JPH0677284B2 - Playback device - Google Patents

Description

The present invention relates to a reproducing device for reproducing data recorded in a magnetic storage device.

[Conventional technology]

FIG. 4 is a block diagram of an analog signal system in a reproducing apparatus for a conventional magnetic storage device, which is disclosed in, for example, the document "Digital Magnetic Recording Technology", Chapter 4, "Signal Processing", published by Tri-Ceps Ltd. . In the figure, 1 is a preamplifier, 2 is a low-pass filter (LPF), 3 is a voltage control amplifier (VCA) that varies the gain according to the voltage applied to the gain control input, and 4 is a pulse width of the analog pulse signal that narrows the pulse width of adjacent pulses. Waveform equalizer (EQ) to prevent mutual interference,
6 is a peak position detector (PD) that generates a digital pulse signal corresponding to the peak position of the waveform, and 7 is a waveform equalizer 4
Is a control voltage generating circuit for generating a gain control voltage of the voltage controlled amplifier 3 from the output signal of 10, the input of each of the voltage controlled amplifier 3 and the peak position detector 6, 31 is the gain control input of the voltage controlled amplifier 3. is there.

FIG. 5 is a circuit diagram of the waveform equalizer in the reproducing apparatus of FIG. In the figure, 15 is a matching resistor, 16 is a delay line, and 17
Is an attenuator, 18 is a differential amplifier, 19 is the input of the matching resistor 15, 2
Reference numerals 0 and 21 denote a non-inverting input and an inverting input of the differential amplifier 18, respectively, and 22 denotes an output of the differential amplifier 18.

FIG. 7 and FIG. 8 are waveform diagrams of the reproducing apparatus of FIG. 4 and the waveform equalizer of FIG. 5, respectively.

Next, the operation of the conventional reproducing apparatus shown in FIG. 4 will be described. A signal reproduced from a head (not shown) is amplified by the preamplifier 1 and input to the voltage controlled amplifier 3 via the low pass filter 2. The output signal of the voltage controlled amplifier 3 has its pulse width narrowed by the waveform equalizer 4 and becomes a digital pulse signal corresponding to the peak position by the peak position detector 6.

On the other hand, the output signal of the waveform equalizer 4 is the control voltage generation circuit 7
Then, it is converted into a voltage corresponding to the peak amplitude and applied to the gain control input 31 of the voltage controlled amplifier 3. In this way, by negatively feeding back the peak amplitude of the output signal of the waveform equalizer 4 to the voltage control amplifier 3, the automatic gain control action works and the amplitude of the input signal of the peak position detector 6 becomes constant. ing.

Next, the operation of the waveform equalizer 4 shown in FIG. 5 will be described. The waveform of the input 19 of the matching resistor 15 which is the input signal
If the waveform E ₁₉ shown in the figure is used and the delay time of the delay line 16 is τ, a waveform E ₂₀ is obtained at the non-inverting input 20 of the differential amplifier 18.
Further, the input 19 and the reflected wave at the non-inverting input 20 of the differential amplifier 18 are combined, and a waveform E ₂₁ attenuated by the attenuation rate K by the attenuator 17 is obtained at the inverting input 21 of the differential amplifier 18. Then,
At the output 22 of the differential amplifier 18, a waveform E ₂₂ having a narrow pulse width is obtained with respect to the waveform E ₁₉ . Thus, in the conventional waveform equalizer 4, the delay time τ of the delay line 16 and the attenuation rate K of the attenuator 7 are
The pulse width of the input signal is narrowed by the degree determined by to prevent mutual interference between adjacent pulses.

As described above, in the conventional reproducing apparatus, the peak position detector 6 is controlled by making the peak amplitude of the analog pulse signal waveform at the input 12 of the peak position detector 6 constant and narrowing the pulse width. Peak position detection performance is improved and a highly reliable peak position detection digital pulse signal is generated.

[Problems to be solved by the invention]

Since the above-mentioned conventional reproducing apparatus is configured as described above, it is effective for detecting the peak position of the analog pulse signal waveform. However, if it is attempted to detect the peak amplitude of the analog pulse signal waveform, the automatic gain control action works, which is an obstacle and unsuitable.

