JPH0673236B2 - Digital signal recording level monitoring device - Google Patents

Description

The present invention relates to a digital signal recording level monitoring apparatus used in a digital signal recording / reproducing apparatus or the like.

[Outline of Invention]

The present invention relates to a recording level monitoring apparatus for digital signals, which issues an alarm when the level relationship of the envelopes of the minimum inversion interval portion of a reproduced digital signal and the inversion interval portion of the reproduced digital signal exceeds a predetermined range. This makes it possible to favorably prevent deterioration of the overwrite characteristic.

[Conventional technology]

In digital signal recording, generally without using an erasing head,
The previous recording signal is erased by so-called overwrite recording. In that case, the recording current becomes large, especially when a low-frequency signal is recorded up to the deep layer of the magnetic layer,
At the time of the next recording, when the same portion was recorded as a high frequency signal, the erasing was not completed completely, and there was a risk that the unerased portion would occur and interfere with the signal at the time of reproduction.

That is, Fig. 2 shows the reproduction output (m
V: Corresponding to the recording depth), and shows the characteristics as shown for each frequency (MHz) of the recording signal. In this figure, the two types of numbers on the horizontal axis are
When there is no wear on the recording head in the upper row (the gap depth is
60 μm), and the lower part shows wear when the gap depth becomes 46 μm, and the recording current increases by about 43%.

Therefore, in this figure, the recording current is set to 50 with no wear.
When set to mA, the playback output at high frequency 15 MHz at this time is about 50 m
V, on the other hand, the reproduction output in the low frequency range of 3 to 8 MHz is around 100 mV, and if there is a difference in the recording level of about double, there is no problem in the overwrite characteristic. However, when the gap depth wears to 46 μm with the same recording current of 50 mA, the reproduction output of 15 MHz at that time is about 45 mV, while the reproduction output of 3 MHz becomes about 140 mV, which is about three times that. However, with this, sufficient erasing was not performed, and the overwrite characteristic was deteriorated.

That is, when overwriting is performed, there is a possibility that a portion where a signal of 3 MHz having a large inversion interval is recorded is overwritten with a signal of 15 MHz having a small inversion interval. In this case, if the difference between the reproduction outputs is about twice as in the case of no wear, good overwriting is performed.
On the other hand, when the depth of the gap is worn to 46 μm, the difference in reproduction output becomes about three times. In this state, the portion where the 3 MHz signal with a large inversion interval is recorded has a small inversion interval.
When overwriting with a MHz signal, the 3 MHz signal was not sufficiently erased, and there was a risk that a residual signal would occur and overwrite could not be performed properly.

[Problems to be solved by the invention]

As described above, the conventional technique has a problem that when the head is worn while the recording current remains constant, the recording level in the low range is increased and the overwrite characteristic is deteriorated.

[Means for solving problems]

The present invention is a reproducing head (not shown) for reproducing this recording in the rear of the recording head for magnetically recording an arbitrary digital signal.
And an envelope detecting means (resistor (2) to capacitor (19)) for detecting the envelope of the reproduced digital signal (input terminal (1)), and the reproduced digital signal of the detected envelope. Sampling means (switches (20) (21), capacitors (22) (23)) for sampling the level of the minimum inversion interval portion (post preamble) and the inversion interval portion (data) larger than that, and Level difference detection means (operational amplifier (24)) for detecting the difference in level
Is provided so that an alarm is issued (output terminal (26)) when the level difference between the minimum inversion interval part of the digital signal and the inversion interval part larger than that exceeds a predetermined range (comparator (25)). The recording level monitoring device for digital signals is characterized in that

[Action]

According to this, the recording level is estimated from the envelope of the reproduced digital signal, so that the warning of deterioration of the overwrite characteristic can be issued.
With this alarm, necessary measures such as adjustment of recording current can be taken.

〔Example〕

In FIG. 1, a digital signal recorded by a recording head (not shown) is reproduced by a so-called confirmation reproducing head, and the reproduced digital signal is supplied to an input terminal (1).

