JPS60179967A - Data discriminator - Google Patents

Abstract

PURPOSE:To reduce a reproduction error of a pulse code with simple constitution even in a modulation system which contains a large number of low band frequency components, by obtaining a differential of the reproduction outputs. CONSTITUTION:A differential signal of a reproduction output signal is supplied to a transversal filter 5 after A/D conversion done by a differential A/D converter 8. This A/D converted signal undergoes the equalization of waveform through the filter 5. An amplitude comparator 13 delivers 1 when the absolute value of the output signal of the filter 5 is larger than or equal to the specific threshold value and then delivers 0 when said absolute value is smaller than the specific threshold value. A delay differential device 16 detects the changing point of the output of the filter 5. A zero cross phase detector 17 works only when the output of the comparator 13 is set at 1 and delivers its time position as a zero cross phase signal when a zero cross point is produced to the output of the device 16. A data reproducer 7 delivers the pulse code signals synchronous with the clock signals of the filter 5 and a detector 6. Thus it is possible to reduce the reproduction error of the pulse code.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention (c) relates to a data identification device for a magnetic tape recorder that records and reproduces audio signals using pulse code modulation.

Conventional Structures and Problems Therein, in recent years, in order to increase the recording density, various data identification devices have been proposed that use a pulse code modulation method and obtain a pulse code from a reproduced signal of a magnetic tape.

A conventional data identification device will be explained below.

Figure 1 shows a conventional data identification device, in which 1 is a reproducing head using a magnetoresistive element, 2 is a low frequency F wave filter (LPF), and the offset voltage and noise of the output of the reproducing head 1 are Removes low frequency components. 3 is an amplifier, and 4 is an analog-to-digital converter (hereinafter referred to as an A/D converter).

), 6 is a transversal filter that equalizes the output of the converter 4, 6 is a zero or difference phase detector, and when a zero crossing occurs in the output of the transversal filter 6, A/1)
/D converter 4's sampling phase-outputs the zero-crossing phase relative to the synchronized reference phase. 7 is a data regenerator that determines and outputs a binary pulse code signal from the zero-crossing phase signal output from the zero-crossing phase detector 6; Transversal filter 6, zero crossing phase detector 6
．． The data regenerator 7 constitutes a data identification device.

FIG. 2 shows an example of signal waveforms at each part of the conventional configuration example configured as described above, and its operation will be described below.

First, a pulse code modulated acoustic signal is reproduced by a reproduction head 1 having a magnetoresistive element, and a low-frequency p-wave device 2.
A reproduced output signal is obtained by the amplifier 3. A/D converter 4 whose reproduced output signal is a signal total sampling clock having a frequency that is an integral multiple of the clock frequency of the pulse code signal.
A/D conversion is performed. The output of the A/D converter 4 is waveform-equalized by a transversal filter 6 and input to a zero-crossing phase detector 6. When a zero crossing occurs in the output of the transversal filter 6, the zero crossing phase detector 6 outputs the temporal position information as a zero crossing phase signal.

Digital signal processing in the transversal filter 6 and zero-crossing phase detector 6 operates using the sampling clock of the A/D converter 4 as a synchronous clock, and the zero-crossing phase detector 6 uses this clock signal as a reference phase to generate a zero-crossing phase signal. Outputs sound. In this operation, the zero crossing phase fluctuates due to jitter or waveform equalization error in the reproduced output signal, but the data reproduction 57 smoothes this phase fluctuation and converts the data clock signal included in the reproduced output signal. Transversal filter 6 by extracting and comparing this with the zero crossing phase. Zero crossing phase detector 6
outputs a pulse code signal synchronized with the clock signal.

However, in the above-mentioned conventional configuration, due to the large low frequency noise characteristic of the magnetoresistive head, the low frequency
In a modulation method that has a relatively large number of frequency components near DC, which requires the cutoff frequency of wave generator 2 to be high, the loss of low frequency components causes large zero-crossing phase fluctuations, causing pulse code reproduction errors. Ta. In addition, in order to compensate for the loss of low frequency components, it is necessary to add a DC regenerator, but in this case the configuration becomes complicated and the average value of the reproduced signal changes due to the loss of low frequency components. This has led to the problem that the dynamic range of digital signal processing has to be increased because of the increase in the number of signals.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides a data identification device with a simple configuration and a small pulse code reproduction error even in a modulation method with many low frequency components by using a difference detection means. It is something.

