio from the signal, converts them into analog video and analog audio, and outputs them to the outside; a system control unit 108 that controls the entire receiver system; and a program guide and graphic screen Consists of graphic unit 109 for creating It has been.

  Next, a conventional carrier wave recovery (AFC circuit) and QPSK lock signal calculation method will be described.

  FIG. 3 of Patent Literature 1 shows a conventional AFC circuit, and FIG. 5 of Reference Literature shows a diagram for explaining carrier wave lock.

  From Patent Document 1, when the AFC circuit operation is correctly performed, the value of Θ in FIG. 5 approaches zero as much as possible, and a signal indicating that QPSK demodulation is locked is output. When Θ moves away from zero, a signal indicating that QPSK demodulation is unlocked is output.

If the reference value is r, a signal QPSK demodulation lock is output when Θ is smaller than r, and QPSK demodulation unlock is output when Θ is greater than r.
JP 2001-16285 A OC-SP-HOST2.0-CFR-I05-050503

  The problem to be solved is that when the lock / unlock is determined by the carrier wave lock signal of the conventional QPSK demodulation, the accuracy of the display is not 100%.

As in the prior art, when the value of Θ is zero and locked, and otherwise unlocked, the receiver is vulnerable to noise and interference. In this respect, in consideration of the fact that noise and interference are superimposed on the received signal, a practical receiver does not make a misjudgment even if a certain range (0 ≦ Θ <noise or interference is superimposed) on the lock reference value. A certain angle).
Therefore, if there is only one type of signal transmitted from the transmission side, the problem of inaccuracy of locking and unlocking does not occur.

  However, in the FDC system of the US cable system, one of three types of 1.544 Mbps, 2.048 Mbps, and 3.088 Mbps is determined to be transmitted. Is not informed. In this situation, by giving a certain range to this reference value, there is a high possibility of lock determination at all three transmission rates, and another transmission rate different from the transmission rate set by the receiving side. When the signal is received, it is erroneously determined that the carrier wave is locked.

  For example, when the receiving side is set to 1.544 Mbps, even if a 2.048 Mbps or 3.088 Mbps signal is received from the transmitting side, it may be erroneously determined that the carrier wave is locked, and the lock is not 100% accurate. This creates a problem.

  In the present invention, the carrier lock status of STATUS of FDC is not a QPSK carrier lock signal that may be erroneously locked as described above, but a POD (Point of Device) located at the subsequent stage of the QPSK demodulator. The lock / unlock of the Carrier lock Status of Status of FDC is displayed depending on whether or not information (billing information, user information, channel information, etc.) sent by Out of Band is acquired from the transmission side.

  The US OpenCable compatible digital cable broadcasting receiver of the present invention improves the accuracy of the lock / unlock display of Carrier lock Status of STATUS of FDC to 100%.

(Embodiment 1)
FIG. 1 is a block diagram showing the configuration of a US OpenCable compatible digital cable broadcasting receiver according to a first embodiment of the present invention.

  The signal input unit 101 to which both the FAT (FORWARD APPLICATION TRANSPORT CHANNEL) signal and the FDC (FORWARD DATA CHANNEL) signal from the cable company are input, and the frequency of the channel selected from the FAT signal and the local signal are mixed and specified frequency The IF tuner signal, the adjacent channel is removed, the FAT tuner unit 102 that outputs an appropriate signal for the QAM demodulation unit to operate correctly, the QAM demodulation unit 103 that demodulates the QAM modulated signal, An error correction unit 104 that corrects an error in the transmission path and outputs a transport stream signal (TS signal), MPEG decoding and audio decoding from the transport stream signal, and generating a digital image signal and a digital audio signal MPEG decoding unit + audio decoding unit 105 to output, Video DAC unit 106 for converting a digital image signal to an analog image signal, Audio DAC unit 107 for converting a digital audio signal to an analog audio signal, a system control unit 108, and OPEN CABLE HOST A screen that mixes a graphic unit 109 that creates a cable reception status (STATUS) screen of a receiver called DIAGNOSTICS, a digital image signal output from the MPEG decoding unit, and a screen that indicates the reception status of a channel output from the graphic unit 109 The system control information is output from the mixing unit 110, the analog image signal output unit 111 that outputs an analog image signal, the analog audio signal output unit 112 that outputs an analog audio signal, and a remote controller or an external button. The frequency at which the FDC signal set in the POD (Point of Deployment) unit exists is selected from the external control signal input terminal 113 to which the signal is input and the FDC signal, and the frequency is converted into an IF signal, which is adjacent to the FDC signal. An FDC tuner 114 that outputs an appropriate signal for removing the channel and the QPSK demodulator operates correctly, a QPSK demodulator 115 that demodulates the QPSK modulated signal, and the frequency of the FDC signal sent from the cable company, A POD unit 116 that receives information (channel arrangement information, billing information, customer information) included in the FDC signal and sends information on lock / unlock of Carrier lock Status of STATUS of FDC to the system control unit. Has been.

