JPH04251405A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To provide the magnetic recording and reproducing device, which can relax the limit condition of a reproducing gap and simplify production processes, in the magnetic recording and reproducing device to record and reproduce binarized digital signals, especially, in the magnetic recording and reproducing device improving the magnetic head part. CONSTITUTION:At the magnetic recording and reproducing device to record signals to a magnetic tape as digital signals, to read the relevant recorded digital signals from the magnetic head and to reproduce those signals, the gap length of the above-mentioned magnetic head is formed llonger than the shortest bit interval among the above-mentioned recorded digital signals.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording and reproducing apparatus for recording and reproducing binary digital signals, and more particularly to a magnetic recording and reproducing apparatus with an improved magnetic head.

0002

[Prior Art] Conventional magnetic recording and reproducing devices are used for magnetic recording and reproducing in compact cassette decoders, video tape recorders (VTRs), digital audio tape recorders (DATs), etc., and the gap length of this magnetic head is the shortest in magnetic recording. The wavelength is set to 1/2 or less of the recording wavelength. This gap in the magnetic head causes gap loss during recording and reproduction. This gap loss can be expressed by the following equation.

Gap loss=sin(π×1.12×g/λ)/
(π×1.12×g/λ)


...(1) Here, g is the gap length, λ is the recording wavelength, 1
．． 12 is a correction term. In the above equation (1), at the point where the recording wavelength λ and the gap length g become approximately equal, the gap loss becomes approximately sinπ and the output voltage becomes zero (transmission zero point). Normally, if the transmission zero point exists within the transmission signal band, the output voltage becomes zero, so the gap length g is set to 1/2 or less of the shortest recording wavelength λ of magnetic recording.

In terms of recording characteristics, the narrower the gap length and the greater the coercive force Hc of the recording medium, the higher the saturation magnetic flux density required of the core material of the head. On the other hand, the larger the coercive force Hc of a recording medium, the better its short wavelength characteristics and the higher density recording becomes possible. In many magnetic recording systems, a recording head and a reproduction head are shared, so the gap length is set as a compromise between recording and reproduction.

[0005] Also, as an example of the high-density recording, R-D
AT (Rotary Head Digital Au
dioTape recorder), and this R-
Since the shortest recording wavelength in DAT is 0.67 μm, the reproduction gap length g is set to 0.3 μm or less. Further, the recording medium of R-DAT is a so-called metal tape, and the coercive force Hc is about 1500 Oe. In order to perform sufficient recording on a recording medium with the value of the gap length g (0.3 μm), the saturation magnetic flux density Bs of the core material is required to be 7500 G (Gauss) or more.

FIG. 9 shows a schematic configuration of a conventional magnetic recording/reproducing device.
In the figure, the conventional device records information on a magnetic tape 1 based on a recording current, and also includes a magnetic head 2 that induces and outputs magnetic flux by the recording magnetism of the magnetic tape 1, and a head output signal of this magnetic head 2. an amplifier 3 that amplifies the output signal of the amplifier 3, a second-order differential equalization circuit 4 that performs waveform shaping to equalize the output signal of the amplifier 3, a low-pass filter 5 that removes noise from the waveform-equalized signal that has been shaped, and a noise The integrated circuit 6 includes an integrating circuit 6 that integrates the waveform equalized signal from which has been removed and outputs an integrated signal, and a determination circuit 8 that outputs a data string signal based on the integrated signal based on a predetermined threshold hold level. .

[0007]

[Problem to be Solved by the Invention] Since the conventional magnetic recording/reproducing device is constructed as described above, when the recording head is formed of single-crystal ferrite, the saturation magnetic flux density B
Since s is as low as about 5000 G (Gauss), it cannot be used as is, and the problem is that the gap length must be set to 1/2 or less of the recording wavelength. In order to increase the saturation magnetic flux density Bs, it is possible to use a high saturation magnetic flux density material such as Sendust as the core material of the magnetic head, but this has the problem that the frequency characteristics deteriorate due to large eddy current loss. That will happen. In addition, high saturation magnetic flux density (
A so-called MIG head has been developed in which a thin film of metallic magnetic material (approximately 8,000 to 10,000 G) is deposited, but since it requires a sputtering process to form the thin film, the manufacturing process becomes complicated and costs increase. We had the challenge of becoming.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to propose a magnetic recording/reproducing device that can ease the constraints on the reproduction gap and simplify the manufacturing process.

[0009]

[Means for Solving the Problems] A magnetic recording and reproducing apparatus according to the present invention records digital signals on a magnetic tape and reads and reproduces the recorded digital signals from a magnetic head. The gap length is formed to be larger than the shortest bit interval among the recorded digital signals.