Structure of the Invention The present invention is a differential type A/D that outputs changes in an input signal.
an i converter, a transversal filter that inputs the entire output of the A/D converter, a delay difference device that outputs a change in the output of the transversal filter, and an absolute difference and identification of the output of the transversal filter. an amplitude comparator that compares and outputs the magnitude with respect to the opening of the eyes; the output of the amplitude comparator and the output of the delay differentiator are input, and the amplitude comparator operates only when the absolute value of the input is larger than a threshold value. and a zero-crossing phase detector that outputs the zero-crossing phase of the output of the delay difference detector, and a data regenerator that reproduces a binary pulse code from the output of the zero-crossing phase detector. , the pulse code is detected from the reproduced output signal by differential detection, and the pulse code reproduction error is greatly reduced without requiring almost all the low frequency components of the reproduced output signal.

DESCRIPTION OF EMBODIMENTS FIG. 3 shows the configuration of a data identification device in an embodiment of the present invention. In FIG. 3, 9 is an analog subtracter, 10 is an A/D converter, and 11 is a delay device.
), 12 is a digital-to-analog converter (hereinafter referred to as a D/A converter), and analog subtracter 9, A/Df
Exchanger 10. The delay device 11 and the D/A converter 12 constitute a differential analog-to-digital converter 8. 6 is a transversal filter that performs waveform equalization, 13 is an amplitude comparator, 14 is a delay device, and 16 is a subtracter, which constitute the delay device 14, the subtracter 16, and the delay difference device 16. 17 is a zero-crossing phase detector, and 7 is a data regenerator.

FIG. 4 shows an example of the operation waveforms of each part of this embodiment configured as described above. In FIG. 3, components having the same functions as those in the prior art example of the first cause are indicated by the same numbers, and the explanation thereof will be omitted, and the operation of FIG. 3 will be explained below.

Instead, the A/D converter 10 subtracts and outputs the difference between the reproduced output signal and the output signal of the D/A converter 12 using the analog subtracter 9, and performs A/D conversion. The delay device 11 delays the output of the A/D converter 10 by a specific delay time, and the D/A
Output to the FI converter 12. The D/Afi converter 12 converts the output sound of the delay device 11 into a D/A converter and outputs it to the analog subtracter 9. The above operation constitutes a differential analog-to-digital converter 8 for the delay time difference of the delay device 11, and the differential signal of the reproduced output signal is A/DI converted and outputted to the transversal filter 6 -xt'E. The amplitude comparator 13 outputs "1" when the absolute value of the output signal of the transversal filter 6 is greater than or equal to a specific threshold Xref,
When it is small, it outputs “0°°.The M-differentiator 16 outputs the difference between the output of the delay device 14 having a specific delay time and the output of the transversal filter 5, and changes the output of the transversal filter 6. The zero-crossing phase detector 17 operates only when the output of the amplitude comparator 13 is "1゛°", and the delay difference detector 1
When a zero crossing occurs in the output of 6, the temporal position thereof is output as a zero or difference phase signal. The above digital signal processing is performed in synchronization with the frequency of the pulse code, which is an integral multiple of the data clock, as in the conventional configuration shown in FIG. will be carried out.

As described above, according to this embodiment, waveform equalization can be performed by reducing the fluctuation in the average value by taking all the differences in the reproduced output, so that the dynamic range of digital signal processing can be made relatively small. Since the pulse code is reproduced by roughly taking the difference t of the waveform equalization output and adjusting the phase of the zero difference point, there is less need to record and reproduce low frequency components.
Pulse code reproduction error is small and its magnitude is relatively small.
・A data identification device can be provided.

Effect of the invention The present invention is a differential analog-to-digital converter.

By providing a delay differentiator and an amplitude comparator, it is possible to realize an excellent data identification device that can obtain the effect that the code reproduction error is small even when there is a loss of low frequency components in the reproduced signal.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a conventional data identification device, and Figure 2 is a diagram of a conventional data identification device.
FIG. 3 is a diagram showing the configuration of a data identification device according to an embodiment of the present invention, and FIG. 4 is a waveform diagram showing the operation of each part in FIG. 3. -6...Transversal filter, 7...-Data regenerator, 8...
Differential analog-digital converter, 9...analog subtracter, 1o...analog-digital converter, 11...delay device, 12-...
Digital-analog converter, 13... Amplitude comparator, 14... Delay device, 16... Subtractor, 16... Delay difference device, 17. ...-Zero crossing phase detector. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure → Time

Claims (1)

[Claims] a differential analog-to-digital converter that outputs a decoded portion of an input signal; a transversal filter that receives the output of the analog-to-digital converter; and a delay difference device that outputs all changes in the output of the transversal filter. and an amplitude comparator that compares and outputs the magnitude of the absolute value of the output of the transversal filter with a specific threshold value; a zero-crossing phase detector that operates only when the value is greater than a threshold and outputs the zero-crossing phase of the output of the delay differentiator; and a binary pulse code from the output of the zero or difference phase detector. A data identification device comprising: a data regenerator for reproducing data.