JP2000293805A - Magnetic recording / reproducing device - Google Patents

Abstract

[PROBLEMS] To provide an erasing circuit capable of setting an erasing frequency to a minimum point (for example, fb / 2) of a reproduction equalization characteristic with a resonance configuration advantageous in circuit scale and power consumption. A magnetic recording / reproducing apparatus which facilitates removal of an erasure component in a reproducing system. SOLUTION: An erasing circuit has an oscillation circuit configuration, and an erasing amplifier 8 oscillates by positive feedback by feedback resistors 10 and 11. The oscillation frequency is adjusted by the variable capacitance diode 37 to a minimum point (frequency fb / 2) of the reproduction equalization characteristic. The erase signal is supplied to the erase head 7 as an erase current 39 via the erase rotary transformer 5. The control circuit 101 of the variable capacitance diode 37 will be described. The clock having the frequency fb / 2 synchronized with the recording data and the erasing signal 38 are input to the phase comparison circuit 33. The output of the phase comparison circuit 33 is amplified to a voltage required for controlling the variable capacitance diode 37.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus, and more particularly to a magnetic recording / reproducing apparatus having a simultaneous reproducing function for reproducing data substantially simultaneously with a recording operation.

[0002]

2. Description of the Related Art In a video tape recorder for a broadcasting station, it is often difficult to re-record, and in order to prevent recording failure, a simultaneous reproduction function for reproducing and confirming recorded contents almost simultaneously during recording is provided. is necessary. In order to realize this simultaneous reproduction function, an erasing head, a recording head, and a reproducing head, which are arranged close to each other, and a rotary transformer for erasing, recording, and reproducing for transmitting signals to them are simultaneously operated. Therefore, it is necessary to suppress the crosstalk interference from the erase signal and the recording signal mixed in the weak reproduction signal to a sufficiently low level. In particular, since the erase signal has a larger amplitude than the recording signal, crosstalk interference is also large.

In addition, the fact that the erasure signal itself is recorded on the tape and mixed with the reproduction signal (residual component of the erasure signal)
As a result, the error rate deteriorates.

Therefore, conventionally, the erasing frequency is set to a high frequency side outside the reproduction band, and a crosstalk component included in the reproduction signal is removed by a trap or a low-pass filter.
You've avoided interference.

By the way, in order to perform recording with high image quality, the data rate increases, and accordingly, the erasing frequency needs to be shifted to a higher frequency. However, to increase the erasing frequency, it is necessary to expand not only the band of the erasing amplifier but also the output dynamic range. This means that as the frequency increases, the amplitude of the output voltage is required,
This is because a large current is required to reduce the efficiency of the erase head. Therefore, in a video tape recorder for a broadcasting station, it is necessary to increase a power supply voltage and a current capacity for an erasing amplifier.

Therefore, it is desirable to set the erasing frequency as low as possible within a range that does not adversely affect the reproduced signal.

Hereinafter, a case where the erasing frequency is set to fb / 2 (fb: bit frequency) in a video tape recorder for a broadcasting station in which the recording and coding method is scrambled interleaved NRZI will be described with reference to the drawings. I do.

FIG. 6 shows the relationship between the PR4 equalization characteristic, the reproduction amplifier band, and the erasing frequency in terms of a standardized frequency. In FIG. 6, the solid line A indicates the PR4 equalization characteristic, the dashed line B indicates the reproducing amplifier band, and the erasing frequency is fb /
It is set to 2. As shown in FIG. 6, fb / 2 is P
This is the minimum point (null frequency) of the R4 equalization characteristic, and it is possible to completely remove the crosstalk and the residual component of the erasure signal.

FIG. 7 is a block diagram of the erasing circuit. The erasing circuit has an oscillation circuit configuration, and the erasing amplifier 8 oscillates by positive feedback by the feedback resistors 10 and 11. The oscillation frequency is adjusted to fb / 2 by the oscillation frequency adjusting capacitor 9 as a capacitance element. In other words, in this erasing circuit, the erasing amplifier operates at a frequency determined by the resonance of the inductance of the path from the erasing amplifier 8 to the erasing head 7 including the erasing rotary transformer 5 and the capacitance of the variable capacitance diode 37 as the oscillation frequency adjusting capacitance element. By oscillating 8, the frequency of the erasing current is determined.

An erasing signal (erasing current) output from the erasing amplifier is supplied to an erasing head 7 as an erasing current 6 through an erasing rotary transformer 5.

FIG. 8 is a simplified version of FIG. The frequency of the erasing signal (erasing current) is the resonance frequency of the total inductance 21, the stray capacitance 20, and the oscillation frequency adjusting capacitor 9, including the erasing rotary transformer 5, the erasing head 7, and the wiring. The oscillation circuit configuration is
This is because the circuit scale is small, the power utilization factor is good, and low power supply voltage and low power consumption are possible.