Here, as an example, a case of a so-called embedded servo system having a servo track in which head positioning information is written in the middle of a data track will be described. Sixth
FIG. 1 is a diagram showing a positional relationship between a data track and a servo track in a conventional embedded servo type disc. Assuming that the head 25 is at the position shown in FIG. 6, when the disk rotates in the direction of the arrow in the figure, the input of the voltage control amplifier 3
At 10, the waveform E ₁₀ shown in FIG. 7 is obtained. The relative position shift amount of the head 25 with respect to the track width from the center of the data track 23 appears as a ratio of the amplitudes of the servo waveforms A29 and B30 of the waveform E ₁₀ . However, the waveform E ₁₂ is obtained at the input 12 of the peak position detector 6 by the automatic gain control action. Thus, in the conventional playback device, each servo waveform A29 and A30
Is distorted, the ratio of the amplitudes is not maintained, and the amount of displacement of the head 25 from the center of the data track 23 cannot be detected. In FIG. 6, 26 and 27 are servo track patterns A and B, respectively.

As described above, the conventional reproducing device has a problem that the peak amplitude of the signal waveform cannot be detected correctly.

The present invention has been made in order to solve such a problem, and is a reproduction in which the function of correctly detecting the peak position of the input signal waveform and the function of correctly detecting the peak amplitude are switched according to the use of the input signal. The purpose is to obtain the device.

[Means for solving problems]

In the reproducing apparatus according to the present invention, the output of the control voltage generating circuit in the control voltage generating means is input to the gain control input of the voltage controlled amplifier via the sample and hold circuit, and the sampling and holding of the sample and hold circuit is performed. The means for switching between and is provided.

[Action]

In the reproducing apparatus of the present invention, the sample-hold circuit applies the output voltage of the control voltage generating circuit immediately before entering the hold state as the hold voltage to the gain control input of the voltage control amplifier in the hold state. Is fixed to the value immediately before entering the hold state, and the automatic gain control action is canceled.

Further, by means of the sampling / holding switching means of the sample-hold circuit, it is possible to select whether the gain of the voltage controlled amplifier is made variable so that the automatic gain control action is exerted or the gain is fixed so as to cancel the automatic gain control action.

As described above, in the reproducing apparatus according to the present invention, the peak amplitude of the input signal waveform is made constant, the peak position is correctly detected, and the input signal waveform is uniformly amplified to determine the peak amplitude of the waveform. It works to switch the correct detection depending on the use of the input signal.

〔Example〕

FIG. 1 is a block diagram showing a reproducing apparatus for a magnetic storage device according to an embodiment of the present invention. The same or corresponding portions as those in FIG. 4 are indicated by the same reference numerals, and detailed description thereof will be omitted. To do. In the figure, 34 is a control voltage generating means,
As its constituent elements, 8 is a sample and hold circuit (S / H) that samples and holds the output signal of the control voltage generation circuit 7 and outputs it to the gain control input 31 of the voltage control amplifier 3, and 9 is the sampling and sampling circuit of the sample and hold circuit 8. A first control logic circuit for controlling switching to holding, 14 is its control line. Reference numeral 4 is a waveform equalizer.

FIG. 2 is a waveform diagram in each part of the reproducing apparatus of FIG.

Next, the operation of the reproducing apparatus according to the embodiment of the present invention shown in FIG. 1 will be described. First, when the head reproduction signal of the embedded servo system shown in FIG. 6 is given as the input analog pulse signal of FIG. 1, the waveform E shown in FIG. _{Get 10} . Of these, the servo waveforms A29 and B30 need to detect the peak amplitude, and the data waveform 28 needs to detect the peak position. Therefore, for the data waveform 28, the sample hold circuit 8 is set to the sampling mode. For each servo waveform A29 and B30, the sample hold circuit 8 is set to the holding mode. By doing so, the waveform E ₁₂ is obtained at the input 12 of the peak position detector 6.

At the time of the data waveform 28, since the output signal of the control voltage generating circuit 7 is directly applied to the gain control input 31 of the voltage control amplifier 3, the automatic gain control action works and the same operation as that of the conventional reproducing apparatus is performed. To do.

Next, for each servo waveform A29 and B30, the voltage control amplifier 3
Since the input signal of the gain control input 31 is the output signal of the control voltage generation circuit 7 immediately before the sample hold circuit 8 is switched to the olding mode,
The gain of the voltage controlled amplifier 3 is fixed to the value immediately before holding, and the automatic gain control action is canceled. As a result, the peak amplitude of the waveform E ₁₂ is not distorted in the shape of the waveform E ₁₀ , and the ratio of the amplitudes of the servo waveforms A29 and B30 is maintained.

As described above, in the reproducing apparatus of the present invention, the peak amplitude of the input signal waveform is made constant and the peak position is correctly detected and the input signal waveform is uniformly amplified according to the use of the input signal. , The peak amplitude can be switched to correct detection.

Further, in the above embodiment, the case where the low-pass filter 2 is placed in the output stage of the preamplifier 1 and the waveform equalizing means 33 is placed in the output stage of the voltage controlled amplifier 3 has been described. Has the same effect. That is, the low-pass filter 2 may be placed at the output stage of the voltage controlled amplifier 3 as in the other embodiment of the present invention shown in FIG.

