JPH01224978A - Device for recording digital signal - Google Patents

Abstract

PURPOSE:To enable a stable data discrimination at reproducing time by recording the data subjected to digital modulation by its AM modulation with a reference clock signal as a carrier and executing multiple recording on the AM modulation signal by converting the reference clock signal into the signal of the outside of the band of the AM modulation signal. CONSTITUTION:The PCM data subjected to a digital modulation by a digital modulation circuit 2 is subjected to an AM modulation 4 with the reference clock signal CK of digital modulation as the carrier and recorded as the signal occupying a specified frequency band. Also the signal SC in the frequency of (n) time or 1/n time the reference clock signal CK is subjected to frequency multiple recording by an adder circuit 6 at the outside of the band of an AM modulation signal SAM. An add output signal is the fed to a recording magnetic head 8 through a recording amplifier 7 and recorded on a magnetic tape T. A stable data discrimination can thus be done by using the reproduced reference clock signal CK at reproducing time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording device for recording, for example, PCM data on a tape.

[Summary of the invention]

This invention performs digital modulation such as NRZI or MFM on PCM data, and then uses the reference clock signal used in this digital modulation as a carrier to convert the digitally modulated PCM data into
CM data is converted to AM and recorded, and the standard clock signal is converted to a signal outside the AM converted open wave band.
This is a system in which multiple signals are recorded on the modulated signal, and the feature is that during reproduction, stable data discrimination is possible using the reproduced reference clock signal.

[Conventional technology]

When recording PCM data on a recording medium such as a magnetic tape, optical disk, or magnetic disk, "1°.

Digital modulation must be performed to record the code consisting of "0" in correspondence with what waveform, and N1
(Modulation methods such as Zl method and MFM method are generally employed.

Since this digital modulation is performed based on a reference clock signal, when demodulating PCM data and performing data discrimination during reproduction, it is necessary to perform it in synchronization with this reference clock signal.

Therefore, conventionally, when performing digital recording by performing digital modulation such as MFM, a reference clock is included in the recorded data after digital modulation, and when playing back, the reference clock signal is extracted from the playback signal, and this is sent to the PLL circuit. A reference clock signal synchronized with the data is obtained from this PLL circuit, and the data is discriminated based on this signal, thereby counteracting the speed deviation caused in the recording/reproducing yarn. This is called a self-crofter.

In the case of a digital modulation method such as NRZI in which this self-clocking method cannot be used, a reference clock signal is recorded on a track separate from the recording data.

[Problem to be solved by the invention]

The method of recording the clock signal on a separate track from the recording data is because there is a time lag between the data track and the clock track due to errors in the installation of the recording and playback heads and the accuracy of the running speed of the recording medium. , there is a problem that compatibility cannot be compensated for.

According to the self-clock method, such problems do not occur, but due to the speed deviation in the reproduction system being too large and the effects of noise etc., it is difficult to obtain a clock that is completely synchronized with the data from the PLL circuit. was impossible.

This invention aims to eliminate these drawbacks.

[Means to solve the problem]

The digital signal recording device according to the present invention includes a digital modulation circuit (2) that digitally modulates the data LO^TA based on the clock signal CK, and an AM modulation of the output of the digital open circuit (2) using the clock signal GK as a carrier. AM modulation circuit V&14) and a signal obtained by multiplying or lowering the clock signal CK, and the AM modulation circuit tl!
a circuit (5) for obtaining a signal SC having a frequency outside the signal band;
AM modulation signal SAM from AM modulation circuit (4) and the above A
It comprises an adder circuit (6) for adding the signal SC having a frequency outside the band of the M modulated signal, and means (7) (81) for recording the output signal of the adder circuit (6).

Further, in order to multiplex record the clock signal CK as a signal outside the band of the AM modulation signal SAM, an FM modulation circuit (lO) may be provided in place of the circuit (5).

[Effect]

Digitally modulated PCM data is AM-modulated using a digitally modulated reference clock signal as a carrier, and is recorded as a signal occupying a predetermined frequency band. and,
A signal having a frequency n times or 1/n times that of the reference clock signal is frequency multiplexed and recorded outside the band of the AM modulated signal. Alternatively, the clock signal is FM modulated, and the FM modulated signal is frequency-multiplexed and recorded on the AM modulated signal.

