JP2658021B2 - Television signal processing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a television signal processing method for multiplexing and transmitting another signal to an existing television broadcast signal.

2. Prior Art The current NTSC in Japan [National Tele-vision System C
ommittee)] Color television broadcasting in the Showa era
More than 25 years have passed since it was launched in 35 years. in the meantime,
With the demand for high-definition screens and the improvement in the performance of television receivers, various new television systems have been proposed. In addition, the content of the service program itself is changing from a mere studio program or a relay program to a program having a higher image quality and a more realistic image, such as a cinema-size movie broadcast.

The current broadcast has various specifications of 525 scanning lines, 2: 1 interlaced scanning, luminance signal horizontal bandwidth of 4.2 MHz, and aspect ratio of 4: 3 (for example, Literature Broadcasting Technology Sansou Color Television Japan Broadcasting Corporation, edited by Japan Broadcasting Corporation) Association, 1961). Under such a background, a television signal configuration method has been proposed which aims at compatibility with current broadcasting and improvement of horizontal resolution. An example is described below. To illustrate the television signal of the NTSC system in a two-dimensional plane of temporal frequency f ₁ and the vertical frequency f ₂ is as Figure 5. The color signal C exists in the second and fourth quadrants from the phase relationship of the color subcarrier fsc. Here, high-frequency components of the luminance signal are multiplexed in the first and third vacant quadrants, and the receiving side separates the chrominance signal and the multiplexed high-frequency component by a field operation to improve the horizontal resolution. (See Japanese Patent Application Laid-Open No. 59-171387) Problems to be Solved by the Invention As described above, in the current television broadcasting, the signal band is limited by the standard, and it is necessary to add some multiplexed information. Is not easy. For example, a method for improving the horizontal resolution has been proposed, but there remains a problem from the viewpoint of compatibility with the current television broadcast and deterioration of the high-frequency component demodulation characteristic at the time of a moving image. In addition, from the viewpoint of effective use of radio resources, it is impossible to extend the transmission band.

The present invention has been made in view of such a problem, and has an object to provide a television signal processing method which is compatible with the current television system and can multiplex-transmit a large amount of information within a band defined by a standard. Aim.

Means for Solving the Problems In order to solve the above problems, the television signal processing method of the present invention uses the same frequency and phase as the video carrier.
Carrier wave different by 90 degrees is subjected to double-sideband amplitude modulation with a multiplexed signal, attenuated by half at the frequency of the video carrier, and converted into a residual sideband by a Nyquist filter having an odd-symmetric amplitude characteristic with respect to the frequency of the video carrier. Is removed in the flyback period, and the video carrier is superimposed in the band of the television signal subjected to the residual sideband amplitude modulation.

Function The present invention generates a television signal that enables multiplex transmission of other information within the band of the current television broadcasting standard according to the above-described method. In addition, it is possible to obtain multiplexed information, and it is possible to receive a conventional television broadcast image with almost no trouble even with a current television receiver.

Embodiment Hereinafter, a television signal processing method according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a spectrum diagram showing a television signal processing method on the transmission side according to one embodiment of the present invention. FIG. 1A is a spectrum diagram of a television signal subjected to vestigial sideband amplitude modulation in the current television system. It is shown here when the lower sideband of the video carrier P ₁ is a vestigial sideband. In Figure 1 (b) another multiplexed signal from the television signal shown in FIG. 1 (a), the picture carrier P ₁ and the same frequency at and phase 90 ° different carrier P _2, in the blanking period it is obtained by double sideband amplitude-modulated so as to remove the carrier P _2. FIG. 1 (c) shows a case where the double sideband amplitude modulation in the above is changed to a single sideband amplitude modulation. FIG. 1 (d) shows a case where the above-mentioned double sideband amplitude modulation is replaced with the residual sideband amplitude modulation. FIG. 1 (e) is a signal obtained by multiplexing the signal of FIG. 1 (d) with the television signal of FIG. 1 (a), which is a television signal synthesized according to the present invention.
In FIG. 1 (e), the signal to be multiplexed is the signal of FIG. 1 (d), but may be the signal of FIG. 1 (b) or FIG. 1 (c). The multiplex signal is not limited to an analog signal but may be a digital signal.