  The operation will be described below with reference to FIG. First, a FAT signal from a cable company (FAT: FORWARD APPLICATION TRANSPORT. US cable transmits video and audio mainly in a frequency band from 54 MHz to 864 MHz) and an FDC signal (FDC). : Abbreviation of FORWORD DATA CHANNEL. In the US cable, information related to the user is mainly transmitted in a frequency band of 70 MHz to 130 MHz). A signal from the signal input unit 101 is supplied to the FAT tuner unit 102 and the FDC tuner unit 114.

  Next, the frequency channel information of the FDC signal designated by the POD module is transmitted from the POD unit 116 (customer management card called a POD module inserted by the customer) to the system control unit 108, and the system control unit 108 determines the frequency. The FDC tuner unit 114 is instructed to select a channel.

  The FDC tuner unit 114 selects a frequency at which the FDC signal transmitted from the system control unit 108 exists, converts the frequency to an IF signal, removes an adjacent channel, and performs an appropriate operation so that the QPSK demodulation unit operates correctly. Output a signal. Thereafter, the data is transmitted to the subsequent QPSK demodulator 115, and the QPSK demodulator 115 performs QPSK demodulation.

  Thereafter, channel arrangement information, billing information, customer information, and the like from the cable company are delivered to the POD unit 116, and the system control unit 108 manages these information.

  When the POD unit 116 receives packet acquisition information, channel arrangement information, billing information, customer information, etc. from the QPSK demodulator 115, determines whether or not these information are correctly received, and determines that they are correctly received Information to that effect is sent to the system control unit 108.

  When the system control unit 108 receives information indicating that “information has been received correctly” from the POD unit 116, the system control unit 108 recognizes “lock” and instructs the graphic unit to display “LOCK”. When information indicating that “information cannot be received correctly” is received, “unlock” is recognized and “UNLOCK” display is commanded to the graphic unit. Note that “POD synchronization information” described in the claims means “information received correctly” sent from the POD unit 116 to the system control unit 108, and the system control unit 108 receives this information. Indicates the “lock” information to be determined.

  After that, when the channel desired by the customer is selected by the remote controller or the external button, the information is inputted from the external control signal terminal 113 and sent to the system control unit 108. The system control unit 108 sends the information to the FAT tuner unit 102. Communicate information. The FAT tuner unit 102 selects the channel selection frequency of the channel, converts the frequency into an IF signal of a specified frequency, removes the adjacent channel, and outputs an appropriate signal for the subsequent QAM demodulation unit 103 to operate correctly. .

  The QAM demodulator 103 QAM demodulates the QAM modulated signal and passes it to the error correction unit 104 at the subsequent stage. The error correction unit 104 corrects the transmission path error and outputs a transport stream signal including error information.

  The transport stream output from the error correction unit 104 is subjected to MPEG decoding and audio decoding in the MPEG decoding unit + audio decoding unit 105, and a digital image signal and a digital audio signal are generated.

  Thereafter, the digital image signal is converted into an analog image signal by the VideoDAC unit 106 and output from the analog image signal output terminal 111. The digital audio signal is converted into an analog audio signal by the AudioDAC unit 107 and output from the analog audio output terminal 112.

