JPH0470187A - Chrominance signal transmission device - Google Patents

Abstract

PURPOSE:To improve a horizontal resolution without enlarging an occupied band by providing a line sequentiality means, a band means, a frequency conversion means and an orthogonal modulation means. CONSTITUTION:The band division means 100 divides the color difference of a wide band into a low frequency component and a high frequency component and the frequency modulation means 200 frequency-shifts the high frequency component of the color difference signal so that a band becomes the same as that of the low frequency component. The orthogonal modulation means 300 orthogonally modulates a carrier by two phases by the low frequency component and the high frequency component of the color difference signal. Namely, the color difference signal is made into line-sequentiality 32 and it is resolved into two high and low bands. Then, the high frequency component is frequency- shifted to a low band-side and two frequency components are orthogonally modulated 300 and transmitted. Thus, the chrominance signal of the high band can be transmitted without enlarging the width of the occupied frequency band and the interference of the low component and the high component by orthogonal modulation hardly exist. Thus, a picture quality can be greatly improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a color signal transmission device for transmitting color signals, and particularly to one that aims to improve horizontal resolution.

[Prior Art] As a method for efficiently transmitting television signals, 1. NTSC method, which frequency-interleaves and multiplexes the color signal in the high frequency range of the luminance signal, and PAL method, which creates a color difference signal and inverts the phase of the carrier parallel wave of this color difference signal for each line and sends it out.
This method is currently the mainstream for television broadcasting. Fifth
The figure is a block diagram of a color signal transmission device using the NTSC color signal transmission method described in, for example, page 69 of "Revised Electronic Application Technology" published by Corona Publishing.
1.2 is a color difference signal input terminal, 3 is a first balanced modulator, 4
is a second balanced modulator, 5 is a carrier wave generator, 6 is a first phase delay circuit, 7 is a second phase delay circuit, 8 is an adder, 9 is a burst generation circuit, and 10 is an output terminal.

The operation will be explained below. Incidentally, in actual transmission of color signals in a television, the (1) signal and the Q signal are transmitted, but for the sake of simplicity, the explanation will be based on the color difference signals, that is, the R-Y and B-Y signals.

Color difference signals R-Y and B-¥ signals as shown in FIGS. 6(a) and (b) are input to terminal 1 and terminal 2, respectively, and
The R-Y signal is sent to the first balanced modulator 3, and the B-Y signal is sent to the second balanced modulator 3.
balanced modulators 4-1 are supplied, respectively.

Further, the carrier wave generation circuit 5 generates a continuous signal of approximately 3.58 MHz, and the output signal thereof is supplied to the first phase delay circuit 6 and delayed in phase by 90 degrees. Next, the output signal of the first phase delay circuit 6 is supplied to the second phase delay circuit 7 and further delayed by 90 degrees. The phase relationship among the output signal of the carrier wave generating circuit 5, the output signal of the first phase delay circuit 6, and the output signal of the second phase delay circuit 7 is as shown in FIG. 7(a). Next, the output signal of the first phase delay circuit 6 is sent to the first balanced modulator 3, and similarly to the second phase delay circuit 6.
The output signal of the phase delay circuit 7 is supplied to the second balanced modulator 4 as a carrier wave.

The first and second balanced modulators 3.4 are carrier wave suppression amplitude modulators, and amplitude modulate the carrier waves of the respective phases with the color difference signals B-Y and B-Y signals.

Next, the output signal of the first balanced modulation circuit 3 and the output signal of the second balanced modulation circuit 4 are supplied to the adder 8 and combined.

This ladder is shown in FIG. 7(b). As you can see from the diagram,
The phase and amplitude of the adder 8 output signal change depending on the amplitudes of the two color difference signals.

Here, a change in phase corresponds to a change in hue, and a change in amplitude corresponds to a change in saturation.

Furthermore, since the carrier wave is suppressed and transmitted, it is necessary to regenerate the carrier wave in the demodulation process.

For this purpose, the output signal of the carrier wave generation circuit 5 is supplied to the Haas generation circuit 9 to generate a color burst signal of about 10 cycles. This color burst signal is supplied to an adder 8, and is multiplexed and transmitted during the horizontal retrace period of the video signal. The phase of the color burst signal is B as shown in Figure 7 0)).
- It is aligned with the Y axis. The adder 8 output signal is supplied to an output terminal 10 and output as a carrier color signal. FIG. 8 shows the output waveform.

