EP1053638A1 - Data transmission in a television signal using quadrature amplitude modulation - Google Patents

Data transmission in a television signal using quadrature amplitude modulation

Info

Publication number
EP1053638A1
EP1053638A1 EP99965408A EP99965408A EP1053638A1 EP 1053638 A1 EP1053638 A1 EP 1053638A1 EP 99965408 A EP99965408 A EP 99965408A EP 99965408 A EP99965408 A EP 99965408A EP 1053638 A1 EP1053638 A1 EP 1053638A1
Authority
EP
European Patent Office
Prior art keywords
television signal
quadrature amplitude
video
signal
data
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP99965408A
Other languages
German (de)
French (fr)
Inventor
Marinus Van Splunter
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Koninklijke Philips Electronics NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips Electronics NV filed Critical Koninklijke Philips Electronics NV
Priority to EP99965408A priority Critical patent/EP1053638A1/en
Publication of EP1053638A1 publication Critical patent/EP1053638A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/08—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division
    • H04N7/087—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division with signal insertion during the vertical blanking interval only
    • H04N7/088—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division with signal insertion during the vertical blanking interval only the inserted signal being digital
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/08—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division
    • H04N7/081—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division the additional information signals being transmitted by means of a subcarrier

Definitions

  • the invention relates to a method and an arrangement for transmitting data packets in video lines of a television signal.
  • a method of transmitting data in video lines of a television signal is generally known as teletext.
  • the data is accommodated in a television line in the form of a non-return-to zero (NRZ) signal.
  • NRZ non-return-to zero
  • the maximum bit rate in such a transmission system is restricted. For example, in PAL television systems having a video bandwidth of 5 MHz the teletext bit rate is approximately 6.9 Mb/s.
  • the method is characterized by quadrature amplitude modulating each data packet, using a predetermined carrier frequency which is located within the baseband video bandwidth of said television signal, and inserting said quadrature amplitude- modulated data packet in selected video lines of the television signal which are not used for video signal transmission.
  • the carrier frequency is substantially half the baseband video bandwidth of the television signal.
  • the corresponding method of receiving data packets comprises the step of quadrature amplitude-demodulating said data packets.
  • FIG. 1 shows schematically an arrangement for transmitting data in accordance with the invention.
  • Fig. 2 shows a schematic diagram of a quadrature amplitude modulator.
  • Figs. 3-5 show diagrams to illustrate the operation of the arrangement which is shown in Fig. 1.
  • Fig. 6 shows schematically an arrangement for receiving data in accordance with the invention.
  • Fig. 7 shows a schematic diagram of a quadrature amplitude demodulator.
  • Fig. 1 shows schematically an arrangement for transmitting data in accordance with the invention.
  • the arrangement receives a conventional composite video and blanking signal CVBS and a data signal DA.
  • the transmitter includes a sync processing circuit 11 which identifies the video lines that are used for data transmission. Any line of the video signal may be used for this purpose. Usually, they are selected lines in the vertical blanking interval.
  • the identification signal ID generated by the sync processing circuit 11 is applied to a packetizing circuit 12 which receives the data DA to be transmitted and creates packets of, for example, 800 data bits at a bit rate of, for example, 16 Mbit/s.
  • the data packet is applied to a clock-run-in inserter 13 which places a predetermined clock-run-in (CRI) bit pattern in front of the packet.
  • CRI clock-run-in
  • the packet including the CRI is then quadrature amplitude-modulated in a quadrature amplitude modulation (QAM) circuit 14.
  • QAM quadrature amplitude modulation
  • Fig. 2 shows schematically a more detailed diagram of the quadrature amplitude modulator 14 " which is here assumed to be a QAM-16 modulator.
