DK145900B - COUPLE FOR DECODING A PAL COLOR REMOTE SIGNAL - Google Patents

Description

(19) DENMARK (^)

| p (12) PUBLICATION SCRIPT (11) 11) 5900 B

DIRECTORATE OF

PATENT- 06 TRADE MARKET

(21) Application No. 6085/72 (51) lnt.CI.3 Η OA Ν 9/39 (22) Filing date Dec 6 1972 (24) Race day 6 Dec. 1972 (41) Aim. available Jun 8 1975 (44) Posted 5 Apr 1985 (86) International application no.

(86) International filing day (85) Continuation day - (62) Master application no. -

(30) Priority 7 Dec. 1971, 98825/71, JP

(71) Applicant SONY CORPORATION (SONY KABUSHIKIKAISHA), Tokyo, JP.

(72) Inventor Minoru Morio, JP.

(74) Plenipotentiary Danish Patent Office ApS.

(54) Coupling for decoding a PAL color television signal.

The invention relates to a coupling for color television receivers for decoding a PAL color information signal, whereby by means of a delay link and a line frequency switch a modified chrominance signal consisting of alternately one line is generated and its one line period delayed repeater, which is supplied to two reference signal generator D is supplied with reference signals which, by means of phase shift circuits, have a phase bearing which coincides with the respective modulation axes for the chrominance signals and is used for demodulation of these, which coupling further comprises a control circuit; control of the switch and containing two additional demodulators connected to the two inputs of the switch and the output of the reference signal generator as well as a comparator circuit connected to these demodulator outputs.

In the PAL system, a composite color television signal comprises two color signal components, usually as color difference signals containing color information, which are simultaneously encoded by cross-phase amplitude modulation with suppressed carrier on a color subcarrier within the video frequency band, ° for each line period. Ie the color television signal of the PAL system has two different types of oscillation alternating for successive line periods.

For decoding such a composite color television signal, various systems have been proposed in the past, e.g. the so-called simple PAL system and the standard PAL system. However, these common systems decode the PAL signals with poor quality of the rendered image or greatly increase the complex nature of the system.

A coupling of the kind mentioned in the introduction is known from the description of Danish patent application no. 4152/72. In this known coupling, the reference signals supplied from the reference signal generator to the control circuit demodulators have the same phase. In the wrong position of the switch, a control signal is produced which again brings the switch at the correct rate. However, if the chrominance signals supplied to these demodulators contain only chrominance components of one kind, the switch in the wrong position will not be fed any control signal.

The object of the present invention is to further develop the already known coupling in such a way that the switch is also coupled to the correct position, although only chrominance signals of one kind or another appear.

This is achieved by the coupling according to the invention, characterized in that at least one of the two modulators in the control circuit is connected to the reference signal generator through an additional phase shift circuit for producing reference signals whose phase bearing is symmetrical with respect to the chrominance signal. axes and thus different from the phase bearings of the reference signals used for demodulation.

By producing the reference signals such that they are symmetric to one axis, the RY axis or the BY axis, and the signal supplied to the control circuit demodulators contains only components corresponding to one axis, a control signal can still be generated, since the reference signal is no longer fixed on one of these axes and can therefore perceive components of both axes.

The invention will be explained in more detail by some exemplary embodiments with reference to the drawing, in which fig. 1 and 2 show vector diagrams for explaining color television signals according to the PAL system; 3 is a block diagram of an example of the coupling according to the invention; FIG. 4 and 5 are vector diagrams to explain the coupling of FIG. 3, FIG. 6 is a diagram of an example of a portion of the coupling of FIG. 3, FIG. 7, 8, 9, 10, 11, and 12 vector diagrams to explain the coupling of FIG. 3, FIG. 13 is a block diagram of another example of the coupling according to the invention; and FIG. 14, 15, 16, 17, 18 and 19 vector diagrams to explain the coupling of FIG. 13th

The distinctiveness of the PAL color television system lies in the phase relationship between the two color difference signals modulated on a common subcarrier to form the color information signal. This phase relationship is shown in FIG. 1. One of the color information components, E

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there is information about blue components in the television picture. The second, E -E, contains information related to red components. Both of these color information components are modulated on the same carrier or, more specifically, the same sub carrier, but the modulation is performed separately and in such a way that in a given time interval corresponding to one line nine of the color television image, the color information component Eg-Ey is modulated by the carrier with a modulation axis. CPQ. In the same time interval, the second color information component Εβ-Εγ is modulated on the carrier by a modulation axis of the phase cpQ ~ U ?. This is why the color information component (Eg-Ey) n, & represents blue information in the given line interval n, is shown as a horizontal arrow, and the red color information component (Eg-Ey) ^ in the same line interval n is shown as a vertical arrow. The vector sum of these two fave information components yields a resultant signal F, which is a complex voltage which can be "determined by the term; (E ^ -Ey) + + which is hereinafter referred to as a plus line signal.

