JP2002083472A - Servo control device and servo control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a servo control device in which information stored in a servo region can be read surely, a servo region is compressed, and recording capacity of a recording medium can be increased. SOLUTION: An AGC control circuit 11 generates an AGC signal SG8 for controlling the gain of an AGC circuit 1 based on an output signal SG4 of an A/D converter 4. The AGC control circuit 11 is provided with a preceding control section outputting a control signal for generating an AGC signal corresponding to the AGC region or a phase detecting region prior to read-out operation of the AGC region or the phase detecting region based on an amplitude ratio of a first input signal read out from a R/W recovery region and a second input signal read out from the AGC region or the phase detecting region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a servo control device for performing embedded servo control by providing a servo area in a track direction on a data surface in a recording medium such as a magnetic disk.

In recent years, some recording / reproducing apparatuses using a magnetic disk or the like as a recording medium perform embedded servo control in order to improve data reading accuracy. In such a recording / reproducing apparatus, there is a problem of further increasing the recording capacity. In order to improve the recording capacity on a recording medium, there is a configuration in which the servo area is reduced while the servo area is reliably performed to increase the data area. In order to reduce the servo area, it is necessary to increase the operation speed of the automatic gain control circuit (AGC circuit) of the data reading circuit.

[0003]

2. Description of the Related Art FIG. 16 shows a data reading device for reading data from a recording medium such as a magnetic disk.

The AGC circuit 1 receives data read from a recording medium via a read head (not shown) as an input signal in. The AGC circuit 1 has a D
The gain is set based on the AGC control voltage SG1 output from the / A converter 2, and the input signal in is amplified based on the gain to output the output signal SG2 to the filter circuit 3.

The filter circuit 3 is composed of a low-pass filter, and outputs an output signal SG3 obtained by removing unnecessary high-frequency components from the output voltage SG2 of the AGC circuit 1 to the A / D converter 4.

The A / D converter 4 includes a filter circuit 3
Is converted into a digital output signal SG4 and output to the servo processing circuit 5.
The servo processing circuit 5 performs a processing operation for performing servo control of a reading position by a reading head based on the digital output signal SG4 of the A / D converter 4, and outputs read data to the next stage.

The output signal SG4 of the A / D converter 4 is
It is also input to the AGC control circuit 6. The AGC control circuit 6 receives a target value PA stored in a register or the like in advance. The target value PA is a value that causes the output signal SG3 of the filter circuit 3 to have a substantially full range with respect to the input level of the A / D converter 4.

Then, the AGC control circuit 6
The output signal SG4 of the / D converter 4 is compared with the target value PA, and a digital output signal SG5 obtained by integrating the error component is output to the D / A converter 2.

The D / A converter 2 converts the digital output signal SG5 of the AGC control circuit 6 into an analog signal and outputs the analog signal to the AGC circuit 1 as an AGC control voltage SG1.

The A / D converter 4, servo processing circuit 5, AGC control circuit 6, etc. operate based on a clock signal CLK generated by a PLL circuit or the like. FIG.
FIG. 3 shows servo areas in which a large number of portions are partially recorded on each track of a recording medium such as a magnetic disk. That is, the servo area includes an R / W recovery area 7, a servo mark area 8,
It is composed of an AGC area 9 and a phase detection area 10.

FIG. 18 shows an input signal in when the recorded contents of such a servo area are read. The input signal “in” shown in the figure is actually a Lorentz waveform, but is represented by a sin waveform for simplification.

When reading the servo area,
As shown in the figure, first, the R / W recovery area 7 is read at a predetermined amplitude and frequency at a first read time t1, and then the servo mark area 8 is continuously read at 0 level at a second read time t2. Is read as

Next, the AGC area 9 is read as a signal having a lower frequency and a larger amplitude than the R / W recovery area 7 at a read time t3, and then the phase detection area 10 has the same frequency as the AGC area 9 at a read time t4. Read with the same amplitude.

A when reading such a servo area
The GC control voltage SG1 will be described with reference to FIG. When a read operation of the R / W recovery area 7 is started by the read head, the output signal S of the A / D converter 4 based on the input signal in read from the R / W recovery area 7
An error between G4 and the target value PA is calculated by the AGC control circuit 6, and an AGC control voltage SG1 is output from the D / A converter 2 based on the output signal SG5 of the AGC control circuit 6.

At this time, the amplitude of the input signal in based on the read operation of the R / W recovery area 7 is small, and the A / D
If the error between the output signal SG4 of the converter 4 and the target value PA input to the AGC control circuit 6 is large, the voltage level of the AGC control voltage SG1 increases.

By such an operation, the output signal SG4 of the A / D converter 4 converges to coincide with the target value PA. Next, during the read operation of the servo mark area 8, A / A
The output signal SG4 of the D converter 4 is continuously at the 0 level.

Then, the output signal SG of the AGC control circuit 6
5 is fixed, and the AGC control voltage SG1 is also fixed. Next, the read operation of the AGC area 9 is started,
The error between the output signal SG4 of the A / D converter 4 based on the input signal in read from the area 9 and the target value PA is again A
The D / A converter 2 outputs an AGC control voltage SG1 calculated by the GC control circuit 6 and based on the output signal SG5 of the AGC control circuit 6.

