JPH0664853B2 - Data identification device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for recording / reproducing a PCM signal, for example, a data identifying apparatus in a magneto-optical disk apparatus.

2. Description of the Related Art In recent years, a magneto-optical disk device has been actively developed as a large-capacity data file device capable of high-density recording / reproduction, and a phase synchronization device for reproducing a clock in a reproduction signal has been developed for a reproduction signal data identification device. Has been done. As this phase synchronization device, a device using digital signal processing has been developed as a device capable of high-speed pull-in and highly stable tracking. (For example, Japanese Patent Application No. 60-228039 "Data Identification Device" Shimada) Hereinafter, a conventional data identification device as described above will be described with reference to the drawings. FIG. 4 shows the configuration of a conventional data identification device, and FIG. 5 shows the signal waveform of each part. 6 and 7 show examples of reproduced signal waveforms of the magneto-optical disk. The PCM signal recorded / reproduced here is 2 /
It is a signal modulated by 7 modulation (Japanese Patent Publication No. 55-26494, etc.), and the data discrimination with respect to the reproduced signal is performed by detecting the maximum point.

In FIG. 4, 1 is an analog-digital converter, 2 is
Is a phase calculator, 3 is a digital-analog converter, 4 is a low-pass filter, and 5 is a voltage controlled oscillator.

First, the analog-digital converter 1 samples an input signal, which is a reproduction signal of the magneto-optical disk, at a specific clock, converts it into a binary signal, and outputs it. The phase calculator 2 is a signal processing circuit that operates synchronously with the specific clock, and uses the output of the analog-digital converter 1 when the maximum point occurs in the input signal, that is, the continuous obtained by this output. When a maximum point occurs between the three sampling points, the three sampling values are used to calculate and output the phase difference between the clock component included in the input signal and the specific clock, and 0 otherwise. Outputs (zero). At the same time, the phase calculator 2 outputs "1" when the maximum point occurs and "0" when the maximum point does not occur, as the identification data output of the present data identification device. Digital-
The analog converter 3 converts the output of the phase calculator 2 into an analog signal and outputs it. The low-pass filter 4 amplifies the output of the digital-analog converter 3 and low-pass outputs it.
The voltage controlled oscillator 5 has a free-running frequency equal to the clock frequency of the input signal, receives the output of the low pass filter 4, and outputs a reproduced clock signal showing a frequency change proportional to this. This reproduced clock signal is one of the output signals of the present data identification device and is the specific clock signal.

In the above series of operations, the voltage controlled oscillator operates so that the sampling point coincides with the maximum point of the input signal as shown in the signal waveform example of FIG. 5, and thus the regenerated clock signal synchronized with the clock component of the input signal. And a data identification signal is obtained.

Problems to be Solved by the Invention However, in the reproduction signal of the magneto-optical disk device, it is necessary to cut off the low frequency component in order to remove the low frequency noise component. However, as shown in FIG.
The reproduced signal had a large envelope variation because the low frequency component also decreased at the same time. In addition, an address portion written in advance on the disk surface and obtained by the intensity change of the reflected light and a data portion obtained by rotation of the deflecting surface of the reflected light recorded / reproduced by using the magneto-optical effect are formed by the same data identification device. In order to identify the data, the reproduction signal of the address portion and the reproduction signal of the data portion are switched by a switch, and this is done, but in this case also, it was difficult to keep the envelope constant. Therefore, even if these amplitude variations occur, the resolution of the analog-to-digital converter 1 must be increased in order to reduce the deterioration of the discrimination margin, resulting in poor efficiency.

In view of the above problems, the present invention provides a data discriminating apparatus which can relatively reduce the resolution of an analog-digital converter.

Means for Solving the Problems In order to achieve this object, the data identification device of the present invention comprises:
Envelope detector, subtractor, analog-digital converter, phase calculator, digital-analog converter,
It is composed of a low pass filter and a voltage controlled oscillator.

