JPH01190192A - Color reproducing circuit for color signal high frequency part sequential transmission color tv signal - Google Patents

Abstract

PURPOSE:To simplify entire constitution and to avoid the production of flicker by using two LPFs, calculating the outputs, applying residual side band correction and extracting an interpolation signal. CONSTITUTION:A residual side band correction filter and a BPF for extracting interpolation signal are constituted by an LPF 15 of 1.5MHz and an LPF 16 of 0.5MHz having a simple filter characteristic, and the arithmetic unit calculating outputs of the LPFs 15, 16. The the grain of the output of the LPF 15 is doubled (17), fed to a subtractor 18, the output of the LPF 16 is subtracted to obtain a characteristic shown in figure A. Then the output of the LPF 16 is subtracted from the output of the LPF 15 by the subtractor 19 to obtain a characteristic shown in figure B. Then an interpolated high frequency part and the output low frequency of the LPF 14 are added to match the characteristic of the outputs of the adder 13 and the subtractor 18 easily, then the unbalanced signal gain between fields is not caused.

Description

[Detailed Description of the Invention] According to the present invention, the low frequency parts of the first color signal and the second color signal are always sent in the double-sided band, and the high frequency parts of these signals are sent in the single-sided band. The present invention relates to a circuit for reproducing color television signals that are sent alternately at regular intervals.

Prior ArtCurrently, such color television signals are called EDTV
(extended definition tele
vision) system has been proposed as one color signal method. In this color signal system, as shown in Figure 5, the low frequency part (0 to 0.5MHz) (I
L) and the low frequency part (0 to 0.5 MHz) of the Q signal (QL
) is transmitted over the entire field in both sidebands, but
These high frequency parts (IH) (Ql() are sent alternately for each field.

That is, the high frequency part (II) of the ■ signal is transmitted in the odd field, and the high frequency part (QH) of the Q signal is transmitted in the even field, so that the field sequential system is adopted. Furthermore, the high frequency section (IH) (QH) is not a double-side band but a single-side band.

Next, a conventional color signal reproducing circuit for reproducing color television signals of this type will be explained with reference to FIGS. 3 and 4. In Fig. 3, the color signal (C) of the above-mentioned color signal high-frequency sequential transmission method color television signal applied to the terminal (1) is sent to the signal demodulator (2) and the Q signal demodulator (3). These demodulators (2) (3)
I-axis demodulation by respectively.

Receives Q-axis demodulation. On the output side of each demodulator (2) (3), there are first and second demodulators connected to each other. Second changeover switch (SW,
) (shz) is provided. These switches (S
W, ) (S6) is switched to the (a) side in an odd field and to the (b) side in an even field. The switching control signal is transmitted from the field discrimination circuit (not shown) to each switch (sw, ) (SWz
) is a field discrimination signal given to Third. Fourth
Changeover switches (Sl'13) (SW4) are provided before the output terminals (5) and (6), and these switches (SW3) and (SW4) are also controlled by the changeover signal, and the first . Second switch (SWl) (SWt
).

Regarding color signal reproduction, ■signal and Q signal are the same, so
Below, only the ■signal will be explained. As shown in FIG. 3, when the field is an odd number, the switches (SW1) to (SW4) are all switched to the (a) side. At this time, the band of the ■ signal demodulated by the I signal demodulator (2) is 0 to 1.5 MHz.
However, as mentioned above, since the high frequency part (II) is transmitted in one side band, the low frequency part (IL) is transmitted in both side bands.
It has only half the amplitude compared to . Therefore, the I signal is outputted to the output terminal (5) through a residual sideband correction filter (7) that doubles the gain of the high frequency section (IH) as shown in FIG. 4(a). Also, since the high frequency part (IH) of the I signal is missing in the even field, an interpolation circuit is provided to interpolate it to the even field.
As shown in the figure, a bandpass filter (8) with a passband of 0.5 to 1.5MHz, a 1-field delay circuit (9), a 1-line delay circuit (10), and a straight line (11) are used. , adders (12) and (13), and the high frequency part (IH) of the I signal extracted by the bandpass filter (8) is processed by a one-field delay circuit (9).
This delayed signal is delayed by one line so that it occurs in an even field, and the one line delayed by the one line delay circuit (10) and the one that has passed through the straight line (11) are added together by an adder (12). As shown in FIG. 4(C), a high frequency signal with twice the amplitude is formed. This interpolation high-frequency signal is transmitted from the I-axis demodulator (2) to the I-axis demodulator (2) in the even field when the switches (sh l) to (SW4) are switched to the (b) side, and has a pass characteristic as shown in Figure 4 (d). The low frequency part (IL) of the I signal given through the low-pass filter (14) is added in the adder (13), and a signal with characteristics as shown in FIG. 4(e) is output to the 1x output terminal (5). be done.

Regarding the Q signal, the only difference is that the field of the current signal and the field of the interpolated signal are different from the above case, and it is reproduced in the same manner as the J signal and is obtained at the Q signal output terminal (6).