That is, when the read operation is switched from the servo mark area 8 to the AGC area 9, the AGC area 9
Of the input signal in based on the read operation of R / W
Input signal in based on read operation of recovery area 7
Larger than the amplitude. Therefore, the output signal SG3 of the filter circuit 3 has an amplitude exceeding the target value.

Then, by the operation of the AGC control circuit 6,
The AGC control voltage SG1 gradually decreases, and the A / D
Output signal SG4 of converter 4 converges on target value PA. By such an operation, the output signal SG of the filter circuit 3
The read operation of the phase detection area 10 is started in a state where 3 is almost in the full range with respect to the input level of the A / D converter 4.

Since the frequency and amplitude of the input signal in by the read operation of the phase detection area 10 are equal to those of the AGC area 9, the read operation of the phase detection area 10 is performed by the output signal SG3 of the filter circuit 3 Is performed in a state where the input level is almost full range from the beginning.

Therefore, it is possible to read out the phase information stored in the phase detection area 10 without fail, and to quickly perform the servo control for correcting the read position.

[0022]

In the above-described read operation of the servo area, the output signal S of the filter circuit 3 is used.
Each time the read area is switched, AGC is performed so that G3 has an almost full range input level to the A / D converter 4.
Switching of the control voltage SG1 is performed.

Therefore, it takes time for the output signal SG3 of the filter circuit 3 to converge on the A / D converter 4 to an almost full-range input level every time the area is switched,
It is difficult to compress the servo area.

In particular, at the start of the read operation of the phase detection area 10, the output signal SG3 of the filter circuit 3 is set to A / D
The AGC area 9 needs a sufficient sample data amount and data storage area so that the input level of the converter 4 becomes almost the full range from the beginning.

An object of the present invention is to provide a servo control device capable of compressing a servo area and increasing the recording capacity of a recording medium while reliably reading information stored in the servo area.

[0026]

As shown in FIG.
The C circuit 1 includes an R / W recovery area constituting a servo area recorded on a recording medium, a servo mark area,
The input signals in having different amplitudes read from the C region and the phase detection region are amplified to have a predetermined amplitude based on the AGC control voltage SG1. The filter circuit 3
An unnecessary frequency component is removed from the output signal SG2 of the AGC circuit 1. The A / D converter 4 includes the filter circuit 3
A / D-converts the output signal SG3. AGC control circuit 1
1 generates an AGC signal SG8 for controlling the gain of the AGC circuit 1 based on the output signal SG4 of the A / D converter 4. The D / A converter 2 converts the AGC signal SG8 into an analog signal,
As an AGC control voltage SG1. Based on an amplitude ratio between a first input signal read from the R / W recovery area and a second input signal read from the AGC area or the phase detection area, the read operation of the AGC area or the phase detection area is performed. Prior to this, the AGC control circuit 11 includes a preceding control unit that outputs a control signal for generating the AGC signal corresponding to the AGC area or the phase detection area.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 shows a first embodiment of a servo control device embodying the present invention. This embodiment has the same configuration as that of the conventional example except for the AGC control circuit 11, and the same components are denoted by the same reference numerals, and detailed description thereof will be omitted.

The AGC control circuit 11 includes an error calculator 12, a multiplier 13, and an integrator 14, as shown in FIG. The error calculator 12 is similarly provided in the AGC control circuit 6 of the conventional example, and the A / D converter 4
Output signal SG4, clock signal CLK and target value P
A is input.

The error calculator 12 outputs the clock signal C
An error between the digital signal sequentially input from the A / D converter 4 and the target value PA is sequentially calculated based on the LK, and an average value of the two consecutively calculated errors is calculated based on the clock signal CLK. The multiplier 13 outputs the output signal SG6.
Are output sequentially.

The specific configuration of the multiplier 13 will be described with reference to FIG. The multiplier 13 includes a multiplier 15 and a selector 16. The multiplier 15 receives the output signal SG 6 of the error calculator 12 and the coefficient μ from the selector 16.

The selector 16 receives coefficient values C and D and an AGC high-speed pull-in signal W which are stored in advance in registers and the like of the data reader.
The coefficient values C and D are set so that C> D.

As shown in FIG. 5, the high-speed pull-in signal W is an H-level pulse signal input from the CPU of the data reading device during the reading operation of the R / W recovery area 7.

The selector 16 outputs the coefficient value C as the coefficient μ to the multiplier 15 when the high-speed pull-in signal W is at the H level, and outputs the coefficient value D as the coefficient μ when the high-speed pull-in signal W is at the L level. The value is output to the multiplier 15 as μ.

Therefore, the multiplier 13 is connected to the error calculator 12
Is output by multiplying the output signal SG6 by the coefficient μ. The specific configuration of the integrator 14 will be described with reference to FIG. The integrator 14 includes an adder 17, a flip-flop circuit 18, a multiplier 19, and a selector 20.

The output signal SG7 of the multiplier 13 is input to an adder 17, which has the multiplier 19
Is input. The output signal of the adder 17 is input to a flip-flop circuit 18, and the flip-flop circuit 18 outputs an output signal of the adder 17 to the multiplier 19 based on the clock signal CLK.

The multiplier 19 receives a coefficient NNN from a selector 20. The selector 20 receives the servo mark detection signal V and the coefficient values N and 1 stored in advance in the register.

When the servo mark detection signal V is at the H level, the selector 20 outputs the coefficient value N as the coefficient NNN to the multiplying section 19, and outputs the servo mark detection signal V
Is the L level, the coefficient value 1 is output to the multiplier 19 as the coefficient NNN.

