JPS58147814A - Data signal detecting circuit - Google Patents

Abstract

PURPOSE:To detect a data signal securely at any time by leading out the sum output of the positive and negative detection signals of the detected data signal through a loop filter which has a large time constant and thus varying the reference level of a comparator according to the variation in reference level of an input reproduced signal. CONSTITUTION:When the reproduced signal HF of a digital audio disk is supplied to an input terminal 2, the comparator 1 decides on the reproduced signal HF on the basis of a reference voltage V to generate data signals DS of ''H'' and ''L'', which are detected by a positive polarity detecting circuit 3 and a negative polarity detecting circuit 9. The output of the positive detecting circuit 9 and that of the negative polarity detecting circuit 10 are summed up by the adding circuit 10 consisting of resistances 11 and 12 and also biased to a prescribed level by a resistance 13 and outputted. The output signal of the loop filter 14 corresponding to the difference between the reference value Vr of the input reproduced signal HF detected as mentioned above and the reference value VR of the comparator 1 is supplied to an operational amplifier 18 to detect its difference from a zero level, thereby feeding the difference back to the comparator 1 as the reference value VR through voltage limiter circuit 19.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data signal detection circuit, and particularly to a digital signal detection circuit.
“1” of the data signal supplied as a serial digital value such as in an audio disc player, etc.
The present invention relates to a data signal detection circuit for reliably detecting 0''.

A digital audio disc is a disc in which audio signals and synchronization signals are digitized and optically recorded at high density on the surface of the disc at a constant linear velocity.The signal format recorded on the disc is shown in Figure 1, for example. In this method, each frame is divided into a certain number of pits (for example, 5 pits).
88 bits), and these frames are consecutively recorded on the same disk at a constant linear velocity.

The signal format of each frame is divided into a synchronization part and information gB, and the synchronization part is located at the beginning of each frame. lW1 period is #
! As shown in Figure 1, it consists of 22 pits and 9
, if the first 11 pits are @0'' consecutively, the following 1
If one bit becomes "1" consecutively, and the first 11 bits are "1" consecutively, it is set so that the first 11 bits become "0" consecutively.

In this case, the first 011 bit of the leech is set to be the opposite of the last bit of the previous frame,
In this way, the predetermined 7-ohm bit consisting of 9 unit pits (11 bits) and a series of °0" or "l" is limited to this synchronization part only in one frame. That is, the information part B is The configuration is such that a format in which @0° or @1° in 11-bit units is continuous does not occur under any circumstances.In addition, information sB is configured to prevent conversion to DC when there is no signal. A 1° signal or a 10° signal is always continuous over 3 bits or more. Finally, the information portion B is represented as a continuous signal only over the range of 2<B<11 bits.

The digital audio disc configured in this manner can easily obtain high-fidelity audio signals by keeping the linear velocity constant on the disc.

The most important point in performing fidelity reproduction is to accurately determine @1'' and 10'' of the data signal reproduced from the information recorded on the surface of the disk.

In this case, in a conventionally commonly used data signal detection circuit, by comparing the data signal supplied from the optical pickup that reproduces the recorded information on the disc with the reference value v8, The detection signal is configured to be sent out as detection data.

However, if the reference value is fixed at a constant value like this, the disc reference rail will fluctuate due to variations in disc manufacturing, resulting in rounding and detection data! @) has a problem. In other words, in digital audio discs, the narrowband POM method is used, and the output level of the pickup varies greatly depending on the width of the recorded pulse.
The oscilloscope waveform line of the reproduced signal for O-bit recording is as shown in wave form ~h in FIG. 2, for example. The information pit in this waveform is a diamond-shaped portion centered at the reference level Vr, indicated by a diagonal line, and the intersection point of this diamond-shaped portion with the reference value Vr becomes the boundary of the pit. The disc has a standard level V from the manufacturing point of view.
The standard allows r to fluctuate up and down by ±20%. For this reason, information that exists only within a range of about the total number around the reference level Vr is ±20
Therefore, if you try to fix the reference value vR and perform detection, there is a problem that the signal may not be detected due to irregularities during disk manufacturing. ing.

Therefore, an object of the present invention is to provide a data signal detection circuit that can accurately detect data signals of ``1#'' and ``0°'' from a reproduced signal supplied from a pickup.

In order to achieve such an object, the data signal detection circuit according to the present invention has a reference value vR of a comparator that compares the reproduced signal and extracts the data signal in response to fluctuations in the reference value Vr of the disc reproduced signal. It changes the Hereinafter, a data signal detection circuit according to the present invention will be explained in detail using the drawings.