  • the modulator comprises a symbol generator 141 which divides the data packet into successive series of 4 data bits, and creates two 2-bit symbols Sj and S q for each series. Each symbol is represented by a predetermined signal amplitude. More particularly, an amplitude -3 represents data bits "00", an amplitude -1 represents "01”, an amplitude +1 represents “10”, and an amplitude +3 represents "1 1". As shown in Fig. 3, there are 16 combinations of symbols S, and S q . Each ⁇ S cosmeticS q ⁇ pair of symbols in Fig. 3 represents one series of 4 data bits.
  • the sequences of symbols S, and S q are subjected to low-pass filters 142 and 143, respectively, preferably square-root Nyquist filters.
  • the filtered sequences are subsequently modulated on respective carriers having a frequency f c by respective multipliers 144 and 145.
  • the symbols Sj are modulated on an in-phase carrier.
  • the symbols S q are modulated on a carrier, the phase of which has been shifted by 90° through a phase shifter 146.
  • the resultant in-phase signal I and quadrature signal Q are added by an adder 147 and processed by a post-processor 148.
  • the post-processor 148 scales the modulated signal and shifts its DC level in such a manner that the output signal complies with the relevant television standard (PAL or NTSC).
  • the modulator 14 is preferably implemented as a digital processing circuit operating at a 13.5 MHz line-locked frequency.
  • Fig. 4 shows a line of the television signal with data.
  • Numeral 41 denotes a data packet with 800 bits of QAM-modulated data
  • numeral 42 denotes the clock-run-in
  • numeral 43 denotes the horizontal synchronization pulse.
  • the function of the clock-run-in is to assist a receiver in regenerating the carrier f c with sufficient phase accuracy.
  • the clock-run-in is preferably an alternating sequence of diagonal symbol pairs such as the symbol pairs ⁇ 3,-3 ⁇ and ⁇ -3,3 ⁇ (numerals 31 and 32 in Fig. 3).
  • Fig. 5 shows the frequency spectrum 51 of the quadrature-modulated data signal.
  • Fig. 6 shows schematically an arrangement for receiving data in accordance with the invention.
  • the arrangement receives the television signal and applies it to a quadrature amplitude demodulator 61 and a sync separation circuit 62.
  • the signal is also applied to a conventional television receiver 63.
  • the sync separation circuit 62 identifies the lines in the vertical blanking interval and activates the demodulator 61 during these lines.
  • the data DA are further processed by a data processor 64, for example, a personal computer.
  • Fig. 7 shows a schematic diagram of the quadrature amplitude demodulator 61.
  • the demodulator comprises a pre-processor 611 which receives the television signal and the signal ID identifying the vertical blanking interval.
  • the pre-processor removes the DC component and performs automatic gain control.
  • the pre-processed signal is applied to a clock regeneration circuit 612 and multipliers 613 and 614.
  • the clock regeneration circuit 612 regenerates the carrier frequency f c (2.5 MHz) and a sample clock f s (4 MHz) in response to the clock-run-in CRI.
  • the multipliers 613 and 614 multiply the QAM data signal by an in-phase component and a quadrature phase component of the regenerated carrier f c , respectively. The latter component is obtained by means of a 90° phase shift of the regenerated carrier in phase shifter 615.
  • the symbols S, and S q are reconstructed by low-pass filtering the multiplied signals using square - root Nyquist filters 616 and 617.
  • Analog-to-digital converters 618 and 619 convert the symbols back into the original data bits DA.
  • the demodulator 61 is preferably implemented as a digital processing circuit operating at a 13.5 MHz line-locked frequency.
  • the bit rate of 16 Mbit/s is approximately 2.3 times the bit rate of a conventional teletext system.
  • QAM-64 in which the input data at a bit rate of 24 Mbit/sec (3.5 times the conventional bit rate) is divided into series of 6 bits, or even QAM-256 in which the input data at a bit rate of 32 Mbit/sec (4.6 times the conventional bit rate) is divided into series of 8 bits.
  • a method and a system for transmitting data in lines of a video signal are disclosed.
  • the data is packetized (12), provided with a clock-run-in sequence (13) and quadrature amplitude-modulated (14), using a carrier (f c ) which is located in the middle of the video bandwidth.
  • the modulated data signal is then inserted (15) in selected video lines.
  • QAM-16 is used so that data can be transmitted in the vertical blanking interval of a television signal at a higher bit rate (approximately 16 Mbit/s) than conventional teletext (6.9 Mb/s).
  • QAM-64 or even QAM-256 may be used to obtain a bit rate of approximately 24 or 32 Mbit s, respectively.