Next, when looking at the above-mentioned operation on the frequency axis using FIG. 9, FIG. 9(a) shows the baseband band of the color difference signal. The frequency bandwidth of the color difference signal is similar to that of the luminance signal, but the frequency band width is limited to about 500 KHz in consideration of interference with the luminance signal. Such color difference signals are transmitted to first and second balanced modulators 3.4.
When the signal is modulated by , the signal is converted into a signal having a width of 500 HKzO on both sides centered on the frequency fsc of the output signal of the carrier wave generation circuit 5, as shown in FIG. The band of the signal obtained by combining these signals by the adder 8 is exactly the same as that shown in FIG. 8(b), as shown in FIG.

In this way, when two orthogonal carrier waves are combined by carrier suppression amplitude modulation using two different signals, it is possible to simultaneously transmit two signals that increase the occupied band. However, although the occupied band of the color difference signal is the same as the band of the luminance signal, which is about 4 MHz, the reality is that it is generally possible to transmit only about 500 kHz when the problem of interference with the luminance signal is considered.

Therefore, the horizontal resolution of the image is significantly lower than the vertical resolution, resulting in an unbalanced image.

[Problem to be solved by the invention] Since the conventional color signal transmission device is configured as described above, it is possible to obtain a high vertical resolution, but the horizontal resolution becomes extremely low, resulting in an imbalance between the horizontal and vertical resolutions. However, there was a problem in that the image quality deteriorated.

The present invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a color signal transmission device that can improve horizontal resolution without expanding the occupied band.

[Means to solve the problem]

The color signal transmission device according to the present invention includes a line sequential means for sequentially inputting an input color difference signal, a band means for dividing the serialized color difference signal into a low frequency component and a high frequency component, and a band means for dividing the divided high frequency component into a low frequency component. It is equipped with a frequency conversion means for frequency shifting to a band of frequency components, and an orthogonal modulation means for performing orthogonal two-phase modulation of a low frequency component and a high frequency component whose frequency has been shifted.

Effect C] According to the present invention, the band division means divides a wideband color difference signal into a low frequency component and a high frequency component, and the frequency modulation means divides the high frequency component of the color difference signal into the same band as the low frequency component of the color difference signal. Since the carrier wave is orthogonally two-phase modulated by the low frequency component and the high frequency component of the color difference signal using the frequency shift and orthogonal modulation means, the horizontal bandwidth can be expanded without expanding the occupied band.

[Example] Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram of a color signal transmission device according to an embodiment of the present invention, in which 30.31 is a color difference signal input terminal, 32
33 is a low-pass filter, 34 is a high-pass filter,
35 is a frequency conversion circuit, 36 is a first carrier generation circuit,
37 is a second low-pass filter, 38 is a first balanced modulation circuit, 39 is a second balanced modulation circuit, 40 is a second carrier generation circuit, 41 is a first phase delay circuit, and 42 is a second balanced modulation circuit. slow phase circuit,
43 is an adder, 44 is a burst generation circuit, 45 is an output terminal, the low-pass filter 33 and the high-pass filter 34 constitute a band dividing means 100, and the frequency conversion circuit 35
．． The first carrier generation circuit 36 constitutes the frequency conversion means 200, and the first balanced modulation circuit 38. Second balanced modulation circuit 39 Second carrier generation circuit 40, First phase delay circuit 4
1 second phase delay circuit 42. Adder 43. The burst generation circuit 44 constitutes orthogonal modulation means 300.

Next, the operation will be explained.

Color difference signals R-Y, B-Y with waveforms as shown in FIG. It is converted into a line sequential signal.The sequential color difference signal is shown in Fig. 3 (a
), and its bandwidth is about IMHz. The serialized color difference signals are then supplied to a low-pass filter 33 and a high-pass filter 34. The low-pass filter 33 extracts the low-frequency components of the serialized color difference signal to obtain the CL-multiplied signal shown in FIG. The 0th order to extract and obtain the CH signal,
The high-pass filter 34 output signal is supplied to the frequency conversion circuit 35.The zero-frequency conversion circuit 35 converts the high-frequency component of the color difference signal, which is the high-pass filter 34 output, using the continuous wave from the first carrier generation circuit 36 as a carrier. Converts to low frequency. At this time, the high frequency component converted to the low frequency component is adjusted to the cutoff frequency of the high pass filter 34 and the output frequency of the first carrier generation circuit 36 so that the frequency component converted to the low frequency component is approximately the same as the CL multiplied signal band obtained from the low frequency component. Select. and frequency conversion circuit 3
5. Since the output signal contains unnecessary frequency components, the second
A necessary component CHL as shown in FIG. 3 (C1) is extracted by a low-pass filter 37.

Next, the orthogonal modulation operation will be described.