However, it is generally known that the inductance values of the erasing head 7 and the erasing rotary transformer 5 vary by about ± 10%. The stray capacitance and the capacitance value of the oscillation frequency adjusting capacitor 9 are also ± 10%.
It has a degree of variation. Here, what is dominant in determining the resonance frequency is the inductance value of the erasing head 7 and the capacitance value of the oscillation frequency adjusting capacitor 9.

The above-mentioned variations include not only variations in values of respective elements, but also variations due to aging, temperature changes, and the like.

Therefore, the worst case of the erase frequency is ±
It is necessary to assume a 10% variation. That is, the erasing frequency varies from fb / 2 to f1 or f2 in FIG. When the erasing frequency varies by ± 10%, the erasing crosstalk in the reproducing circuit system and the elimination rate of the residual component recorded on the magnetic tape are shown in FIG. 6 based on fb / 4.
As shown in FIG. In this case, not only simultaneous reproduction is impossible, but also a normal reproduction signal is affected as a residual component in a band, and an error rate is deteriorated.

Here, in order to eliminate variations in the erase frequency, a configuration as shown in FIG. 9 can be considered. A clock (bit frequency fb) synchronized with the recording data is input to the frequency dividing circuit 2 via the input terminal 1. Fb /
The erase signal 3 which has become 2 is supplied to the erase amplifier 4, and its output passes through the erase rotary transformer 5 and the erase current 6.
And is supplied to the erasing head 7. In this configuration, although there is no frequency variation, the configuration is not the oscillation configuration but is basically the same as that of the recording amplifier, and the power usage rate is reduced and the power consumption is greatly increased.

[0016]

As described above, when the erasing frequency is set to fb / 2 to remove the erasing component in the reproducing circuit system, a high erasing frequency accuracy is required. However, the erasing circuit having the resonance circuit configuration cannot satisfy the frequency accuracy, and a general amplifier configuration is disadvantageous in terms of circuit scale, power supply voltage, and power consumption.

Accordingly, an object of the present invention is to be advantageous in circuit scale and power consumption, and to accurately set an erasing frequency to a minimum point of reproduction equalization characteristics, thereby facilitating removal of erasure components in a reproduction circuit system. It is an object of the present invention to provide a magnetic recording / reproducing apparatus which can perform the above-mentioned operations.

[0018]

To achieve this object, a magnetic recording / reproducing apparatus according to claim 1 of the present invention comprises: an erasing head for erasing a recording data signal on a magnetic recording medium;
A recording head that records a new recording data signal on a magnetic recording medium simultaneously with an erasing operation by an erasing head, a reproducing head that simultaneously reproduces a new recording data signal recorded on a magnetic recording medium, and an erasing current supplied to the erasing head Erasing amplifier, and an oscillation frequency adjusting capacitance element provided in the erasing amplifier, and oscillating the erasing amplifier at a frequency determined by resonance due to the inductance of the path from the erasing amplifier to the erasing head and the capacitance of the oscillating frequency adjusting capacitance element. In the magnetic recording / reproducing apparatus, the frequency of the erasing current is determined by
Control means is provided for controlling the oscillation frequency of the erasing amplifier to be near the minimum point of the reproduction equalization characteristic.

According to this configuration, since the control means for controlling the oscillation frequency of the erasing amplifier to be near the minimum point of the reproduction equalization characteristic is provided, even if the resonance configuration is advantageous in circuit scale and power consumption. In addition, it is possible to suppress the variation of the erasing frequency and accurately set the minimum point (for example, fb / 2) of the reproduction equalization characteristic. As a result, it is possible to easily remove the erasure component in the reproduction circuit system.

According to a second aspect of the present invention, there is provided the magnetic recording / reproducing apparatus according to the first aspect, wherein the oscillation frequency adjusting capacitance element is a variable capacitance diode, and the control means controls the capacitance of the variable capacitance diode. The voltage is controlled so that the oscillation frequency of the erasing amplifier is controlled to be near the minimum point of the reproduction equalization characteristic.

According to this configuration, since the oscillation frequency of the erasing amplifier is controlled to be near the minimum point of the reproduction equalization characteristic by controlling the capacitance of the variable capacitance diode by voltage, the frequency of the erasing current is adjusted. Can be easily performed by voltage control. Other operations are the same as those of the first aspect.

According to a third aspect of the present invention, there is provided the magnetic recording / reproducing apparatus according to the second aspect, wherein the control means includes a divided signal of a clock signal synchronized with the recording data signal and an output current of the erasing amplifier. And a phase comparison circuit that controls the oscillation frequency of the erasing amplifier to be close to the minimum point of the reproduction equalization characteristic by changing the capacitance of the variable capacitance diode according to the phase comparison result. I do.