〔Example〕

FIG. 1 shows an embodiment in which the invention of claim 1 is applied to a recording system of a data recording/reproducing apparatus.

That is, PCM data DATA is supplied to the digital modulation circuit (2) through the input terminal (1), and the frequency f from, for example, a crystal oscillator is supplied to the digital modulation circuit (2) through the input terminal (3).
o clock signal CK is supplied to this digital*open circuit (2), and in this digital modulation circuit (2), based on the clock signal CK, N)? Digital modulation using a modulation method such as Zl or MFM is applied to the manual PCM data DATA.

In this case, the frequency fs of the output data DM of the digital modulation circuit (2) is set such that rs≦fo/2. Modulation data L from this digital modulation circuit (2)
M is supplied to the AM modulation circuit (4). - On the other hand, the clock signal CK through the input terminal (3) is applied to this AMi open circuit (
4) as a carrier, this carrier is AM modulated (for example, balanced modulation) by data DM, and from this, the AM modulated signal SA? which occupies a predetermined frequency band as shown in the frequency spectrum diagram of FIG. I is obtained and supplied to the adder circuit (6).

Then, the clock signal CK through the input terminal (3) is supplied to the multiplier circuit (5) and the frequency is multiplied by n (n=2°3·
...), and as shown in Fig. 2, a signal SC with a higher frequency than the AM modulation signal SAM is obtained, and this signal S
C is supplied to the adder circuit (6), and the AM modulated signal SAW
is added.

The addition output signal from the addition circuit (6) is supplied to the recording magnetic head (8) through the recording amplifier (7) and recorded on the magnetic tape r.

This recorded signal is reproduced as follows.

That is, (11) is a reproduction magnetic head, and the signal picked up from the tape 1 by this head (11) is passed through a reproduction amplifier (12) to a low-pass filter (
13) and a bandpass filter (17).

The playback AM changes from the low-pass filter (13)! J [word SAM" is obtained, which is supplied to the AM demodulation circuit (14).

In addition, a reproduced signal sc'' of the signal SC is obtained from the band pass filter (7), and this is supplied to the frequency divider circuit (18) where it is down-done to a frequency of 1/n.
) from which the reproduced clock signal CK'' is obtained.

This reproduced clock signal CK" is supplied to the AMfjta1 circuit (1
4), thereby producing a reproduced AM modulated signal SAM
"is AM demodulated (synchronous detection), and reproduced modulated data DM" is obtained from this. This reproduced modulation data DM'' is supplied to the data discrimination circuit (15).On the other hand, the frequency dividing circuit (15)
The reproduced clock signal CK'' from 8) is supplied to this data discrimination circuit (15), and from this the reproduced PCM data D
ATA'' is obtained and led out to the output terminal (16).

In this case, since the reproduced clock signal CK'' and the reproduced modulated data include the same time axis fluctuations that occur in the recording and reproduction string, the synchronization relationship between the two is the same as the recording time, and the discrimination circuit (1
In 5), stable and reliable data discrimination is performed.

In the above example, during recording, the frequency of clock No. 16 CK was multiplied by n and frequency-multiplexed on the high frequency side of AM modulation signal SAM, but the frequency of clock signal CK was stepped down to 1/n. Frequency multiplexing may be performed on the lower frequency side of the AM* tone signal.

Also, digital modulation circuit (2) and AM modulation circuit (4)
The clock signal CK to be supplied to 1/n
or n times, and the clock signal CK itself is AM
Frequency multiplexing may be performed on the high frequency side or the low frequency side of the i-key signal SAM.

FIG. 3 shows an embodiment in which the invention of claim Lji2 is applied to a recording system of a data recording/reproducing apparatus, and the same parts as in the example of FIG. 1 are given the same numbers and the explanation thereof will be omitted.

In this example, the PCM data IIAT^ is digitally modulated based on the clock signal GK, and the digitally modulated data L)M is sent to A using the clock signal CK as a carrier.
The process of performing M modulation to form the AM modulation signal SAM is similar to the example in FIG. 1, but the clock signal CK is
The method of frequency multiplexing to M is different from the example in FIG.