The first low-pass filter 33 output signal CL and the second low-pass filter 37 output signal CHL are supplied to first and second balanced modulation circuits 38 and 39, respectively. On the other hand, the second
The carrier wave generation circuit 4o generates a frequency that satisfies the frequency interleaving relationship with the luminance signal, and its output signal is supplied to the first phase delay circuit 41 where the phase is delayed by 90 degrees, and the output signal is further delayed by 90 degrees. Further 9
The phase is delayed by degrees. First and second phase delay circuits 41゜42
The phase relationship of the output signals is orthogonal as shown in FIG. 4(a). Next, the first phase delay circuit 41 output signal is the first balanced modulation circuit 38-, and the second phase delay circuit 42 output signal is
The second balanced modulation circuit 39 is supplied as a carrier.

The first balanced modulation circuit 38 modulates the output signal of the first phase delay circuit 41 with the signal CL obtained from the low frequency component of the color difference signal, and the second balanced modulation circuit 39 modulates the output signal of the first phase delay circuit 41 with the high frequency component CHL of the color difference signal. The second phase delay circuit 42 output signal is modulated. Next, each balanced modulation circuit 38, 39 output signal is sent to an adder 43.
is synthesized with The frequency spectrum of the adder 43 output signal is shown in FIG. 3(d). its phase and amplitude change.

Furthermore, since the balanced modulator is an amplitude modulator that suppresses the carrier wave, it is necessary to regenerate the carrier wave during demodulation.

For this purpose, with the output signal of the second carrier wave generating circuit 4o as input, about 10 cycles are extracted by the burst signal generating circuit 44, which is supplied to the adder 43 and multiplexed during the horizontal retrace period. The adder 43 output signal is supplied to an output terminal 45 and output.

As shown in FIG. 3(d), the occupied frequency bandwidth in this system is exactly the same as in the conventional example, and the transmittable frequency bandwidth is about twice that of the conventional example.

As described above, according to this embodiment, the two color difference signals R-Y,
B-Y is line-sequentialized and divided into a high frequency component and a low frequency component by the band division means 100, and the frequency conversion means 200
The frequency of the divided high frequency component is shifted to the low frequency component side band, and these two frequency signals are quadrature two-phase modulated by the orthogonal modulation means 200, so the horizontal bandwidth is doubled compared to the conventional method. It can be expanded, and since orthogonal modulation is used, there is no interference with high frequency components.

In the above embodiment, the output signal of the first phase delay circuit 41 is supplied to the first balanced modulation circuit 38, and the output signal of the 20th phase delay circuit 42 is supplied to the second balanced modulation circuit 39. , there is no problem even if the respective signals are replaced.

〔Effect of the invention〕

As described above, 1. According to the color signal transmission device according to the present invention, after converting the color difference signal to line sequential, it is divided into two bands, high and low, and the high frequency component is frequency shifted to the low band side.
Since two frequency components are orthogonally modulated and transmitted, it is possible to transmit high-band color signals without widening the occupied frequency bandwidth.Moreover, since multiplexing is performed by orthogonal modulation, there is no interference between low-frequency and high-frequency components. This has the effect of significantly improving image quality.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a color signal transmission device according to an embodiment of the present invention, and FIG. 2 is a diagram showing the case where two color difference signals are line-sequentialized using the color signal transmission device according to an embodiment of the present invention. 3 is a diagram showing the frequency characteristics of each part of the color signal transmission device according to an embodiment of the present invention, and FIG. 4 is a diagram showing the modulation operation of the color signal transmission device according to an embodiment of the present invention. , FIG. 5 is a block diagram of a conventional color signal transmission device,
FIG. 6 is a diagram showing the waveforms of various parts in a conventional color signal transmission device, FIG. 7 is a diagram showing the modulation operation in the conventional color signal transmission device, and FIG. 8 is a diagram showing the carrier color signal in the conventional color signal transmission device. The waveform diagram in FIG. 9 is a diagram showing the frequency characteristics of each part in a conventional color signal transmission device. In the figure, 30 and 31 represent input terminals, 32 a serialization circuit (sequentialization means), 100 a band division means, 200 a frequency conversion means, and 300 an orthogonal modulation means. Note that the same reference numerals in the figures indicate the same or equivalent parts. Fig. 2 Fig. 4 i--'H--1 Fig. 3 Fig. 5 r Fig. 6 Fig. 7 R-Y-L replacement-Y

Claims (1)

[Claims] (1) A sequential means for inputting two color difference signals and line sequentially superimposing the input color difference signals; a band dividing means for dividing the output of the sequential means into a low frequency component and a high frequency component; frequency converting means for shifting the frequency of the high frequency component so that it occupies approximately the same band as the band of the band-divided low frequency component; A color signal transmission device characterized by comprising orthogonal modulation means for modulating.