JPH0783501B2 - Television signal transmission method - Google Patents

Description

The present invention relates to a color television signal transmission method, and more particularly to a wideband transmission method compatible with a standard NTSC system.

(Prior Art) As a prior art of the present invention, there is a standard NTSC system, which includes, for example, literature, broadcasting technology bibliography, Volume 2 broadcasting system, 13
Pages 2 to 153, edited by the Japan Broadcasting Corporation, published by the Japan Broadcasting Corporation, published on January 20, 1983, the first edition, etc.

(Problems to be solved by the invention) In the conventional standard NTSC system, it is assumed that the transmission bandwidth is limited to 4.2 MHz. Therefore, if the transmission bandwidth of the NTSC signal is wider than 4.2 MHz, Even if the color signal can be transmitted, the band of the I signal in the color signal cannot be 1.5 MHz and the band of the Q signal cannot be 0.5 MHz or more.

Therefore, an object of the present invention is to eliminate this drawback and further widen the Q signal transmission band and further the I signal transmission band when the transmission bandwidth of the NTSC system can be wider than 4.2 MHz.
And, in order to widen it, it is not only necessary to widen the band of the color signal, but it is intended to provide a television signal transmission method having transmission characteristics superior to the conventional method described at the beginning of the embodiment section. is there.

(Means for Solving Problems) In order to achieve this object, a television signal transmission method of the present invention is a color television signal transmission method,
When transmitting an NTSC signal with a bandwidth wider than its standard bandwidth, the bandwidth of the luminance (Y) signal is expanded beyond the standard bandwidth, and the I signal and Q of the chrominance signal are used.
The frequency spectrum of the carrier color signal of the signal is vertically asymmetrical about the color subcarrier, the high frequency component of the Q signal is transmitted by the upper sideband of the carrier color signal, and the high frequency component of the I signal is transmitted by the carrier color. The signal is transmitted from the lower sideband of the signal and the upper sideband of the I signal carrier chrominance signal in a frequency range higher than the band used for transmitting the high frequency component of the Q signal.

(Example) With reference to the accompanying drawings, the present invention will be described in detail below with reference to an example.

FIG. 1 (c) shows an invention made prior to the present invention that enables the transmission bands of Q signals and I signals to be widened (Japanese Patent Laid-Open No. 63-
In the invention described in Japanese Patent No. 72288, hereinafter, a transmission signal frequency spectrum of a television signal transmission method according to the related art) is shown, which will be referred to as a first example. In this case, the transmission bandwidth is shown as approximately 5 MHz. In this example, the bandwidth is not limited to this, and the bandwidth can be narrowed or widened depending on the required luminance signal resolution or Q signal resolution.

A circuit configuration block diagram of a television signal transmitting side encoder for obtaining a transmission signal having the frequency spectrum shown in FIG. 1 (c) is shown in FIG. 1 (a), although it is different from the one described in the above publication. .

In FIG. 1 (a), the red (R), green (G), and blue (B) color signals from the camera are input to the input terminals 1, 2, and 3, respectively, and the same matrix circuit 4 as the standard NTSC system is used. Y
(Luminance signal), I (wideband signal), Q (narrowband color signal)
Is converted to a signal. The Y signal is delayed by the delay circuit 5 and applied to one input of the adder 13. The delay time of the delay circuit 5 is LPF (low pass filter) 6,7 for color signal system, modulator
8, 9 and BPFs (band pass filters) 10 and 11 and the delay time by the adder 12 are made equal to eliminate the delay time difference between the Y signal and the color signal.

The I and Q signals output from the matrix circuit 4 are LP
Applied to F6,7. In this first example, the cutoff frequency of the LPFs 6 and 7 is set to 1.5 MHz so that the frequency spectrum shown in FIG. Motivation These bandwidths are variable as needed. The outputs of LPF 6 and 7 are modulator 8 and 9 respectively.
Applied to. A color subcarrier (f _SC ≈3.58 MHz) generated by the color subcarrier oscillator 16 is applied to the modulator, but the phase of the color subcarrier applied to the I signal modulator is applied to the Q signal modulator. The phase is shifted by the phase shifter 15 so as to be delayed by 90 ° with respect to the phase of the applied color subcarrier. This color subcarrier is exactly the same as in the NTSC system.

