JP2726270B2 - Magnetic recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording and reproducing apparatus for recording and reproducing analog signals such as audio signals on a magnetic recording medium such as a magnetic tape. .

[Conventional technology]

2. Description of the Related Art In a conventional magnetic recording / reproducing apparatus, in order to record / reproduce a signal on / from a magnetic recording medium, a wound magnetic head having a coil wound around a magnetic core is often used. Due to its structure, it is difficult to reduce the thickness of this type of magnetic head, and the distance between the heads cannot be reduced. Therefore, for example, in the case of a multi-track tape recorder that records a plurality of independent signals on an arbitrary sub-track among a plurality of tracks provided on a magnetic tape having a predetermined width, the number of recordable tracks is increased. It is difficult to plan.

Therefore, in recent years, a magnetic head using a thin film technology has been used in order to reduce the thickness of a recording / reproducing head. For example, a multi-track induction type thin-film magnetic head as a recording magnetic head and a multi-track thin-film magnetoresistive head as a reproducing magnetic head are used, so that the number of tracks can be greatly increased. Had become.

[Problems to be solved by the invention]

However, in the above-described conventional magnetic recording / reproducing apparatus, in the case of a peritoneal magnetoresistive head used as a reproducing magnetic head, the linearity of the output signal level with respect to the magnetic field strength and the frequency characteristics are not so good, so that AC bias recording When an analog signal is recorded and reproduced by using a method or a pulse width modulation method, there is a problem that a large distortion tends to occur in a reproduced signal.

Therefore, it is conceivable that the signal to be recorded is frequency-modulated for recording. In this case, for example, as shown in FIG. 3, a current always flows through the recording magnetic head at a duty ratio of 1/2. Become. For this reason, power consumption is increased, and the amount of heat generated by the recording magnetic head is increased.

Further, a so-called pulse, which further differentiates the frequency-modulated signal as described above and generates a pulse having a predetermined time width and a cycle according to the level of the signal to be recorded, for example, as shown in FIG. It is also conceivable to perform recording using a train method. However, in this case, the power consumption and the heat generation amount of the recording magnetic head can be reduced by appropriately setting the pulse width. Will occur frequently. Moreover, the time during which no current flows through the recording magnetic head tends to be longer as the degree of modulation is higher.

That is, the average current flowing through the recording magnetic head fluctuates. If the time during which no current flows continuously in the recording magnetic head is long, it is assumed that another signal has been recorded on the recording medium in advance. However, the other signals recorded in advance may remain without being erased, and other signals may be mixed in the newly recorded signals, so that a normal reproduced signal may not be obtained.

[Means for solving the problem]

In order to solve the above-mentioned problems, a magnetic recording / reproducing apparatus according to the present invention includes a frequency modulation unit that outputs a pulse signal having a frequency corresponding to an input analog signal level, and a frequency modulation unit that is cleared when the level of the pulse signal is switched. A recording pulse having a polarity opposite to each other when the pulse signal is at a high level and a low level based on an output of the counting means, and having a predetermined period and a predetermined duty ratio. A recording pulse signal generating means for outputting a signal; a recording magnetic head for recording on a magnetic recording medium based on the recording pulse signal; a reproducing magnetic head for reproducing a signal recorded on the magnetic recording medium; Frequency demodulation means for converting a signal reproduced from a magnetic recording medium by a magnetic head into an analog signal.

(Operation)

According to the above configuration, a pulse signal having a frequency corresponding to the input analog signal level is output from the frequency modulation unit, and a predetermined period is output from the recording pulse signal generation unit.
At a predetermined duty ratio, a recording pulse signal composed of pulses whose polarity is inverted every number corresponding to the level of the analog signal is output. Note that the recording pulse signal can be output based on the output of the counting means that is cleared when the level of the pulse signal switches, so that the recording pulse signal is output from the moment the level of the pulse signal switches. Can be. A current flows through the recording magnetic head in response to the recording pulse signal, and a magnetic field is generated, thereby performing recording on the magnetic recording medium.

The duty ratio of the recording pulse signal can be set relatively arbitrarily. Therefore, it is possible to easily reduce the average current flowing through the recording magnetic head and reduce the power consumption and the calorific value of the recording magnetic head.

Also, the period of the recording pulse signal can be arbitrarily set within a range not to be longer than the period of the signal output from the frequency modulation means. Therefore, the time during which no current continuously flows through the recording magnetic head should not be longer than a certain time, and even if another signal has been recorded on the recording medium in advance, the signal is not recorded beforehand. It is possible to ensure that other signals that have been erased are erased.

Therefore, even when a thin-film magnetoresistive head or the like having poor linearity of the output signal level with respect to the magnetic field strength and frequency characteristics is not so good as the reproducing magnetic head,
Without causing significant distortion in the reproduced signal,
To reduce power consumption and the amount of heat generated by the recording magnetic head, and to reliably prevent other previously recorded signals from remaining without being erased and being mixed in newly recorded signals. Can be.

〔Example〕

As an embodiment of the present invention, an example of a tape recorder for recording and reproducing an audio signal on and from a magnetic tape as a magnetic recording medium will be described with reference to FIGS. 1 and 2. is there.

As shown in FIG. 1, for example, as shown in FIG. 1, only a low frequency component of an input audio signal is applied to a tape recorder 12 which records and reproduces an audio signal which is an analog signal on a magnetic tape 11 which is a magnetic recording medium. A low-pass filter 13 that allows the light to pass is provided. The low-pass filter 13 is connected to an input amplifier 14 that amplifies a signal output from the low-pass filter 13.

The input amplifier 14 is connected to a voltage controlled oscillator 15 whose oscillation frequency changes according to the level of an input signal. The voltage controlled oscillator 15 converts the pulse signal oscillated by the voltage controlled oscillator 15 into a predetermined dividing ratio.
It is connected to a counter 16 that divides by 1 / M. The voltage control oscillator 15 and the counter 16 constitute a frequency modulating means 17 for outputting a pulse signal having a frequency corresponding to the input audio signal level.

The counter 16 of the frequency modulating means 17 is connected to an active low clear terminal of the counter 22 (counting means) and to an active high clear terminal of the counter 23 (counting means). Also,
The crystal oscillator 21 is connected to the clock terminals of the counters 22 and 23.

The counter 22 divides the signal output from the crystal oscillator 21 by a preset division ratio 1 / N only when the pulse signal output from the counter 16 of the frequency modulation unit 17 is at a high level, A pulse signal having a predetermined cycle and a predetermined duty ratio is output. The counter 23 outputs a pulse signal similar to that of the counter 22 only when the pulse signal output from the counter 16 of the frequency modulation means 17 is at a low level.

Counters 22 and 23 are pulse train amplifiers 24
It is connected to the. The pulse train amplifier 24 inverts the signal output from the counter 23 and combines the inverted signal with the signal output from the counter 22 to amplify.

That is, the frequency modulator 17 is controlled by the crystal oscillator 21, the counters 22 and 23, and the pulse train amplifier 24.
The recording pulse signal generating means 25 for outputting a recording pulse signal having a polarity opposite to each other when the frequency-modulated pulse signal is at a high level and a low level and having a predetermined period and a predetermined duty ratio is provided. It is configured.

The pulse train amplifier 24 is a pulse train amplifier 24
Magnetic field is generated by the current output from the
11 is connected to an induction type thin film magnetic head 26 which is a recording magnetic head for performing recording.

On the other hand, a thin-film magnetoresistive head 31 which is a reproducing magnetic head for reproducing a signal recorded on the magnetic tape 11 is connected to a reproducing amplifier 32 for amplifying the reproduced signal. The reproduction amplifier 32 converts the amplified signal into a binary signal composed of a high level and a low level.
It is connected to the.

The comparator 33 is connected to a mono-multi 34 that outputs a pulse signal having a predetermined pulse width in synchronization with the binary signal output from the comparator 33. Mono Multi 34
Is connected to a low-pass filter 35 that outputs a pulse signal output from the mono multi 34 as an audio signal that is an analog signal.

The reproduction amplifier 32, the comparator 33, the mono multi 34,
The low pass filter 35 constitutes a frequency demodulating means 36 for converting a signal reproduced by the thin film magnetoresistive head 31 into an output audio signal.

In the above configuration, for example, as shown in FIG. 2, a signal A whose signal level changes continuously is input to the low-pass filter 13 as an input audio signal,
The following operation is performed when the information is recorded in the.

First, the input audio signal A is supplied to the low-pass filter 13.
After the high frequency component is removed in step (a), the signal is amplified by the input amplifier 14, the level is adjusted, and the signal B is output from the input amplifier 14 to the voltage controlled oscillator 15 as a control voltage.

In the voltage controlled oscillator 15, a pulse signal whose frequency changes in accordance with the level of the signal input from the input amplifier 14 is output, the frequency is divided by the counter 16 into a frequency of 1 / M, and the frequency is adjusted according to the input audio signal level. Frequency pulse signal C
Is output from the counter 16 and input to the counters 22 and 23.

Therefore, when the output signal C of the counter 16 is at a high level, the counter 22 outputs a pulse signal obtained by dividing the signal output from the crystal oscillator 21 to a frequency of 1 / N as the output signal D. When the 16 output signals C are at a low level, a signal that is cleared and maintained at a low level is output.

The counter 23 outputs the output signal E
Conversely, when the output signal C of the counter 16 is at a low level, a pulse signal obtained by dividing the signal output from the crystal oscillator 21 to a frequency of 1 / N is output, while the output signal C of the counter 16 is at a high level. At the time of the level, a signal that is cleared and maintained at the low level is output.

The pulse train amplifier 24 synthesizes and amplifies the output signal D of the counter 22 and a signal obtained by inverting the output signal E of the counter 23, and outputs an output current F to the induction type thin-film magnetic head 26 as a recording pulse signal. , Magnetic tape 11
Record to

On the other hand, when reproducing the signal recorded on the magnetic tape 11 as described above, the following operation is performed.

First, a signal reproduced by the thin-film magnetoresistive head 31 is amplified by a reproduction amplifier 32, and an output signal G is obtained. The output signal G is compared with a reference voltage by the comparator 33. When the signal level is higher than the reference voltage, the output signal G becomes high level, and when the signal level is lower than the reference voltage, the binary signal becomes low level. , Output signal H from the comparator 33.

The mono multi 34 outputs a pulse signal having a predetermined pulse width, which rises in synchronization with the output signal of the comparator 33 changing from a low level to a high level, as an output signal I. The output audio signal J is reproduced by passing only the low frequency component of the output signal I of the mono multi 34 through the low pass filter 35.

Thus, the audio signal, which is an analog signal,
Since it is recorded and reproduced as a pulse signal, regardless of the linearity and frequency characteristics of the thin film magnetoresistive head, etc.
Distortion in the reproduced analog signal can be reliably reduced.

By the way, the power consumption when performing recording on the magnetic tape 11 as described above, and the heat generation amount of the induction type thin-film magnetic head 26 are mainly determined by the duty ratio of the pulse signals output from the counters 22 and 23, This duty ratio can be set relatively arbitrarily.

The time during which no current flows continuously through the induction type thin-film magnetic head 26 is determined by the cycle of the pulse signal output from the counters 22 and 23. This cycle is also determined by the cycle of the modulation signal output from the counter 16. Can be set arbitrarily as long as it does not become long.

Therefore, power consumption and the amount of heat generated by the recording magnetic head can be easily reduced, and even if other signals have been recorded on the magnetic tape in advance, the other signals previously recorded are It can be surely erased.

Therefore, for example, the recording and reproduction of high-quality analog signals are performed using a thin-film magnetoresistive head or the like, which is not very good in the linearity of the output signal level with respect to the magnetic field strength and the frequency characteristics are not so good. So you can
A multi-track tape recorder in which the number of sub-tracks on which signals can be independently recorded on a magnetic tape is greatly increased can be easily configured.

〔The invention's effect〕

As described above, the magnetic recording / reproducing apparatus according to the present invention includes the frequency modulation unit that outputs a pulse signal having a frequency corresponding to the input analog signal level, and the counting unit that is cleared when the level of the pulse signal is switched. Prepared,
A recording pulse for outputting a recording pulse signal having a polarity opposite to each other when the pulse signal is at a high level and a low level based on an output of the counting means, and having a predetermined period and a predetermined duty ratio. Signal generating means;
A recording magnetic head for performing recording on a magnetic recording medium based on the recording pulse signal, a reproducing magnetic head for reproducing a signal recorded on the magnetic recording medium, and a signal reproduced from the magnetic recording medium by the reproducing magnetic head And a frequency demodulating means for converting the signal into an analog signal.

As a result, a pulse signal having a frequency corresponding to the input analog signal level is output from the frequency modulation means, and the recording pulse signal generation means changes the analog signal level at a predetermined cycle and a predetermined duty ratio. A recording pulse signal composed of pulses whose polarity is inverted at every corresponding number is output. Note that the recording pulse signal can be output based on the output of the counting means that is cleared when the level of the pulse signal switches, so that the recording pulse signal is output from the moment the level of the pulse signal switches. This has the effect that it can be performed. Further, even when a thin-film magnetoresistive effect type head having poor linearity of the output signal level with respect to the magnetic field strength and frequency characteristics is not so good as the reproducing magnetic head, for example, the reproduced signal does not cause a large distortion, Recording and reproduction of high quality analog signals can be performed. In addition, by appropriately setting the duty ratio and period of the recording pulse signal, the average current flowing through the recording magnetic head is reduced, thereby reducing power consumption and the amount of heat generated by the recording magnetic head. The time during which no current continuously flows through the magnetic head should not be longer than a certain time, and even if another signal has been recorded on the recording medium in advance, the other signal that was previously recorded Can be surely erased.

[Brief description of the drawings]

FIGS. 1 and 2 show an embodiment of the present invention. FIG. 1 is a block diagram showing a configuration of a tape recorder, and FIG. 2 is a time chart showing signals in respective parts of the tape recorder. . FIGS. 3 and 4 show a conventional example, and are time charts showing the state of a current flowing through a recording magnetic head in a conventional magnetic recording / reproducing apparatus. 11 is a magnetic tape (magnetic recording medium), 12 is a tape recorder (magnetic recording / reproducing device), 17 is a frequency modulating means, 25 is a recording pulse signal generating means, 26 is an induction type thin film magnetic head, 31 is a thin film magnetoresistive effect type The head 36 is frequency demodulation means.

Claims (1)

(57) [Claims] 1. A frequency modulation means for outputting a pulse signal having a frequency corresponding to an input analog signal level; and a count means for clearing when the level of the pulse signal is switched, based on an output of the count means. Recording pulse signal generating means for outputting a recording pulse signal having a polarity opposite to each other when the pulse signal is at a high level and a low level and having a predetermined period and a predetermined duty ratio; A recording magnetic head for recording on a magnetic recording medium based on a signal; a reproducing magnetic head for reproducing a signal recorded on the magnetic recording medium; and an analog signal for reproducing a signal reproduced from the magnetic recording medium by the reproducing magnetic head. And a frequency demodulating means for converting the data into a signal.