FIG. 3 is a circuit diagram showing one embodiment of a data signal detection circuit according to the present invention. In the figure, 1 is a comparator that compares the disc playback signal HF supplied to input terminal 2 with a reference value vIL and outputs a data signal D8, and 3 is a positive detection circuit that receives the output of comparator 1 as input. There it is,
Coupling capacitor 4. Diode 5 for positive detection
．． It is composed of a resistor 6.7 and capacitors 8 and K. Reference numeral 9 denotes a negative polarity detection circuit which receives the output of the converter 1 as an input, and, like the positive polarity detection circuit 3, includes a coupling capacitor 4' and a negative polarity detection diode connected in the opposite direction to the detection diode 5. 5' resistors 6, 7 and a capacitor 8'. Reference numeral 10 denotes an adding circuit which adds together the output of the positive polarity detection circuit 1g1M3 and the output of the negative polarity detection circuit 9 and outputs the result, and is constituted by resistors 11 and 12 for addition and resistor 13 for bias. Reference numeral 14 denotes a loop filter that takes out only the DC component included in the addition output supplied from the addition circuit 10, and is composed of capacitors 15, 16 and resistors 17, and is set to have a sufficiently large number. 18 is an operational amplifier serving as a surge amplifier that compares the output of the loop filter 14 with the zero level and outputs the difference; 19 is a voltage limiter circuit that connects the output terminal of the operational amplifier 18 and the reference voltage of the condenser 1; By limiting the reference voltage E-, which is interposed between the input terminal and the converter and the R-lator l, to a certain range, the reference voltage during initial operation can be
This is provided in order to prevent excessive f# and ensure reliable determination. This voltage limiter circuit 19 has a resistor 2
0, 21 and a capacitor 22. In the mourning data signal discriminating circuit constructed in this manner, a playback signal HP of a digital audio disc is supplied to the input terminal 2 from an optical pickup (not shown). Then, the comparator 1 discriminates the reproduced signal HP based on the reference voltage ■8, and determines "He, @L".
ll data signal D8 is generated. The data signal D8 generated from the comparator 1 is detected by the diodes 5゜5' provided in the positive detection circuit 3 and the negative detection circuit 9, so that the positive polarity component and the negative polarity component are respectively extracted. become. The outputs of the positive polarity detection circuit 3 and the negative polarity detection circuit (b) 9 are added together in an adder circuit 10 constituted by resistors 11 and 12, and are biased to a predetermined level by a resistor 13 and output. Ru.

In this case, the format of the recording signal for the digital audio disc is as described in FIG. There is.

Then, this redundant portion satisfies the condition that the same signal continues only within the range of 3 bits or more and 11 bits or less, and furthermore, the @ Hm and @ L II multiplication signal ratios from several sindels ago become the smallest and become DC. The amount is added so that the amount decreases. Therefore, when the reference value vR of the comparator 1 matches the reference value Vr of the reproduced signal HP shown in FIG. It is standardized to Nonoiasu Repel. And the reference value of comparator l■
When R deviates from the reference value Vr of the reproduced signal HP in the positive polarity direction, the Norms width for the "L" portion of the data signal 8 is widened, and the output of the loop filter 14 becomes
The noise level is lowered by the level corresponding to the amount of deviation. 9. If the reference value ①8 of the comparator 1 deviates in the negative direction with respect to the reference value VrVc of the reproduced signal HP, the data signal D8 output from the comparator 1
The pulse width for the “H” portion of
It will rise from Easlepel.

The reference value V of the reproduced input signal HF detected in this way
The output signal of the loop filter 14 corresponding to the difference between r and the reference value 8 of the comparator 1 is outputted after the difference from the zero level is detected by the operational amplifier 518. and,
The output signal of the operational amplifier 18 is sent to the comparator '1 via the voltage limiter circuit 19 as a reference value (8). Therefore, the reference value vR of the comparator 1 is changed in response to fluctuations in the input reproduced signal9, and accordingly, accurate data signals can always be extracted.

Note that the voltage riser circuit 19 is provided to prevent malfunctions caused by large fluctuations in the output of the operational amplifier 18 during initial operation, and such problems cannot be solved with other configurations. If it is possible, it is not necessarily a must-see.

As explained above, the data signal detection circuit according to the present invention focuses on the fact that the DC component of the input reproduced signal is set to be small, and the positive and negative detection signals of the detected data signal are By taking out the added output through a loop filter with a large time constant, the difference between the reference value of the reproduced signal and the reference value of the converter 7 which extracts the data signal from the reproduced signal is detected, and this difference is dealt with. This changes the reference value of the comparator.

Therefore, since the reference levels of the converters 7 and 7 are varied in response to variations in the reference level of the input reproduced signal, there is an excellent effect that data signals can always be reliably detected.

[Brief explanation of drawings]

The first problem is a diagram showing an example of the signal format of digital information recorded on a digital audio disc.
Fig. ig2 is a waveform diagram of an h raw signal of a digital audio disc, and Fig. 3 is a circuit diagram showing an embodiment of a data signal detection circuit according to the present invention. 1...Comparator, 3...Positive detection circuit, 9...
- Negative pole detection circuit, 10... Addition circuit, 14... Loop filter, 18-... Operational amplifier, 19... Voltage dependent tsuta circuit. Agent: Patent attorney Akio Suzuki. 1. of

Claims (1)

[Claims] (1) Compare the reference value with the reproduction signal supplied from the pickup that combines time-divisionally recorded information in a signal format determined to reduce the DC component, and determine the values of ``H'' and @L'. A converter/(litter) that scatters the data signal, a positive and negative polarity detection circuit that receives the output signal of this converter, an adder circuit that adds the outputs of the positive and negative polarity detectors, and an output of this adder circuit. A loop filter that averages the signal and a reference value of the comparator are controlled in accordance with the difference between the output of the loop filter and the reference value, so that the reference value of the comparator is controlled in response to fluctuations in the reference level of the reproduced signal. and an operational amplifier that changes the reference value of the comparator.