FIG. 2 is a block diagram showing a television signal processing method on the transmitting side according to one embodiment of the present invention. 1 is a video baseband signal input terminal, 2 is an amplitude modulator, 3 is a first filter, 4 is an oscillator, 5 is a phase shifter, 6 is a multiplexed signal input terminal, 7 is a modulator, 8 is a second filter, 9 Is an adder,
Reference numeral 10 denotes a composite television signal output terminal. A video baseband signal input from a video baseband signal input terminal 1 is used to convert a carrier wave P ₁ obtained from an oscillator 4 into an amplitude modulator 2.
Amplitude modulation. The obtained amplitude-modulated wave is band-limited by the first filter 3 to be a residual sideband, and then added to the adder 9. The carrier wave P ₁ obtained from the oscillator 4 is converted by the phase shifter 5 to 90
° those obtained by phase-shifting the carrier wave P _2. In multiplexed signal inputted from the multiplex signal input terminal 6, and the carrier removed double sideband amplitude modulation with the carrier P ₂ a double sideband amplitude modulation retrace period. Although the phase shift direction of the phase shifter 5 may be fixed, the phase shift direction may be changed for each horizontal scanning period, for example. The modulated signal is added to the adder 9 after band limitation by the second filter 8. The output of the adder 9 is a composite television signal. That is, the multiplexed signal is superimposed on the video baseband signal to form a composite television signal. Due to the frequency characteristics of the second filter 8, the multiplexed signal has a band as shown in FIGS. 1 (b), 1 (c) and 1 (d). The output of the amplitude modulator 2 and the output of the second filter 8 may be added and then input to the first filter 3, and the output may be used as the composite television signal output terminal 10.

Next, a television signal processing method on the receiving side according to one embodiment of the present invention will be described. In the following, the case of terrestrial broadcasting is taken as an example. FIG. 4 (a) is a block diagram of a current television receiver which performs video synchronous detection. 41 is an antenna, 42 is a tuner, 43 is a video intermediate frequency filter, 44 is a video detector, 45 is a carrier reproduction circuit, and 46 is a video baseband signal output terminal. The signal transmitted from the transmitting side is received by the antenna 41, frequency-converted to an intermediate frequency band by the tuner 42, and band-limited by the video intermediate frequency filter 43. The band-limited signal is output from the video detector 44,
The signal is supplied to the carrier recovery circuit 45. The carrier recovery circuit 45 to recover the carrier I ₁ for synchronous detection. Band-limited signal is detected in the video detector 44 in carrier I _1, the video baseband signal. Here, the frequency characteristics of the video intermediate frequency filter 43 will be described. FIG. 4B shows the frequency characteristics. That is, the video carrier I ₁
Amplitude is 6dB attenuation at the, has a Nyquist filter characteristic having a substantially odd symmetrical amplitude characteristic with respect to the picture carrier I _1. On the other hand, as shown in FIG.
If the multiplex signal is band-limited by a filter having characteristics opposite to the frequency characteristics of the video intermediate frequency filter 43 of the receiver,
The multiplexed signal component in the hatched portion in FIG. 4 (b) is substantially a double sideband. FIG. 4 (c) shows a vector representation of this. Where I ₁ is the video carrier, I ₂ is I ₁ with the same frequency as a and phase 90 ° different carriers in the carrier of the multiplex signal of the video baseband signal. Since the video baseband signal has to think about the carrier I ₁ and vestigial sideband,
The upper and lower sidebands become vectors a _U and a _L and become vectors a ₁ and a ₂ when decomposed into orthogonal vectors. Further, since the multiplexed signal has almost both sidebands, if the upper and lower sidebands are a vector b _U and a vector b _L , their combined vector is b ₂ , which is only a component orthogonal to the vector I ₁ . That vector a ₂ When synchronous detection at the carrier I _1, vector
b No quadrature distortion due to _two components is generated, and interference with multiplexed signals does not occur in principle on current television receivers that perform video synchronous detection. If the signal to be multiplexed is a signal as shown in FIG. 1 (b), it will not be a double sideband when the band is limited by the video intermediate frequency filter 43.
Orthogonal distortion can occur. However, multiplexing at lower levels, for example, reduces the interference to current television receivers. The same applies to the case where the signal to be multiplexed is a signal as shown in FIG. 1 (c), but the degree of interference is further reduced due to the spectrum.