However, in the conventional color signal reproducing circuit described above,
The hardware scale of the vestigial sideband correction filter (7) itself having characteristics such as a) becomes large and the overall cost increases.
The output characteristic in the field interpolated with the output characteristic of 7) [Figure 4 (a)], that is, the output characteristic calculated from the outputs of the band pass filter (8) and the low pass filter (14) [
It is actually difficult to make the characteristics exactly the same as shown in FIG. 4(e), and if the characteristics differ, it will cause flicker and deteriorate the image quality.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a color reproduction circuit which has a simple filter configuration and which can obtain color signal outputs with uniform characteristics between fields. shall be.

In order to achieve the above-mentioned object of "1", in the present invention, the low frequency parts of the first color signal and the second color signal are always sent in both sidebands, and the high frequency part of the first color signal and the second color signal are constantly transmitted. In a circuit for reproducing a color television signal in which the high frequency part of the color signal is sent alternately at fixed intervals in a single side band, the output of a first demodulator that demodulates the first color signal and the second color signal are combined. a first low-pass filter that alternately receives the output of the second demodulator at regular intervals and passes the output of the demodulator up to the high-frequency range; and a second low-pass filter that passes only the low-frequency range of the output of the demodulator. - a pass filter; a first calculation means for calculating the output of the first and twentieth pass filters to perform residual sideband correction;
A second calculation means is provided for calculating the output of the 0-pass filter and extracting a high frequency part for interpolation.

-■ According to such a configuration, the filter may have simple low-pass filter characteristics, so the configuration is simple and inexpensive. Moreover, it becomes easy to obtain output with uniform characteristics.

Group 111 In FIG. 1, in which the present invention is implemented, the same parts as those in the conventional example of FIG. In this embodiment, a vestigial sideband correction filter and a bandpass filter for extracting interpolated signals are used as a filter with simple filter characteristics.
5MHz 10th-pass filter (15) and 0.5M
It is constituted by a 20th-pass filter (16) of H2 and calculation means for calculating the outputs of these low-pass filters (15) and (16).

In other words, the first
The gain of the output of the 0-pass filter (15) is doubled by the doubling circuit (17) as shown in FIG. In addition, if we subtract the output of the 20th pass filter (16) with the pass characteristic shown in Figure 2 (B), we get Figure 2 (D).
A characteristic as shown in is obtained at the output of the subtractor (18). With this simple configuration, the same output characteristics as the passband characteristics of the vestigial sideband correction filter (7) shown in FIG. 3 can be obtained.

Furthermore, by using a simple configuration in which the output of the 20th-pass filter (16) is subtracted from the output of the 10th-pass filter (15) by the subtracter (19) constituting the second calculation means, the result shown in FIG. Output characteristics as shown are obtained. This output characteristic is equivalent to the characteristic of the bandpass filter (8) in FIG. 3. Above 1st. 20th-pass filter (15)
Since the characteristic (16) may be a simple pass characteristic, its configuration is extremely simple. Further, it is possible to easily match the characteristics of the output of the adder (13), which is generated by adding the interpolated high-frequency part and the output low-pass part of the low-pass filter (14), and the output of the subtracter (18). There is no imbalance in signal gain between fields.

Note that this embodiment can be configured to handle analog signals or can be configured to handle digital signals. Also, the color signals handled are I signal and Q signal (,
It may be the RY signal and the BY signal.

Effects of the Invention According to the present invention, it is possible to realize residual sideband correction by using two low-pass filters with simple pass characteristics and calculating their outputs, and to extract a signal for interpolation. This has the effect of simplifying the overall configuration and reducing costs.
Output characteristics between fields can be easily made uniform, thereby eliminating flicker.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a color reproduction circuit embodying the present invention, and FIG. 2 is a characteristic diagram showing the characteristics of each part thereof. Third
The figure is a block diagram of a conventional example, and FIG. 4 is a characteristic diagram related thereto. FIG. 5 is a diagram for explaining the color signals handled. (IL) - Low frequency part of I signal. (IH) -4 times higher region. (QL) - Low frequency part of Q signal. (QH) ---High frequency part of Q signal. (2)... ■signal demodulator, (3) ---Q signal demodulator. (15) --- 10th-pass filter. (16)...20th pass filter. (17) -2x circuit, (1B) (19) -
Subtractor.

Claims (1)

[Claims] (1) The low-frequency parts of the first color signal and the second color signal are constantly transmitted in both sidebands, and the high-frequency parts of the first color signal and the high-frequency parts of the second color signal are sent in single-sideband at regular intervals. In a circuit for reproducing a color television signal of a method in which the first color signal is demodulated and the output of a second demodulator that demodulates the second color signal are output at regular intervals, a first low-pass filter that alternately receives the output of the demodulator and passes the output of the demodulator up to the high-frequency range; a second low-pass filter that passes only the low-frequency range of the output of the demodulator; and the outputs of the first and second low-pass filters. A color reproducing circuit comprising: a first calculating means for calculating residual sideband correction by calculating the residual sideband correction; and a second calculating means for calculating the outputs of the first and second low-pass filters to extract a high frequency part for interpolation.