The phase relationship of the following line n + 1 is also shown in FIG. 1. In this case, the color information component Eg-Ey on the carrier is also modulated by the modulation axis with the phase cpQ- and accordingly the color information component (Eg-Ey) n + y for the line n + 1 is shown in the same direction as the component (Eg-Ey) ^. However, the color information component Ep-Ey is modulated in accordance with the PAL system on the carrier by a modulation axis having a phase φ - ττ (= - φ), i.e., phase inverted to the preceding line n, and therefore the color information component (Eg-Ey) ^^ for the line n + 1 shown in the opposite direction of the component (Eg-Ey) ^. The signal F ^ y can therefore be determined by the expression (Eg-Ey) n + y_ a '(E] j-Ey) + i, which in the hereinafter referred to as a minus line signal.

The color information signal contains a color synchronization signal. The color synchronization signal has different phase in signal F1 and signal Fn + y respectively. That is, the phase of the color synchronization signal. in the signal F 1, as shown in FIG. 2, is 45 ° ahead of phase cp0, which is represented by B +, and the phase of the color synchronization signal in signal Fn + 1 is 45 ° backward of phase cpo-rr (-cpQ), which is represented by B-.

In the following, an exemplary embodiment of the invention will be explained with reference to FIG. 3 and more.

In FIG. 3 represents 1 a bandpass amplifier which separates a color information signal from a composite color television signal. The color information signal thus separated is directly applied to one input terminal of a switching circuit 2 and the other input terminal through a delay circuit 3 which delays a supply signal one line period. The switching circuit 2 is reversed with a switching signal from a multivibrator circuit 5? which is reversed for each line interval with a horizontal synchronization pulse 4 from a deflection deflection circuit, not shown, and this rescheduling occurs to the position shown in the figure when e.g. a plus line signal is applied but to the opposite position when a minus line signal is applied. The output of the rewinding circuit 2 is applied to a first and a second demodulator. 6 and 7 * The respective demodulators 6 and 7 are thus supplied with only plus-line signals, i.e. the same signals that are repeated twice in succession, e.g.

in other words, the signal in which the minus signals are replaced by the plus lines signals which are one line interval prior to these, the demodulators 6 are supplied. and 7 · The output of the switching circuit 2 is additionally applied to an opening circuit 8 to periodically provide a color synchronization signal B + contained in the plus line signal, which is applied to a carrier generator 9 with a quartz crystal resonant circuit. The carrier generator 9 generates a carrier signal which in phase is equal to the color synchronization signal B +, which is then used to drive an oscillator 10 to produce a reference signal of the same phase. The reference signal from the oscillator 10 is applied to a phase shift circuit 11 which in phase delays an input signal of 45 °. The phase shift circuit 11 outputs a reference signal with a phase coinciding with the R-Y axis, as shown in FIG. 4. The reference signal S1 is applied to the first demodulator 6. The reference signal from the phase shift circuit 11 is also applied to a phase shift circuit 12 which in phase delays an input signal 90 ° to produce a reference signal S2 with a phase coinciding with the BY axis, as shown in FIG. . 4. The reference signal Sg is applied to the second demodulator 7 · The plus line signals periodically supplied to the demodulators 6 and 7 are thus demodulated with the signals and S2 with the same axes as the axes of the respective modulators, so that a first and a second, predetermined, are obtained from the demodulators. demodulated color information signal.

In this case, however, there is a danger that for some reason the triggering of the multi-vibrator circuit 5 is reversed relative to its normal trigger and the switching circuit 2 is switched to the opposite position upon receiving the plus line signal, but to the one in FIG. 3 when receiving the minus line signal. In such a condition, the demodulators 6 and 7 are periodically supplied through the switching circuit 2 only the same negative line signals in a twice repeated manner, e.g. the signals ^ n + l '^' n + l '^ + 3' n + 3 '...... .. In other words, the signals in which the plus line signals are replaced by the minus lines signals are one prior to these line demodulators 6 and?. Accordingly, in this case, a color synchronization signal B- contained in the minus line signal B- will be obtained from the opening circuit 8, and therefore a reference signal with the same phase will be output from the oscillator 10. As shown in FIG. 5, this gives a reference signal S ^ with the phase coinciding with the - (BY) axis applied to the demodulator 6, while a reference signal S ^ with the phase coinciding with the RY axis is applied to the demodulator 7. Thus, the demodulators 6 and 7 cannot deliver the desired demodulated color information signals.