0010

[Operation] In the present invention, since the gap length of the magnetic head is formed in a certain relationship with the shortest bit interval of the recorded digital signal, the constraint on the gap length of the magnetic head during reproduction can be relaxed, and the manufacturing process can be simplified. Simplify.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 8. (a) General description of the present invention First, a general magnetic recording/reproducing apparatus is configured as shown in FIG. 1, and operates as shown in FIG. 2 based on this configuration. Referring to FIGS. 1, 2, and 3, this general magnetic recording/reproducing device encodes an input audio signal, applies appropriate interleaving, and adds redundant codes (bits). The converted signal sequence shown in FIG. 1 is created by modulation. This converted signal is converted into NRZI (Non R
The NRZI signal is generated by modulating the NRZI signal based on the zero inverse (eturn to zero inverse) conversion. Information is recorded on the magnetic tape 1 by causing a recording current to flow through the magnetic head 2 based on this NRZI signal.

The magnetic head 2 is usually an inductive head, and the head output of the inductive head is a time differential waveform of magnetic flux, and ideally the head output waveform is an impulse waveform in the positive and negative directions. However, since there are various types of losses in the magnetic tape 1 and the magnetic head 2, the waveform that is actually output is a waveform with a predetermined width (dull) as shown in the head output signal in FIG. This will cause interference with matching pulses. For this reason, in the case of R-DAT, after the head output signal is amplified by the amplifier 3, the second-order differential equalization circuit 4 performs waveform shaping for waveform equalization to form a waveform equalized signal as shown in FIG.

The waveform equalized signal is passed through a low-pass filter (L
After noise is reduced by PF) 5, it is integrated by an integrating circuit 6 and an integrated signal is output. This integrated signal is transmitted to the detection circuit 7.
After the signal is detected, the determination circuit 8 performs a binary determination of "0" and "1" based on a predetermined threshold level and outputs it as a data string signal. This data string signal is inverted by a NOT circuit 9 and output as a determination signal. This determination signal is converted into a serial signal of "0" and "1" based on a clock signal by a logic operation unit (not shown), and then an exclusive logic is applied between this serial signal and the serial value one clock before. The sum condition is determined and a logical serial signal is output as the final output signal.

Next, the waveform reproduction of one differential pulse corresponding to part a of the waveform equalized signal in FIG. 2 will be considered. This differential pulse in part a corresponds to one magnetization transition on the actual magnetic tape 1. This magnetic tape 1
The signal reproduced by the magnetic head 2 is ideally a pulse with no width, and in this ideal case, no matter how narrow the interval between adjacent pulses, they do not interfere with each other. However, in reality, the pulses are reproduced as pulses with a predetermined width, so they interfere with each other and weaken each other.

This will be explained based on FIGS. 3 and 4. This FIG. 3(A) shows one independent pulse, and FIG. 3(A) shows one independent pulse.
B) and (C) show the case where these independent pulses are made into a continuous pulse train at predetermined intervals. In addition, Fig. 4 (A) is a spectrum characteristic diagram of the head output signal and waveform equalized signal when the gap length g = 0.2 [μm].
(B) shows a time waveform diagram of the spectrum described in (A) of the same figure. In spectra a in FIG. 4(A), if the head output signal is an ideal differential pulse with no width, it would have a completely flat spectrum, so the frequency characteristics of the actual head output signal are extremely degraded. It is something. The time waveform of the pulse itself corresponding to this spectrum a is waveform c in FIG. 4(B). The waveform equalization by the second-order differential equalization circuit 4 is to correct the deteriorated frequency characteristics. The transfer function T(jω) of this second-order differential equalization circuit 4 can be expressed by the following equation.

T(jω)={1+(ω/ωo)2}
…
(2) Here, ω is the angular frequency, and ω1 is the angular frequency of high-frequency enhancement. When the head output signal is corrected by the second-order differential equalization circuit 4 having the characteristic expressed by the above equation, the spectrum becomes as shown in spectrum b in FIG. 3(A). This spectrum b has higher frequency components increased compared to the spectrum a. Correspondingly, the pulse waveform is narrowed and "equalized" (waveform shaped) as shown by waveform d in FIG. 4(B). Since the head output signal has a differential waveform as described above, the original waveform can be reproduced by integrating the pulses of waveform d in FIG. 4(B).