Abstract

Method and system for transmitting data in lines of a video signal. The data is packetized (12), provided with a clock-run-in sequence (13) and quadrature amplitude-modulated (14), using a carrier (fc) which is located in the middle of the video bandwidth. The modulated data signal is then inserted (15) in selected video lines. In the preferred embodiment, QAM-16 is used so that data can be transmitted in the vertical blanking interval of a television signal at a higher bit rate (approximately 16 Mbit/s) than conventional teletext (6.9 Mb/s). Optionally, QAM-64 or even QAM-256 may be used to obtain a bit rate of approximately 24 or 32 Mbit/s, respectively.

Description

DATA TRANSMISSION IN A TELEV IS ION SIGNAL US ING QUADRATURE AMPLITUDE MODULATION
FIELD OF THE INVENTION
The invention relates to a method and an arrangement for transmitting data packets in video lines of a television signal.
BACKGROUND OF THE INVENTION
A method of transmitting data in video lines of a television signal is generally known as teletext. In known teletext systems, the data is accommodated in a television line in the form of a non-return-to zero (NRZ) signal. The maximum bit rate in such a transmission system is restricted. For example, in PAL television systems having a video bandwidth of 5 MHz the teletext bit rate is approximately 6.9 Mb/s.
OBJECT AND SUMMARY OF THE INVENTION
It is an object of the invention to provide a data transmission method with a higher bit rate. To this end, the method is characterized by quadrature amplitude modulating each data packet, using a predetermined carrier frequency which is located within the baseband video bandwidth of said television signal, and inserting said quadrature amplitude- modulated data packet in selected video lines of the television signal which are not used for video signal transmission. Preferably, the carrier frequency is substantially half the baseband video bandwidth of the television signal.
The corresponding method of receiving data packets comprises the step of quadrature amplitude-demodulating said data packets.
BRIEF DESCRIPTION OF THE FIGURES Fig. 1 shows schematically an arrangement for transmitting data in accordance with the invention.
Fig. 2 shows a schematic diagram of a quadrature amplitude modulator.
Figs. 3-5 show diagrams to illustrate the operation of the arrangement which is shown in Fig. 1. Fig. 6 shows schematically an arrangement for receiving data in accordance with the invention.
Fig. 7 shows a schematic diagram of a quadrature amplitude demodulator.
DESCRIPTION OF A PREFERRED EMBODIMENT
Fig. 1 shows schematically an arrangement for transmitting data in accordance with the invention. The arrangement receives a conventional composite video and blanking signal CVBS and a data signal DA. The transmitter includes a sync processing circuit 11 which identifies the video lines that are used for data transmission. Any line of the video signal may be used for this purpose. Usually, they are selected lines in the vertical blanking interval. The identification signal ID generated by the sync processing circuit 11 is applied to a packetizing circuit 12 which receives the data DA to be transmitted and creates packets of, for example, 800 data bits at a bit rate of, for example, 16 Mbit/s. The data packet is applied to a clock-run-in inserter 13 which places a predetermined clock-run-in (CRI) bit pattern in front of the packet. The packet including the CRI is then quadrature amplitude-modulated in a quadrature amplitude modulation (QAM) circuit 14. The modulated data packet is subsequently inserted in the selected video line by an adder 15.
Fig. 2 shows schematically a more detailed diagram of the quadrature amplitude modulator 14"which is here assumed to be a QAM-16 modulator. The modulator comprises a symbol generator 141 which divides the data packet into successive series of 4 data bits, and creates two 2-bit symbols Sj and Sq for each series. Each symbol is represented by a predetermined signal amplitude. More particularly, an amplitude -3 represents data bits "00", an amplitude -1 represents "01", an amplitude +1 represents "10", and an amplitude +3 represents "1 1". As shown in Fig. 3, there are 16 combinations of symbols S, and Sq. Each { S„Sq } pair of symbols in Fig. 3 represents one series of 4 data bits.