According to this configuration, since the frequency-divided signal of the clock signal is used as the reference signal for phase comparison,
No special reference signal source is required and the circuit configuration is simple. Other operations are the same as those of the second aspect.

According to a fourth aspect of the present invention, there is provided the magnetic recording / reproducing apparatus according to the third aspect, wherein the number of erasing heads is n (n is an integer of 2 or more), and the number of erasing heads corresponds to n. Recording head, playback head, erase amplifier,
There are n variable capacitance diodes and n phase comparators, and the phase of the frequency-divided signal of the clock signal applied to the n phase comparators is shifted by a fixed amount for each erase head.

According to this configuration, the phase of the frequency-divided signal of the clock signal applied to the n phase comparison circuits is shifted by a fixed amount for each erase head, so that the crosstalk components corresponding to each erase head cancel each other. That is, crosstalk from the erasing circuit system to the reproducing circuit system can be reduced. Other operations are the same as those of the third aspect.

According to a fifth aspect of the present invention, there is provided the magnetic recording / reproducing apparatus according to the second aspect, wherein the control means cross-links the reproduction signal from the output signal of the reproduction equalization circuit which processes the reproduction signal. An erasing frequency component extracting means for extracting an erasing frequency component mixed as a talk; and an oscillating frequency of an erasing amplifier by changing the capacitance of a variable capacitance diode according to the frequency of the erasing frequency component extracted by the erasing frequency component extracting means. And frequency detecting means for controlling so as to be near the minimum point of the reproduction equalization characteristic.

According to this configuration, the oscillation frequency of the erasing amplifier is changed to a minimum point of the reproduction equalization characteristic by changing the capacitance of the variable capacitance diode in accordance with the frequency of the erasing frequency component mixed as crosstalk into the reproduction signal. Since the control is performed so as to be in the vicinity, even when the minimum value of the reproduction equalization characteristic deviates from fb / 2, the frequency of the erasing current can be accurately set to the minimum value of the reproduction equalization characteristic. It is possible to easily remove the erasure component in the reproduction circuit system. Actions other than the above are the same as those of the second aspect.

According to a sixth aspect of the present invention, there is provided the magnetic recording / reproducing apparatus according to the first aspect, wherein an input signal of an erasing amplifier whose oscillation frequency is set near a minimum point of the reproduction equalization characteristic is provided by: It is characterized by using a recording clock frequency-divided to a frequency of 1 / k (k is an integer of 1 or more).

According to this configuration, even in the resonance configuration,
The erasure frequency can be accurately set to the minimum point of the reproduction equalization characteristic, and as a result, the erasure component can be easily removed in the reproduction circuit system.

According to a seventh aspect of the present invention, there is provided the magnetic recording / reproducing apparatus according to the sixth aspect, wherein there are n erasing heads and n erasing amplifiers for the n erasing heads. , The phase of the recording clock divided by 1 / k added to the n erase amplifiers is shifted by a fixed amount for each erase head.

According to this configuration, the phases of the erasing signals supplied to the n erasing heads are shifted by a fixed amount, so that the crosstalk components corresponding to the respective erasing heads cancel each other. Crosstalk to the reproduction circuit system can be reduced. Other functions are described in claim 6
Is the same as

According to the magnetic recording / reproducing apparatus of the present invention, when recording / reproducing at a plurality of data rates in the magnetic recording / reproducing apparatus of the sixth or seventh aspect, the oscillation frequency is adjusted according to the data rate. The erasing amplifier set near the minimum point of the equalization characteristic is switched between input and non-input of a recording clock frequency-divided to 1 / k.

According to this configuration, even at the time of low data rate recording, the erasing frequency is maintained near the minimum point of the reproduction equalization characteristic at the highest data rate, that is, outside the band at the low data rate. There is little effect on the system, and there is no need to provide a circuit for removing the erasure component for each data rate. Other functions are the same as those of the sixth or seventh aspect.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

(First Embodiment) FIG. 1 is a block diagram of an erasing circuit in a magnetic recording and reproducing apparatus according to a first embodiment of the present invention. Blocks having the same functions as those of the conventional example shown in FIGS. 7, 8, and 9 are denoted by the same reference numerals. The difference from the conventional example of FIG. 7 is that the oscillation frequency adjusting capacitor (capacitance element) 9 is changed to a variable capacitance diode 37, and a control circuit 101 corresponding thereto is newly provided. 7 is the same as the conventional example. . The control circuit 101 controls the oscillation frequency of the erasing amplifier 8 so as to be near the minimum point (fb / 2) of the reproduction equalization characteristic. More specifically, the control means 101 controls the oscillation frequency of the erasing amplifier 8 to be near the minimum point of the reproduction equalization characteristic by voltage-controlling the capacitance of the variable capacitance diode 37.

The erasing circuit shown in FIG. 1 has an oscillation circuit configuration as in FIG. 7, and the erasing amplifier 8 oscillates by positive feedback by feedback resistors 10 and 11. The oscillation frequency is adjusted to fb / 2 by the variable capacitance diode 37. The erasing signal is sent to the erasing head 7 via the erasing rotary transformer 5.
Is supplied as an erasing current 39.

The control circuit 101 for controlling the variable capacitance diode 37 will be described in detail. A clock having a frequency fb synchronized with the recording data passes through an input terminal 31 and is 1 /
The frequency is input to a frequency dividing circuit 32 that divides the frequency into two. The output clock having the frequency fb / 2 of the frequency divider 32 and the erasure signal 38 are input to the phase comparator 33. Here, the clock having the frequency fb / 2 is a reference input signal of the phase comparison circuit 33. The output of the phase comparison circuit 33 is input to a gain adjustment circuit 35 via a low-pass filter (LPF) 34, and is amplified to a voltage required for controlling the variable capacitance diode 37. As a result, the erasing frequency is phase-compared with the recording clock as the reference signal, so that the erasing frequency is accurately set to fb / 2.

FIG. 2 is a schematic diagram showing the relationship between the erasing oscillation frequency, the signal 36 (the output of the gain adjustment circuit 35, that is, the control voltage of the variable capacitance diode), and the capacitance value of the variable capacitance diode 37.

When the oscillation frequency falls below fb / 2, the phase comparison circuit 33 detects the oscillation frequency, and the signal 36 (reverse voltage applied to the variable capacitance diode) DC (direct current) value increases, the capacitance decreases, and oscillation occurs. Frequency goes up. On the other hand, when the oscillation frequency is f
If b / 2 is exceeded, it is detected by the phase comparison circuit 33 and the signal 36 (reverse voltage applied to the variable capacitance diode) DC
The value decreases, the capacitance increases, and the oscillation frequency decreases.

As described above, in the conventional example, the oscillation frequency fluctuates due to variations in the inductance of the erasing head 7 and the erasing rotary transformer 5, but in this embodiment, the oscillation frequency is always fb by applying feedback. / 2 is maintained. Therefore, in a small-scale and low-power-consumption resonance configuration, the oscillation frequency is fb / 2.
An erasing circuit that is set with high accuracy is realized.

As described above, according to this embodiment,
Since the control means 101 for controlling the oscillation frequency of the erasing amplifier 8 to be in the vicinity of the minimum point of the reproduction equalization characteristic is provided, the variation of the erasing frequency is suppressed even in a resonance configuration advantageous in circuit scale and power consumption. Then, the minimum point (for example, fb / 2) of the reproduction equalization characteristic can be accurately set, and as a result, the erasure component can be easily removed in the reproduction circuit system.

Since the oscillation frequency of the erasing amplifier 8 is controlled by controlling the capacitance of the variable capacitance diode 37 so as to be near the minimum point of the reproduction equalization characteristic, the frequency of the erasing current is adjusted by the voltage. It can be easily controlled.

Further, since the frequency-divided signal of the clock signal is used as a reference signal for phase comparison, no special reference signal source is required and the circuit configuration is simple.

(Second Embodiment) Next, a second embodiment of the magnetic recording / reproducing apparatus of the present invention will be described.
FIG. 3 is a block diagram of the erasing circuit of this embodiment. Blocks having the same functions as those of the conventional example shown in the embodiment of FIG. 1 and FIGS. 7, 8 and 9 are denoted by the same reference numerals.

This embodiment is different from the first embodiment in that two erase heads 7 and 90 operate simultaneously, and correspondingly, an erase amplifier 84 and a feedback resistor 82,
83, the variable capacitance diode 85, the erasing rotary transformer 88, and the control circuit 102, so only the parts added to the first embodiment will be described.

The positional relationship between the two erasing heads 7, 90 is adjacent on the rotating cylinder and operates simultaneously. Therefore, erasing currents of opposite phases flow from two adjacent erasing heads, so that the crosstalk components leaking into the reproducing head cancel each other out.

In FIG. 3, as in the first embodiment, the erasing circuit has an oscillation circuit configuration, and
Is oscillated by positive feedback by the feedback resistors 82 and 83. The oscillation frequency is set to f
It is adjusted to b / 2. The erase signal is supplied to an erase head 90 as an erase current 89 via an erase rotary transformer 88.

The control circuit 102 for controlling the variable capacitance diode 85 will be described. A clock having a frequency fb synchronized with the recording data is input via an input terminal 31 to a frequency dividing circuit 32 that divides the frequency into half the frequency. Dividing circuit 3
The clock having the frequency fb / 2 of 2 is inverted by the inverting circuit 80 and input to the phase comparing circuit 81 together with the erase signal 91. Here, the inverted clock of the frequency fb / 2 is a reference input signal of the phase comparison circuit 81. The output of the phase comparison circuit 81 passes through a low-pass filter 86, is input to a gain adjustment circuit 87, and is amplified to a voltage required for controlling the variable capacitance diode 85. As a result, the erasing frequency is
Since the phases are compared using the recording clock as a reference signal, f
b / 2 is set accurately.