That is, the clock signal CK through the input terminal (3) is supplied to the frequency dividing circuit (9) and is divided into l/(s+-1°2
．． 3...), and the frequency-divided output signal is supplied to the FM modulation circuit (10) and subjected to T'M modulation. In this case, the FM modulation signal SFM from the FMJk modulation circuit (10) has an FM center frequency fc on the high frequency side outside the band of the AM modulation signal SAM, as shown in the frequency spectrum diagram of FIG. It is considered a signal. This FM modulation signal SFM is converted into an AM modulation signal SA in an adder circuit (6).
It is added to M and the number of questions is recorded.

Also, on the playback side, the playback AM modulation signal SAN'' is separated from the output of the playback amplifier (12), and is modulated by AMijj.
The data discrimination is the same as in the example shown in FIG. 1, but the method of extracting the reproduced clock signal CK'' is different from the example shown in FIG.

That is, the output of the reproducing amplifier (12) is supplied to the bypass filter (19), from which a reproduced FM signal, sM signal 5FI-1', is obtained. This reproduced M modulation signal S output 2
is supplied to an M demodulation circuit (20) for FMII modulation, and then the output is supplied to a multiplier circuit (2), where the frequency is multiplied by m, thereby obtaining a reproduced clock signal CK''.

In the case of the example shown in FIG. 3, the reproduced clock signal CK'' is F
Since the data is M-modulated and recorded, it has the advantage that it can be taken out stably. Also, to M-hen 11i1 signal SA
M has the advantage that it is biased by the FM change signal SFM and does not require a separate bias signal source.

〔Effect of the invention〕

According to this invention, digital data is converted to A by using the reference clock signal as a carrier during digital modulation.
In addition to recording the signal as a signal that is M-modulated and occupies a predetermined band, the reference clock signal is converted to a signal outside the band of the AM modulation signal and multiplexed and recorded on the AM modulation signal. Stable data discrimination becomes possible using the reproduced clock signal. Furthermore, since the problem of J1 compatibility that occurs when the clock signal is recorded on a different track from the data does not occur, NRZI, etc., which cannot use the one-select-one-select method, can be used as a digital modulation method.

In addition, since the clock signal is frequency-multiplexed, time axis fluctuations during recording and playback are also affected by the clock signal for each PCM data, making it more stable than when reproducing the clock signal using a conventional self-clocking PLL circuit. Data discrimination can be performed.

Furthermore, when the clock signal is FM modulated and multiplexed recorded, this clock signal can be reproduced more stably.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an example of a data recording/reproducing device to which the invention of this application is applied, Fig. 2 is a frequency spectrum diagram for explaining the same, and Fig. 3 is a data recording/reproducing device to which the invention of this application is applied. FIG. 4 is a block diagram of an example of a recording/reproducing device, and is a frequency spectrum diagram for explaining the same. (11 is the PCM data input terminal, (2) is the digital modulation circuit, (3) is the reference clock signal input terminal, (4
) is an AM modulation circuit, (5) is a frequency multiplier circuit, and (6) is an addition circuit.

Claims (1)

[Claims] 1. a) a digital modulation circuit that digitally modulates a digital signal based on a clock signal; b) an AM modulation circuit that performs AM modulation on the output of the digital modulation circuit using the clock signal as a carrier; c ) a circuit that obtains a signal that is a signal obtained by multiplying or stepping down the clock signal and whose frequency is outside the band of the AM modulation signal; A digital signal recording device comprising: an adder circuit for adding a signal of an external frequency; e) means for recording an output signal of the adder circuit. 2. a) a digital modulation circuit that digitally modulates a digital signal based on a clock signal; b) an AM modulation circuit that uses the clock signal as a carrier to perform AM modulation on the output of the digital modulation circuit; and c) modulates the output of the digital modulation circuit using the clock signal as a carrier. an FM modulation circuit for converting the AM modulation signal into a signal outside the band; d) an addition circuit for adding the AM modulation signal from the AM modulation circuit and the FM modulation signal from the FM modulation circuit; and e) this addition. A digital signal recording device comprising means for recording an output signal of a circuit.