To avoid such error, the color information signal from the band-pass amplifier 1 is applied to a third demodulator 13 and the color information signal passed through delay circuit 3 is applied to a fourth demodulator 14, as shown in Figure 3 · The third demodulator 13 is supplied the reference signal from the oscillator 10 through, for example, a phase shift circuit 13 which in phase delays a signal 90 °, while the fourth demodulator 14 is supplied to the reference signal from the phase shift circuit 15 through a second phase shift circuit 16, which in phase further delays a signal 90 °. demodulated output signals from demodulators 13 and 14 are added to an additional circuit 17, the added output of which is provided with a detector circuit 18. For performing amplitude detection of the input signal, the detected output signal is then applied to one input terminal of a differential amplifier 19. for example, it demodulates The output of the demodulator 14 from the demodulated output of the demodulator 13. The subtracted output of the subtraction circuit 20 is applied to a detector circuit 21 which also performs e.g. amplitude detection of the input signal. The detected output signal from here is then applied to the second input terminal of the differential amplifier 19. The output of the differential amplifier 19 is applied to a control signal generator 22 for generating a control signal from the circuit 22 when the differential amplifier 19 produces a predetermined output signal. The control signal is then applied to the multivibrator circuit 5 ·

An example of the portion comprising the differential amplifier 19 and the control signal generator 22 will now be explained with reference to FIG. 6. In this example, the output of the detector circuit 18 is applied to the base of a transistor 23 which is one of the transistors damaging the differential amplifier 19, while the output of the detector circuit 21 is applied to the base of another transistor 24 of the differential amplifier 19 · The conductor 23 of the transistor 23 is connected through a resistor 23 to the emitter of a transistor 26, while the collector of the transistor 24 through a diode 27 is connected to the base of the transistor 26. The vertical synchronization signal V is applied through a resistor 28 to the collector of the transistor. 26, and the collector output signal is differentiated by a differentiation circuit 29 · The differential output thus obtained is applied to the base of a transistor 30, and the collector output of the transistor 30 is supplied through a diode 31 the multivibrator circuit 5- In the case where the plus line signal is periodically supplied to the demodulators 7 , the switching circuit 2 must be in real work and a reference signal obtained from the oscillator 10 with the same phase as the color synchronization signal B + is applied to the phase shift circuit 13, which provides the demodulator 13 with a reference signal S, - which carried the O ^ phase offset 90 backward for the phase of the color synchronization signal B +. offset 4-5 ° to the rear of the R-Y axis, while signal S, - is applied to the phase shift circuit 16, which supplies demodulator 14- with a reference signal Sg which carried the phase offset 180 ° backward for the phase of the color synchronization signal B +, i.e. offset 4-5 ° backwards from the B-Y axis, as shown in FIG. 7, the demodulators 13 and 14- thus always produce demodulated outputs which are of equal magnitude and carry overall polarity in each line interval, as shown in FIG.

8 and 9 · Mel other words, fig. 8 shows that the plus line signal 1 is demodulated with the phase of the reference signal in demodulator 13 to obtain a positive demodulated signal, and at the same time the minus line signal is demodulated with the phase of reference signal Sg in demodulator 14- to obtain a positive demodulated signal. Rich. 9 shows a state one line following the state of FIG. 8, the plus line signal Bn is demodulated with the phase of the reference signal Sg in demodulator 14- to obtain a positive demodulated signal, and at the same time the minus line signal En + 2 is demodulated with the phase of the reference signal in demodulator 13 to obtain a positive demodulated signal. Therefore, in this case, the addition circuit 17 always outputs a predetermined, added output signal, while the subtraction circuit 20 produces no output signal. This results in the added output of the additive circuit 17 being amplitude detected in the detector circuit 18 and applied to the transistor 23 in the differential amplifier 19 as a positive voltage, while no positive voltage is applied to the second transistor in the differential amplifier 19 from the detector circuit 21. the transistor 26 in the circuit 22 is made conductive and the vertical synchronization signal V passes unchanged through the collector-emitter section of the transistor 26 to the frame, so that the transistor 30 receives no differentiated output and therefore the transistor 30 does not produce a control signal. on his colleagues. Therefore, the multivibrator circuit 5 retains its original trigger function, and the switching circuit 2 operates properly so that demodulators 6 and 7 output predetermined demodulated color information signals.

However, in the case where the demodulators 6 and 7 are periodically fed to the minus signal if the switching circuit 2 is changed to its wrong state and a reference signal S 1 obtained from the oscillator 10 is applied, as shown in FIG. 10, with the phase coinciding with color vision. the synchronization signal B- to the phase shift circuit 15, which delivers to the demodulator 13 the reference signal with the phase 90 ° backwards for the color synchronization signal B-, i.e. 9-5 prior to the R-Y axis, while the signal from the phase shift circuit 15 is also applied to the phase shift circuit 16 which outputs to the demodulator 14- the reference signal S, - with the phase 180 ° backward for the color synchronization signal B-, -d.e. 9-5 ° to the rear of the R-Y axis, the demodulators 13 and 14 demodulate output signals which are equal but opposite in polarity for each line period, as shown in FIG. 11 and 12.

In other words, FIG. 11 is a state where the plus line signal 3? Is demodulated with the phase of the reference signal in demodulator 13 to obtain a negative demodulated signal, and at the same time the minus line signal is demodulated with the phase of the reference signal in demodulator 19- to obtain a positive demodulated signal, equal. 12 shows a state one line following the state of FIG. 11, where the plus line signal 1 is demodulated with the phase of the reference signal in demodulator 19- to achieve a positive demodulated signal, and at the same time the minus line signal * n + 1 is demodulated with the phase of the reference signal in demodulator 13 to obtain a negative demodulated signal. Accordingly, in this case, the addition circuit 13 does not output an added output signal, while the subtraction circuit 20 outputs the subtracted output signals which

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is reversed in polarity for each line interval. Therefore, unlike the previous case, no output signal is output from the detector circuit 18 to the transistor 23 of the differential amplifier 19, but the detector circuit 21 outputs a positive output signal to the second transistor 24 of the differential amplifier 19 and makes the transistor 26 of the circuit 22 non-existent. Accordingly, the vertical synchronization signal V supplied to the transistor 26 is differentiated by the differential circuit 29, and the transistor 30 is made conductive by the positive polarity differential pulse to output a control signal 32 from its collector, the control signal 32 is then supplied through the diode 31 multivibrator circuit. This causes the switching circuit 2 to immediately return to its correct operating state and the demodulators 6 and 7 are periodically supplied plus line signals to output predetermined color information signals.

In this case, if the phase of the plus line signal, when the switching circuit is in its proper working condition, coincides with the demodulation axis in demodulator 13 'or with an axis displaced 180 ° therefrom, and the phase of the minus line signal coincides with demodulation axis in demodulator 14 or with an axis 180 ° from there, or if the phase of the plus line signal, when the switching circuit is in its wrong working state, coincides with the demodulation axis in demodulator 14 or with the axis displaced 180 ° therefrom, and the phase of the minus line signal coincides with the demodulation axis in demodulator 13 or 180 ° from there, the demodulators 13 and 14 do not output any output voltage for a certain line period, as can be seen in FIG. 9 and 11. However, as shown in FIG. 8 and 12, modulators 13 and 14 will always produce the predetermined demodulated output during the neighboring period, so that even if the color information signal carried such a phase $, the control function can be achieved in the correct manner, as explained above.

The demodulation axes in demodulators 13 and 14 can also be varied in other ways than in the above examples. As an example, the phase shift circuit 15 can be removed as shown in FIG. 13, and the reference signal from the oscillator is continuously applied to the demodulator 13, while the signal from the oscillator 10 is applied to the phase shift circuit 16 to advance its phase 90 ° before and then to the demodulator 14. If the switching circuit 2 is in its proper articulator state, in this case, the reference signal S ^ with the phase coinciding with the color synchronization signal ignored B +, and the demodulator 14 can be supplied with the reference signal Sy with the phase 90 ° prior to the phase of the color synchronization signal, i.e. coinciding with the color synchronization signal B-, as shown in FIG. 14, whereas the demodulator 13, If the switching circuit 2 is in its wrong working state, can be supplied with the reference signal Sy with the phase coinciding with the color synchronization signal B-, and the demodulator 14 can have the reference signal Sg with the phase delayed 90 ° from the phase of the synchronization signal B , ie delayed 45 ° from the B-Y axis, as shown in FIG. 15th

As another example of the same construction as in FIG. 13, the reference signal from oscillator 10 can be directly applied to demodulator 13, and at the same time signal from oscillator 10 can be applied to phase shift circuit 16 to displace its phase 90 ° backward and then to demodulator 14. 16 and 17, in this case, the demodulator 13 may be supplied with reference signals having the same phases as those of FIG. 14 and 15, but the demodulator 14 can be supplied with reference signals with the phases stay. 180 ° offset from these in FIG. 14 and 15.

As yet another example of the same construction as that of FIG. 3, the reference signal from the oscillator 10 can be phase-reversed by the phase-shift circuit 15 before it is applied to the demodulator 13, and the reference signal applied to the demodulator 13 is phase-shifted 90 ° to the rear of the phase-shift circuit 16, before it is applied to the demodulator 14 the demodulator 13 can be applied to the reference signal Sg with the phase opposite the phase of the color synchronization signal B +, i.e. 45 ° backwards for the B-Y axis and demodulator 14 can be applied to the reference signal Sy with the phase 90 ° backwards for the reference signal Sg, i.e. coinciding with the synchronization signal B-, as shown in FIG. 18, while the demodulator 13, If the switching circuit 2 is in its wrong working state, can be applied to the reference signal S, - with the phase 45 ° backwards for the RY axis, and the demodulator 14 can be applied to the reference signal Sg with the phase 45 ° backwards for the BY axis. as shown in FIG. 19th

However, in the last two examples, the output of the addition circuit 17 and the subtraction circuit 20 is opposite to that of the previous example. Therefore, if the portion containing the differential amplifier 19 and the control signal generating circuit 22 is constructed as explained above, the output of the detector circuit 18 is instead applied to the base of the transistor 24 · and the output of the detector circuit 21 is applied to the base of the transistor 23.

The demodulation axes in demodulators 13 and 14- may not always be exactly in the middle between the R-Y or - (R-T) axis and the B-Y or - (B-Y) axis, but they may be slightly offset therefrom.

Also, the demodulating axes of demodulators 13 and 14- do not have a phase difference of 90 °. However, demodulators 6 and 7 may also be periodically supplied at all times to the minus signals of the same construction as in FIG. 3 · 1, in contrast to the preceding examples, the reference signal from the oscillator 10 must be offset 4-5 ° ahead of the phase shift circuit 11 and the reference signal from the phase shift circuit 11 be shifted a further 90 ° ahead of the phase of the phase shift circuit 12. This causes the demodulator 6 , if the switching circuit 2 is in its proper working state and the demodulators 6 and 7 are periodically supplied with the minus line signals, a reference signal with a phase coincident with the - (RY) axis is applied and the demodulator 7 is supplied with a reference signal with a phase coinciding with the BY axis.

Furthermore, the demodulator 13 can only be applied to the color synchronization signal in the color information signal from the bandpass amplifier 1, and the demodulator 14- can only be applied to the color synchronization signal in the color information signal from the delay circuit 3. In particular, according to the present invention, it is always possible to obtain a predetermined output signal independently of the phases of the signals to be demodulated in demodulators 13 and 14, as explained above, so that a stable function can always be expected.

Claims (2)

In the above examples, the original color information signals separated in the bandpass amplifier 1 and the signal which is delayed a line interval are alternately derived for each line interval and fed to the demodulators 6 and 7. However, the original color information signal and which is delayed from this by up to several, odd times one line period, alternately delivered for each line interval. In this case, demodulator 14 is supplied with the signal delayed from the original color information signal by several, odd times one line period, or the color synchronization signal contained in this signal. Furthermore, the demodulator 7 can be applied to the color information signal altered from the bandpass amplifier 1. Furthermore, the present invention can be used in cases where two color signal components are I and Q signals or the like. A color television receiver coupling for decoding a PAL color information signal, whereby a delay chord (2) and a line frequency switch (2) produce a modified chrominance signal alternating one line and its two-period delay repeater, to which two delayed repeaters are applied. (6.7), which is additionally provided by a reference signal generator (9,10) with reference signals (S - ^, 82) which, by means of phase shift circuits (11,12), have a phase bearing which coincides with the respective modulation axes for the chrominance signals. and used for demodulating these, the coupling further comprising a control circuit for controlling the switch (2) and containing two further demodulators (13, 14) connected to the two inputs of the switch and the output of the reference signal generator as well as one to these the outputs of the demodulators (13,14) connected to the comparator circuit, characterized in that at least one of the two demodulators (13,14) in the control circuit is connected to the reference signal generator (9,10) through an additional phase shift circuit (15, 16) to produce reference signals (S4, S5) whose phase bearing is symmetrical to the chrominance signal's modulation axes and thus different from the reference signals used for the demodulation.