JPH1051749A - Transmission signal reception method/device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably receive and reproduce a multiplex signal by multiplexing and transmitting signals different in contents in a video information period and a period except for the video information period, multiplexing and transmitting signals becoming the important reference of a synchronizing signal and a control signal in the period except for the video information period and demodulating the multiplex signal with the signal becoming the reference as a reference. SOLUTION: A digital signal processing circuit 8 divides the most significant pit and other pits. Error correction codes are added to them and the processings of scrambling and the like are executed and they are stored in a memory 9. The most significant pit is read from the memory 9 in a vertical feedback period and the other pits are controlled to be read from the other period. Then, they are serial/parallel-converted and an unnecessary high frequency component is eliminated through a low pass filter 10. A PCM sound signal which is digitally encoded modulates a carrier which is phase-shifted by 90 degrees through a phase shifter 11 in a digital modulation circuit 12. The output is added in a first adder 4.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission signal for receiving a transmission signal transmitted by multiplexing a multiplexed signal, in particular, a PCM audio signal digitally encoded into a video signal. The present invention relates to a receiving method and apparatus. 2. Description of the Related Art A method of multiplexing a digitally encoded PCM audio signal and a video signal is described in the first part of the report of the Technical Committee on Satellite Broadcasting Reception Technology edited by The Radio Technology Association, published in June 1983. It has been reported in satellite receiver ", etc., since the multiplexed PCM voice signal using the subcarrier 5.7272MH _Z to the video signal of the current NTSC, not satisfy the bandwidth of the current terrestrial television broadcasting Therefore, it is difficult to use it for terrestrial television broadcasting. On the other hand, regarding the possibility of multiplex transmission to the current terrestrial television broadcasting, a broadcasting technology souscript 2 edited by the Japan Broadcasting Corporation published by the Japan Broadcasting Publishing Association in January 1983.
Although described in "Broadcasting System" on pages 205 to 208, there is no description of a system capable of securing a transmission capacity of about 1 Mbit / s for transmitting two channels of high quality audio. [0004] In the above prior art, there is no system for multiplexing a high quality PCM audio signal in the current terrestrial television broadcast. An object of the present invention is to provide a transmission signal receiving method and apparatus for receiving a transmission signal in which a signal such as a PCM audio signal digitally encoded with high quality is multiplexed and transmitted in a current television broadcast. . SUMMARY OF THE INVENTION It is an object of the present invention to provide an image processing apparatus comprising a PCM digitally encoded within a band in which both sidebands of a carrier wave are transmitted, at least for a video information period including video information in a video signal. This is achieved by modulating a multiplexed signal such as an audio signal so as to have an orthogonal relationship with a video signal of a carrier wave, and transmitting data of high importance such as a synchronization signal and a control signal during a period other than the video signal period. At least the video information period has both sidebands in the residual sideband amplitude-modulated video signal carrier and is limited to a general amplitude-modulated band (DSB).
