JPH0713090Y2 - Data recorder - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a data recorder, and more specifically, in a data recorder using a magnetic tape such as a cassette tape, during data reproduction, an extremely low data signal level due to dropout or The present invention relates to a data recorder capable of correcting a zero level fluctuation of a data signal and reproducing an accurate digital data signal by correcting the fluctuation.

A data recorder of a fixed magnetic head using a magnetic tape such as a cassette tape is used as a data storage means of a personal computer.

When this type of data recorder is used, computer data is converted into 1.2KHZ and 2.4KHZ FSK signals for recording and reproduction.

Fig. 1a shows the FSK data signal recorded on the magnetic tape, and when this is reproduced by the magnetic head, the 2.4KHZ signal part has a substantially sinusoidal waveform because the harmonic components are cut (differentiated). (Fig. 1b). In order to reproduce the original FSK data signal from the obtained sinusoidal data signal, conventionally, a level comparator was used or a high-gain amplifier was used to obtain a saturated output and a predetermined level position based on the zero level (Fig. Then, the waveform is sliced at zero level (Fig. 1, b, c).

However, if the zero level of the data signal fluctuates due to low frequency noise such as power hum of the data recorder or flicker noise generated in the reproduction amplifier of the data recorder, the slice level will be greatly different and the accurate pulse width cannot be reproduced. . That is, FIG. 2a shows a partial waveform of the data signal reproduced by the magnetic head, and the zero level of the signal in the period P fluctuates to become O '. Therefore, if the zero level O is the slice level and there is no zero level fluctuation, the pulse-shaped data signal D1 shown in FIG. 2b is obtained, but in reality, the data signal D2 shown in FIG. e was generated and it became impossible to accurately reproduce the FSK data signal.

Further, even when the level of the data signal is extremely lowered due to dropout or the like, the accurate reproduction of the data is also impossible (Fig. 2c). The present invention solves the above-mentioned conventional drawbacks by forming a pulse wave having a positive and negative peaks adjacent to each other of a sinusoidal data signal reproduced by a magnetic head as a zero level, that is, a rising and falling point. