JPS6174489A - Synchronous coupled circuit - Google Patents

Abstract

PURPOSE:To simplify the circuit constitution by coinciding phases of PAL pulse signals by means of the output of a phase comparator. CONSTITUTION:A color video signal based on a PAL system at an input terminal 1, a burst signal is taken out by a burst signal separator circuit 2, and the signal which has passed through a positive 90 deg. phase shifter 3 and that which has not passed through are supplied to a switch circuit 4. The circuit 4 is switched by a PAL pulse signal at every 1H, and outputs the burst signal which has been subjected to the positive 90 deg. phase shift and that which has not. These outputs are inputted to one input of a phase comparator 5 as a comparison reference signal, while the other input of the comparator 5 is used as the output of a subcarrier oscillator 6. The output of the comparator 5 is supplied to the reset terminal of a PAL pulse signal generating FF9 through a pulse amplifier 8. Accordingly, the PAL pulse of a correct phase is supplied to the circuit 4 from the Ff9, and the comparison reference signal of the oscillator 6 always goes to a burst signal of -135 deg.. Therefore, a stable subcarrier wave is outputted and phases of PAL pulse signals coincide.

Description

[Detailed Description of the Invention] <Industrial Field of Application> The present invention relates to PAL system subcarriers and PAL pulses (PAL
This circuit relates to a synchronous coupling circuit for synchronously coupling PAL pulse (PAL pulse) signals, and is an external synchronizing circuit for a sync signal generating circuit in the PAL color television system, and further controls the phase of the PAL pulse (PAL Pulse) signal during synchronous coupling. The present invention relates to a synchronous coupling circuit that is simplified and takes into consideration the stabilization of a subcarrier (SC) oscillator.

(Prior Art) In the PAL color television system, a pulse pulse signal is obtained from a synchronization signal generator. This pulse pulse signal is a pulse signal that is inverted every horizontal scanning period <IH>, and is used, for example, in an encoder as a signal to switch the output of a subcarrier oscillator for balanced modulation of a color video signal every day. .

Conventionally, when trying to obtain a pulse signal and subcarrier (hereinafter also referred to as subcarrier) synchronously coupled to an external video signal using a simple method, for example, a burst signal separated by a burst signal separation circuit is used as a comparison reference signal. , a method to control the subcarrier oscillator was considered.

Since the PAL burst signal has a 90' phase difference every day as shown in Figure 2, the phase comparison output between the subcarrier and the burst signal, which controls the subcarrier oscillator, is as shown in Figure 3. In response to the burst signal shown in (a), a subcarrier oscillator suppressing voltage yA as shown in FIG. 3(b) is generated.

The subcarrier oscillators are synchronously coupled using the average value of the control voltages shown in FIG. 3(b). Furthermore, the phases of the pulse pulse signals can be matched by extracting only the ten-polarity or - polarity signal component of the generated control m+ voltage and making it the set signal or reset signal of the flip 70 knob that generates the pulse pulse signal. The purpose of synchronous connection can be easily achieved.

However, with this method, the phase of the burst signal (±135°) is compared and the subcarrier oscillator control signal (
Since the output of the subcarrier oscillator to be controlled uses a voltage that changes every 1H (a voltage that changes with respect to the center voltage) for the output of the phase comparator, the phase of the output of the controlled subcarrier oscillator changes slightly every 1H, and the subcarrier This was causing career jitters. Therefore, in order to reduce the phase error for each 1H, if the above jitter is improved using a low-pass filter (LPF), etc., the AC (alternating current) loop gain will decrease, and the subcarrier pull-in frequency range will decrease. There were some problems. Incidentally, the pull-in frequency range P can be expressed by the following equation.

P(H,)-to-upper≦elbow22 1) d-no-shi-fu-0-in However, K is a proportionality constant.

On the other hand, as another synchronous coupling method, a burst signal separated by a burst signal separation circuit is used as a comparison reference signal every other day, and the +135° burst signal or -
There was a method of synchronizing internal subcarriers with a 135° burst signal. In this method, only one of the +135' burst signal or the -1356 burst signal is used, so unlike the above method, different subcarrier-based till voltages are not generated every 1H, and the +135' burst signal is used.
Since the subcarrier oscillator is synchronized to only one of the 5° burst signal and the -1351 burst signal, the above-mentioned problem does not occur. However, as it is, the synchronized subcarriers depend on the external signal input timing.

Since it is not determined whether it is synchronized with a +135° burst signal or -135° burst signal, a circuit to fix this to either one of the burst signals,
It was necessary to provide a separate circuit to control the phase of the pulse signal.

Further, as the above-mentioned specific methods, for example, there are the following.

That is, the oscillator is driven based on the signal (shown in FIG. 4(b)) for bursts separated by the burst signal separation circuit to which the color video signal is supplied, and the burst flag signal ( M4 (shown in Figure (C))) and horizontal drive signals are formed. Furthermore, based on this horizontal drive signal, a pulse signal with a daily cycle is formed using a flip 70, etc., and the AND output of this pulse signal with a cycle of 1H and the above-mentioned burst flag signal is shown in Fig. 4 (e'). A gate signal corresponding to a burst signal of one phase is obtained, and a burst signal of one phase as shown in FIG. 4(f) is extracted based on this gate signal. and,
This drives the subcarrier oscillator, inputs this oscillation output and the separated burst signal to a phase comparator, operates a voltage comparator based on this phase comparison output, and performs this voltage comparison. By outputting a 7-lip, 70-tub set signal or preset signal, a synchronously coupled pulse pulse signal (shown in FIG. 4(d)) is obtained from this flip-flop.

Now, looking at the above phase comparison output, if the subcarrier oscillator is synchronized with the +135° burst signal,
A negative pulse signal is obtained, and the subcarrier oscillator is -
If synchronized with the 135° burst signal, a positive pulse signal will be generated. Therefore, the target phase of the pulse pulse signal and subcarrier can be determined by resetting the seven lip flops for pulse pulse signal generation based on this positive or negative pulse signal.
It is possible to fix the pulse signal to one side, and also to match the phases of the pulse pulse signals.

However, this method requires both a phase comparator for subcarrier synchronization and a phase comparator for phase determination, so there is a problem that the circuit system becomes complicated.

(Objective of the Invention) Therefore, an object of the present invention is to utilize the advantages of the above two conventional methods and compensate for each other's problems in order to solve the problems of the prior art described above, thereby simplifying the circuit configuration. The object of the present invention is to provide a synchronous coupling circuit.

(Means for Solving the Problems) In order to achieve the above objects, the present invention provides a burst signal separation circuit to which a PAL composite video signal is supplied, and a burst signal separated by the burst signal separation circuit. A delay circuit that delays the phase by 90 degrees, a switch circuit that alternately switches a burst signal whose phase is delayed by 90 degrees and a burst signal that is not delayed through this delay circuit every horizontal scanning period, and this switch circuit. A phase comparator that outputs a control signal for controlling the phase of the subcarrier oscillator using the obtained burst signal as a comparison reference signal is provided, and the output of the phase comparator is configured to match the phases of the pulse pulse signals. The present invention provides a synchronous coupling circuit that achieves the following.

(Embodiment) An embodiment of the synchronous coupling circuit according to the present invention will be described below with reference to the drawings of FIGS. 1 and 5.

FIG. 1 is a diagram showing an embodiment of a synchronous coupling circuit according to the present invention.

In the figure, an input terminal 1 is supplied with a color video signal based on the PAL system. This color video signal consists of a video signal, a horizontal synchronizing signal, a 4.43 MHz burst signal having a phase difference of 90' from each other every 1H, a vertical synchronizing signal, an equivalent pulse, and the like. This color video signal is applied to a burst signal separation circuit 2, and a burst signal (+135", -135') is extracted. This burst signal is phase-shifted by +90" through a +90° phase shifter 3. , otherwise are supplied to each input terminal of the switch circuit 4. switch circuit 4
is switched by a pulse pulse signal every 1H, and outputs a burst signal with a phase shift of +90° and a burst signal with a phase shift of +90°. This output is supplied to one input end of the phase comparator 5 as a comparison reference signal. Furthermore, subcarrier oscillation/
The output of the device 6 is supplied.

The output of the phase comparator 5 is supplied to a subcarrier oscillator 6 to control the oscillator 6, and the controlled subcarrier is output from an output terminal 7.

Furthermore, in the burst signal that has passed through the +90° phase shifter 3, burst signals of -135° and -45° exist alternately as shown in FIG. a
), there are burst signals of +135° and -135°.

By the way, the pulse pulse signal for switching of the switch circuit 4 that switches these burst signals<PAL p
If the timing of ulse) coincides by chance, it is always -1
The 35° burst signal becomes a comparison reference signal (shown in FIG. 5(d)), and the phase comparator 5 as shown in FIG. 5(e)
The output of the subcarrier oscillator 6 is always -13.
A signal synchronized with the 5° burst signal is obtained, and the control n pressure is not output differently every day as in the first method of the prior art described above. Therefore, the output of the subcarrier oscillator The problem that the phase changes slightly every day, which causes subcarrier jitter, is eliminated.

In addition, if the switching timing is reversed from the above, 135° and -45° burst signals
The burst signals with a phase difference of 80° serve as the comparison reference signal (shown in Figure 5 (d')), and the output of the phase comparator 5 as shown in Figure 5 (e') is obtained. As in the first method of the technique, a different control voltage is output every 1H.Therefore, one of these outputs (positive or negative pulse) is amplified by the pulse amplifier 8, as shown in Fig. 5(f). ), 7 lips and 70 tubes for pulse signal generation (FF
) 9 to reset the flip-flop 9.

Therefore, by resetting the flip-flop 9, the phase of the pulse signal is reversed (as shown in diagram M5 (g)), and the correct phase is supplied to the switch circuit 4. Comparison of the subcarrier oscillator 6! ! The quasi-double signal is always a -135° burst signal (Figure 5 (e'))
(shown in the latter half of the figure), a stable subcarrier is obtained, and the phases of the pulse pulse signals also match.

Note that a pulse with a cycle of -1 (one horizontal scanning period) is supplied to the input of the flip knob 9, and its output is a pulse pulse signal that is a switching signal for the switch circuit 4, while a pulse signal is supplied to the output terminal 10. also supplies the same pulse pulse signal.

Therefore, the present invention uses a delay line (delay circuit) such as a phase shifter to adjust the phase of the color burst signal by one horizontal scanning period IJ(1)-1), and adjusts the phase to +135° or -135°.
By performing phase comparison after aligning the phases to one of the angles, jitter caused by a phase error every 1H is reduced.

(Effects of the Invention) As described above, according to the present invention, it is possible to simplify the phase control of the pulse signal during synchronous coupling and to stabilize the subcarrier oscillator, thereby obtaining a stable subcarrier signal. Moreover, by taking advantage of the advantages of conventional synchronous coupling circuits,
It has the advantage of being able to realize a simple circuit configuration.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the synchronous coupling circuit according to the present invention, Fig. 2 is a b vector diagram for explaining the conventional synchronous coupling circuit, and Figs. 3 and 4 are diagrams showing the conventional synchronous coupling circuit. Signal waveform diagram (time chart) for explanation, Figure 5 is the first
1 is a signal waveform diagram (time chart) of each part of an embodiment of the illustrated synchronous coupling circuit according to the present invention; FIG. 1... Input terminal, 2... Burst signal separation circuit, 3
...+90° phase shifter, 4... switch circuit, 5...
・Phase comparator, 6... Subcarrier oscillator, 7...
Output terminal, 8...Pulse amplifier, 9...Flip 7
0 Tsubu (FF).

Claims (1)

[Claims] A burst signal separation circuit to which a PAL system composite video signal is supplied, a delay circuit that delays the phase of the burst signal separated by this burst signal separation circuit by 90 degrees, and a phase delay of 90 degrees through this delay circuit. A switch circuit that alternately switches between a burst signal and a non-delayed burst signal every horizontal scanning period, and a phase comparison that outputs a control signal for controlling the phase of a subcarrier oscillator using the burst signal obtained from this switch circuit as a comparison reference signal. Set up a container,
A synchronous coupling circuit characterized in that it is configured to match the phases of pulse pulse signals using the output of the phase comparator.