Since the carrier wave is modulated so that the video signal and the PCM audio signal have an orthogonal relationship, the influence of the PCM audio signal on the reproduced video signal can be reduced. By making the modulation degree of the PCM audio signal lower than that of the video signal, the influence of the PCM audio signal on the video signal reproduced by the envelope detection can be reduced. Further, since the PCM audio signal is synchronously detected and reproduced, the orthogonally modulated video signal is not demodulated, and the influence is reduced. [0008] In the current terrestrial television broadcasting, band with a double-sideband of the vestigial sideband amplitude level adjustment is about 1.25MH _Z
There are 2 channels of digitally encoded high quality PCM audio signals of about 1 Mbit / sec (eg, 12 bits × 2 channels × 32K sampling × 1.3 redundancy 1 Mbps)
s) can be made transmittable. Further, since the frequency and the modulation method are different from those of the current FM voice signal, they are compatible with each other without affecting each other. Further, since there is no video information in the vertical retrace period, the video signal is not easily affected by the video signal. Therefore, a signal used as a reference for data of high importance multiplexed in this period (for example, a synchronizing signal, control signal, etc.) Signal). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an example of a transmitting apparatus for multiplexing and transmitting a digitally encoded PCM audio signal to the current terrestrial transmission television shown in FIG. 2 will be described. 1 is a video signal input terminal, 2 is a carrier oscillator, 3 is an AM modulation circuit, 4
Is a first adder, 5 is a VSB filter for vestigial sideband transmission, 6 is a PCM audio signal input terminal, 7 is an analog / digital conversion circuit (hereinafter abbreviated as ADC), 8 is a digital signal processing circuit, and 9 is a digital signal processing circuit. Memory circuit, 10 is a reduction filter,
11 is a phase shifter, 12 is a digital modulation circuit, 13 is a synchronization signal input terminal, 14 is a clock generation circuit, 15 is an audio signal input terminal for FM modulation, 16 is an FM modulation circuit, 17 is a second adder, Reference numeral 18 denotes a transmitting antenna. The output of the carrier wave oscillator 2 is supplied to the AM modulation circuit 6 by the video signal input from the video signal
Modulated. This AM-modulated signal is band-limited by the VSB filter 5 to a television broadcast band. On the other hand, the audio signal input from the audio signal input terminal 15 is FM-modulated by the FM modulation circuit 16, added to the AM-modulated video signal by the second adder 17, and transmitted from the antenna 18. The above is the same as the conventional terrestrial transmission television broadcast. Next, a high-quality PC which is the gist of the present invention is described.
The multiplexing of M audio signals will be described below. The clock generation circuit 14 generates a clock phase-synchronized with the horizontal synchronization signal in the synchronization signal of the video signal input from the synchronization signal input terminal 13. For example, in the case of the NTSC system, the horizontal repetition frequency f _H is 1
So 5.734KH _Z, clock 1.038444MH _Z is obtained when the phase-synchronized with the 66-fold frequency. 3 × f _H 47K obtained by dividing the frequency by 1/22
PCM audio signal input terminals by using a sampling pulse of the H _Z 6
Is sampled by the ADC 7. At this time, even in a 16-bit quantization level, when the transmission rate and 66f _H, the transmission rate for transmitting 16 bits so 48f _H, (6 bits in i.e. 3f _H reference) remainder 18f _H content is It can be allocated to additional data such as an error correction code and a header indicating a scramble reference position. Therefore, the digital signal processing circuit 8 separates the most significant bit from the other bits, performs processing such as adding an error correction code and scrambling each of them, and stores the result in the memory 9.
According to the vertical synchronization in the synchronization signal input from 3,
It is controlled so that it is read from the memory 9 during the vertical blanking period and the other bits are read from other periods. Further serial-to-parallel conversion, after being a serial data bit rate of 66f _H, remove unwanted high-frequency components through a lowpass filter 10 which is suitable for this rate. The digitally encoded PCM audio signal is modulated by a digital modulation circuit 12 on a carrier wave that has been phase-shifted by 90 ° through a phase shifter 11. Since this output is added by the first adder, the video transmission signal and the PCM audio signal are modulated in an orthogonal relationship. FIG. 3 shows the signal spectrum to be modulated. FIG. 5A shows a video signal, and the spectrum of the processed video signal in the NTSC transmission format is 4.25.
MH _Z band there is. Subsequently, the spectrum of an output obtained by AM-modulating the video carrier fc is shown in FIG. 3B, which is a double-sideband amplitude modulation (DSB) signal. On the other hand, FIG.
2 shows an output spectrum of the digital modulation circuit 12 with a digitally modulated PCM audio signal. Where PCM
Spectrum of the audio signal transmission rate 66f _H (about 1M
4 shows a spectrum when a carrier wave is modulated by a signal having a roll-off of about 0.44 (bit) / sec. Figure (d)
Is a spectrum obtained by adding an AM-modulated video transmission signal and a digitally-modulated PCM audio signal.
FIG. 5E shows the spectrum of an FM-modulated audio signal, in which the audio carrier fs is 4.5 from the video carrier fc.
MH _{Z is} far away. FIG. 6F shows the spectrum of the output signal of the adder 17. The video transmission signal is V
It is attenuated from the -0.75 MHz _Z point from the video carrier by the SB filter. The one shown by the dotted line is the digital modulation spectrum of the PCM audio signal carrier which is shifted by 90 degrees from the video carrier. The video signal band 4.25MH _Z
The 4.5MH _Z vicinity of the upper of the spectrum sound carrier is FM-modulated exists. ± for video carrier
Since both sidebands are transmitted for 0.75MH _Z,
It can be considered as a general amplitude modulation (DSB). FIG. 4 is a vector representation of the relationship between the video carrier and the PCM audio signal. As shown in FIG. 2 (c), ± 0.75M perpendicular to the carrier having both sidebands
When a signal within H _Z to be equivalent to 1 and 0 of digital codes modulated with the amplitude A and -A, when the carrier wave vector is taken as 1 the picture carrier amplitude Vc, modulated signal Vcp is [0018] Equation 1] becomes a _{Vcp = cosw c t ± Asinw c} t ............... (1). Where w _c is the angular frequency of the carrier. When the equation (1) is expanded, the following equation is obtained. ## EQU1 ## [0022] In general, the picture carrier Vc cosw _c t
If the modulated with a signal Vm cosw _c t, in the DSB region, the modulated signal Vc is [0023] Equation 3] The carrier amplitude Vc is set to 1, and this V
A quadrature modulation component based on a PCM audio signal is added to c, and the signal Vcp is given by: ## EQU1 ## The vector is shown in FIG. Next, an embodiment of the transmission signal receiving apparatus of the present invention for stably receiving and demodulating a multiplex signal shown in FIG. 1 will be described.
101 is an antenna, 102 is a high frequency amplifier, 103 is a frequency converter, 104 is an intermediate frequency amplifier, 105 is a video signal detector, 106 is a video signal amplifier, 107
Is a color difference signal demodulation circuit, 108 is a primary color signal demodulation circuit, 10
9 is a cathode ray tube, 110 is an audio intermediate frequency amplification circuit, 11
1 is an audio FM detection circuit, 112 is an audio signal output terminal, 1
13 is a bandpass filter, 114 is a synchronous detection circuit, 11
5 is a carrier recovery circuit, 116 is a code identification circuit, 117 is a clock recovery circuit, 118 is a digital signal processing circuit,
Reference numeral 119 denotes a digital / analog conversion circuit (hereinafter, referred to as DAC); 120, an output terminal of a multiplexed PCM audio signal; and 121, a memory circuit. A television signal input from an antenna 101 is amplified by a high frequency amplifier circuit 102, frequency-converted by a frequency conversion circuit 103 to an intermediate frequency for demodulation, and amplified by an intermediate frequency amplifier circuit 104. Tuning is performed by the frequency conversion circuit 103
Is performed by changing the local oscillation frequency. The video signal band is detected by the video signal detection circuit 105 from the signal amplified by the intermediate frequency amplification circuit 104, and the luminance signal output from the video signal amplification circuit 106 and the color difference signal demodulation circuit 10
7 from the output color difference signal,
The three primary colors of R, G and B are obtained and projected on the cathode ray tube 9. On the other hand, regarding the audio band, the audio intermediate frequency amplification circuit 110
, And demodulated and demodulated by an audio FM detection circuit 111 to obtain an audio signal at an audio signal output terminal 112. The above is the same as the conventional television receiver. In addition to the above, a PCM audio signal band multiplexed and transmitted by the band-pass filter 113 is selected and amplified from the output of the frequency conversion circuit 103 in order to demodulate a PCM audio signal multiplexed and transmitted by digital modulation and coding. In the synchronous detection circuit 114, the carrier recovery circuit 115
A signal modulated with a component orthogonal to the amplitude modulation component of the carrier wave is detected and demodulated using a signal synchronized with the carrier wave reproduced in step (1). The signal obtained as a result is converted into a digital code at a point with a small error rate using a code identification circuit 116, and an error generated during transmission is detected and corrected by a digital signal processing circuit 118 using an error correction code. The clock recovery circuit 117 is a circuit for extracting a transmission clock from a signal output from the synchronous detection circuit 114, and identifies data at a point where the error rate of the signal output from the synchronous detection circuit 114 is low (a so-called maximum opening of an eye pattern). Required for digital coding. The signal whose error has been detected and corrected is stored in the memory circuit 1
