JPH04102386U - Circulating burst signal amplification circuit - Google Patents

Abstract

(57) [Summary] [Purpose] To correct the attenuation of the cyclic signal when the reproduced burst signal that occurs intermittently circulates. [Structure] During the burst signal generation period, the second burst level detection circuit 15 samples and holds the burst signal level, the first burst level detection circuit 17 samples and holds the delayed burst signal level, and both hold outputs are used as a level comparison circuit. 16, and the comparison output controls the amplification gain of the gain control amplifier 13 to match the burst signal levels before and after the delay.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention is a cyclic burst signal amplification circuit installed in a color burst signal continuation circuit. Regarding improvements.

0002

[Conventional technology]

In Japanese Patent Application Laid-Open No. 1-69189 (H04N9/45), the applicant A burst signal serialization circuit is proposed.

0003 This continuous circuit outputs the reproduction color burst signal and the 1/4 frequency division of the oscillation circuit output. The phase comparison circuit compares the phase of the In the circuit, a delay circuit such as a CCD that uses the oscillation output as the clock input is installed to The delay is longer than the burst generation period, and this occurs during the period when the reproduced color burst signal is inactive. While deriving the output of the delay circuit cyclically, the output is supplied to the phase comparator circuit for phase control. The point is to make it continuous.

0004

[Problem that the idea aims to solve]

However, the conventional circuit described above circulates the delayed feedback output without amplifying it. The signal level is attenuated each time it passes through a delay circuit, and continuous jitter Positive and AGC control became difficult.

[0005] Therefore, the present invention circulates the reproduced color burst signal without attenuation to provide reliable This paper proposes a circuit that prevents signal level attenuation and guarantees the operation of subsequent circuits. be.

[0006]

[Means to solve the problem]

This invention consists of an attenuation detection circuit that detects the amount of attenuation of a burst signal, and a and a gain control circuit for controlling the amplification factor of the burst signal.

[0007]

[Effect]

Therefore, according to the present invention, the burst signal is circulated without attenuation, Guarantees the operation of subsequent circuits.

[0008]

【Example】

The present invention will be described below with reference to illustrative embodiments.

[0009] First, a first embodiment shown in FIG. 1 will be described. In this example, pickup 1 The reproduced signal is demodulated by the next stage FM demodulator 2, and the jitter of the output is Optical video disc player that derives reproduced color signals by suppressing them with 1 CCD3 The present invention is adopted in this case.

0010 In order to correct jitter, in this embodiment, the burst signal separated by the burst gate 7 is is supplied to the second CCD 18 via the adder 8, and the carrier period of the burst signal is The multiplication period and the delay time are approximately H/16 periods (H is the horizontal synchronization period). The burst signal is delayed so that

[0011] This delayed signal is sent to the gain control amplifier 13 (gain control circuit) as described later. during the deactivation period of the burst gate pulse through the switching circuit 14. and is fed back to the adder 8.

0012 Therefore, in this embodiment, the burst signal is accompanied by a level attenuation within one horizontal synchronization period. It is delayed 15 times and made to circulate without any delay.

[0013] In this embodiment, the burst signal is delayed by H/16 in synchronization with the burst signal. A PLL circuit is formed to form a transfer clock.

[0014] This PLL circuit uses the circulating burst signal as the reference input of the phase comparator 9, and The feedback 1/4 frequency divided output is used as comparison input, and the phase comparison output is used as low-pass filter. It is used as a control input for VCO 11 via router 10, and the center frequency is set as a color subkey. The VCO 11, which is set to four times the carrier, sends its oscillation output to the first and second CCs. It is used as the transfer clock input of D and also as the feedback input of the 1/4 frequency divider circuit 19. .

[0015] The configuration of the PLL circuit described above is the same as that of the prior art described above, and the features of this embodiment are This is because the gain control amplifier 13 and the attenuation detection circuit that controls its gain are be.

[0016] First, the first burst level detection circuit 17 which inputs the addition output is a burst gate. The burst signal level before delay is sampled and held in synchronization with the pulse. The second burst level detection circuit 15 inputting the output of the gain control amplifier Sample the burst signal level after exactly 16 delays in synchronization with the pulse. I'm doing it.