The sequences of symbols S, and Sq are subjected to low-pass filters 142 and 143, respectively, preferably square-root Nyquist filters. The filtered sequences are subsequently modulated on respective carriers having a frequency fc by respective multipliers 144 and 145. The carrier frequency is substantially half the video bandwidth, for example, fc=2.5MHz. The symbols Sj are modulated on an in-phase carrier. The symbols Sq are modulated on a carrier, the phase of which has been shifted by 90° through a phase shifter 146. The resultant in-phase signal I and quadrature signal Q are added by an adder 147 and processed by a post-processor 148. The post-processor 148 scales the modulated signal and shifts its DC level in such a manner that the output signal complies with the relevant television standard (PAL or NTSC). The modulator 14 is preferably implemented as a digital processing circuit operating at a 13.5 MHz line-locked frequency. The 2.5 MHz carrier frequency
5 8
( — X13.5 ) and the 4 MHz frequency for forming the symbols ( — xl3.5 ) can easily be
derived from said frequency. Fig. 4 shows a line of the television signal with data. Numeral 41 denotes a data packet with 800 bits of QAM-modulated data, numeral 42 denotes the clock-run-in, numeral 43 denotes the horizontal synchronization pulse. The function of the clock-run-in is to assist a receiver in regenerating the carrier fc with sufficient phase accuracy. To achieve this, the clock-run-in is preferably an alternating sequence of diagonal symbol pairs such as the symbol pairs {3,-3} and {-3,3} (numerals 31 and 32 in Fig. 3). Fig. 5 shows the frequency spectrum 51 of the quadrature-modulated data signal.
Fig. 6 shows schematically an arrangement for receiving data in accordance with the invention. The arrangement receives the television signal and applies it to a quadrature amplitude demodulator 61 and a sync separation circuit 62. Optionally, the signal is also applied to a conventional television receiver 63. The sync separation circuit 62 identifies the lines in the vertical blanking interval and activates the demodulator 61 during these lines. After demodulation, the data DA are further processed by a data processor 64, for example, a personal computer.
Fig. 7 shows a schematic diagram of the quadrature amplitude demodulator 61. The demodulator comprises a pre-processor 611 which receives the television signal and the signal ID identifying the vertical blanking interval. The pre-processor removes the DC component and performs automatic gain control.
The pre-processed signal is applied to a clock regeneration circuit 612 and multipliers 613 and 614. The clock regeneration circuit 612 regenerates the carrier frequency fc (2.5 MHz) and a sample clock fs (4 MHz) in response to the clock-run-in CRI. The multipliers 613 and 614 multiply the QAM data signal by an in-phase component and a quadrature phase component of the regenerated carrier fc, respectively. The latter component is obtained by means of a 90° phase shift of the regenerated carrier in phase shifter 615. The symbols S, and Sq are reconstructed by low-pass filtering the multiplied signals using square - root Nyquist filters 616 and 617. Analog-to-digital converters 618 and 619 convert the symbols back into the original data bits DA. The demodulator 61 is preferably implemented as a digital processing circuit operating at a 13.5 MHz line-locked frequency. With the QAM-16 modulation system described above, the bit rate of 16 Mbit/s is approximately 2.3 times the bit rate of a conventional teletext system. In cable systems having a good signal-to-noise ratio, it is also possible to use QAM-64, in which the input data at a bit rate of 24 Mbit/sec (3.5 times the conventional bit rate) is divided into series of 6 bits, or even QAM-256 in which the input data at a bit rate of 32 Mbit/sec (4.6 times the conventional bit rate) is divided into series of 8 bits.
In summary, a method and a system for transmitting data in lines of a video signal are disclosed. The data is packetized (12), provided with a clock-run-in sequence (13) and quadrature amplitude-modulated (14), using a carrier (fc) which is located in the middle of the video bandwidth. The modulated data signal is then inserted (15) in selected video lines. In the preferred embodiment, QAM-16 is used so that data can be transmitted in the vertical blanking interval of a television signal at a higher bit rate (approximately 16 Mbit/s) than conventional teletext (6.9 Mb/s). Optionally, QAM-64 or even QAM-256 may be used to obtain a bit rate of approximately 24 or 32 Mbit s, respectively.