  The graphic unit 109 creates a screen (OPENCABLE HOST DEVICE DIAGNOSTICS) for displaying the channel status shown in FIG. 2 from the FAT information sent from the system control unit 108 and the FDC information sent from the POD. To do. At this time, in the present invention, the lock / unlock information of the carrier lock status of the Status of FDC is the information sent from the POD unit 116 indicating that “information has been received correctly”, and system control in response thereto. It is created based on “lock” information determined by the unit 108.

  When any of the above information is transmitted from the POD 116 to the system control unit 109 that it is correctly received, it is displayed that it is locked in the carrier lock status of Status of FDC, and it is transmitted that it is not correctly received. Is displayed as unlocking in the Carrier lock Status of Status of FDC.

  Only when a control signal for displaying a screen for displaying the channel state is received from the external signal input terminal 113, the screen mixing unit 110 mixes the reception screen and the screen indicating the channel reception state, and the VideoDAC unit 106. And output to the analog image output terminal 111.

  The present invention can be applied not only to a digital cable broadcast receiver compatible with US OpenCable but also to a DVD recorder having a digital cable broadcast reception function.

1 is a block diagram showing the configuration of a digital cable broadcast receiver compatible with the US OpenCable according to a first embodiment of the present invention. The figure which showed one Example of the screen (OPENCABLE HOST DEVICE DIAGNOSTICS) which displays the state of the channel in 1st Embodiment Block diagram showing the configuration of a conventional US OpenCable compatible digital cable broadcast receiver

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Signal input part 102 FAT tuner part 103 QAM demodulation part 104 Error correction part 105 MPEG decoding part + audio | voice decoding part 106 VideoDAC part 107 AudioDAC part 108 System control part 109 Graphic part 110 Screen mixing part 111 Analog image signal output terminal 112 Analog audio | voice Signal output terminal 113 External control signal input terminal 114 FDC tuner section 115 QPSK demodulator section 116 POD section 401 Front end section 402 Back end section

Claims (2)

In the carrier lock status of the item of the FDC reception state (Status of FDC) of the receiver on the screen (OPEN CABLE HOST DEVICE DIAGNOSTICS) that displays the state of the channel being selected,
A receiver for digital cable broadcasting corresponding to the US OpenCable that displays synchronization information of POD (Point of Device) located at the subsequent stage of the QPSK demodulator instead of the carrier lock signal of the QPSK demodulator as a carrier lock status. A signal input unit to which both a FAT (FORWARD APPLICATION TRANSPORT CHANNEL) signal and an FDC (FORWARD DATA CHANNEL) signal from a cable company are mixed, and the frequency of a channel selected from the FAT signal and a local signal are mixed to a specified frequency. Frequency conversion to IF signal, removal of adjacent channels, a FAT tuner unit that outputs an appropriate signal for proper operation of the QAM demodulation unit, a QAM demodulation unit that demodulates a QAM modulated signal, and an error in the transmission path Correction unit that corrects the error and outputs a transport stream signal (TS signal), and MPEG decoding unit that generates MPEG image and digital audio signal by MPEG decoding and audio decoding from the transport stream signal + Cable receiving state of a receiver called an audio decoding unit, a VideoDAC unit that converts a digital image signal into an analog image signal, an AudioDAC unit that converts a digital audio signal into an analog audio signal, a system control unit, and an OPENABLE HOST DEVICE DIAGNOSTICS ( STATUS) A graphic unit for creating a screen, a digital image signal output from the MPEG decoding unit, a screen mixing unit for mixing a screen indicating the reception state of a channel output from the graphic unit, and an analog image for outputting an analog image signal From a signal output unit, an analog audio signal output unit that outputs an analog audio signal, an external control signal input terminal to which system control information is input from a remote control, an external button, or the like, and an FDC signal, POD (Point of D FDC tuner unit that selects the frequency at which the FDC signal set in the transmission unit is present, converts the frequency to an IF signal, removes the adjacent channel, and outputs an appropriate signal for the QPSK demodulator to operate correctly And a QPSK demodulator that demodulates the QPSK modulated signal, the frequency of the FDC signal sent from the cable company, and the information (channel arrangement information, billing information, customer information) contained in the FDC signal US OpenCable compatible digital cable broadcasting receiver configured by a POD unit which sends information on lock / unlock of Carrier lock Status of STATUS of FDC to the system control unit.

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