JPH0365893A - Color signal frequency converter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic video recording and reproducing device, and particularly relates to high frequency conversion of a low frequency converted color signal.

[Conventional technology]

FIG. 3 shows a block diagram of a conventional color signal frequency conversion device, and the conventional color signal frequency conversion device will be explained using the diagram. The inputted low-pass conversion color signal is frequency-converted by a signal that is the sum of the input low-pass conversion color signal frequency and the carrier color signal frequency in the main frequency converter (1), and is then frequency-converted by the first bandpass filter (2). Only the carrier color signal is extracted. The extracted carrier color signal is output, and a phase comparator (8) compares the phase of the burst with the output of the crystal oscillator (4). The output of the phase comparator (8) controls a voltage controlled oscillator (6) whose center frequency is 320 times the horizontal frequency, and the output of this voltage controlled oscillator (6)
The frequency is divided into 1/8 by the frequency converter (γ) together with the output of the crystal oscillator (4), and the frequency is converted by the second bandpass filter (8) into the low frequency converted color signal frequency and the carrier color signal frequency. Only the sum of these is extracted and input to the main frequency converter (1), where the low frequency color signal is frequency converted.

The above configuration forms an automatic phase control (APC) loop in which the phase of the output carrier color signal burst is controlled by a crystal oscillator (4
). However, if this continues, malfunction of the APC loop (so-called side lock) will occur, so the output of the voltage controlled oscillator (5) is counted by the kakunta (9) for a certain period (usually an integral multiple of the horizontal period), and when the frequency exceeds a certain value. Alternatively, when the value is below a certain value, it is determined that the APC loop malfunctions (sidelock), and the detector outputs a control signal to the voltage controlled oscillator (5) to return the PLL loop to its normal operating state, thereby preventing sidelock. It was.

[゛Problems that the invention aims to solve]

Since the conventional color signal frequency conversion device was configured as described above, it is necessary to count the 320fa frequency over several horizontal periods, which requires a large-scale digital circuit with a complicated configuration. It had the disadvantage that.

The present invention was developed to solve the above-mentioned drawbacks, and it is an object of the present invention to obtain a color signal frequency conversion device that detects side lock and corrects APC malfunction without using a large-scale digital circuit. With the goal.

[Means to solve the problem]

The color signal frequency conversion device according to the present invention uses a continuous wave of a low frequency converted color signal frequency obtained by an automatic frequency control loop (the same applies below the AFO loop) and a continuous wave of a carrier color signal frequency obtained by a crystal oscillator. The center frequency is the sum of the continuous wave obtained by converting the frequency of , the low-pass converted color signal frequency supplied to the main frequency converter for frequency converting the low-pass converted color signal, and the carrier color signal frequency. Compare the phase of the output of the voltage controlled oscillator, detect the presence or absence of side lock from the phase of this phase comparison result, and recover the side lock of the APC loop from the main frequency converter 2 phase comparator and the voltage controlled oscillator. By adopting a configuration in which a signal is generated, a color signal frequency converter can be constructed without using a large-scale kakunta.

[Effect]

The color signal frequency conversion device of the present invention converts the frequency of the low range color signal frequency continuous wave generated by the AFO loop and the carrier color signal frequency output from the crystal oscillator, thereby converting the low range converted color signal and the carrier color signal. By creating a continuous wave with the sum of the frequencies of , and comparing the phase of this continuous wave with the continuous wave with the sum of the carrier color signal frequency and the low-range color signal frequency in the APC loop, the existence and phase of the 1 output signal can be determined. It is possible to detect the presence or absence of side lock and the mode.
The side lock is repaired by controlling the voltage controlled oscillator in the APC loop using this detection output.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. .

FIG. 1 shows a block diagram of a color signal frequency conversion device which is an embodiment of the present invention.

In the figure, (1) is a first frequency converter, (2) is a first bandpass filter, (8) is a first phase comparator,
(4) is a crystal oscillator, (6) is a voltage controlled oscillator, (γ)
is a second frequency converter, (8) is a second bandpass filter, (8) is a detector, and αυ is a second phase comparator.