The coefficient value N is set in the R / W recovery area 7
And the amplitude of the input signal in when reading
Is the ratio to the amplitude of the input signal in when reading is performed.
That is, the ratio between the amplitude of the input signal in when reading the R / W recovery area 7 and the amplitude of the input signal in when reading the AGC area 9 is constant and can be measured in advance.

For example, when the amplitude of the input signal in when reading the AGC area 9 is changed to the R / W recovery area 7
Is n times the amplitude of the input signal in when
The coefficient value N is set to 1 / n.

The multiplying section 19 multiplies the output signal of the flip-flop circuit 18 by a coefficient NNN to output an output signal SG8.
Is output. The adder 17 adds the output signal SG7 of the multiplier 13 and the output signal SG8 of the multiplier 19 and outputs the result to the flip-flop circuit 18.

With such a configuration, the integrator 14 integrates the digital output signal SG8 of the digital output signal SG7 of the multiplier 13 or the digital output signal SG8 obtained by integrating and multiplying the digital output signal SG7 of the multiplier 13 by N times.
Is output to the D / A converter 2 as an AGC signal.

Next, the operation of the servo control device configured as described above will be described with reference to FIG. When a read operation of the servo area starts from a read operation of the R / W recovery area 7 during a read operation of a magnetic disk or the like, an H level servo area signal SAS is output from the CPU controlling the data reading device to the servo processing. Input to the circuit 5.

The AGC high-speed pull-in signal W, which is an H-level pulse signal, is input to the selector 16 of the multiplier 13 with the rise of the servo area signal SAS.
When the read operation of the R / W recovery area 7 is started, the input signal i has the amplitude and frequency corresponding to the R / W recovery area 7 at the first read time t1 shown in FIG.
When n is input, the input signal in is input to the A / D converter 4 via the AGC circuit 1 and the filter circuit 3.

The A / D converter 4 outputs an output signal SG4 obtained by converting the output signal SG3 of the filter circuit 3 into a digital signal to the servo processing circuit 5 and the AGC control circuit 11.

The AGC control circuit 11 includes an error calculator 12
Calculates the average value of the error between the digital output signal SG4 sequentially output from the A / D converter 4 and the target value PA,
The average value is sequentially output to the multiplier 13 as the output signal SG6.

In the multiplier 13, when the H-level AGC pull-in signal W is input to the selector 16, the coefficient μ input from the selector 16 to the multiplier 15 has a large coefficient value C, and the coefficient μ is input. The signal SG6 is multiplied and output as an output signal SG7.

In the integrator 14, the servo mark detection signal V
Is still at the L level, the input signal SG7 is integrated with the coefficient NNN = 1, and the output signal SG8 is output to the D / A converter 2.

The D / A converter 2 outputs the digital input signal SG
8 is converted to an analog signal, and the AGC control voltage SG1 is output to the AGC circuit 1. By such an operation, FIG.
As shown in (1), when the read operation of the R / W recovery area 7 is started, the AGC control voltage SG1 rapidly changes based on the rise of the AGC high-speed pull-in signal W.

The output signal SG of the filter circuit 3
3 converges so as to be substantially in the full range with respect to the input level of the A / D converter 4, and the output signal SG4 of the A / D converter 4
Converges to the target value PA.

Next, when the read operation of the servo mark area 8 is started and the 0 level signal is continuously input to the AGC control circuit 11 h times, the operation of the error calculator 12 causes the output of the error calculator 12 to output. The signal SG6 becomes 0.

Then, the output signal S of the AGC control circuit 11 is
G8 is at a constant level, and the AGC control voltage SG1 output from the D / A converter 2 is at a constant level. Next, when an H-level servo mark detection signal V is input from the servo processing circuit 5 to the selector 20 of the integrator 14 in accordance with the read operation of the servo mark area 8, the coefficient NNN output from the selector 20 to the multiplier 19 Is selected and output.

Then, the output signal SG8 of the integrator 14 decreases instantaneously based on the preset ratio, and the AGC
The control voltage SG1 also instantaneously drops to a constant level. Next, when the read operation of the AGC area 9 is started and the input signal in having a large amplitude is input, the error calculator 12 outputs the output signal SG4 of the A / D converter 4 and the target value PA.
Is performed.

However, the maximum value of the output signal SG4 of the A / D converter 4 is already close to the target value PA by the AGC control voltage SG1 set at the time of the read operation of the AGC area 9.

Then, the output signal SG of the filter circuit 3
Reference numeral 3 denotes an amplitude close to the full range of the input level of the A / D converter 4. Then, after the end of the read operation of the AGC area 9, the read operation of the phase detection area 10 is started, and the data stored in the phase detection area 10 is stored in the A / D.
The signal is converted into a digital signal with high accuracy by the converter 4 and output to the servo processing circuit 5.

With such an operation, the integrator 14 constitutes a leading control section that outputs the output signal SG8 corresponding to the AGC area 9 in advance during the reading operation of the servo mark area 8.