According to the present invention, with the above configuration, the envelope on the opposite side of the maximum point to be detected of the input signal is fixed to one of the voltages in the input voltage range of the analog-digital converter to reduce the envelope fluctuation and perform the analog-digital conversion. By performing data discrimination, the resolution of the analog-digital converter can be reduced.

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

FIG. 1 shows a basic configuration of a data identification device in one embodiment of the present invention, FIG. 2 is a detailed view of a main part of FIG. 1, and FIG. 3 is a signal waveform of each part. Incidentally, in FIG. 1, the same components as those of the conventional example shown in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 1, 6 is an envelope detector, and 7 is a subtractor. In FIG. 2, 8 is a buffer, 9 and 10 are diodes, 11 is a capacitor, and 12 and 13 are resistors.

The operation of the data identification device configured as described above will be described below.

First, the envelope detector 6 detects and outputs the lower envelope of the input signal. The subtractor 7 subtracts the output of the envelope detector 6 from the input signal and outputs it. Therefore, the output of the subtractor 2 is such that the lower envelope of the input signal is fixed to a constant voltage as shown in FIG. 3, and is input to the analog-digital converter 1 for data discrimination. Here, the envelope detector 6 and the subtractor 7 are realized by a simple circuit as shown in FIG. In the figure, the lower envelope is detected from the input signal buffered by the buffer 8 by the diode 9, the capacitor 11, and the resistor 12 with a specific time constant. The diode 10 and the resistor 13 operate so as to cancel the voltage drop caused by the diode 9 during the envelope detection described above, so that the subtractor 7 fixes the lower envelope of the input signal near 0 [V]. Output. The minimum point near the maximum point of the reproduced signal waveform is at a position separated by more than 1.5 cycles of the reproduction clock according to the 2/7 modulation rule, and the recording / reproducing characteristics of the magneto-optical disk are low-pass characteristics. The level of the minimum point does not become extremely higher than the lower envelope detected as described above. It is necessary to detect the local maximum points by using three consecutive points near the local maximum point.
Since it is a sampling point and the accuracy of these three sampling points should be guaranteed, analog-
This data discriminating apparatus can be realized by adding a relatively simple circuit as shown in FIG. 2 without requiring accuracy near 0 [V] with respect to the input voltage range of the digital converter.

EFFECTS OF THE INVENTION The present invention can realize an excellent data discriminating apparatus in which the resolution of the analog-digital converter can be made relatively small by providing the envelope detector and the subtractor.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a data identification device according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing details of essential parts of FIG. 1, and FIG. 3 is for explaining the operation of FIG. 4 is a block diagram showing the configuration of a conventional data discriminating apparatus, FIG. 5 is a waveform diagram showing signals of respective parts in FIG. 4, and FIGS. 6 and 7 are envelopes of reproduced signals. It is a waveform diagram. 1 ... Analog-digital converter, 2 ... Phase calculator, 3 ... Digital-analog converter, 4 ... Low-pass wave detector, 5 ... Voltage-controlled oscillator, 6 ... Envelope detector, 7
...... Subtractor, 8 …… Buffer, 9,10 …… Diode, 11
...... Capacitors, 12,13 ...... Resistors.

Claims (1)

[Claims] 1. An envelope detector that detects and outputs a one-sided envelope of an input signal, a subtractor that outputs a difference between the input signal and an output of the envelope detector, and a subtractor output that is specified. An analog-digital converter that outputs a binary signal by sampling and quantizing with a clock, a phase calculator that calculates and outputs a phase difference between the output of the analog-digital converter and the specific clock, and the phase calculator A digital-analog converter for converting the output of the above into an analog signal and outputting the analog signal, a low-pass filter for amplifying the output of the digital-analog converter to a low-frequency wave, and an output of the low-pass filter as an input A data identification device comprising a voltage controlled oscillator that oscillates and outputs a specific clock.