FIG. 5A shows an eye pattern formed by superimposing the cases where random signals are input in this state. In the figure, the waveform corresponds to either positive or negative magnetization direction on the magnetic tape, so it is a binary eye pattern (equivalent to "+" or "-", "1" or "0"). becomes. In this eye pattern, the part e in FIG. 5A is called the "eye", and the fact that this part is open is called "the eye is open". As a comparative example, FIG. 5(D) shows an eye pattern in the case where the spectrum a in FIG. 4(A) is not subjected to waveform shaping by the second-order differential equalization circuit 4. In the figure, it can be seen that the "eye" of the eye pattern does not open, making it impossible to distinguish data at all.

In the case of the head output signals shown in FIGS. 4A and 4B, the gap length g of the magnetic head 2 is 0.2.
[μm]. Regarding R-DAT, the shortest recording wavelength for magnetic recording is 0.67 [μm], which is more than twice this, so the gap length g is sufficiently narrow, and in this example, there is almost no effect of gap loss. Good to say. (b) Description of one embodiment of the present invention Next, the gap length g in the reproducing magnetic head 2 is set to 0.
．． Examples in the case of 6 [μm] are shown in Fig. 1, Fig. 6, and Fig. 7.
The explanation will be based on.

In each of the above figures, the magnetic recording/reproducing apparatus according to this embodiment is formed in the block configuration shown in FIG. 1 like the general apparatus described above, and the width of the gap length g of the magnetic head 2 is different. First, when information is recorded on the magnetic tape 1 by the magnetic head 2, interleaving is applied, a redundant code (bit) is added, and a converted signal string that is 8-10 converted becomes an 8-10 converted signal. (See Figure 6). An NRZI signal is generated by modulating this 8-10 converted signal based on NRZI conversion. This N
Information is recorded on the magnetic tape 1 by passing a recording current through the magnetic head 2 based on the RZI signal.

The case of reproducing information from the recorded magnetic tape 1 is as follows. When this information is reproduced, the recorded information undergoes various losses, and even larger gap losses, and the magnetic head 2 outputs a head output signal as a differential waveform (see FIG. 6). This head output signal is amplified by an amplifier 3 and then subjected to waveform equalization by a second-order differential equalization circuit 4 to form a waveform equalized signal shown in FIG.

[0021] The waveform equalized signal is processed by an LPF formed by, for example, a fifth-order Bessel filter that does not affect the waveform.
Noise is reduced in step 5, and an integral signal is output after being integrated by an integrating circuit. Although the integral signal is reversed in polarity, this is not essential and the winding polarity of the magnetic head 2 is not determined. After the integrated signal is detected by the detection circuit 7, the detected signal is subjected to a binary determination of "0" and "1" based on a predetermined threshold level, and a data string signal is output (FIG. 6). (see inside). This data string signal is inverted by a NOT circuit 9 and output as a determination signal.

Next, FIG. 7 shows whether data can be read from the waveform equalized signal output by the above embodiment.
This will be explained with reference to (A) and (B). In the figure, if the gap length g of the reproducing magnetic head 2 is 0.6 [μm], the wavelength is 0.67 [μm] according to the above equation (1).
(The frequency is 4.7 [MHz]) and the output becomes zero. The reproduced spectrum of the independent pulses in this case is as shown in f in FIG. 7(A). In the diagram, the dip that should appear at 4.7 [MHz] in the spectrum f does not clearly appear due to the relationship of the scale of the graph (the vertical axis is linear). Corresponding to this spectrum f, the waveform becomes extremely wide as waveform h in the time waveform diagram 7(B).

The reproduced spectrum after the pulse is subjected to waveform shaping by the second-order differential equalization circuit 4 is shown as spectrum G in FIG. 7(A). Note that this spectrum g has slightly different characteristics from those of the general device shown in FIGS. 4(A) and 4(B). In the spectrum g, a dip at a frequency of 4.7 [MHz] clearly appears. The time waveform corresponding to the spectrum g at this time is shown as waveform i in FIG. 7(B), and this waveform i has a nearly rectangular waveform with a predetermined width.

The waveform i is output as an integral signal by the integrating circuit 6, and an eye pattern of this integral signal is shown in FIG. 5(B). As mentioned above, an eye pattern like that shown in Figure 5 (A) should be observed at this discrimination point, so in that sense it can be said that the eye is not open. There is an "Ai" itself that is different from what is shown. In this case, a ternary eye opening is obtained when viewed at the times indicated by broken lines in the figure. This indicates that the data can be read by using some appropriate decoder.

Further, the data reading operation will be explained in detail. The NRZI signal in FIG. 6 includes a waveform j (see FIG. 6) which is a signal component of 4.7 MHz, which is the shortest recording wavelength. The waveform corresponding to the waveform j, which is the signal component of 4.7 MHz, is completely lost in the integrated signal outputted from the integrated signal, as shown in the k portion of the integrated signal in FIG. In other words, if there is no RF signal, which is the head output signal, is there no signal or 4.7
It is not possible to determine whether a signal corresponding to MHz continues to be output. Therefore, in a situation such as when the magnetic head 2 is clogged, the determination circuit 8 outputs a continuous data string of "1" as the determination signal. However, R-
In DAT, there is no state in which the shortest repetition of the shortest recording wavelength continues (that is, a state in which the 4.7 MHz signal component continues to be output alone), and even if all binary data "1" continued to be output. However, since the data is no longer significant, error detection will function and muting will be applied even in the worst case. Therefore, there is no practical problem, and there is no need to add a separate circuit to suppress the output of a certain number or more of consecutive "1"s.

In this way, taking R-DAT as an example, it becomes possible to perform reproduction using a magnetic head with a gap length of about 0.6 μm. This value is more than 2.5 times that of the normally used DAT magnetic head,
At this level, even single crystal Mn--Zn ferrite with a low saturation magnetic flux density (approximately 5000 G) can record on a metal tape. Generally, magnetic heads for DAT (the same goes for VTRs) require head inductance to be a predetermined value, but as the gap length increases, the inductance decreases, so a larger number of turns is required. You will be able to do it. Further, the core efficiency during head playback is expressed by the following equation.

Core efficiency=Rg/(Rg+Rc)

...(3) Here, Rg is the magnetic resistance of the gap, R
c is the magnetic resistance of the core. However, if the magnetic resistance Rg of the gap increases due to an increase in the gap length g, the efficiency of the magnetic head 2 itself will also improve. Therefore, the head output signal of the magnetic head 2 increases. This increase in the head output signal results in the exclusion of the vicinity of 4.7 MHz in the case of 0.6 μm.

Note that the gap length g of the magnetic head 2 is set to 0.
An example in which the thickness is 9 μm is shown in FIGS. 8(A) and 8(B). Each of these corresponds to the case of 0.6 μm described above. The eye pattern after integration in this case is shown in FIG. 5(C). In this case, the eye opening has four values (the broken line in the figure). By the way, if it is set to 1.2 μm, it becomes a five-level eye opening. In this case as well, data can be read in the same manner as in FIGS. 7(A), 7(B), and 5(B).

[0029]

[Effects of the Invention] As explained above, in the present invention,
Since the gap length of the magnetic head is formed to have a certain relationship with the shortest bit interval of the recorded digital signal, the constraint on the gap length of the magnetic head during reproduction can be relaxed, and the production process can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a general schematic diagram of a magnetic recording and reproducing apparatus of the present invention.

FIG. 2 is an operation timing chart for explaining the general operation of the device of the present invention.

FIG. 3 is an explanatory diagram of output characteristics of independent pulses for explaining the general operation of the device of the present invention.

FIG. 4 is a spectrum characteristic diagram of a head output signal and a time waveform diagram of a waveform equalized signal corresponding thereto, for explaining the general operation of the apparatus of the present invention.

FIG. 5 shows eye patterns for explaining the general operation of the device of the present invention.

FIG. 6 is an operation timing chart for explaining one embodiment of the magnetic recording/reproducing apparatus of the present invention.

7 is a spectrum characteristic diagram of a head output signal and a time waveform diagram of a waveform equalized signal corresponding thereto, for explaining the embodiment shown in FIG. 6; FIG.

FIG. 8 is a spectrum characteristic diagram of a head output signal and a time waveform diagram of a waveform equalized signal corresponding thereto, for explaining another embodiment of the apparatus of the present invention.

FIG. 9 is a schematic configuration diagram of a conventional magnetic recording/reproducing device.

[Explanation of symbols]

1...Magnetic tape 2...Magnetic head 3...Amplifier 4...Second-order differential equalization circuit 5...Low pass filter 6... Integral circuit 7...Detection circuit 8...Discrimination circuit 9...NOT circuit

Claims (2)

[Claims] 1. In a magnetic recording and reproducing apparatus that records digital signals on a magnetic tape and reads and reproduces the recorded digital signals from a magnetic head, the gap length of the magnetic head is determined by the gap length of the recorded digital signals. A magnetic recording/reproducing device characterized by forming a bit interval larger than the shortest bit interval. 2. The magnetic recording and reproducing apparatus according to claim 1, wherein the gap length of the magnetic head is formed to be an integral multiple of the shortest bit interval of the recorded digital signal. playback device.