With the servo control device configured as described above, the following operational effects can be obtained. (1) In the read operation of the servo mark area 8 prior to the read operation of the AGC area 9, the R / W recovery area 7
The AGC control voltage SG1 can be switched in advance based on the ratio of the amplitude of the input signal read from the AGC to the amplitude of the input signal read from the AGC area 9.
When the read operation of the AGC area 9 is started, A /
The maximum value of the output signal SG4 of the D converter 4 can be set to a value close to the target value PA. (2) When the read operation of the AGC area 9 is started, the maximum value of the output signal SG4 of the A / D converter 4 can be set to a value close to the target value PA. Also, the phase detection area 10 can be accurately read. Also, without providing the AGC region 9,
Even if the phase detection area 10 is provided subsequent to the servo mark area 8, the phase detection data recorded in the phase detection area 10 can be accurately read. (3) Since the AGC area 9 can be reduced or omitted, the amount of data in the servo area can be reduced and the recording capacity of the data area can be increased, so that the recording capacity of the recording medium can be increased. it can. (4) At the time of the read operation of the R / W recovery area 7,
Based on the input of the high-speed pull-in signal W to the multiplier 13, A
By rapidly changing the GC control voltage SG1, the average value of the output signal SG4 of the A / D converter 4 can be quickly brought close to the target value PA. (Second Embodiment) FIG. 6 shows a second embodiment. In this embodiment, two types of target values PA1 and PA2 can be set in the error calculator 12 of the first embodiment, and a coefficient NNN inputted to the multiplication unit 19 of the integrator 14 is set.
Is fixed to 1 and the other configuration is the same as that of the first embodiment.

That is, two types of target values PA1 and PA2 preset in a register or the like are input to the selector 21, and the selector 21 receives the servo mark detection signal V.

If the servo mark detection signal V is at L level, the selector 21 outputs the target value PA1 to the error calculator 12, and if the servo mark detection signal V is at H level, the selector 21 outputs the target value PA2. Is the error calculator 1
Output to 2.

The target values PA1 and PA2 are determined based on the amplitude of the input signal in based on the read operation of the R / W recovery area 7 and the input signal i based on the read operation of the AGC area 9.
It is set based on the ratio of n to the amplitude.

The target value PA1 is set such that the output signal SG3 of the filter circuit 3 is in the full range of the input level of the A / D converter 4 during the read operation of the R / W recovery area 7, and for example, R / W W recovery area 7
And the ratio of the amplitude of the input signal in from the AGC area 9 is 1: 2
Then, the ratio of the target values PA1 and PA2 is set to 1: 2.

The operation of the servo control device thus configured will be described with reference to FIG. When the read operation of the R / W recovery area 7 starts, the servo mark detection signal V
Is the L level, the selector 21 sets the target value PA
1 is selected and output to the error calculator 12.

The operation of the AGC control circuit 11 based on the target value PA1 changes the AGC control voltage SG1 so that the average value of the output signal SG4 of the A / D converter 4 converges on the target value PA1 and the filter circuit The output signal SG3 of the A / D converter 3 has an almost full range with respect to the input level of the A / D converter 4. This operation is the same as in the first embodiment.

Next, when the read operation of the servo mark area 8 is started, the output signal SG6 of the error calculator 12 is fixed to 0, and the AGC control voltage SG1 becomes a constant level. Next, when the servo mark detection signal V becomes H level, the target value input to the error calculator 12 is changed from PA1 to P1.
Switch to A2.

In this state, when the read operation of the AGC area 9 is started, the amplitude of the input signal in changes. However, since the target value has been switched to PA2 in advance, the output signal SG6 of the error calculator 12 becomes 0, the level of the AGC control voltage SG1 hardly changes.

After the read operation of the AGC area 9 is completed, the read operation of the phase detection area 10 is performed in a state where the output signal SG3 of the filter circuit 3 is maintained in a substantially full range with respect to the input level of the A / D converter 4. Operation starts,
The data stored in the phase detection area 10 is accurately converted to a digital signal by the A / D converter 4 and output to the servo processing circuit 5.

With such an operation, the error calculator 12 performs the read operation of the servo mark area 8 in the AGC area 9.
The preceding control unit that outputs the output signal SG6 corresponding to.

The servo control device of this embodiment can obtain the following operation and effect, and (3) and (4) of the operation and effect obtained in the first embodiment.
The same operation and effect as those obtained in the above can be obtained. (1) In the read operation of the servo mark area 8 prior to the read operation of the AGC area 9, the R / W recovery area 7
The target value of the average value of the output signal SG4 of the A / D converter 4 can be previously switched from PA1 to PA2 based on the ratio of the amplitude of the input signal read from the AGC area 9 to the amplitude of the input signal read from the AGC area 9. AGC
When the read operation of the area 9 is started, the average value of the output signal SG4 of the A / D converter 4 can be set to a value close to the target value. (2) When the read operation of the AGC area 9 is started, the average value of the output signal SG4 of the A / D converter 4 can be set to a value close to the target value PA1, so that the AGC area 9 is reduced. Also, the phase detection area 10 can be accurately read. Further, even if the phase detection area 10 is provided following the servo mark area 8 without providing the AGC area 9, the phase detection data recorded in the phase detection area 10 can be accurately read. (Third Embodiment) FIG. 8 shows a third embodiment. In this embodiment, the cut-off frequency fc of the filter circuit 3 of the first embodiment is switched to perform the read operation of the R / W recovery area 7 and the AG.
At the time of the read operation of the C region 9, the filter circuit 3
Of the input signal of the A / D converter 4 is substantially in the full range.