The outputs of modulators 8 and 9 are then applied to the inputs of BPFs 10 and 11, respectively. The pass band of the BPF 10 is set so that the I signal modulation number spectrum of FIG. 1 (c) can be obtained. That is, in this case, assuming that the color sub-carrier frequency is f _SC , f _SC −1.5 MHz to f _SC +
Up to 0.5MHz. The passband width of BPF11 is f _SC −0.5M.
From Hz to f _SC + 1.5MHz. After the output signals of the BPFs 10 and 11 are added by the adder 12, the output thereof is further added with the Y signal by the adder 13 and becomes a transmission signal at the output end 17 via the LPF 14. The LPF14 does not necessarily have to be put in the encoder, but if the cutoff frequency of the LPF14 is 4.2 MHz, then NTSC
It has the same signal spectrum as the signal. Since the burst signal and the addition of the synchronizing signal are exactly the same as those of the NTSC encoder, the description thereof will be omitted.

Next, the receiving side decoder for demodulating the television signal of the first example will be described.

The television transmission signal processed by the encoder of FIG. 1 (a) is applied to the input end 18 of the circuit block diagram of the receiving side decoder of FIG. 1 (b) via the transmission line. This input signal first passes through the color subcarrier trap 19 and then the delay circuit.
Applied to 20. This signal is the Y signal, and the output of the delay circuit 20 is applied to the matrix circuit 21. The delay circuit 20 is for eliminating the time difference from the color signal at the input of the matrix circuit 21. On the other hand, the input television transmission signal is also applied to the BPFs 22 and 23 for demodulating the color signal. The pass band characteristics of the BPFs 22 and 23 are the same as the characteristics of the BPFs 10 and 11 of the transmission side encoder, respectively. The output signal of BPF22,23 is the synchronous detector 2
I and Q signals are demodulated from the carrier color signals by being applied to 4, 25.

The color subcarrier generated by the color subcarrier oscillator 29 (f _SC ≈ 3.58 MHz) is applied to the synchronous detectors 24 and 25.
Since the phase of the color subcarrier applied to 24 passes through the phase shifter 28, the phase of the color subcarrier applied to the synchronous detector 25 is delayed by 90 °. The outputs of the synchronous detectors 24 and 25 are applied to the matrix circuit 21 via LPFs 26 and 27, respectively. The cutoff frequency of LPF26,27 is 1.5MHz in this example,
The demodulation R,
G and B signals are obtained.

In the demodulation of a transmission television signal, the standard NTSC system performs YC separation by a comb filter in order to remove cross color interference and the like, but it is naturally applicable to this example.

Next, a second example of the case where the transmission bandwidth of the I and Q signals is widened to 1.5 MHz or more for transmission will be shown. The basic configurations of both the transmission side encoder and the reception side decoder are the same as those in FIGS. 1 (a) and 1 (b), respectively.

This example shows a case where the bandwidth of the I signal is expanded to 1.5 MHz or more. In the encoder shown in FIG. 1 (a)
The cutoff frequency of LPF6 is set to 1.5 MHz or higher, and is set to 2.4 MHz, for example. In this case, the band of the Q signal is kept at 1.5 MHz. LPF6
The output of is balanced-modulated by the balanced modulator 8 and then band-limited by the BPF10. The pass band of the BPF10 is f _SC −2.4MHz to f
_SC + 0.5MHz Other points on the encoder side
This is the same as when transmitting I and Q signals in the 1.5 MHz and 0.5 MHz bands, respectively. FIG. 2 shows the frequency spectrum of the television signal in the second example. In this example, the cutoff frequency of the LPF 14 shown in FIG. 1 (a) is 6 MHz.