21 and time alignment of the most significant bit and the other bits is performed. The output of the digital signal processing circuit 118 after signal processing such as error detection and correction is output to the DAC 119
Then, the audio signal is converted into an analog signal and returned to an audio signal. Here, the interference of the PCM audio signal with the video signal in the existing general television receiver will be described. Co regardless of the value of A for which the video signal detection circuit is synchronous detection in cosw _c t (see Equation (1))
sw _c coefficient t only (i.e. video signal only) does not become interference is reproduced. In the case where the video signal detection circuit performs envelope detection, the interference can be reduced by lowering the value of A from 1. For example, assuming that A is 0.1, A signal of 0.005 (approximately -46 dB) is affected as compared with 1, but if the signal level to noise ratio (hereinafter, referred to as SN ratio) of the video signal is 40 dB or more, there is no practical problem. . If A is further reduced from 0.1, the influence on the video signal is further reduced. On the other hand, the interference of the PCM audio signal from the video signal to the detection circuit is caused by the synchronous detection circuit 11 shown in FIG.
By demodulating only the component orthogonal to the carrier in step 4, it can be eliminated. Considering the SN ratio, the SN ratio of the video signal is 4
When 0dB is a practical level, because the bandwidth is about 4 times that of the transmission bandwidth 1 MH _Z of the PCM audio signals, PCM
The SN ratio of the voice is 46 dB, but when the modulation level A of the PCM voice signal is 0.1, the SN ratio is about 26 dB. On the other hand, considering the relationship between the SN ratio of a digital signal and the bit error rate using a general binary signal,
N ratio is 17.4 dB and bit error rate is 1 × 10 ^-4
(General theoretical value). Video signal SN ratio is 40dB
In the case of, the SN ratio of the PCM audio signal is 26 dB,
This is a practically sufficient value for digital signal transmission. Here, the most significant bit is multiplexed in the vertical flyback period, but there is no video information in the vertical flyback period, and only the synchronizing signal and the burst signal, the modulation degree of the video signal is low, and the spectrum is fc. (Where fc is a color sub-carrier frequency fsc), so that the phase of the synchronous detection carrier can be reproduced very stably, so that even if the S / N ratio of the video signal further deteriorates below 40 dB, Since the upper bits can maintain sufficient performance for practical use, there is no significant deterioration in sound quality. Although the embodiment of the present invention has been described with reference to the upper bits and the like of the PCM audio signal as the reference signal transmitted in a portion other than the video signal period, the synchronization signal of the digitally encoded data and the like are described. All signals important for reproducing a multiplexed signal such as a digitally encoded PCM audio signal such as a control signal such as an identification signal have the effect of similarly stably receiving and demodulating the multiplexed signal. According to the present invention, a carrier wave that is amplitude-modulated with a video signal is multiplex-modulated with a PCM audio signal that is digitally coded into quadrature components of the carrier wave, and the video information period and other than the video information period. In the period other than the video information period, signals having different contents are multiplexed and transmitted in a period other than the video information period, such as a synchronization signal, a control signal, and other important reference signals. Since the interference with the multiplexed signal is small, the transmitted reference signal is less likely to be interfered with high reliability, so the multiplexed signal is demodulated based on the reference signal, so that the stable reception and reproduction of the multiplexed signal can be achieved. There is an effect that becomes possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of one embodiment of the present invention. FIG. 2 is a configuration diagram of an example of a transmission signal transmission device. FIG. 3 is a spectrum diagram of a signal obtained by the configuration of FIG. 2; FIG. 4 is a spectrum diagram of a signal. FIG. 5 is a spectrum diagram of a signal. [Description of Codes] 103: frequency conversion circuit, 104 to 108: video signal demodulation circuit, 110, 111: audio signal demodulation circuit, 113: band-pass filter, 114: synchronous detection circuit, 115: carrier wave reproduction circuit, 116: code Identification circuit 117: Clock recovery circuit.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Akihide Okuda             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Hitachi, Ltd.