When the cutoff frequency fc of the filter circuit 3 is switched, the output signal SG of the filter circuit 3
No. 3 changes. That is, R
In the read operation of the / W recovery area 7, the filter circuit 3 is operated at the first cutoff frequency fc1, and the amplitude of the output signal SG3 of the filter circuit 3 becomes
The input level of the A / D converter 4 is set to substantially the full range.

The AGC area 9 and the phase detection area 10
In the read operation, the filter circuit 3 is operated at the second cutoff frequency fc2 so that the amplitude of the output signal SG3 of the filter circuit 3 becomes substantially the full range of the input level of the A / D converter 4. .

Further, a first cut-off frequency fc1 and
Switching to the second cutoff frequency fc2 is performed by the servo mark detection signal V as in the first and second embodiments.

Further, the means for switching the cutoff frequencies fc1 and fc2 of the filter circuit 3 can be easily performed by switching circuit constants in the same manner as in a normal filter circuit. In the servo control circuit of this embodiment, the following operation and effect can be obtained, and among the operation and effect obtained in the first embodiment, the same operation and effect as that obtained in (3) can be obtained. The operation and effect can be obtained. (1) In the read operation of the servo mark area 8 prior to the read operation of the AGC area 9, the R / W recovery area 7
Since the cutoff frequency of the filter circuit 3 can be switched in advance based on the ratio of the amplitude of the input signal read from the AGC region to the amplitude of the input signal read from the AGC region 9, the read operation of the AGC region 9 is started. Sometimes, the output signal SG3 of the filter circuit 3 is A / D
The input level of the converter 4 can be set to be substantially the full range. (2) When the read operation of the AGC area 9 is started, the output signal SG3 of the filter circuit 3 can be set to substantially the full range of the input level of the A / D converter 4, so that even if the AGC area 9 is reduced. , The phase detection area 10 can be read out with high accuracy. Further, even if the phase detection area 10 is provided following the servo mark area 8 without providing the AGC area 9, the phase detection data recorded in the phase detection area 10 can be accurately read. (Fourth Embodiment) FIG. 9 shows the operation of a servo control circuit according to a fourth embodiment. In this embodiment, the coefficient values input to the multiplication unit 19 of the integrator 14 of the first embodiment are set to 1, and each of the regions 7, 8,
The reading operations 9 and 10 are performed.

Then, the R / W recovery area 7 and the AG
The CPU captures and latches the output signal SG8 of the AGC control circuit 11 with the latch signal LA output at the timing when the AGC control voltage converges to a constant level in the C area 9.

Then, the output voltage SG8 of the AGC control circuit 11 when the output signal SG4 of the A / D converter 4 converges to the target value PA can be latched in each of the areas 7, 9. Then, based on the latch data, the target value to be output to the error calculator 12 is switched by firmware preset in the CPU so that the ACG control voltage SG1 switches at high speed when the servo area is switched.

With this configuration, the servo area can be reduced in the same manner as in the above embodiment. (Fifth Embodiment) FIGS. 10 to 12 show a fifth embodiment. This embodiment is a modification of the above-described embodiments.
When the operation speed of the A / A converter 2 cannot keep up with the operation speed of the AGC control circuit 11, the frequency of the output signal SG8 of the integrator 14 of the AGC control circuit 11 matches the operation frequency of the D / A converter 2. It is like that.

As shown in FIG. 10, the output signal SG 8 of the integrator 14 is input to the flip-flop circuit 22. Further, the clock signal CLK input to the integrator 14 is frequency-divided by a frequency divider 23 into two, and
2 is input as a clock signal CK.

The flip-flop circuit 22 outputs the output signal S of the integrator 14 every time the clock signal CK is input.
G8 is fetched and output to D / A converter 2 as output signal SG9.

With such a configuration, the output signal SG8 of the integrator 14 shown in FIG.
Is output as an output signal SG9 shown in FIG. Then, the output signal SG9 of the flip-flop circuit 22 becomes D
The signal is converted into an analog signal AGC control voltage SG1 by the / A converter 2 and output to the AGC circuit 1.

With such an operation, the AGC control circuit 1
In the case where the operation speed of the D / A converter 2 is lower than the operation speed of the A / D converter 1, the output signal SG8 of the AGC control circuit 11
After the conversion into G9, the D / A converter 2 converts it into an AGC control voltage SG1 and outputs it to the AGC circuit 1.

The output signal SG of the AGC control circuit 11
Although the conversion accuracy of converting the AGC circuit 8 into the AGC control voltage SG1 is reduced, there is substantially no problem in consideration of the operation speed of the AGC circuit 1. (Sixth Embodiment) FIG. 13 shows a sixth embodiment. In this embodiment, in the first embodiment, the input signal “in” indicating a circuit for calculating a coefficient N to be input to the selector 20 of the integrator 14 is input to an absolute value calculation unit 24. . The absolute value calculator 24 generates an absolute value of the amplitude of the input signal in input as an analog value and outputs the absolute value to the first and second average value calculators 25 and 26.

The first average value calculator 25 calculates the average value of the input signal in based on the read operation of the R / W recovery area 7, and includes an adder 27a, a flip-flop circuit 28a, a counter 29a, And a division unit 30a.

The input signal in is input to the adder 27a, and the output signal of the adder 27a is input to the flip-flop circuit 28a. The flip-flop circuit 28a
Receives the clock signal CLK, latches the output signal of the adder 27a based on the clock signal CLK, and outputs the latched signal.