This input terminal (1) is connected to the base of a pnp type transistor (5) through a bias circuit consisting of resistors (2), (3) and (4), and the emitter of this transistor (5) is connected to a resistor (6) ( 7) Connected to the power supply terminal (10) through the capacitors (8) and (9). Further, the collector of the transistor (5) is grounded through the resistors (11) and (12), the collector is connected to one end of a capacitor (13), and the other end of the capacitor (13) is a resistor (14).
And a capacitor (15) and a coil (16) in parallel with a series circuit to be grounded. Also this capacitor (13)
The other end of is connected to one end of a resistor (18) through a diode (17), and the other end of this resistor (18) is connected to a capacitor (1
Grounded through 9). The numbers in the figure indicate the values of each element.

As a result, the envelope is detected, the shortest wavelength portion of the digital signal is extracted by setting the values of the capacitor (15) and the coil (16), and the resistors (11) (12) ( The desired peaking can be applied by 14) or the like.

By the way, generally, in a digital signal, a so-called preamble or postamble portion is provided with a minimum inversion interval portion, and a synchronization pattern in a data portion is formed by a signal with a maximum inversion interval.

Therefore, the signal from the other end of the above-mentioned resistor (18) passes through the switch (20) which is turned on during the pre- or post-amble period of the digital signal and the switch (21) which is turned on during the data period to the capacitors (22) ( 23), and the stored signal is supplied to the operational amplifier (24) to extract the difference component. Then, the signal of the difference component is supplied to the comparator (25), and when the difference component has a magnitude larger than a predetermined value, an alarm signal is output to the output terminal (26).

Therefore, in this circuit, the level difference of the envelope between the minimum inversion interval part of the reproduced digital signal and the inversion interval part larger than that is taken out from the amplifier (24), and when this difference opens 2.5 times or more, for example. , It is possible to determine the deterioration of the overwrite characteristics and issue an alarm. The reproduction output envelope corresponds to the recording depth of the signal, which corresponds to the recording level.

In this way, a warning of deterioration of overwrite characteristics is issued,
This makes it possible to maintain the overwrite characteristic by taking measures such as adjusting the recording current.

It should be noted that a digital signal having a minimum inversion interval has a small energy, and when an envelope is detected, it cannot be detected at the same rate as a signal having an inversion interval larger than that.
For this reason, the difference component may not be detected well, but according to the above circuit, the energy is increased by applying the desired peaking to the minimum inversion interval portion,
The detection is made to work well.

〔The invention's effect〕

According to the present invention, the level difference between the minimum inversion interval portion and the inversion interval portion larger than that of the reproduced digital signal is detected, and when the level difference exceeds the predetermined range, good overwrite cannot be performed. Since there is a fear that this detection signal will give an alarm for deterioration of the overwrite characteristic, it becomes possible to take necessary measures such as adjustment of the recording current by this alarm.

[Brief description of drawings]

FIG. 1 is a block diagram of an example of the present invention, and FIG. 2 is a diagram for explaining a conventional technique. (1) is an input terminal, (2) (3) (4) (6) (7)
(11) (12) (14) (18) are resistors, (5) are transistors, (8) (9) (13) (15) (19) (22) (23) are capacitors, and (10) are Power terminal, (16) coil, (1
7) is a diode, (24) is an operational amplifier, (25) is a comparator, and (26) is an output terminal.

Claims (1)

[Claims] 1. A reproducing head for reproducing this recording is provided at the rear of a recording head for magnetically recording an arbitrary digital signal, and an envelope detecting means for detecting the envelope of the reproduced digital signal, and the detected envelope of the detected envelope. Sampling means for sampling the level of the minimum inversion interval portion and the inversion interval portion of the reproduced digital signal larger than that, and level difference detection means for detecting the difference between these sampled levels are provided. A recording level monitoring device for a digital signal, wherein an alarm is issued when the level difference between the minimum inversion interval part and the inversion interval part larger than that exceeds a predetermined range.