Next, a description will be given focusing on the relationship between the two systems of erase currents.

In FIG. 3, the erasing signals 38 and 91 of the erasing heads 7 and 90 operating at the same time are supplied to the phase comparing circuit 3 respectively.
3,81. As described in the first embodiment, the reference input signal of the phase comparison circuit 33 is obtained by dividing the frequency fb of the clock synchronized with the recording data by half. On the other hand, the reference input signal of the phase comparison circuit 81 is obtained by inverting the reference input signal of the phase comparison circuit 33 by the inversion circuit 80.

Therefore, the erasing current 89 supplied to the erasing head 90 depends on the erasing current 3 supplied to the erasing head 7.
Compared with No. 9, the phase has an inversion relationship. as a result,
Crosstalk from the erasing circuit system to the reproducing circuit system is reduced because the crosstalk components of the erasing heads 7 and 90 cancel each other.

In this embodiment, the number of erase heads operating simultaneously is two. However, even if the number of erase heads is n (n is an integer of 2 or more), the reference input signal of the phase comparison circuit for each erase head is not changed. For example, similar effects can be obtained by setting different phases shifted by the same angle.

(Third Embodiment) Next, a third embodiment of the magnetic recording / reproducing apparatus of the present invention will be described.
This embodiment differs from the first and second embodiments in the method of controlling the variable capacitance diode 37.

In the first and second embodiments, the erasing frequency is fixed at fb / 2. This means that the minimum point (null point) in the reproduction equalization characteristic of PR4 is always fb /
2 is assumed to be fixed.

However, in the case of a reproduction equalization circuit using an analog element, the delay amount may be adjusted while checking the error rate. In this case, the minimum point of the equalization characteristic is fb / 2.
Is not always the case. Therefore, even in such a case, the oscillation frequency of the erasing circuit must be set to a minimum value of the equalization characteristic.

FIG. 4 is a block diagram of the erasing circuit of this embodiment. Blocks having the same functions as those of the conventional example shown in FIGS. 7, 8, and 9 are denoted by the same reference numerals.

The erasing circuit has an oscillating circuit configuration, and the erasing amplifier 8 oscillates by positive feedback by the feedback resistors 10 and 11. The oscillation frequency is adjusted by the variable capacitance diode 37 to the minimum value of the reproduction equalization characteristic. The erasing signal is supplied to the erasing head 7 as an erasing current via the erasing rotary transformer 5.

The control circuit 103 for controlling the variable capacitance diode 37 will be described. At the time of simultaneous reproduction in which reproduction is performed simultaneously with erasure and recording operations, a signal reproduced from the reproduction head 41 is input to the reproduction amplifier 43 via the rotary transformer 42 for reproduction. At this time, crosstalk 50 from the erasing system is mixed in the reproduced signal. The frequency characteristic of the output of the reproduction amplifier 43 is adjusted by the reproduction equalization circuit 44 so as to minimize the error rate, including the delay amount of the delay element. The output of the reproduction equalization circuit 44 is
The signal is supplied to the detection circuit 45 and is converted into a digital signal.

On the other hand, the output of the reproduction equalization circuit 44 is fb
Band-pass filter (BPF) with / 2 as center frequency
46. The band-pass filter 46 extracts an erasure frequency component mixed in the reproduction signal as crosstalk. The output of the band-pass filter 46 is supplied to a frequency detection circuit 47, and a DC value corresponding to the erasing frequency is output. The output of the frequency detection circuit 47 is supplied to a gain adjustment circuit 49 via a low-pass filter 48, and is amplified to a voltage necessary for controlling the variable capacitance diode 37.

The band-pass filter 46 corresponds to an erasing frequency component extracting means for extracting an erasing frequency component mixed as crosstalk into the reproduced signal from the output signal of the reproducing equalizing circuit 44 for processing the reproduced signal. . Further, the frequency detection circuit 47 changes the capacitance of the variable capacitance diode according to the frequency of the erasing frequency component extracted by the erasing frequency component extracting means, so that the oscillation frequency of the erasing amplifier becomes near the minimum point of the reproduction equalization characteristic. Corresponds to a frequency detecting means that performs control as described above.

In this embodiment, the frequency detection circuit 47
Used an FM demodulation circuit. Regarding the characteristics of the band pass filter 46, the center frequency was fb / 2, and the cutoff frequency (-3 dB frequency) was fb / 2 ± 10%. As a result, the minimum value of the reproduction equalization characteristic is fb /
Even in the case of deviation from 2, the minimum value is set with high accuracy.