The output signal of the flip-flop circuit 28a is input to the divider 30a and also to the adder 27a. Therefore, the adder 27a and the flip-flop circuit 28a perform the same integration operation as the adder 17 and the flip-flop circuit 18 of the integrator 14.

The clock signal CLK is input to the counter circuit 29a. The counter 29a counts the clock signal CLK and outputs the count value to the divider 30a.

The reset signal RS1 is input to the counter circuit 29a. As shown in FIG. 14, the reset signal RS1 is input when the servo mark detection signal V goes high, and
Is released at the end of the read operation.

The divider 30a calculates and outputs the average value A of the input signal in by dividing the integrated value output from the flip-flop circuit 28a by the count value counted by the counter 29a.

With such a configuration, the first average value calculator 25 calculates and outputs the average value A of the amplitude of the input signal in based on the read operation of the R / W recovery area 7.
The second average value calculator 26 has the same configuration as the first average value calculator 25 except that the reset signal RS2 is input to the counter 29b.

As shown in FIG. 14, the reset signal RS2 is input based on the completion of the read operation of the phase detection area 10, and is released a predetermined time after the servo mark detection signal V becomes H level.

With such a configuration, the second average value calculation section 26 calculates and outputs the average value B of the amplitude of the input signal in based on the read operation of the AGC area 9 and the phase comparison area 10.

The first recording signal RA shown in FIG. 14 is a signal for taking the average value A calculated by the first average value calculating section 25 into a register or the like, and the second recording signal RB is
This is a signal for taking the average value B calculated by the second average value calculation unit 26 into a register or the like.

Since the lengths (the number of samples) of the areas in which the reading operation is performed are known in advance, the signals RA and RB can be generated by a counter that counts the number of the samples.

Next, the amplitude ratio between the R / W recovery area 7 and the phase detection area 10 can be calculated based on the average values A and B calculated as described above. What is necessary is just to store it in a register.

With the above configuration and operation, the coefficient N can be calculated and stored in the register. In FIG. 14, if there is a period in which the reset signals RS1 and RS2 are both at the H level, the first and second average value calculation units 25 and 26 can be shared. (Seventh Embodiment) FIG. 15 shows a seventh embodiment. In this embodiment, the servo mark detection signal V is generated by the sample number counter 31, and other configurations are the same as those of the first embodiment.

That is, in the servo mark area 8, the length of the area (the number of samples) is known in advance,
There are about 0 to 40 samples. Then, the number of samples is counted by the sample number counter 31 during the reading operation of the servo mark area 8, and when the predetermined number of samples is counted, the servo number detection signal V is output from the sample number counter 31 to the AGC control circuit 11. I do. With such a configuration, the servo mark detection signal V can be generated.

Since the output timing of the servo mark detection signal V is not required to be very strict, the clock signal CLK for operating the sample number counter 31 is
A clock signal CLK obtained by dividing a normal sample clock by n, for example, by 8 may be used.

With such a configuration, it is possible to use a counter having a low operating speed, to reduce the number of bits of the counter, and to reduce the circuit area.

(Supplementary Note 1) An AGC circuit for amplifying input signals having different amplitudes read from a plurality of areas in a servo area recorded on a recording medium to have a predetermined amplitude based on an AGC control voltage; A filter circuit for removing unnecessary frequency components from the output signal of the AGC circuit, an A / D converter for A / D converting the output signal of the filter circuit, and the AG based on the output signal of the A / D converter
A for generating an AGC signal for controlling the gain of the C circuit
A servo control apparatus comprising: a GC control circuit; and a D / A converter that converts the AGC signal into an analog signal and outputs the analog signal to the AGC circuit as an AGC control voltage. A servo control unit for outputting a control signal for generating the AGC signal corresponding to the area prior to a read operation of each area based on an amplitude ratio of an input signal to be read. apparatus. (1) (Supplementary note 2) R / W recovery area, servo mark area, and AG that constitute a servo area recorded on a recording medium
An AGC circuit for amplifying input signals having different amplitudes read from the C region and the phase detection region to have a predetermined amplitude based on an AGC control voltage; and an unnecessary frequency component from an output signal of the AGC circuit. A filter circuit for removing, and an A / D converter for A / D converting an output signal of the filter circuit
An A / D converter, an AGC control circuit for generating an AGC signal for controlling a gain of the AGC circuit based on an output signal of the A / D converter, and converting the AGC signal into an analog signal; What is claimed is: 1. A servo control device comprising: a D / A converter that outputs an AGC control voltage to the AGC circuit; wherein the first input signal read from the R / W recovery area and the AGC area or the phase detection area Based on the amplitude ratio with the second input signal to be read,
A servo control unit for outputting a control signal for generating the AGC signal corresponding to the AGC area or the phase detection area prior to a read operation of the AGC area or the phase detection area; apparatus.
(2) (Supplementary note 3) The preceding control unit performs the AGC based on the amplitude ratio during a read operation of the servo mark area.
3. The servo control device according to claim 2, wherein a switching unit for switching a signal is provided in the AGC control circuit. (3) (Supplementary Note 4) The AGC control circuit is configured to output the A / D converter output signal and the filter circuit output signal from the A / D converter.
An error calculator for calculating an error from a preset target value so as to be in a full range with respect to the input level of the / D converter, and multiplying an output signal of the error calculator by a predetermined first coefficient. A switching unit configured to integrate the output signal of the multiplier to generate the AGC signal, wherein the switching unit performs a second operation based on the amplitude ratio during a read operation of the servo mark area. 4. The servo control device according to claim 3, wherein the integrator performs an integration operation in which the second coefficient is multiplied based on the input of the coefficient. (4) (Supplementary Note 5) The second coefficient is an average value of the amplitude of the input signal based on the read operation of the R / W recovery area and the average value of the amplitude of the input signal based on the read operation of the AGC area. 5. The servo control device according to claim 4, wherein the ratio is calculated by a coefficient calculation circuit. (5) (Supplementary note 6) The AGC control circuit may be configured to output the A / D converter output signal and the filter circuit output signal from the A / D converter.
An error calculator for calculating an error from a preset target value so as to be in a full range with respect to the input level of the / D converter, and a multiplier for multiplying an output signal of the error calculator by a preset coefficient. And an integrator that integrates an output signal of the multiplier to generate the AGC signal, wherein the switching unit switches the target value based on the amplitude ratio during a read operation of the servo mark area. 4. The servo control device according to claim 3, wherein the servo control device comprises an error calculator. (6) (Supplementary note 7) A counter for outputting a servo mark detection signal when a predetermined number of samples are counted during the read operation of the servo mark area is provided. 4. The servo control device according to claim 3, wherein the AGC signal is switched.