〔The invention's effect〕

As described above, the present invention is configured so that the gain of the voltage controlled amplifier can be switched between fixed and variable in the reproducing device. Therefore, the peak of the input signal waveform can be changed according to the use of the input signal. Keep the amplitude constant,
This has an excellent effect that it is possible to switch between the correct detection of the peak position and the uniform detection of the peak amplitude by uniformly amplifying the input signal waveform.

[Brief description of drawings]

FIG. 1 is a block diagram showing a reproducing apparatus for a magnetic storage device according to an embodiment of the present invention, FIG. 2 is a waveform diagram of each part of the reproducing apparatus shown in FIG. 1, and FIG. FIG. 4 is a block diagram showing a reproducing apparatus for a magnetic storage device which is an embodiment of the present invention, FIG. 4 is a block diagram showing an analog signal system in a reproducing apparatus for a conventional magnetic storage apparatus, and FIG. 5 is a diagram showing the reproducing apparatus shown in FIG. FIG. 6 is a circuit diagram of a waveform equalizer, FIG. 6 is a diagram showing the positional relationship between a data track and a servo track in a conventional embedded servo type disk, and FIGS. 7 and 8 are the reproducing device of FIG. FIG. 6 is a waveform diagram in each part of the waveform equalizer of FIG. 5. In the figure, 1 ... Preamplifier, 2 ... Low-pass filter (LPF), 3 ... Voltage control amplifier (VCA), 4 ... Waveform equalizer (EQ), 6 ... Peak position detector (PD), 7 ......
Control voltage generation circuit, 8 ... Sample hold circuit (S /
H), 9 ... First control logic circuit, 10, 12, 19 ... Input, 1
4 …… Control line, 15 …… Matching resistance, 16 …… Delay line, 17 ……
Attenuator, 18 …… Differential amplifier, 20 …… Non-inverting input, 21 ……
Inverted input, 22 …… output, 23 …… data track, 24 ……
Servo track, 25 …… Head, 26 …… Servo track pattern A, 27 …… Servo track pattern B, 28 ……
Data waveforms, 29, 30 ... Servo waveforms A and B, 31 ... Gain control input, 34 ... Control voltage generating means. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (4)

[Claims] 1. A low-pass filter for removing high frequency noise in a reproducing device of a magnetic storage device used both for detecting a peak position on a time axis and for detecting a peak amplitude from a reproduction signal of a head. , A waveform equalizer that narrows the time width of the reproduction signal, a voltage control amplifier that controls the gain by an external voltage, and an external voltage that is applied to this voltage control amplifier. And a control voltage generating means for setting a fixed gain mode when the peak amplitude is detected. 2. An input signal is input to an input terminal of the low pass filter, an output terminal of the low pass filter is connected to a signal input terminal of the voltage controlled amplifier, and an output terminal of the control voltage generating means is connected to the voltage controlled amplifier. Connected to the control input terminal of
The output terminal of the voltage controlled amplifier is connected to the input terminal of the waveform equalizer, the output terminal of the waveform equalizer is connected to the input terminal of the control voltage generating means, and at the same time, it is used as the signal output terminal of the present apparatus. The reproducing apparatus according to claim 1, wherein: 3. An input signal is input to an input terminal of the waveform equalizer, an output terminal of the waveform equalizer is connected to a signal input terminal of the voltage controlled amplifier, and an output terminal of the control voltage generating means is connected. At the same time as connecting to the control input terminal of the voltage controlled amplifier, connecting the output terminal of the voltage controlled amplifier to the input terminal of the low pass filter, and connecting the output terminal of the low pass filter to the input terminal of the control voltage generating means, The reproducing apparatus according to claim 1, wherein the reproducing apparatus is a signal output terminal of the apparatus. 4. The control voltage generating means includes a control voltage generating circuit for generating a control voltage according to the amplitude of an input signal, and a sample hold circuit for switching between outputting the control voltage as it is and fixing it at a constant voltage. A first control logic circuit that detects either the feedback control mode or the fixed gain mode and determines the state of the sample hold circuit is provided, and an input signal is input to the input terminal of the control voltage generation circuit, and this control is performed. The output terminal of the voltage generating circuit is connected to the signal input terminal of the sample and hold circuit, the output terminal of the first control logic circuit is connected to the control input terminal of the sample and hold circuit, and the output terminal of the sample and hold circuit is connected. The output terminal of the control voltage generating means is connected to the control input terminal of the voltage controlled amplifier. Reproducing apparatus according to any Re.