Claims

CLAIMS:
1. A method of transmitting data packets in video lines of a television signal, characterized by quadrature amplitude-modulating (14) each data packet, using a predetermined carrier frequency (fc) which is located within the baseband video bandwidth of said television signal, and inserting (15) said quadrature amplitude-modulated data packet in selected video lines of the television signal which are not used for video signal transmission.
2. A method as claimed in claim 1, wherein said carrier frequency is substantially half the baseband video bandwidth of the television signal.
3. A method as claimed in claim 1, wherein each data packet includes a clock-run- in sequence formed by an alternating sequence of diagonal symbols (31 ,32) in the (I,Q) space of the modulated signal.
4. A method as claimed in claim 1, wherein said video line is a line of the vertical blanking interval of the television signal.
5. A method as claimed in claim 1, wherein said quadrature amplitude modulation is QAM-16, QAM-64 or QAM-256.
6. A method of receiving data packets accommodated in video lines of a television signal, comprising the step of quadrature amplitude-demodulating (61) said data packets.
7. An arrangement for transmitting data packets in video lines of a television signal, characterized in that the arrangement comprises a quadrature amplitude modulator (14) for quadrature amplitude-modulating each data packet, using a predetermined carrier frequency (fc) which is located within the baseband video bandwidth of said television signal, and means (15) for inserting said quadrature amplitude-modulated data packet in selected video lines of the television signal which are not used for video signal transmission.
8. An arrangement for receiving data packets accommodated in video lines of a television signal, comprising a quadrature amplitude demodulator (61) for demodulating said data packets.
9. A television signal comprising data packets in lines of the television signal which are not used for video transmission, characterized in that said data packets are quadrature amplitude-modulated, using a predetermined carrier frequency which is located within the baseband video bandwidth of said television signal.
EP99965408A 1998-12-08 1999-11-24 Data transmission in a television signal using quadrature amplitude modulation Withdrawn EP1053638A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP99965408A EP1053638A1 (en) 1998-12-08 1999-11-24 Data transmission in a television signal using quadrature amplitude modulation

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP98204138 1998-12-08
EP98204138 1998-12-08
PCT/EP1999/009204 WO2000035195A1 (en) 1998-12-08 1999-11-24 Data transmission in a television signal using quadrature amplitude modulation
EP99965408A EP1053638A1 (en) 1998-12-08 1999-11-24 Data transmission in a television signal using quadrature amplitude modulation

Publications (1)

Publication Number Publication Date
EP1053638A1 true EP1053638A1 (en) 2000-11-22

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP99965408A Withdrawn EP1053638A1 (en) 1998-12-08 1999-11-24 Data transmission in a television signal using quadrature amplitude modulation

Country Status (4)

Country Link
EP (1) EP1053638A1 (en)
JP (1) JP2002532974A (en)
AU (1) AU2093800A (en)
WO (1) WO2000035195A1 (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU2001290941A1 (en) * 2000-09-15 2002-03-26 En Technology Corporation Video signal with integral data transmission
US7057666B2 (en) 2000-10-24 2006-06-06 Harris Corporation System and method for encoding information into a video signal
JP2004531185A (en) * 2001-06-19 2004-10-07 ハリス　コーポレイション System and method for encoding information into a video signal
DE602004032058D1 (en) * 2004-03-30 2011-05-12 Modesat Comm Ou SYSTEM AND METHOD FOR TRANSMITTING AND RECEIVING QAM SIGNALS AT LOW SIGNAL / NOISE RATIO
KR100817499B1 (en) * 2006-09-26 2008-03-31 모디새트 커뮤니케이션즈 오유 System and method for transmission and reception of qam signals at low signal to noise ratio

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Publication number Priority date Publication date Assignee Title
US5309235A (en) * 1992-09-25 1994-05-03 Matsushita Electric Corporation Of America System and method for transmitting digital data in the overscan portion of a video signal
DE19544582A1 (en) * 1995-11-30 1997-06-05 Deutsche Telekom Ag Transmission of additional information in unused lines of video signal

Non-Patent Citations (1)

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Title
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Also Published As

Publication number Publication date
AU2093800A (en) 2000-06-26
WO2000035195A1 (en) 2000-06-15
JP2002532974A (en) 2002-10-02

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