Claims (1)

[Claims] 1. A first carrier is amplitude-modulated in a vestigial sideband with a video signal, and a second carrier having a phase substantially different from the first carrier by + or -90 degrees within a band having both sidebands in the vestigial sideband. A multiplexed signal such as a digitized audio signal and a signal serving as a reference for receiving and reproducing the multiplexed signal such as the digitized audio signal are respectively provided so that a basic signal band exists in the video signal. The carrier suppression amplitude modulation is performed on the transmission digital coded signal that is time-division multiplexed between the video information period and the period other than the video information period, and the first carrier and the carrier suppression amplitude modulation that are subjected to the residual sideband amplitude modulation. A second carrier is synthesized, and the first carrier and the third carrier having a frequency different from that of the second carrier frequency-modulated with an audio signal are synthesized by frequency multiplexing and transmitted. After receiving a multiplexed television signal and extracting a signal in the basic signal band of the second carrier, which is carrier-suppressed and amplitude-modulated with the time-division multiplexed transmission digitally encoded signal, the signal is synchronized with the second carrier. The synchronous detection is performed to obtain the time-division multiplexed transmission digital coded signal, and the digital signal transmitted in the video information period with reference to the reference signal transmitted in a period other than the video information period. A method for receiving a transmission signal, comprising demodulating a multiplexed signal such as a digitized audio signal and reproducing the multiplexed signal such as the digitized audio signal. 2. 2. The reference according to claim 1, wherein a period other than the video information period is a vertical blanking period of the video signal, and wherein the vertical blanking period is determined as a period other than the video information period and the multiplexed reference is used. A method for receiving a transmission signal, comprising: obtaining a signal that: 3. 3. The audio signal according to claim 1, wherein the multiplex signal is a digitized audio signal, and the content of the digitized audio signal and the content of the audio signal for frequency-modulating the third carrier wave. Reproducing the one or both of the digitized audio signal transmitted on the second carrier and the audio signal transmitted on the third carrier. Transmission signal receiving method. 4. 3. The method according to claim 1, wherein the multiplexed signal is a time-compressed digitized audio signal, and the time-division multiplexed signal transmitted on the second carrier. A transmission signal receiving method characterized by extending a transmission digital coded signal in a time axis. 5. 2. The method according to claim 1, wherein the transmission rate of the multiplexed signal is a signal transmitted at an integral multiple of a horizontal synchronizing signal frequency of the video signal. When reproducing a reproduced audio signal or the like, a signal processing is performed in synchronization with a horizontal synchronization signal of the video signal. 6. Claim 1 or Claim 2 or Claim 3 or Claim 4 or Claim 5 wherein the vestigial sideband amplitude modulated first carrier and the carrier suppressed amplitude modulated second carrier. The combination with the carrier is performed by setting the ratio of the maximum value of the amplitude of the carrier suppressed amplitude-modulated second carrier to the maximum value of the amplitude of the first carrier modulated by the vestigial sideband amplitude to be 0.1 or less. And the ratio of the maximum value of the amplitude of the carrier-suppressed amplitude-modulated second carrier is different between the video information period of the video signal and a period other than the video information period, and the multiplexed television signal is transmitted after being synthesized. Transmitting a multiplexed signal such as the digitized audio signal by demodulating signals in a period other than the video information period and the video information period. 7. A first carrier is amplitude-modulated in a vestigial sideband with a video signal, and a second carrier having a phase substantially different from the first carrier by + or -90 degrees within a band having both sidebands in the vestigial sideband. A multiplexed signal such as a digitized audio signal and a signal serving as a reference for receiving and reproducing the multiplexed signal such as the digitized audio signal are respectively provided so that a basic signal band exists in the video signal. The carrier suppression amplitude modulation is performed on the transmission digital coded signal that is time-division multiplexed between the video information period and the period other than the video information period, and the first carrier and the carrier suppression amplitude modulation that are subjected to the residual sideband amplitude modulation. A second carrier is synthesized, and a third carrier having a frequency different from that of the first carrier and the second carrier, which is frequency-modulated with an audio signal, has a frequency.
