JPS62177703A - Digital signal recorder - Google Patents

Abstract

PURPOSE:To reduce the nonlinear distortion even in case of the use of a head consisting of the combination of a metal and a ferrite by inserting an equalizing circuit which reduces the gain of the low band component of a digital signal relatively in comparison with the high band component when the digital signal to be recorded is supplied to a recording head. CONSTITUTION:The equalizing circuit consists of transistors 21 and 22, resistances 23 and 24, a capacitor 26, and a current source 25. Resistance values of resistances 23 and 24 are set to R/2. The gain of the low band component of the input signal voltage supplied to a terminal 28 is reduced relatively, and the phase of the high band component is delayed relatively. The output of the equalizing circuit is converted to voltages by resistances 29 and 30, and signal voltage outputs whose phases are opposite to each other are supplied to a recording amplifier 34 through a drive amplifier 32 and a rotary transformer 33, and the output of the recording amplifier 34 is supplied to a winding 36 of a magnetic head 35. Thus, the amplitude and the phase are compensated for the nonlinear distortion at the recording time to reduce the nonlinear distortion.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital signal recording device used for recording digital signals on a magnetic tape.

[Summary of the invention]

The present invention provides a digital signal recording device used for recording digital signals on a magnetic tape, in which the gain of the low-frequency component of the digital signal to be recorded is relatively lowered compared to the high-frequency component of the digital signal. This method is designed to reduce nonlinear distortion by compensating for and recording on magnetic tape.

[Conventional technology]

For example, as disclosed in Japanese Unexamined Patent Publication No. 55-135316, when recording a high frequency digital signal such as a digital video signal, a recording circuit as shown in FIG. 7 has conventionally been used.

In FIG. 7, the emitters of transistors 51 and 52 are commonly connected, and this junction is connected to the collector of transistor 53, which operates as a constant current source. The base of the transistor 53 is connected to a terminal 54 to which a constant voltage is applied. The emitter of transistor 53 is connected to -VEE power supply terminal 56 via resistor 55.

The bases of the transistors 51 and 52 are connected to the input terminal 5.
7 and 58, respectively. Transistors 51 and 5
Two collectors are connected to one terminal 60 and the other terminal 61 of the magnetic navel F' 59, respectively. A terminal 62 at the center of the magnetic head 59 is connected to a power terminal 63 at the center of the magnetic head 59 .

The conventional recording circuit shown in FIG.
1 and 52 are turned on and off, currents in opposite directions are caused to flow through the windings 64 of the 6-air head 59, respectively, and signals are recorded on the magnetic tape. That is, input terminal 5
When the digital signal supplied to input terminal 7 is high level and the digital signal supplied to input terminal 58 is low level, transistor 51 is turned on, transistor 52 is turned off, and winding 64 is driven t in the direction shown by arrow a. The flow is carried away.

When the digital signal supplied to the input terminal 58 is at a high level and the digital signal supplied to the input terminal 57 is at a low level, the transistor 52 is turned on and the transistor 51 is turned off, as already indicated by the arrow 64. A current is passed in the direction.

However, when magnetic recording is performed at a high recording density, such as when recording digital video signals on magnetic tape, a large amount of nonlinear distortion inherent to magnetic recording occurs. cannot be removed.

In the conventional recording circuit described above, equal recording currents are always applied to the high-frequency components and the low-frequency components with the same phase, and no compensation for nonlinear distortion is performed.

Therefore, there is a problem in that a large amount of nonlinear distortion occurs during recording.

Nonlinear distortion in the recording process is thought to occur due to interference between the immediately written pulse and the next written pulse. On the other hand, if the recording current waveform is appropriately compensated, the occurrence of this can be reduced.

Therefore, a recording circuit has been proposed in which phase distortion is applied in advance to the digital signal to be recorded. That is, as shown in FIG. 8, a digital signal to be recorded is supplied from an input terminal 71 to an A bus filter 72, and a bypass filter 72 adjusts the phase of the digital signal to be recorded in advance to compensate for the occurrence of nonlinear distortion. Give some distortion. The output of this bypass filter 72 is divided into two by a comparator 73.
It is converted into a value and supplied to the magnetic head 75 via the recording amplifier 74. In this way, phase compensation is applied in advance to the digital signal to be recorded (thereby, nonlinear distortion is reduced).

Further, as shown in FIG. 9, a digital signal to be recorded is supplied from an input terminal 81 to a peaking circuit 82, and the output of the peaking circuit 82 is supplied to a magnetic node 85 via an attenuator 83 and a recording amplifier 84. A recording circuit has been proposed. This recording circuit is described in detail in IEICE 236 (1985). As shown in FIG. 1O, the peaking circuit 82 has a resistor 88 and a capacitor 89 connected in parallel between an input terminal 86 and an output terminal 87, and a connection point between the output terminal 87 and the resistor 88 and capacitor 89. One in which a resistor 90 is connected between ground is used. Furthermore, the recording amplifier 84 must have linear amplitude characteristics.

In the recording circuit shown in FIG. 10, amplitude and phase compensation for nonlinear distortion is performed in advance by a peaking circuit 82. This reduces nonlinear distortion.

[Problem that the invention seeks to solve]

Relatively mild nonlinear distortion can be reduced to some extent by using the recording circuit shown in FIGS. 8 and 9 described above. However, the tape coercive force Hc
+ Large nonlinear distortion that occurs when recording, for example, a metal tape with a high residual magnetic flux density Br, onto a metal tape with a high saturation magnetic flux density Bs, such as M&F (metal & ferrite (a combination of sendust, amorphous, and ferrite)) with a gutter. However, the above-mentioned conventional recording circuit cannot sufficiently remove the noise.

That is, in the recording circuit shown in FIG. 8, only the phase characteristics are compensated for nonlinear distortion, but the amplitude is not compensated.

The recording circuit shown in FIG. 9 cannot sufficiently compensate amplitude and phase characteristics for large nonlinear distortions that occur when magnetically recording on a metal tape using an M&F. In other words, the transfer function H(s) of the peaking circuit 82 (FIG. 10) in the recording circuit shown in FIG.
Letting the capacitance of 9 be C8, it becomes as follows.

1/C,R,=a.

Assuming that (R1+R2)/(CI RI R2) = baa, this transfer function H(S) becomes. Therefore, the amplitude characteristic 1 phase characteristic 1 of this peaking circuit
The group delay characteristics are shown in FIGS. 11A to 11C, respectively.

As is clear from the characteristics shown in FIGS. 11A to 11C, this peaking circuit 82 cannot obtain steep amplitude characteristics and cannot perform sufficient phase compensation. Furthermore, when this peaking circuit is used, there is a problem in that the recording amplifier 84 must have linear amplitude characteristics.

Therefore, it is an object of the present invention to provide a digital signal recording device that is capable of suppressing large nonlinear distortions such as those that occur when recording metal tapes on M&F at low frequencies.

Another object of the present invention is to provide a digital signal recording device that can reduce power consumption of a recording amplifier.

[Means for solving problems]

The present invention is a digital signal recording device in which a digital signal to be recorded is supplied to a recording head through an equalization circuit that relatively lowers the gain of low-frequency components of the digital signal compared to high-frequency components. .

ε Effect] Nonlinear distortion in the recording process is thought to occur due to interference between the already written pulse and the next written pulse. Therefore, transistor 1°2, resistor 5. Capacitor 6, current source 3.4. An equalization circuit configured by is used, the gain of the low frequency component of the recording signal is relatively lowered compared to the high frequency component, the phase of the high frequency component is delayed relative to the low frequency component, Compensation for nonlinear distortion is made during recording. Thereby, nonlinear distortion can be reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

As described above, nonlinear distortion during the recording process is thought to be caused by interference between the already written pulse and the next written pulse. Saturation magnetic flux density Bs at M&F hand where tape coercive force Hc and residual magnetic flux density Br are both high
When high-density recording is performed on a metal tape with a high density, it is thought that there will be interference not only from the preceding and succeeding pulses but also over several time slots. However, M&F
When performing high-density recording on a metal tape using a head, it is thought that a large amount of nonlinear distortion occurs. In addition, there is a tendency for a large amount of nonlinear distortion to occur when wide pulses, that is, a series of 1's or O's occur, and this is thought to be due to the part where the wide pulses are occurring being involved in nonlinear distortion. It will be done.

From the above, the gain of the low-frequency component is relatively lowered compared to the high-frequency component, and the phase of the high-frequency component is delayed relative to the low-frequency component, so that the recording current waveform is sufficiently compensated for amplitude and phase. If this is done, it is conceivable that nonlinear distortion can be sufficiently reduced even when high-density recording is performed on a metal tape using an M&F head.

In one embodiment of the present invention, the equalization circuit shown in FIG. 4 is used to provide amplitude and phase compensation for nonlinear distortion to the recording current waveform, thereby reducing nonlinear distortion.

In FIG. 4, current sources 3 and 4 are connected to the emitter of the transistor 1 and the emitter of the transistor 2, respectively, and a resistor 5 and a capacitor 6 are connected between the emitters of the transistors 1 and 2. Connected.

The other ends of current sources 3 and 4 are connected to -VEE power supply terminals 7 and 8, respectively.

The base of transistor 1 is connected to input terminal 9. The base of transistor 2 is grounded. The collector of transistor 1 is connected to the -vce power supply terminal. The collector of transistor 2 is connected to output terminal 12 .

When input signal voltage V, (1) is supplied to input terminal 9,
Based on the potential difference generated between the emitter of transistor 1 and the emitter of transistor 2, a signal current flows through resistor 5 and capacitor 6. Therefore, assuming that the resistance value of the resistor 5 is R, the capacitance of the capacitor 6 is C1, the current value of the current sources 3 and 4 is 1, the output signal current 1o(t) of the output terminal 12 is as follows: 1o(t)=T = v, (t)<1 = j (
LICR) /R-・(t).

By the way, in the formula (i+), the first term is the bias current determined by the current sources 3 and 4, and the second term is the signal current converted by the input voltage. From formula (1), the output signal current i. 1) is the cutoff frequency ω. Therefore, it increases as the frequency becomes higher. However, the signal current in the first term in equation (1) never exceeds the current value of 1 of current sources 3 and 4. Therefore, i v, (t) (10j
ωcR) /R, ≦1−(2i, and from equation (2),
The maximum value of the output signal current i (υ) is limited by the current value ■ of the current sources 3 and 4.

As a result, at frequencies above the frequency determined by the current values r of the current sources 3 and 4, the output signal type t
i i o (t) is clipped, and even if it becomes higher than this frequency, the output signal current to(t) does not increase. By appropriately determining the current value I of the current sources 3 and 4, Unnecessary increases in power consumption can be suppressed.Furthermore, although the amplitude does not increase at high frequencies, as is clear from FIG. 5, the current waveform becomes steeper and the resolution of the recorded flow is improved.

From equation (1) above, the transfer function H(
s) is H(s)=C(S+1/CR) =(S-C0)/Rω
G −<3) Qo: Obtained as the cutoff frequency. When the amplitude characteristics, phase characteristics, and first group delay characteristics of this equalizing circuit are obtained from this transfer function H(s), the results are shown in FIGS. 6A to 61NC. Note that the amplitude characteristic is limited by the frequency ω due to the current value I of the current sources 3 and 4, but the phase characteristic and the group delay characteristic obtained by differentiating it are limited by the current value I of the current sources 3 and 4. There are no restrictions. As is clear from the characteristics shown in FIGS. 6A to 6C, this equalization circuit lowers the gain of the low frequency component compared to the high frequency component, and lowers the phase of the high frequency component compared to the low frequency component. It has the property of slowing down.

FIG. 1 shows an embodiment of the present invention, in which the emitter of a transistor 21 and the emitter of a transistor 22 are connected to a current source 25 with a current value of 2 through a resistor 23 and a resistor 24, respectively. At the same time, a capacitor 26 is connected between the emitters of the transistors 21 and 22. The other end of the current source 25 is connected to a power supply terminal 27. The base of the transistor 21 is the input terminal 28
connected to. The base of transistor 22 is grounded. The collector of the transistor 21 is connected to -V through the resistor 29.
It is connected to the power supply terminal 31 of the cc, and also connected to one input terminal of the drive amplifier 32. transistor 2
2 collector is connected to +vCC power supply terminal 3 via resistor 30.
1 and the other input terminal of the drive amplifier 32 -2.

An output terminal of the drive amplifier 32 is connected to the primary winding of the rotary transformer 33. A secondary winding of the rotary transformer 33 is connected to an input terminal of the recording amplifier 34. The output terminal of the recording amplifier 34 is connected to the winding 36 of the head 35.

This embodiment is suitable for use when the recording amplifier 34 is mounted on a rotating drum.

Transistors 21, 22. Resistors 23, 24. Capacitor 26. The current source 25 constitutes the equalization circuit shown in FIG. 4 described above. Note that the resistance values of the resistors 23 and 24 are each set to R/2. With respect to the input signal voltage supplied to the terminal 28, this equalization circuit compensates for nonlinear distortion. In other words, by supplying this input signal voltage to the equalization circuit, the gain of the low frequency component is relatively lowered and the phase of the high frequency component is relatively lowered according to the characteristics shown in FIGS. 6A to 6C. be delayed. The output of this equalization circuit is converted into a voltage by resistors 29 and 30, and signal voltage outputs having mutually opposite phases are passed through a drive amplifier 329 and a rotating transformer 33 to a recording amplifier 34.
The output of the recording amplifier 34 is supplied to the winding 36 of the magnetic head 35.

In this way, since the amplitude and phase are compensated for nonlinear distortion during recording, nonlinear distortion is reduced.

FIG. 2 shows another embodiment of the invention. This example is
This equalization circuit is also used as a recording amplifier.

In FIG. 2, transistors 21, 22 . Resistance 23.2
4. Capacitor 26. An equalization circuit is configured by the current a25. The collectors of transistors 21 and 22 are connected to a winding 36 of a voltage head 35. Winding wire 36
The midpoint of is connected to the -VCC power supply/terminal 31. The bases of transistors 21 and 22 are connected to one and the other output terminals of buffer amplifier 44, respectively.

The digital signal supplied to the input terminal 41 is sent to a drive amplifier 422, a rotary transformer 43. The signal is supplied to the transistor 2 and base 220 via the buffer amplifier 44. The i3 current is caused to flow through the winding 36 in accordance with the current flowing through the transistors 21 and 22. In this way, transistors 21, 22°, resistors 23, 24 . Capacitor 26. The equalization circuit constituted by the current source 25 provides compensation for nonlinear distortion to the recording current, and also operates as a recording amplifier.

In addition, as shown in FIG.
The collector of the transistor 21 is connected to the power supply terminal 31 via the current -tA 45 and 46, respectively, whose current value is I, and the connection point between the collector of the transistor 21 and the current 845, and the I transistor 2.
If the connection point between the collector No. 2 and the current source 46 is connected to the winding 36 of the magnetic node 35, the tap at the center of the winding 36 becomes unnecessary.

That is, when the voltage at the collector of transistor 22 is higher than the voltage at the collector of transistor 22, current flows through the winding 36 in the direction shown by arrow C, and the voltage at the collector of transistor 22 is higher than the voltage at the collector of transistor 21. At times, a current is passed through the winding 36 in the direction indicated by arrow d.

C. Effects of the Invention] According to the invention, since amplitude and phase compensation for nonlinear distortion is performed on the recording current, nonlinear distortion can be reduced.

The present invention will be described in detail below while comparing actually measured reproduced waveforms.

As shown in FIG. 12A, after consecutive data of "000...", "2l" and "O" are alternately reversed.
If a recording signal in which the data of o...2 is continuous and the data of "111..." is continuous is recorded by a conventional recording circuit (FIG. 7) that does not compensate for nonlinear distortion, The reproduced waveform becomes as shown in FIG. 12B. On the other hand, when a similar recording signal is recorded by a recording circuit to which the present invention is applied, the reproduced waveform becomes as shown in FIG. 12C.

Since the tape head system has differential characteristics, if nonlinear distortion does not occur, the differential waveform of the recording signal shown in FIG. 12A should be obtained as the reproduced waveform. However, as shown in FIG. 12B, when this signal is recorded with a conventional recording circuit that does not compensate for nonlinear distortion, nonlinear distortion occurs.

