JPS6242368A - Cosine equalizing system - Google Patents

Abstract

PURPOSE:To apply a waveform shaping by switching the constant of a cosine equalizing circuit in response to the change in the resolution and changing the constant respectively at the outside and inside of a disc. CONSTITUTION:The control voltage of an automatic gain amplifier 5 provided to plural heads enters the non-inverting terminal of an operational amplifier 4. A comparison voltage representing the position of a head to a disc is determined in advance corresponding to the control voltage and fed to the inverting terminal of the operational amplifier 4 from a terminal A. The resolution is deteriorated sequentially as the head moves from the outside of the disc to the inside. When the control voltage of the automatic gain amplifier 5 is higher than the compared voltage, the operational amplifier drives a switch 3, and e.g., a contact is opened. Thus, a resistor R3 connected in parallel with a resistor R2 is removed, the constant (k) is switched at this point of time and when the head reaches the predetermined position of the disc, the operational amplifier 2 applies equalization with a different constant from the outside and inside of the disc.

Description

[Detailed Description of the Invention] [Summary] When reading data recorded on a disk such as a magnetic disk or an optical disk, the resolution is different between the outside and inside of the disk disk, so the waveform of the read data is converted into a binary format. By switching the constants of the cosine equalization circuit that shapes the signal to make it easier to convert,
Data is reproduced in the optimal equalization state.

[Industrial application field]

The present invention relates to a recording and reproducing circuit for reproducing data recorded on a disk, and more particularly to a cosine equalization circuit that switches constants of the equalization circuit in response to changes in resolution of data successively output from the disk.

When reading data recorded on a disk and converting it into a binary signal in a magnetic disk device, optical disk device, etc., a cosine equalization circuit is used to shape the readout waveform of the head and make it easier to convert it into a binary signal. It is used.

By the way, a disk usually consists of a disk and rotates at a constant speed, so the resolution changes between the outside and inside of the disk.
The further inside it gets, the worse it gets. That is, the recording density of the bits is low on the outside, and the recording density becomes higher on the inside, resulting in a difference in peak shift and a difference in waveform distortion.

Therefore, when shaping a read waveform using a cosine equalization circuit, it is desirable to be able to deal with it in an equalization state that is optimal for the resolution.

[Conventional technology]

FIG. 4 is a block diagram showing an example of a conventional cosine equalization circuit.

A waveform based on the data read from the disk by the head 1 is sent out to the inductance via the internal impedance Z, and enters the ten terminal of the operational amplifier 2 after being delayed by τ time. Also, the waveform divided by resistors R1 and R2 has a constant =R
It is reduced by the voltage division ratio determined by z/(R1+R2) and enters one terminal of the operational amplifier 2.

The waveform that enters the + terminal with a delay of τ time and the original waveform reduced to a constant are synthesized and shaped by the operational amplifier 2, and are sent out as a waveform that is easy to convert into a binary signal. .

[Problem that the invention seeks to solve]

As mentioned above, the constant k is conventionally constant, but the resolution differs between the outside and inside of the disk as described above. That is, when modifying the waveform using the same constant, there is a problem that equalization cannot always be performed in an optimal state.

In view of these problems, the present invention provides a constant k between the outside and inside of the disk so as to correspond to the change in resolution.
It is possible to respond with the optimum equalization state by switching the

[Means for solving problems]

FIG. 1 is a block diagram of the principle of the present invention.

In FIG. 1, a constant switching means 6 is added to FIG.
This is to obtain head position information.

The constant switching means 6 compares a predetermined comparison voltage input from the terminal A with the control voltage of the automatic gain amplifier 5, which changes depending on the position of the head on the disk disk, and changes the control voltage of the automatic gain amplifier 5. The position of the head on the disk disk is detected from , and the constant k is changed between the outside and inside of the disk disk.

[Effect]

With the above configuration, in response to changes in resolution,
Waveform shaping can be performed by changing the constants of the cosine equalization circuit and changing the constants for the outside and inside of the disk.

〔Example〕

FIG. 2 is a block diagram of a circuit showing an embodiment of the present invention.
FIG. 3 is a diagram illustrating the operation of FIG. 2.

In FIG. 2, the control voltage of an automatic gain amplifier 5 provided for a plurality of heads is input to the ten terminal of an operational amplifier 4. In FIG. As shown in FIG. 3<al>, this control voltage gradually increases as the head moves from the outside to the inside of the disk, for example.

Therefore, corresponding to this control voltage, a comparison voltage indicating the position of the disk disk of the head is predetermined as shown in (■), and the terminal A
and supplies it to one terminal of the operational amplifier 4. As shown in FIG. 3(b), the resolution gradually deteriorates as the head moves from the outside to the inside of the disk.

When the control voltage of the automatic gain amplifier 5 becomes higher than the comparison voltage (2), the operational amplifier 4 drives the switch 3 to open, for example, a contact. Resistor R3, which was connected in parallel with resistor R2, is therefore removed and the constant k is switched at this point, as shown in FIG. 3 (C1).

Therefore, when the head reaches a predetermined position on the disk, the operational amplifier 2 can perform equalization using different constants on the outside and inside of the disk.

〔Effect of the invention〕

As explained above, the present invention makes it possible to switch the constant of the cosine equalization circuit using a simple method, and it is possible to perform equalization by switching the constant between the outside and inside of a disk having different resolutions.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a block diagram of a circuit showing an embodiment of the present invention, Fig. 3 is a diagram explaining the operation of Fig. 2, and Fig. 4 is a conventional cosine etc. FIG. 2 is a block diagram showing an example of a conversion circuit. In the figure, l is a head, 2.4 is an operational amplifier, 3 is a switch, 5 is an automatic gain amplifier, and 6 is constant switching means. Is it OK? fl 0.17 figure f7tru tiri 11
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Claims (1)

[Claims] In a cosine equalization circuit that shapes the waveform of data read from a disk in accordance with a constant, an automatic gain amplifier (5) that generates a control voltage in accordance with the position of a head on the disk. Cosine equalization characterized by providing means (6) for switching the constant by comparing the control voltage with a predetermined comparison voltage, and switching the constant of the cosine equalization circuit between the outside and inside of the disc. method.