What is claimed is: 1. A transmission signal receiving apparatus for receiving a multiplexed television signal transmitted in a multiplexed manner and reproducing a multiplexed signal such as the digitized audio signal, comprising: receiving and demodulating the multiplexed television signal. Receiving frequency converting means for converting to an intermediate frequency for use; video signal demodulating means for demodulating the video signal from the output signal of the receiving frequency converting means; and transmission digital time-division multiplexed from the output signal of the receiving frequency converting means. Band-pass filter means for passing and extracting a band in which a basic signal band of the second carrier wave carrier-suppressed and amplitude-modulated with the coded signal is present; and output of the band-pass filter means or the intermediate frequency conversion means from the quadrature signal. A quadrature detection carrier for detecting a multiplexed signal such as the digitized audio signal which is modulated and transmitted to a carrier. Carrier recovery means for recovering a wave; multiplexing of the digitized audio signal and the like which is synchronously detected by the output signal of the band-pass filter means with the output signal of the carrier recovery means, modulated to the orthogonal carrier wave and transmitted. A synchronous detection unit for demodulating a signal; an audio demodulation unit for demodulating the audio signal frequency-modulated from an output signal of one of the reception frequency conversion unit and the video signal demodulation unit; Reference signal separating means for extracting the reference signal transmitted in a period other than the video information period from an output signal; and obtaining the time-division multiplexed transmission digitally encoded signal from the output signal of the synchronous detection means, A multiplexed signal such as the digitized audio signal transmitted in the video information period is re-generated by the output signal of the reference signal separating means. And a digital multiplexed signal reproducing means for generating the multiplexed signal. 8. 8. The vertical blanking period according to claim 7, wherein a period other than the video information period is a vertical blanking period of the video signal, and the reference signal separating unit separates a reference signal based on the vertical blanking period. A transmission signal receiving device comprising reference signal separating means. 9. The multiplex signal according to claim 7 or 8, wherein the multiplexed signal is a digitized audio signal, and the content of the digitized audio signal and the content of the audio signal for frequency-modulating the third carrier wave are described. Have the same content,
A transmission signal receiving apparatus provided with one or both of the digital multiplexed signal reproducing means and the audio demodulating means. 10. 10. The transmission digital code according to claim 7, wherein the multiplexed signal is a digitized audio signal compressed on a time axis, and wherein the transmission digital code is an output of the digital multiplexed signal reproducing means. A transmission signal receiving apparatus characterized by further comprising a time axis extending means for extending an encoded signal on a time axis. 11. 11. The video signal according to claim 7, wherein the transmission rate of the multiplex signal is a signal transmitted at an integral multiple of a horizontal synchronizing signal frequency of the video signal. A transmission signal receiving apparatus, comprising: a control signal reproducing unit that receives the video signal as an output signal of the demodulating unit, reproduces a control signal based on the video signal, and outputs the control signal to the digital multiplexed signal reproducing unit. 12. Claims 7 or 8, claim 9, claim 10, or claim 11 wherein the vestigial sideband amplitude-modulated first carrier and the carrier-suppressed amplitude modulated second carrier are used. The combination with the carrier is performed by setting the ratio of the maximum value of the amplitude of the carrier suppressed amplitude-modulated second carrier to the maximum value of the amplitude of the first carrier modulated by the vestigial sideband amplitude to be 0.1 or less. And a signal transmitted with the ratio of the maximum value of the amplitude of the carrier-suppressed amplitude-modulated second carrier wave being different in a video information period and a period other than the video information period of the video signal, and The reference signal separation unit and the digital multiplexed signal reproduction unit are controlled by reproducing signals in periods other than the video information period and the video information period according to the video signal which is an output signal of the video signal demodulation unit. Specially Transmission signal receiving apparatus according to.