In other words, the beak P that should be output is not reproduced at the boundary between the continuous data part of "2, rooo..." and the repeated data part of "rlolo...". Also,"
000... 2 consecutive data parts, rlolo.
The DC level of the repeating data part of "..." and the continuous data part of "111..." are supposed to be constant, respectively, but as shown in Figure 12B, the DC level is fluctuations are occurring.

When a recording circuit to which this invention is applied is used, FIG.
As shown in the figure, Beak P is played and "000..."
``rioxo...'' data part,
No fluctuation in the DC level occurs in the data portions "111...".

This shows that nonlinear distortion was reduced.

In addition, as shown to the 13th foreigner, the data "10" is inserted between the continuous part of the data "000...!" and the continuous part of the data "111...", and the data "111..." is inserted.
A conventional recording circuit that does not compensate for nonlinear distortion records a recording signal in which data 101'' is inserted between a continuous portion of data of ``000...'' and a continuous portion of data of ``000...''. As shown in FIG. 13B, if the continuous data of [000...j and "ill...
" data of "10" and "111" between consecutive data of
The data of "O12" between the continuous data of "...:" and the continuous data of "Vooo..." cannot be reproduced. On the other hand, when a similar recording signal is recorded by a recording circuit to which the present invention is applied, the data shown in FIG. As shown in C, the VIO between the continuous data of "Vooo..." and the continuous data of "1111..."
Jj data and continuous data of "111..." and [0
Data "01" between continuous data 00...j can be reproduced.

As can be seen from the reproduced waveforms shown in FIGS. 12 and 13 above, according to the present invention, nonlinear distortion can be sufficiently reduced.

Moreover, if this invention is defeated, an equalizer circuit with characteristics shown in FIGS. 6A to 6C using active elements may be used. The characteristics of this equalization circuit are higher than those of the peaking circuit (Figures 11A to 11C) consisting of only passive elements used in the conventional recording circuit shown in Figure 9. The gain is large, and the delay in the high range is large.

Therefore, compensation for nonlinear distortion is sufficient, and even large nonlinear distortion, such as when recording a metal tape with an M&F head, can be sufficiently reduced.

Further, according to the present invention, since the current flowing through the equalization circuit is clipped at high frequencies, the amplitude does not increase beyond a certain value, and power consumption can be reduced. In addition, since the current flowing through the equalization circuit is suppressed to a certain value or less in this way, when a recording amplifier is mounted on a rotating drum, the effects of heat generation can be suppressed in low frequencies.

[Brief explanation of drawings]

Fig. 1 is a connection diagram of one embodiment of this invention, Fig. 2 is a connection diagram of another embodiment of this invention, Fig. 3 is a close-up diagram of still another embodiment of this invention, and Fig. 4 is a connection diagram of another embodiment of this invention. A connection diagram of an example of an equalizer circuit in an embodiment of the invention, FIG. 5 is a waveform diagram used to explain an example of an equalizer circuit in an embodiment of this invention, and FIG. 6 is a diagram used to explain an example of an equalizer circuit in an embodiment of this invention. Frequency characteristics diagram, Figure 7 is a connection diagram of an example of a conventional digital signal recording circuit, Figure 8 is a block diagram of another example of a conventional digital signal recording circuit, and Figure 9 is a further diagram of a conventional digital signal recording circuit. A block diagram of another example, FIG. 10 is a connection diagram of an example of a peaking circuit in still another example of the conventional digital signal recording circuit, and FIG. 11 is a connection diagram of an example of the peaking circuit in still another example of the conventional digital signal recording circuit. An example of frequency characteristic diagrams, FIGS. 12 and 13, are waveform diagrams showing the effects of the present invention. Explanation of main symbols in the drawings 1.2, 21.22 = transistor, 5.23, 24: resistor, 6.26: capacitor, 3.
4, 23.25: Current source, 28, 41: Input terminal,
35: Magnetic head. Agent Patent Attorney Tadashi Sugiura Fig. 4 Fig. 5 ゛$1 I1114-not;l-1 squid, aq,) , l-1 Figure 11B JY-3! i Shadow 1・1 Figure 11C

Claims (1)

[Claims] A digital signal recording apparatus that supplies a digital signal to be recorded to a recording head via an equalization circuit that relatively lowers the gain of low frequency components of the digital signal compared to high frequency components.