In the decoder, according to the signal spectrum of Fig.
It suffices to determine the pass band of BPF22. The pass band is the same as the pass band of BPF10 in this case, and it is f _SC −2.4MHz to f _SC + 0.5MH.
Up to z. Also, the cutoff frequency of the LPF 26 is set to 2.4 MHz (the description up to here is conventional technology).

Next, an embodiment of television signal transmission according to the transmission method of the present invention will be described. In this case as well, the bandwidth of the I signal is 2.4 MHz and the bandwidth of the Q signal is 1.5 MHz, but the difference from the second example (prior art) described with reference to FIG. Figure (a)
This is a change in the pass band of the BPF 10 shown and the BPF 22 shown in FIG. 1 (b). That is, the passbands of BPFs 10 and 22 are f _SC
From -1.5MHz to f _SC + 0.5MHz and f _SC + 1.5MHz from f _SC +
Up to 2.4MHz. This pass band spectrum characteristic is shown in FIG. 3 (a), and the spectrum of the television signal in this embodiment is shown in FIG. 3 (b). Naturally LP
The passband width of F6 and LPF26 is also 2.4MHz.

(Effects of the Invention) As described above, by using the transmission method of the present invention, in transmission of a color television signal, NT
When transmitting an SC signal with a wider bandwidth than its standard bandwidth,
By simply making a simple change to the standard NTSC transmission side encoder and reception side decoder, each transmission band of the luminance signal, I signal, Q signal can be expanded reasonably, there is no crosstalk between each signal, especially , Do not multiplex the interleave of the signal of 1.5MHz band of the I signal to the low frequency part of the luminance signal, and interleave multiplex it to the frequency range higher than the band used for the transmission of the high frequency component of the Q signal. As a result, it becomes possible to transmit color television signals that are more compatible with the standard NTSC system, such as less crosstalk with the luminance signal.

[Brief description of drawings]

FIGS. 1 (a) and 1 (b) show examples (first examples) of circuit block diagrams of a transmission side encoder and a reception side decoder, respectively, in a television signal transmission method according to the invention made before the present invention. FIG. 1 (c) shows the frequency spectrum of the transmission signal in the same example (first example), and FIG. 2 shows the frequency spectrum of the transmission signal in the second example (also in the prior art). Figures (a) and (b) show the transmission frequency spectra of the I signal (a) and the total signal (b), respectively, in the embodiment of the method of transmitting a television signal according to the present invention. 1,2,3,18 …… Input end, 4,21 …… Matrix circuit 5,20 …… Delay circuit, 6,7,14,26,27 …… LPF 8,9 …… Modulator, 10,11 , 22,23 …… BPF 12,13 …… Adder, 15,28 …… Phase shifter 16,29 …… Color subcarrier oscillator, 17,30,31,32 …… Output end 19 …… Color subcarrier Trap, 24,25 ... Demodulator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Taiichirou Kurita 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the broadcasting technology research institute of the Japan Broadcasting Corporation (72) Ichiro Yuyama 1-10 Kinuta, Setagaya-ku, Tokyo No. 11 Inside the Japan Broadcasting Corporation Broadcasting Technology Laboratory

Claims (1)

[Claims] 1. In a method of transmitting a color television signal, in transmitting an NTSC signal with a bandwidth wider than its standard bandwidth, the bandwidth of a luminance signal is expanded to a standard bandwidth or more and the bandwidth of a chrominance signal is increased. The frequency spectrums of the carrier color signals of the I signal and the Q signal are vertically asymmetrical with respect to the color subcarrier, and the high frequency component of the Q signal is transmitted by the upper sideband of the carrier color signal. A television signal transmitted by the lower sideband of the carrier chrominance signal and the upper sideband of the I signal carrier chrominance signal in a frequency range higher than the band used for transmitting the high frequency components of the Q signal. Transmission method.