The input low-pass conversion color signal is input to the first frequency converter (1) together with the output of the voltage controlled oscillator (6) whose center frequency is the sum of the low-pass conversion color signal frequency and the carrier color signal frequency. Only the carrier color signal is extracted by the first bandpass filter (2). This extracted carrier color signal is output and also input to the first phase comparator (8), which compares the output of the crystal oscillator (4) with the phase of the burst, and uses this comparison output to generate a voltage controlled oscillator. (6) Control the output frequency.

According to the above configuration, (1), (2), (sl,
(51), the phase of the burst of output carrier color signal is synchronized with the phase of the output of the crystal oscillator (4).

Further, the output of the crystal oscillator (4) is inputted to the second frequency converter (γ) together with a continuous wave of the low-range color signal frequency generated by an AFO loop (not shown), and The bandpass filter (8) outputs a frequency that is the sum of the low-pass color signal frequency and the carrier color signal frequency. When the output of the second band pass filter (8) and the output of the voltage controlled oscillator (6) are compared in phase by the second phase comparator αυ, when no side lock occurs, the output is Figure (a
As shown in 1, there is only a DC component. However, when sidelock is occurring, the image shown in Fig. 2 (b) or Fig. 2 (
0), waveforms with different frequencies or phases are output depending on the side lock mode. The side lock mode of this waveform can be detected depending on whether the first peak of (Parse) & is on the upper side or the lower side.

This output is input to the detector (A), the phase of the first peak after the burst is detected, and depending on the mode, a frequency increasing signal or a decreasing signal is output to the voltage controlled oscillator (6). , (”> p <z) p ta
+ Return the side lock of the APC loop consisting of p(6) to its normal state.

As described above, in this embodiment, a color signal frequency conversion device using an APC loop having a function of recovering from a side-locked state can be obtained without using a counter that requires a large-scale digital circuit.

〔Effect of the invention〕

As described above, according to the present invention, a low-pass color signal frequency conversion device can be obtained without using a counter that requires a large-scale digital circuit, and the circuit scale can be reduced.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a color signal frequency conversion device which is an embodiment of the present invention, Fig. 2 is an output waveform diagram of the color signal frequency conversion device of Fig. 1, and Fig. 3 is a conventional color signal frequency conversion device. FIG. In the figure, (1) is the first frequency converter, (2) ii
(8) is the first phase comparator, (4) is the crystal oscillator, (5) is the voltage controlled oscillator, (γ
) is the second frequency converter, (8) is the second bandpass filter, (8) is the detector, and αυ is the second phase comparator. In the figures, the same symbols indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] A first frequency converter that converts the frequency of a continuous wave of a low-pass converted color signal frequency generated by an automatic frequency control loop and an output of a crystal oscillator that oscillates at a carrier color signal frequency. , a bandpass filter whose passband is the sum of the output frequency of the first frequency divider and the output frequency of the crystal oscillator from the output of the first frequency converter, and a carrier color. a second voltage controlled oscillator whose center frequency is a frequency equal to the sum of the signal frequency and the low frequency conversion color signal frequency or an integral multiple thereof; and an output of the voltage controlled oscillator;
a second frequency converter that converts the frequency of the input low-pass conversion color signal; a bandpass filter that uses only the carrier color signal as a passband from the output of the second frequency converter; and the bandpass filter. a first phase comparator that compares the phase of the burst carrier color signal output from the device with the crystal oscillator; and a first phase comparator that compares the phase of the output of the first filter and the output of the second voltage controlled oscillator. a second phase comparator that detects the phase of the output of the second phase comparator, and a detector that detects the phase of the output of the second phase comparator; By controlling the voltage controlled oscillator, a malfunction of the automatic phase control (APC) consisting of the second frequency converter, the first phase comparator, and the second voltage controlled oscillator can be prevented by controlling the second frequency converter, the first phase comparator, and the second voltage controlled oscillator. APC consisting of a phase comparator and a detector
A color signal frequency conversion device characterized by detecting and repairing.