(Supplementary Note 8) A counter for outputting a servo mark detection signal when a predetermined number of samples are counted during the read operation of the servo mark area,
5. The servo control device according to claim 4, wherein the integrator performs an integration operation multiplied by a second coefficient based on the servo mark detection signal.

(Supplementary Note 9) A counter for outputting a servo mark detection signal when a predetermined number of samples are counted during the read operation of the servo mark area,
7. The servo control device according to claim 6, wherein the target value is switched based on the servo mark detection signal.

(Supplementary Note 10) The preceding control unit is configured by a filter constant switching device that switches a cutoff frequency of the filter circuit based on the amplitude ratio during a read operation of the servo mark area. Item 3. The servo control device according to Item 2. (7) (Supplementary Note 11) A counter that outputs a servo mark detection signal when a predetermined number of samples are counted during the read operation of the servo mark area is provided, and based on the servo mark detection signal, a counter of the filter circuit is provided. 11. The servo control device according to claim 10, wherein the cutoff frequency is switched.

(Supplementary note 12) The servo controller according to any one of supplementary notes 4 to 6, wherein the multiplier selects a large value as the first coefficient based on an AGC high-speed pull-in signal. (8) (Supplementary Note 13) A frequency conversion circuit that adjusts the frequency of the output signal of the AGC control circuit to the operating frequency of the D / A converter, between the AGC control circuit and the D / A converter. 13. The servo control device according to any one of supplementary notes 1 to 12, further comprising: (10) (Appendix 14) R / W recovery area, servo mark area, and A / W recovery area constituting the servo area recorded on the recording medium
Input signals of different amplitudes read from the GC area and the phase detection area are amplified by an AGC circuit so as to have a predetermined amplitude based on an AGC control voltage, and unnecessary frequencies are output from an output signal of the AGC circuit by a filter circuit. A / D conversion is performed on the output signal of the filter circuit by an A / D converter, and the AGC is performed based on the output signal of the A / D converter.
A servo control method for generating an AGC signal for controlling a gain of a circuit by an AGC control circuit, converting the AGC signal into an analog signal by a D / A converter, and outputting the analog signal to the AGC circuit as an AGC control voltage. A first input signal read from the R / W recovery area,
Prior to the read operation of the AGC area or the phase detection area, the AGC signal corresponding to the AGC area or the phase detection area is determined based on the amplitude ratio with the second input signal read from the C area or the phase detection area. A servo control method characterized by generating. (9) (Supplementary Note 15) An AGC signal at the time of the read operation of the R / W recovery area and an AGC signal at the time of the read operation of the AGC area are fetched and stored in advance, and the AGC signal is updated by firmware based on the storage result. 14. The servo control method according to supplementary note 14, wherein the method is generated.

[0101]

As described in detail above, the present invention provides a servo control apparatus capable of compressing a servo area and increasing the recording capacity of a recording medium while reliably reading information stored in the servo area. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment.

FIG. 2 is a block diagram illustrating an AGC control circuit.

FIG. 3 is a block diagram showing a multiplier.

FIG. 4 is a block diagram showing an integrator.

FIG. 5 is a timing waveform chart showing the operation of the first embodiment.

FIG. 6 is a block diagram showing a second embodiment.

FIG. 7 is a timing waveform chart showing an operation of the second embodiment.

FIG. 8 is a timing waveform chart showing an operation of the third embodiment.

FIG. 9 is a timing waveform chart showing the operation of the fourth embodiment.

FIG. 10 is a block diagram showing a fifth embodiment.

FIG. 11 is a waveform chart showing the operation of the fifth embodiment.

FIG. 12 is a waveform chart showing the operation of the fifth embodiment.

FIG. 13 is a block diagram showing a sixth embodiment.

FIG. 14 is a timing waveform chart showing a sixth embodiment.

FIG. 15 is a block diagram showing a seventh embodiment.

FIG. 16 is a block diagram showing a conventional example.

FIG. 17 is an explanatory diagram showing a servo area.

FIG. 18 is a waveform chart showing an input signal.