Here, when the erase frequency component included in the reproduced signal is detected and the voltage of the variable capacitance diode 37 is controlled in accordance with the detected frequency, the erase frequency is reduced and the minimum value of the reproduction equalization characteristic is fb / Even if it deviates from 2,
The reason why the minimum value can be accurately set will be described. That is, when the erase frequency component included in the reproduced signal shifts, a voltage (DC) value is output from the frequency detection circuit (which converts the frequency fluctuation into a voltage by the FM demodulation circuit) 47. When the erase frequency increases, the output voltage increases, and when the erase frequency decreases, the output voltage decreases. Therefore, by controlling the variable capacitance diode 37 with this output voltage, the erasing frequency can be accurately controlled.

As described above, according to this embodiment,
By changing the capacitance of the variable capacitance diode 37 according to the frequency of the erasing frequency component mixed as crosstalk into the reproduced signal, the oscillation frequency of the erasing amplifier 8 is controlled so as to be near the minimum point of the reproducing equalization characteristic. Therefore, even when the minimum value of the reproduction equalization characteristic deviates from fb / 2, the frequency of the erasing current can be accurately set to the minimum value of the reproduction equalization characteristic. Removal of components can be facilitated.

In the first and third embodiments,
Although one erase head is used, the same effect can be obtained with n erase heads (n is an integer of 2 or more). (Fourth Embodiment) Next, a fourth embodiment of the magnetic recording / reproducing apparatus of the present invention will be described. FIG. 5 is a block diagram of the erasing circuit of this embodiment. The same numbers are given to the block diagrams of the same functions as those in FIG.

The components of this embodiment differing from the third embodiment are that the variable capacitance diode and the phase comparison circuit, LPF, and gain adjustment circuit for controlling it are eliminated.
The point is that an oscillation frequency adjusting capacitor having a fixed capacitance is provided instead of the variable capacitance diode, and the switch circuit 204 is provided. Therefore, only the functions different from the third embodiment will be described.

In the present embodiment, reproduction equalization is performed by digital signal processing, and is performed in addition to the normal data rate recording.
It is assumed that data rate recording of 1/4 and data rate recording of 1/4 can be performed.

In FIG. 5, similarly to the third embodiment, the erasing circuit has an oscillation circuit configuration, and erasing amplifiers 8 and 84 are positively fed back by feedback resistors 10 and 11 and feedback resistors 82 and 83, respectively. Oscillate. The oscillation frequency is adjusted to approximately fb / 2 by the oscillation frequency adjusting capacitors 202 and 203.

A clock having a frequency fb synchronized with the recording data is inputted to a frequency dividing circuit 201 which divides the frequency into a half frequency via an input terminal 200. The clock having the frequency fb / 2 of the frequency dividing circuit 201 passes through the switch circuit 204,
The signal is input to the erasing amplifier 8 and to the inverting circuit 80.

The switch circuit 204 selects the output of the frequency dividing circuit 201 during normal data rate recording in accordance with the control signal supplied from the input terminal 205, and selects the recording clock during normal 1/2 data rate recording. When recording at the appropriate 1/4 data rate,
This is a three-state switch circuit that is controlled so as to have no output.

Frequency fb / 2 inverted by inversion circuit 80
Is input to the erase amplifier 84. Erasure amplifiers 8 and 84 whose oscillation frequency is adjusted to approximately fb / 2
Supplies an erasing current having a frequency fb / 2 accurately in response to a clock input having a frequency fb / 2. At this time, the phases of the erasing current 39 supplied to the erasing head 7 and the erasing current 89 supplied to the erasing head 90 are in an inverted relationship. As a result, crosstalk from the erasing circuit system to the reproducing circuit system is reduced because the crosstalk components of the erasing heads 7 and 90 cancel each other.

In this embodiment, two erase heads are operated simultaneously. However, even if the number of erase heads is n (n is an integer of 2 or more), the input clock of each erase amplifier is shifted by the same angle, for example. If different phases are used, a similar effect can be obtained.

As described above, according to this embodiment,
With a simpler circuit configuration, the erasing current can be set at a frequency of fb / 2 and in a specific phase relationship, so that the erasing component can be easily removed in the reproducing system.

In addition to the normal data rate, 1 /
Even in the case of recording at three data rates of 2 and 1/4, at the normal data rate, the erasing frequency which is exactly fb / 2, that is, the minimum point of the reproduction equalization characteristic at the data rate, is set. At the rate, the erase frequency is set to be completely the same as that at the normal data rate, that is, outside the band of the reproduction equalization characteristic. At the 1/4 data rate recording, the erase frequency is substantially the same as at the normal data rate, that is, the reproduction equalization characteristic is Set out of band. At the time of １ ／ data rate recording, since the erasing amplifier has no input, the erasing frequency is the oscillation frequency of the erasing circuit itself, that is, a frequency near fb / 2 at the normal data rate. Thereby, even at the time of low data rate recording, the erasure frequency is maintained near the minimum point of the reproduction equalization characteristic at the time of the normal data rate, that is, outside the band at the time of the low data rate. Further, it is not necessary to provide a circuit for removing the erasure component for each data rate.

In this embodiment, it is possible to correct not only the variation of the value of each element but also the variation of the erase frequency due to the variation due to aging or temperature.

In each of the above embodiments, the frequency dividing circuit halves the frequency, but the frequency dividing ratio of the frequency dividing circuit is not limited to this, and 1 / k (k is an integer of 1 or more) ).

[0076]

According to the magnetic recording / reproducing apparatus of the first aspect of the present invention, since the control means for controlling the oscillation frequency of the erasing amplifier to be near the minimum point of the reproduction equalization characteristic is provided, the circuit scale is increased. Even with a resonance configuration that is advantageous in power consumption,
Variations in the erasing frequency can be suppressed, and the minimum point of the reproduction equalization characteristic can be set with high accuracy. As a result, the erasure component can be easily removed in the reproduction circuit system.

According to the magnetic recording / reproducing apparatus of the second aspect of the present invention, the oscillation frequency of the erasing amplifier is controlled to be near the minimum point of the reproducing equalization characteristic by controlling the capacitance of the variable capacitance diode. Therefore, the frequency of the erase current can be easily adjusted by voltage control. Other effects are the same as those of the first aspect.

According to the magnetic recording / reproducing apparatus of the third aspect of the present invention, since the frequency-divided signal of the clock signal is used as the reference signal for phase comparison, no special reference signal source is required, and the circuit configuration is not required. Easy. Other effects are the same as those of the second aspect.

According to the magnetic recording / reproducing apparatus of the fourth aspect of the present invention, the phase of the frequency-divided signal of the clock signal applied to the n phase comparison circuits is shifted by a fixed amount for each erasing head. Since the crosstalk components corresponding to the head cancel each other, crosstalk from the erasing circuit system to the reproducing circuit system can be reduced. Other effects are the same as those of the third aspect.

According to the magnetic recording / reproducing apparatus according to the fifth aspect of the present invention, the capacitance of the variable capacitance diode is changed according to the frequency of the erasing frequency component mixed as crosstalk into the reproduction signal, thereby enabling the erasing amplifier to operate. Since the oscillation frequency is controlled so as to be near the minimum point of the reproduction equalization characteristic, even when the minimum value of the reproduction equalization characteristic deviates from fb / 2, the frequency of the erasing current is minimized. The value can be set with high accuracy, and the removal of the erasure component in the reproduction circuit system can be facilitated. The effects other than the above are the same as those of the second aspect.

According to the magnetic recording / reproducing apparatus of the sixth aspect of the present invention, the input signal of the erasing amplifier whose oscillation frequency is set near the minimum point of the reproduction equalization characteristic is divided into a frequency of 1 / k ( By using a recording clock (k is an integer of 1 or more), the erasing frequency can be accurately set to the minimum point of the reproduction equalization characteristic even in the resonance configuration. As a result, the erasure component in the reproduction circuit system is obtained. Can be easily removed.

According to the magnetic recording / reproducing apparatus of the present invention, the phase of the recording clock divided into a frequency of 1 / k to be applied to the n erase amplifiers is shifted by a fixed amount for each erase head. As a result, the phases of the erasing signals supplied to the n erasing heads are shifted by a fixed amount, so that the crosstalk components corresponding to the respective erasing heads cancel each other, and the crosstalk from the erasing circuit system to the reproducing circuit system is cancelled. Talk can be reduced. Other effects are the same as those of the sixth aspect.

In the magnetic recording / reproducing apparatus according to the present invention, when recording / reproducing at a plurality of data rates, the erasing amplifier whose oscillation frequency is set in the vicinity of the minimum point of the reproduction equalization characteristic in accordance with the data rate. In addition, by switching between input and non-input of a recording clock frequency-divided to a frequency of 1 / k, even at the time of low data rate recording, the erasing frequency is close to the minimum point of the reproduction equalization characteristic at the highest data rate, that is, Since it is kept out of the band at the time of the low data rate, the influence on the reproduction circuit system is small, and there is no need to provide a circuit for removing the erasure component for each data rate. Other effects are the same as those of the sixth or seventh aspect.

[Brief description of the drawings]

FIG. 1 is a block diagram of an erasing circuit of a magnetic recording and reproducing device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a relationship between an erasing oscillation frequency, a control voltage of a variable capacitance diode 37, and a capacitance value of the variable capacitance diode 37 according to the first embodiment of the present invention.

FIG. 3 is a block diagram of an erasing circuit of a magnetic recording and reproducing apparatus according to a second embodiment of the present invention.

FIG. 4 is a block diagram of an erasing circuit of a magnetic recording / reproducing apparatus according to a third embodiment of the present invention.

FIG. 5 is a block diagram of an erasing circuit of a magnetic recording and reproducing apparatus according to a fourth embodiment of the present invention.

FIG. 6 is a schematic diagram showing a relationship between a PR4 equalization characteristic, a reproducing amplifier band, and an erasing frequency by using a normalized frequency.

FIG. 7 is a block diagram of an erasing circuit of a conventional magnetic recording and reproducing apparatus.

FIG. 8 is a simplified schematic diagram of a block diagram of an erasing circuit of a conventional magnetic recording / reproducing apparatus.

FIG. 9 is a block diagram of another erasing circuit of the conventional magnetic recording and reproducing apparatus.

[Explanation of symbols]

 5,88 Rotary transformer for erasing 7,90 Erasing head 8,84 Erasing amplifier 37,85 Variable capacitance diode 32 Divider 33,81 Phase comparator 34,86,48 Low pass filter 35,49,87 Gain adjusting 41 Head 42 Rotary transformer for reproduction 43 Reproduction amplifier 44 Reproduction equalization circuit 45 Detection circuit 46 Bandpass filter 47 Frequency detection circuit 50 Crosstalk 80 Inversion circuit 101 to 103 Control circuit

Claims (8)

[Claims] An erasing head for erasing a recording data signal on a magnetic recording medium; a recording head for recording a new recording data signal on the magnetic recording medium simultaneously with an erasing operation by the erasing head; A reproducing head for substantially simultaneously reproducing a new recording data signal recorded on the erasing head; an erasing amplifier for supplying an erasing current to the erasing head; and an oscillation frequency adjusting capacitance element provided in the erasing amplifier. A magnetic recording / reproducing apparatus wherein the frequency of an erasing current is determined by oscillating the erasing amplifier at a frequency determined by resonance between an inductance of a path from an amplifier to the erasing head and a capacitance of the oscillation frequency adjusting capacitance element. The oscillation frequency of the erasing amplifier is close to the minimum point of the reproduction equalization characteristic. Magnetic recording and reproducing apparatus characterized in that a control means for controlling the so that. 2. The oscillation frequency adjusting capacitance element is a variable capacitance diode, and the control means controls the voltage of the variable capacitance diode by voltage so that the oscillation frequency of the erasing amplifier becomes near the minimum point of the reproduction equalization characteristic. 2. The control method according to claim 1, wherein
The magnetic recording and reproducing apparatus according to claim 1. 3. The erasure by controlling the phase of a frequency-divided signal of a clock signal synchronized with a recording data signal and the output current of an erasing amplifier, and changing the capacitance of a variable capacitance diode according to the phase comparison result. 3. A phase comparison circuit for controlling an oscillation frequency of an amplifier to be near a minimum point of reproduction equalization characteristics.
The magnetic recording and reproducing apparatus according to claim 1. 4. The number of erase heads is n (n is an integer of 2 or more).
There are n recording heads, reproducing heads, erasing amplifiers, variable capacitance diodes, and phase comparators corresponding to the n erase heads, respectively, and the phase of the frequency-divided signal of the clock signal applied to the n phase comparators 4. The magnetic recording / reproducing apparatus according to claim 3, wherein a predetermined amount is shifted for each erasing head. 5. An erasing frequency component extracting means for extracting an erasing frequency component mixed as crosstalk into the reproduced signal from an output signal of a reproducing equalizing circuit for processing the reproduced signal, the control means comprising: Frequency detecting means for controlling the oscillation frequency of the erasing amplifier to be near the minimum point of the reproduction equalization characteristic by changing the capacitance of the variable capacitance diode according to the frequency of the erasing frequency component extracted by the component extracting means. 3. The magnetic recording / reproducing apparatus according to claim 2, wherein: 6. A recording clock obtained by dividing a frequency of 1 / k (k is an integer of 1 or more) as an input signal of an erasing amplifier whose oscillation frequency is set near a minimum point of reproduction equalization characteristics. 2. The magnetic recording / reproducing apparatus according to claim 1, wherein: 7. There are n erasing heads, n erasing amplifiers for the n erasing heads, and a phase of a recording clock divided by 1 / k to be added to the n erasing amplifiers. 7. The magnetic recording / reproducing apparatus according to claim 6, wherein a predetermined amount is shifted for each of said erasing heads. 8. When recording / reproducing at a plurality of data rates, a recording divided into 1 / k frequency is applied to an erasing amplifier whose oscillation frequency is set in the vicinity of a minimum point of reproduction equalization characteristic according to the data rate. 8. The magnetic recording / reproducing apparatus according to claim 6, wherein input / output of a clock is switched.