JP2000306206A - Magnetic recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To record at a different speed by a simple circuit structure and a simple control operation. SOLUTION: A load impedance frequency characteristic of a recording current amplifier is set so as to amplify the amplitude of the current through a head 1 during the reversal of the current direction. An adjustment of a value is set by changing a resistor R so as to realize a suitable multiplication factor for a case of recording at a maximum speed. At the time of recording at a lower speed than the maximum speed, a current source 2 controls for a specific period a current amount to drive the described recording head during the reversal of the current direction. Consequently compatibility in reproducing of data recorded is maintained even for cases of having recorded at a plurality of speeds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording apparatus, and more particularly to a magnetic recording apparatus that performs magnetic recording at a plurality of speeds.

[0002]

2. Description of the Related Art Some tape recorders can perform magnetic recording on a tape at a plurality of speeds. Such a tape recorder requires some contrivance when recording at a higher speed than a normal speed. That is, when magnetic recording is performed at a high speed, the frequency of data to be recorded inevitably increases. However, the recording head has a drop in high-frequency characteristics in electromagnetic conversion. Therefore, when the frequency of the data to be recorded increases, the same recording as the low-frequency signal cannot be recorded during the high-frequency recording if the same current amplitude value as that of the low-frequency signal is used. This means
This is a well-known fact. Here, the term “the same” means “a medium that remains when data of exactly the same content as logic is recorded at a high transfer speed (clock frequency)” and a medium that remains when the transfer speed is low. When a medium and the same reproducing apparatus are reproduced at a certain constant speed, they can be reproduced with a similar degree of error. "

Therefore, in a conventional magnetic recording apparatus, in recording at the time of high-speed recording, only the current amplitude immediately after the current direction of the recording current is reversed (hereinafter, referred to as an edge) is emphasized. In a magnetic recording apparatus in which only one recording speed can be set, the overall frequency characteristics of the recording current circuit may be set so that appropriate edge enhancement is performed. However, in a magnetic recording apparatus capable of setting a plurality of recording speeds, the degree of emphasis must be changed according to each speed. There are two ways to do this.

The first method is a method in which an appropriate edge enhancement is applied to a signal using an analog filter for high-frequency enhancement according to each speed, and then a recording current is driven by a linear amplifier. In this case, regardless of the load characteristics of the recording amplifier, the signal component itself at the time of low-speed recording is pre-
It is limited by F (Low) Pass Filter. As a result, edge enhancement required only at high speed can be suppressed.

[0005] A second method is to switch a constant current from a current source to a recording current amplifier having a load impedance characteristic such that the frequency characteristic becomes flat over a band required at the maximum speed recording. This is a method of obtaining the recording current of FIG. In this case, 1 immediately after the edge portion
By increasing the current value for driving the head current over the period, the edge of the recording current is emphasized. Here, if an increasing current value is set for each speed, a plurality of speeds can be handled.

[0006]

However, in the case of the first conventional method, the power consumption is large because the amplifier is linear. Further, there is a problem that an analog circuit is required for each recording speed, and the circuit scale becomes large.

In the case of the conventional second method, a high-speed operation (edge emphasis portion) is required for the current source of the recording current at the time of the maximum speed recording, and a stable operation is to be ensured. There has been a problem that adjustment during manufacture becomes severe.

As described above, in the magnetic recording apparatus capable of setting a plurality of recording speeds, the apparatus is inevitably complicated and strictly adjusted. The present invention has been made in view of such a point, and an object of the present invention is to provide a magnetic recording apparatus that can perform recording at different speeds with a simple circuit configuration and a simple adjustment operation.

[0009]

According to the present invention, there is provided a magnetic recording apparatus capable of performing magnetic recording at a plurality of speeds, comprising: a recording head for magnetically recording information; The load impedance frequency characteristic is set so that the amplitude of the current flowing through the recording head is amplified when the current direction is reversed, and when recording is performed at a speed lower than the maximum speed, the current is driven to the recording head when the current direction is reversed. And a recording current amplifier for suppressing the amount of current for performing the operation for a predetermined time.

According to such a magnetic recording apparatus, at the time of high-speed recording, amplitude amplification is performed at the time of reversal of the current direction, thereby performing magnetic recording in which the effect of the drop in high-frequency characteristics in electromagnetic conversion is offset. When printing is performed at a speed lower than the maximum speed, the drive current to the print head is suppressed for a fixed time, and the same head current as in the case where there is no amplitude amplification is obtained.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment of the present invention will be described.

FIG. 1 is a diagram showing a configuration of a recording current amplifier in a magnetic recording apparatus according to the present invention. In this recording current amplifier, the direction of the current flowing to the head 1 is controlled by two transistors Q1 and Q2. Transistor Q
An NRZ (Non Return to Zero) signal is supplied to the bases of 1 and Q2. The respective collectors of the transistors Q1 and Q2 are connected to both ends on the primary side of the rotary transformer 3. Further, the emitters of the transistors Q1 and Q2 are both input to the current source 2. The output side of the current source 2 is grounded.

A resistor R is connected to the primary side of the rotary transformer 3 in parallel with both terminals. A DC power supply V is connected to the intermediate tap. The power supply V has a positive terminal connected to the rotary transformer 3 and a negative terminal grounded. A head 1 for performing magnetic recording is connected to the secondary side of the rotary transformer 3.

Here, the load impedance frequency characteristic of the recording amplifier is set so that the amplitude of the current flowing through the head 1 at the time of reversing the current direction is amplified when recording is performed at the maximum speed. The adjustment of the value is performed by changing the resistor R. Further, the current source 2 is composed of two current sources.

FIG. 2 is a diagram showing the configuration of the current source. Thus, the current amount of the recording current amplifier is controlled by the two current sources J1 and J2. During high-speed recording, both current sources J1 and J2 flow current. On the other hand, at the time of low-speed recording, the current source J1 always supplies current, but the current source J2 is turned off for a certain period from the time of signal inversion. In other time zones, the current source J2 also supplies current.

In a magnetic recording apparatus having a recording current amplifier having such a configuration, a differential NRZ signal corresponding to data to be magnetically recorded is input to the bases of the transistors Q1 and Q2. That is, when the signal level supplied to the transistor Q1 is high (H), the signal level supplied to the transistor Q2 is low (L).
When the signal level supplied to the transistor Q1 is low (L), the signal level supplied to the transistor Q2 is high (H). The potential difference between H and L of the NRZ signal is set so that the transistor having the higher base potential of the transistors Q1 and Q2 is turned on. As a result, when one transistor is turned on, the potential difference between the base and the emitter of the other transistor is not turned on but turned off.

When one of the transistors is turned on, a current supplied at a direct current (DC) potential of the power supply V flows into the collector of the turned on transistor via the intermediate tap of the rotary transformer 3. Then, the current flows from the emitter of the corresponding transistor to the ground through the current source 2. When another transistor is turned on, current flows through the turned on transistor. Thereby, the direction of the current flowing to the primary side of the rotary transformer 3 changes according to the NRZ signal. When the direction of the current flowing to the primary side of the rotary transformer 3 changes, the direction of the current on the secondary side of the rotary transformer 3 is reversed accordingly. By supplying the current to the head 1,
Lines of magnetic force are emitted from the head 1 and magnetic recording is performed.

At this time, when the current supplied to the head 1 is inverted, edge emphasis is obtained. This is realized by appropriately adjusting the resistor R. FIG. 3 is a diagram showing a change in current supplied to the head during high-speed recording.
In this figure, the horizontal axis indicates the passage of time, and the vertical axis indicates the current value flowing through the head. As shown in the figure, when the direction of the current is reversed, the edge is emphasized. In this example, the amplitude is emphasized for a time 1T (half of one cycle of the clock frequency of the NRZ signal) corresponding to the signal output time at the maximum speed.

If the load on the recording current amplifier is adjusted so that such emphasis is performed, the emphasis is not changed until the speed is somewhat lower than the maximum speed (1/2 to 1/4 of the maximum speed). Even if it is kept, compatibility at the time of reproduction can be obtained. Note that the compatibility at the time of reproduction indicates that reproduction can be correctly performed by one reproduction system (conditions such as a degree of error guarantee are constant).

Here, how the amplitude emphasis changes depending on the difference between the resistors R will be described. FIG. 4 is a diagram showing a change in head current due to a difference in resistance value. In this figure, the horizontal axis represents frequency, and the vertical axis represents head current. The solid line 11 in the figure shows the characteristics when the resistance value is large. The dashed line 12 shows the characteristic when the resistance value is medium. Dotted line 13 shows the characteristics when the resistance value is small.

When the resistance value of the resistor R is large, a large head current flows. The maximum value is obtained when the resonance frequency is low and when the resonance frequency is high. As the resistance value of the resistor R decreases, the head current is damped accordingly. That is, when the resistor R is reduced, the efficiency is deteriorated in the sense that the current of the current source flows to the head, but the frequency characteristic becomes flat.

The difference in the degree of edge emphasis due to the difference in frequency characteristics is shown below. FIG. 5 is a diagram illustrating frequency characteristics when the resistance value of the resistor R is small. In this figure, the horizontal axis represents frequency, and the vertical axis represents head current. Point A in the figure is the highest repetition frequency, and its cycle is 1T. Point B is half the maximum repetition frequency, and its period is 2T. In this figure, a flat frequency characteristic is obtained up to the vicinity of the point A because the resistance value is small. Thus, a similar head current can be obtained for a pattern excluding a low-frequency signal of the NRZ signal that does not pass through the rotary transformer 3. Note that the resistance value of the resistor R capable of obtaining such characteristics varies depending on the actual values of the transformer, the head, and the switching circuit.

The case where the resistance value of the resistor R is slightly increased will be described below. FIG. 6 is a diagram illustrating frequency characteristics when the resistance value of the resistor R is slightly large. In this figure, the horizontal axis represents frequency, and the vertical axis represents head current. When the resistance value of the resistor R increases, a larger amplitude can be obtained at the frequencies of the points A and B than in the low frequency range.

FIG. 7 is a diagram showing a difference in amplitude due to a difference in resistance value of the resistor R. This indicates the current flowing to the head when the NRZ signal pseudo random pattern is input. In this figure, the horizontal axis represents frequency, and the vertical axis represents head current. A broken line drawn in the horizontal direction in the drawing indicates a head current generated when a steady current flows in the recording current amplifier. The dotted line 21 shows a waveform when the resistance value is small, and the broken line 22 shows a waveform when the resistance value is slightly increased. As can be seen from the figure, when the resistance value is small, edge enhancement hardly occurs.
On the other hand, the amplitude is increased by increasing the resistance value.

As described above, since the amplitude characteristics of the 1T and 2T frequency parts are large, the NRZ signal “L →
In the inverted portion of “H” or “H → L”, the amplitude always increases over a period of 1T.

In order to emphasize the edge by resonance, it seems that the resistor R should be set to the maximum value (for example, infinity). However, if the resistance of the resistor R is too large, the amplification factor due to resonance increases, but the phase of the signal shifts. If the zero point is not periodic due to the phase shift, it causes intersymbol interference. Therefore, the limit of the amplitude emphasis at the time of pattern inversion in this method is to a point where the phase shift is negligibly small. Up to that point, the amount of amplitude enhancement at the time of pattern inversion has a degree of freedom. That is, the resistance value of the resistor R may be increased to increase the enhancement amount, and the resistance value of the resistor R may be decreased to decrease the enhancement amount.

By performing such edge emphasis, high reliability of data writing at the maximum speed can be maintained. Here, when the recording speed is reduced, compatibility up to a certain speed can be maintained during reproduction by the same recording method as at the maximum speed. However, when recording at a slower speed, the compatibility at the time of reproduction cannot be maintained as it is.

That is, at the time of low-speed recording, there is a sufficient frequency band. In other words, even when a signal of a short wavelength is recorded, the frequency is low if recording is performed at a low speed. In that case,
A desired signal can be reliably recorded without performing edge enhancement. On the other hand, in a reproducing system for reproducing information recorded at high speed, equalization is performed to ensure that short-wavelength recording is incomplete during high-speed recording. Therefore, in a reproduction system corresponding to high-speed recording, if short-wavelength components are firmly recorded, over-guaranteeing may occur, which may worsen the error rate. Therefore, in order to reliably read both data recorded at a high speed and data recorded at a low speed with one playback system,
Edge emphasis must be suppressed during low-speed recording.

Therefore, at the time of low-speed recording, the two current sources J1 and J2 constituting the current source 2 of the recording current amplifier are controlled to temporarily cut off the current supplied by the current source J2 when the signal is inverted. , Suppresses emphasis on edges.

FIG. 8 is a diagram showing changes in various signals at the time of low-speed recording in the first embodiment. In this figure, the change of each signal of the data pattern, the current source current, and the head current is shown in order from the top. The current source current is the current source J
The state where the current flows through both 1 and the current source J2 is the maximum value. The current source J1 always supplies a current, but the current source J2 interrupts the current when the data pattern is switched. After a lapse of 1T, a current is supplied.

As a result, when the pattern of the head current is inverted, edge enhancement occurs for a time corresponding to 1T at the maximum speed,
Thereafter, edge enhancement occurs due to an increase in current of the current source J2 for a time corresponding to 1T at the maximum speed. After that, the signal becomes flat.

The amount of edge enhancement at the time of signal inversion or at the time when a current is supplied to the current source J2 depends on the current source J1,
Adjust by choosing J2 appropriately. If the amplitude emphasis determined by the setting of the resistance value of the resistor R is a times as large as the original signal, then for 1T immediately after the pattern inversion, J1 (1
+ A) times the amplitude is obtained. Then, an amplitude of (1 + a) times J2 is obtained for the next 1T.

Here, when J1 = J2 when the amplitude enhancement of 0.5 times is obtained by setting R, the amplitude at the time of signal inversion becomes too weak. FIG. 9 is a diagram illustrating changes in various signals when the amplitude at the time of signal inversion is too weak. In this figure, the change of each signal of the data pattern, the current source current, and the head current is shown in order from the top. As shown in the figure, if “current source J1 = current source J2” is set when the amplitude emphasis at the time of signal inversion is 0.5 times, the head current during 1T immediately after the data pattern inversion becomes “current source J1 + 0.7 in a state where a current of the current source J2 "is supplied and a flat signal is obtained.
It becomes 5 times. In this case, the amplitude is reduced, and the reliability at the time of magnetic writing cannot be maintained.

In this case, "current source J1: current source J2 =
By setting “2: 1”, 1T immediately after inversion becomes flat (no enhancement). Therefore, amplitude emphasis can be enhanced by setting the current source J1 to be at least twice the current source J2.

The appropriate degree of emphasis over 1T immediately after the reversal of the recording current largely depends on the magnetic permeability and frequency characteristics of the recording head. In addition, it is affected by the relative speed of the tape / head, the shape of the drum / head, the amount of spacing caused by the tape path, and the tape material. Therefore, it is difficult to always quantitatively determine an appropriate amount of amplitude emphasis for guaranteeing compatibility of different speed recording.

However, various factors that affect the degree of emphasis impede the degree of recording immediately after reversal. Therefore, generally, by using the above method, an appropriate amplitude emphasis amount can be guaranteed. In addition, any of the above causes has a greater effect as the recording frequency is higher. Therefore, as described above, the emphasis that exceeds the emphasis at the highest speed is set to be the most emphasized, and at the time of low-speed recording that does not require amplitude emphasis, the emphasis is reduced to sufficiently reduce the emphasis at the time of low-speed recording. Guarantee is possible.

Next, a second embodiment will be described. In the second embodiment, the current source current increases and decreases smoothly at the time of pattern inversion during low-speed recording. The configuration of the second embodiment is similar to that of FIGS.
Is the same as that of the first embodiment shown in FIG.

It is an object of the present invention to leave the same recording state on the tape at both high-speed recording and low-speed recording. Normally, in high-speed recording, it is difficult to leave short-wavelength components on a tape due to a drop in frequency characteristics of circuits and devices. For example, as in the first embodiment, setting the resistance of the resistor R of FIG. 1 to a small value and performing emphasis is one means for reliably recording short wavelength components. However, the method described in the first embodiment is not always perfect. In other words,
This may lead to inappropriate amplitude emphasis as shown in FIG.

Therefore, in the second embodiment, the current suppression at the time of the reversal of the current direction in the low-speed recording is made to be a ramp shape (smooth change), so that the setting of the resistor R in FIG. , The rising of the inversion current flowing through the head is made gentle.

FIG. 10 is a diagram showing changes in various signals at the time of signal inversion according to the second embodiment. In this figure,
The change of each signal of a data pattern, a current source current, and a head current is shown from the top. As described above, in the second embodiment, the increase and decrease at the time of turning on and off the current of the current source J2 are performed smoothly. As a result, the edge emphasis of the head current at the time of signal inversion is suppressed low, and a more appropriate head current can be obtained.

Here, a change in a signal when the second embodiment is used (FIG. 10) and an inappropriate edge loss (FIG. 9) according to the first embodiment are compared. Then, when the current is set in a step-like manner, a large step is generated as compared with the case where the current is set in a ramp-like manner. As a result, the state of only the current of the current source J1 is changed to “current source J1 + current source J
At the time of shifting to the current of “2”, the amplitude emphasis appears greatly.

On the other hand, if the current changes like a ramp as in the second embodiment, the current amount becomes “current source J1 + current source J”.
In the case of "2", the amount of emphasis can be reduced. Also, the amount of emphasis at the time of current reversal is not steep as compared with the case of the first embodiment.

As described above, the circuit operation of high-speed recording that requires accurate high-speed operation is simple, and the edge enhancement set at high speed can be reduced during low-speed recording where looseness is sufficient for edge enhancement. By performing the circuit operation, a magnetic recording device capable of recording at a plurality of speeds can be configured. Moreover, there is no need to perform strict timing adjustment.

[0044]

As described above, according to the present invention, when the load impedance is set so that the amplitude is amplified at the time of reversing the current direction, and the recording is performed at a speed lower than the maximum speed,
The drive current to the recording head is suppressed for a certain period of time from the time of signal inversion, so that recording at multiple speeds with compatibility during reproduction is performed with a simple circuit configuration, and strict timing adjustment is not required. It became possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a recording current amplifier in a magnetic recording device of the present invention.

FIG. 2 is a diagram showing a configuration of a current source.

FIG. 3 is a diagram illustrating a change in current supplied to a head during high-speed recording.

FIG. 4 is a diagram illustrating a change in head current due to a difference in resistance value.

FIG. 5 is a diagram showing frequency characteristics when the resistance value of the resistor is small.

FIG. 6 is a diagram illustrating frequency characteristics when the resistance value of the resistor is slightly large.

FIG. 7 is a diagram illustrating a difference in amplitude due to a difference in resistance value of a resistor.

FIG. 8 is a diagram illustrating changes in various signals during low-speed recording according to the first embodiment.

FIG. 9 is a diagram showing changes in various signals when the amplitude at the time of signal inversion is too weak.

FIG. 10 is a diagram illustrating changes in various signals during signal inversion according to the second embodiment.

[Explanation of symbols]

1: Head, 2: Current source, 3: Rotary transformer, Q
1, Q2: transistor, R: resistor, V: power supply

Claims (2)

[Claims] 1. A magnetic recording apparatus capable of performing magnetic recording at a plurality of speeds, a recording head for magnetically recording information, and an amplitude of a current flowing through the recording head being amplified when the current direction is reversed. If the load impedance frequency characteristic is set as follows and recording is performed at a speed lower than the maximum speed,
A magnetic recording apparatus, comprising: a recording current amplifier for suppressing a current amount for driving a current to the recording head during a reversal of a current direction for a predetermined time. 2. The recording current amplifier according to claim 1, wherein when recording is performed at a speed lower than a maximum speed, the amount of current required to supply a current to the recording head during a reversal in the current direction is suppressed for a predetermined time. 2. The magnetic recording apparatus according to claim 1, wherein the magnetic recording medium is smoothly changed.