Next, a multiplexed signal demodulation method on the receiving side according to one embodiment of the present invention will be described. The signal of the video intermediate frequency band, which is the output of the tuner, is band-limited by a filter so that the video baseband signal is in both sidebands as shown in FIG. FIG. 3B shows a vector representation of this. Since multiplex signal has to think about the carrier I ₂ and vestigial sideband, upper and lower sideband vector b _U, vector b _L
When decomposed into orthogonal vectors, vector b ₁ and vector
b ₂ Also, since the video baseband signal is almost double-sideband by the filter, if the upper and lower sidebands are vector a _U and vector a _L , their composite vector will be a ₁ and only the component orthogonal to the vector I ₂ will be . That is, carrier I ₂
When the synchronous detection is performed, no orthogonal distortion due to the vector a ₁ and vector b ₁ components occurs, and only the multiplex signal component can be demodulated. FIG. 3 (c) is an example of a block diagram of a television receiver for demodulating a multiplex signal. 31 is an antenna,
32 is a tuner, 33 is a video intermediate frequency filter, 34 is a video detector, 35 is a carrier recovery circuit, 36 is a video baseband signal output terminal, 37 is a filter, 38 is a phase shifter, 39 is a multiplex signal detector, 40 Is a multiplex signal output terminal. The signal transmitted from the transmitting side is received by the antenna 31, frequency-converted to an intermediate frequency band by the tuner 32, and band-limited by the video intermediate frequency filter 33. The band-limited signal is output from the video detector 34,
The signal is supplied to the carrier recovery circuit 35. The carrier recovery circuit 35 to recover the carrier I ₁ for synchronous detection. Band-limited signal is detected in the video detector 34 in carrier I _1, the video baseband signal. The output of the tuner 32 is band-limited by the filter 37 as shown in FIG. The carrier wave I ₁ obtained from the carrier wave recovery circuit 35 is
In deg carrier I ₂ obtained by phase-shifting, to synchronous detection of band-limited signals in the multiplexed signal detector 39. The detection output becomes a multiplex signal. Even if the multiplex signal is a signal as shown in FIGS. 1 (b) and 1 (c), it can be similarly demodulated.

In the above current receiver as mentioned, by synchronous detection by the video carrier I _1, since multiple signals are substantially canceled, interference due to multipath signal is hardly generated. In the receiver for multiplex signal demodulation, not only the video baseband signal but also filtering and video carrier
By synchronous detection by I _2, multiplexed signals can also be taken out without strain orthogonal.

As is apparent from the above description, the television signal processing method of the present invention is a dual-sideband amplitude modulation of a carrier having the same frequency as a video carrier and a phase different by 90 degrees with a multiplex signal,
Attenuated by half at the frequency of the video carrier, and a signal converted into a residual sideband by a Nyquist filter having an odd-symmetric amplitude characteristic with respect to the frequency of the video carrier, the carrier is removed in a retrace period, and the video carrier is removed. By superimposing in the band of the television signal subjected to the vestigial sideband amplitude modulation, another signal can be multiplexed in the band of the current television system. In addition, when a signal is received by a current television receiver using the television signal processing method of the present invention, it is possible to achieve compatibility with the current television system with little interference. In particular, in the present invention, the signal in the vestigial sideband is removed from the carrier during the retrace period, so that the image quality is not impaired when the image is projected by the receiver. In addition, a dedicated receiver can extract a multiplexed signal without orthogonal distortion, which is very effective from the viewpoint of effective use of radio wave resources.

[Brief description of the drawings]

FIG. 1 (a) is a spectrum diagram of a television signal subjected to vestigial sideband amplitude modulation in a current television system according to an embodiment of the present invention, and FIG. 1 (b), FIG. 1 (c), and FIG. FIG. 1 (d) is a spectrum diagram in which the signal is modulated and band-limited by a signal different from the signal shown in FIG. 1 (a), and FIG. 1 (e) shows the signal shown in FIG. FIG. 2A is a spectrum diagram multiplexed on the signal, FIG. 2 is a block diagram showing a television signal processing method on the transmission side in one embodiment of the present invention, FIG. 3A and FIG. FIG. 3 (c) is a block diagram of a television receiver for demodulating a multiplex signal according to an embodiment of the present invention, and FIG. 4 (a) is a video synchronous detection. FIG. 4 (b), FIG. 4 ( ) Is the spectral diagram and vector diagram at the time of synchronous detection of the current television receivers,
FIG. 5 is a spectrum diagram showing a two-dimensional plane of the television signal the time-frequency f ₁ and the vertical frequency f ₂ of the NTSC system. 5,38 phase shifter, 33,43 video intermediate frequency filter, 8
... second filter, 37 ... filter.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideshi Inoue 1006 Kadoma Kadoma, Matsushita Electric Industrial Co., Ltd. Koji Aono 2-10, Kotobukicho, Takamatsu City Inside Matsushita Kotobuki Electronics Industry Co., Ltd.

Claims (1)

(57) [Claims] A carrier having the same frequency as that of a video carrier and a phase different by 90 degrees is subjected to double-sideband amplitude modulation with a multiplexed signal, attenuated by half at the frequency of the video carrier, and oddly symmetric with respect to the frequency of the video carrier. A signal converted into a residual sideband by a Nyquist filter having amplitude characteristics is subjected to carrier removal in a retrace period, and the video carrier is superimposed in a band of a television signal subjected to amplitude modulation of the residual sideband. Television signal processing method.