[0017] The level comparator circuit 16 inputting both sampling outputs is configured so that the gain control amplifier 13 is The burst gate pulse is A gain control signal is formed synchronously, and this signal is applied to the gain control amplifier 13 during one horizontal synchronization period. Provides gain control signal.

[0018] As a result, the burst signal level that has been cycled 16 times is the input burst signal level. Matched to Bell.

[0019] The embodiment described above outputs the burst signal delayed 16 times and outputs the burst signal at the next timing. The level of the generated burst signal is compared, but the burst signal is delayed by one time. The configuration may be such that the level is compared with the extended output.

[0020] Figure 2 also shows how to interrupt a burst signal by using an analog delay circuit with a short delay time. A circuit showing a second embodiment in which the present invention is applied to a circuit that is continuously formed without breaking. It is a block diagram.

[0021] As shown in the figure, in this embodiment, the burst gate output is connected to the phase comparator 9 and the delay amount is 90 degree analog delay circuit 11, second burst level detection circuit 15 and AP It is supplied to the C detection circuit 5.

[0022] The analog delay circuit 11 sends its output to the phase comparator 9 for 90 degrees phase advance. It is supplied to the phase shifter 12.

[0023] The phase comparator 9 compares the phases before and after the delay, and makes sure that the phase difference is always exactly In order to control the delay amount of the analog delay circuit 11 so that it is maintained at 90 degrees, the phase ratio is A calibration output is supplied to the analog delay circuit 11 via a low-pass filter 10. Ru.

[0024] Further, the phase shift circuit 12 sends an advanced output having the same phase as the addition output to the gain control amplifier 1. 3 to eliminate the attenuation of the advanced phase output.

[0025] This amplifier output is added via the switching circuit 14 immediately after the burst period ends. It is fed back to the calculation circuit 8.

[0026] In addition, the amplifier output is input to the first burst level detection circuit 17, and the burst level detection circuit 17 The amplified burst signal level is sampled and held in synchronization with the pulse.

[0027] Furthermore, the second burst level detection circuit 15 is also synchronized with the burst gate pulse. The burst signal level that has passed through the burst gate is sampled and held.

[0028] The level comparison circuit 16 receives a control signal so that the sample and hold output levels match. The signal is supplied to the gain control amplifier 13. As a result, the burst signal is attenuated. It is continuously formed and extracted without any trouble.

[0029] On the other hand, APC detection inputs the summed output that is derived continuously without attenuation. The circuit compares the reference signal generated by the reference oscillator 6 with the addition output and outputs the comparison output as V. Supply CO4.

[0030] The VCO4 generates a signal whose center frequency is four times the burst carrier frequency. It is an oscillator that controls the oscillation frequency according to the APC detection output, and transfers the oscillation output to the transfer clock. The signal is supplied to the first CCD 3 as a clock to realize jitter correction.

[0031] Each of the above-mentioned embodiments employs the present invention for jitter correction, but continuous burst The present invention can also be adopted when the signal is used for AGC control; It goes without saying that various configurations are also included in the present invention.

[0032]

[Effect of the idea]

Therefore, according to the present invention, since the burst signal is delayed without being attenuated, the jitter is Continuous control such as data correction is reliably guaranteed, and the effect is great.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram of a first embodiment.

FIG. 2 is a circuit block diagram of a second embodiment.

[Explanation of symbols]

17 First burst level detection circuit 15 Second burst level detection circuit 16 Level comparison circuit 13 Gain control amplifier

──────────────────────────────────────────────── ─── Continuation of front page (72) Creator Nobukazu Hosoya 2-18 Keihan Hondori, Moriguchi City Sanyo Electric Co., Ltd. Inside the ceremony company

Claims (1)

[Scope of utility model registration request] 1. A burst signal serialization circuit that returns a color burst signal in a reproduced color video signal via a delay circuit to cyclically generate a color burst signal, comprising:
A cyclic burst signal comprising an attenuation detection circuit that detects the amount of attenuation accompanying the circulation of the color burst signal level, and a gain control circuit that controls the amplification factor of the burst signal fed back based on the attenuation amount. Amplification circuit.