FIG. 19 is a timing waveform chart showing the operation of the conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 AGC circuit 2 D / A converter 3 Filter circuit 4 A / D converter 11 AGC control circuit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshitaka Nakata 2-1844-2 Kozoji-cho, Kasugai-shi, Aichi F-term in Fujitsu VSI Co., Ltd. 5D096 AA02 CC01 DD01 EE03 GG06 HH01 RR01 RR18 RR18 RR18

Claims (10)

[Claims] 1. An input signal having different amplitudes read from a plurality of areas in a servo area recorded on a recording medium,
An AGC circuit for amplifying the signal to have a predetermined amplitude based on the GC control voltage; a filter circuit for removing unnecessary frequency components from an output signal of the AGC circuit; and an A / D converter for A / D converting the output signal of the filter circuit. D
A converter, and an AGC for generating an AGC signal for controlling a gain of the AGC circuit based on an output signal of the A / D converter.
A control circuit, converting the AGC signal into an analog signal,
What is claimed is: 1. A servo control device comprising: a D / A converter that outputs an AGC control voltage to a circuit, wherein a D / A converter outputs an AGC control voltage based on an amplitude ratio of an input signal read from each area in a servo area. A servo control device comprising a preceding control unit for outputting a control signal for generating the AGC signal corresponding to the area. 2. An R / W recovery area constituting a servo area recorded on a recording medium; a servo mark area;
An AGC circuit that amplifies input signals of different amplitudes read from the GC area and the phase detection area to have a predetermined amplitude based on an AGC control voltage; and an unnecessary frequency component from an output signal of the AGC circuit. A filter circuit for removing, and an A / D for A / D converting an output signal of the filter circuit
A converter, and an AGC for generating an AGC signal for controlling a gain of the AGC circuit based on an output signal of the A / D converter.
A control circuit, converting the AGC signal into an analog signal,
A servo control device comprising: a D / A converter that outputs an AGC control voltage to a circuit, wherein the first input signal is read from the R / W recovery area and the D / A converter is read from the AGC area or the phase detection area. Based on the amplitude ratio with the second input signal, the AG
Prior to the reading operation of the C region or the phase detection region,
The AGC corresponding to the AGC area or the phase detection area
A servo control device comprising a preceding control unit that outputs a control signal for generating a signal. 3. The system according to claim 1, wherein the preceding control unit performs the read operation on the servo mark area based on the amplitude ratio.
3. The servo control device according to claim 2, wherein a switching unit for switching the C signal is provided in the AGC control circuit. 4. The AGC control circuit according to claim 1, wherein the output signal of the A / D converter and a target signal set in advance such that the output signal of the filter circuit has a full range with respect to the input level of the A / D converter. An error calculator for calculating an error with the value; a multiplier for multiplying an output signal of the error calculator by a first coefficient set in advance; an output signal of the multiplier is integrated, and the AGC signal is integrated. The switching unit performs an integration operation by multiplying the second coefficient based on the input of the second coefficient based on the amplitude ratio at the time of the read operation of the servo mark area. 4. The servo control device according to claim 3, wherein the servo control device comprises the integrator. 5. The second coefficient is a ratio of an average value of an amplitude of an input signal based on a read operation of the R / W recovery area to an average value of an amplitude of an input signal based on a read operation of an AGC area. 5. The servo control device according to claim 4, wherein the value is calculated by a coefficient calculation circuit. 6. The AGC control circuit according to claim 1, wherein the output signal of the A / D converter and the output signal of the filter circuit have a target set in advance such that the output signal has a full range with respect to the input level of the A / D converter. An error calculator for calculating an error from the value; a multiplier for multiplying an output signal of the error calculator by a preset coefficient; and an integration for integrating the output signal of the multiplier to generate the AGC signal. 4. The servo control device according to claim 3, wherein the switching unit comprises an error calculator that switches the target value based on the amplitude ratio during a read operation of the servo mark area. 5. . 7. The filter control device according to claim 2, wherein the preceding control unit comprises a filter constant switching device that switches a cutoff frequency of the filter circuit based on the amplitude ratio during a read operation of the servo mark area. A servo controller as described. 8. The servo controller according to claim 4, wherein the multiplier selects a large value of the coefficient based on an AGC high-speed pull-in signal. 9. An R / W recovery area constituting a servo area recorded on a recording medium, a servo mark area,
Input signals of different amplitudes read from the GC area and the phase detection area are amplified by an AGC circuit so as to have a predetermined amplitude based on an AGC control voltage, and unnecessary frequencies are output from an output signal of the AGC circuit by a filter circuit. A / D conversion is performed on the output signal of the filter circuit by an A / D converter, and the AGC is performed based on the output signal of the A / D converter.
A servo control method for generating an AGC signal for controlling a gain of a circuit by an AGC control circuit, converting the AGC signal into an analog signal by a D / A converter, and outputting the analog signal to the AGC circuit as an AGC control voltage. The AG signal based on an amplitude ratio between a first input signal read from the R / W recovery area and a second input signal read from the AGC area or the phase detection area.
Prior to the reading operation of the C region or the phase detection region,
The AGC corresponding to the AGC area or the phase detection area
A servo control method characterized by generating a signal. 10. A frequency conversion circuit for adjusting a frequency of an output signal of the AGC control circuit to an operation frequency of the D / A converter is provided between the AGC control circuit and the D / A converter. 9. The servo control device according to claim 1, wherein: