JPS5913084B2 - Magnetic recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention divides an original signal with a certain frequency bandwidth into a plurality of narrowband signals by time division, and records each narrowband signal in each channel using a respective magnetic head. This paper relates to a multi-channel magnetic recording system.

Conventionally, in order to reduce the relative movement speed between a magnetic recording medium and a magnetic head when recording a signal with a certain frequency band width, the signal is decomposed into multiple channels by time division. A multi-channel recording method in which the frequency band width of a recording signal is narrowed is known.

FIG. 1 is a block diagram showing an apparatus used in such a conventional multi-channel magnetic recording system, and shows an example in which an original signal is divided into two and recorded in two channels.

In the figure, 1 is the first channel, 2 is the second channel, c is the clock dedicated channel, 3 is the demultiplexer, 4 is the clock generator, 5 is the bias oscillator, 61 and 62 are the first and second channels, respectively. 1,
The level hold circuits Aw, . . . , Aw 2 and Awc are the recording amplifiers for the first and second clock dedicated channels 1, 2 and C, respectively, and H 1 , H 2 and Hc are the recording head 10 as well. The demultiplexer 3 is configured to receive the original signal and the clock signal output from the clock generator 4 and to divide the original signal into two by time division. According to the sampling theorem, the period Ts of the clock signal during time division is Ts - T/n with respect to the period T of the original signal No. 15.
It is known that if n>2, the original signal waveform can be restored. The divided signals are outputted to the respective level hold circuits 61 or 62 via the transmission line of the first channel 1 or the transmission line of the second channel 2, respectively, and the clock signal is also outputted from the divided signal at the time of reproduction. It is necessary to record it in order to synthesize it, and it is output to the transmission path of the clock dedicated channel C. The divided signals output from the respective level hold circuits 61 and 62 become narrowband signals, but especially in the case of low frequencies, it is necessary to apply a high frequency bias when recording them. In other words, in magnetic recording, reading is performed based on the amount of change in magnetic flux per unit time, so there is a difference in readout output depending on the frequency.
In particular, it is difficult to read out low-frequency, low-level 30-level recording as it is, and even if you increase the gain of the playback amplifier by reducing it, the S/N cannot be maintained, so it is necessary to secure the recording level by applying a small amount of high-frequency bias. There is.

In this case, the frequency of the bias signal is generally higher than twice the frequency of the divided signal, in order to prevent distortion from occurring in the low-frequency signal and to avoid audible frequencies. The period of the signal is ET, and the period of the bias signal TB=IT/m
(However, l≧2, m>2). The bias signal selected in this manner is applied from the bias oscillator 5 to the first and second clock channels 1, 2, and C, and is combined with the signals of the respective channels to drive the respective recording amplifiers AWl, AW2, and AwO. The signals are applied to the respective recording heads H, , H2, Hc via the magnetic recording medium and recorded in respective channels formed on a magnetic recording medium (not shown).

Therefore, in the conventional multi-channel recording system as described above, a device having a dedicated clock channel C and a bias oscillator 5 is required.

In the recording system as described above, the present invention provides that the period TS of the clock signal is in a range smaller than 1/2 of the original signal period T, and the bias signal period TB is in the range of the original signal period T(7)l/
Since the range is smaller than 2, the period T of the clock signal
This was done by focusing on the fact that the allowable range of s is always included in the allowable range of the bias signal period TB, and by sharing the clock signal and the bias signal, the clock dedicated channel C and It is an object of the present invention to provide an improved magnetic recording method that does not require a bias oscillator 5.

FIG. 2 is a block diagram showing an example of a device for dividing an original signal into two and recording it, which is used in the magnetic recording method of the present invention.
The same reference numerals as in FIG. 1 indicate the same parts.

The device has a first channel 1 and a second channel 2, and includes a demultiplexer 3, a clock generator 4, and level hold circuits 61 and 62 belonging to each channel.
, recording amplifiers AW1, AW2, and recording heads H, , H2, and does not have a dedicated clock channel or a bias oscillator. The demultiplexer 3 is configured to have a low impedance when selected by the single-phase clock signal output from the clock generator 4, and a high impedance when not selected.

The clock signal may be either a single-phase clock or a multi-phase clock corresponding to the number of channels, as long as its period Ts is smaller than 1/2 of the original signal period T. Therefore, when an original signal with a certain frequency band width is input to the demultiplexer 3, the demultiplexer 3 time-divides the original signal into two signals, and divides the two divided signals into two signals. The signal is output to the level hold circuits 61 and 62 of the channel.

The level hold circuits 61 and 62 are operational amplifiers ASl and A
S2 and capacitors Cl and C2 connected to the high input resistance side (non-inverting output side) of the operational amplifiers ASl and AS2, and when the demultiplexer 3 is at high impedance, the signals of channels 1 and 2 are divided. maintain the level. The signals output from the level hold circuits 61 and 62 are narrowband signals with respect to the original signal, and if the signal is a low frequency signal, it is a signal with a frequency higher than twice the signal frequency, that is, the original signal period T (7) It is necessary to record by applying a high frequency bias using a signal with a period smaller than 1/2, but since the clock signal period Ts mentioned above is set smaller than 1/2 of the original signal period T, the clock signal By combining, it is possible to achieve the same effect as applying a high frequency bias. Therefore, the level hold circuit 61
, 62 are combined with the clock signal and sent to the recording amplifier AW.
is input to the recording heads Hl and H2 via Hl and AW2,
A signal combined with the clock signal is recorded on a magnetic recording medium (not shown).

Next, a method for reproducing the original signal recorded as described above will be explained.

FIG. 3 is a block diagram showing an example of an apparatus for reproducing signals recorded by the magnetic recording method of the present invention. In the figure, Hll and Hl2 are the first channel 1 and the second channel, respectively.
In the reproduction head of channel 2, 71 and 72 are low-pass filters, 81 and 82 are reproduction amplifiers, 9 is a band-pass filter, and 10 is a multiplexer. The output of each playback head Hll and Hl2 is passed through a low-pass filter 7, respectively.
However, since the output of the reproduction heads H, , H, 2 is a composite signal of a high frequency clock signal and a narrow band low frequency signal, only the low frequency signal component of the signal components is low-pass. After passing through filters 71 and 72, the reproducing amplifier 8
1 and 82 to the multiplexer 10. On the other hand, the output of the reproduction head H12 (or Hll) is connected to the multiplexer 10 via a bandpass filter 9, and if the bandpass filter 9 is set to pass only the frequency band of the clock signal, The clock signal is also separated and input to multiplexer 10.
The multiplexer 10 converts the two narrowband low frequency signals inputted from the first and second channels 1 and 2 into two narrowband low frequency signals in synchronization with the clock signal extracted by the bandpass filter 9. It is possible to convert into a temporally serial signal and output a reproduced signal that approximates the original signal and has a certain frequency bandwidth.

As described above, according to the magnetic recording method of the present invention, by sharing the clock signal for time division and the bias signal for high frequency bias, it is possible to eliminate the need for a dedicated tarot channel or a bias oscillator. , it becomes possible to effectively use all channels, and a broadband magnetic recording device with a simple structure can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an apparatus used in a conventional multi-channel magnetic recording system. FIG. 2 is a block diagram showing an example of a device used in the magnetic recording system of the present invention, and FIG. 3 is a block diagram showing an example of a device for reproducing the same. 1...First channel, 2...Second channel, 3...
... Demultiplexer, 4 ... Clock generator, 5 ... Bias oscillator, Hl
, H2, Hc... Recording head.

Claims (1)

[Claims] 1 In a multi-channel magnetic recording method in which an original signal with a certain frequency band width is time-divided using a clock signal to obtain a plurality of narrowband signals, and each narrowband signal is recorded in each channel by a respective magnetic head. . A magnetic recording method, characterized in that the period of the clock signal is selected to be smaller than 1/2 of the original signal period, and the clock signal and each of the narrowband signals are combined and recorded.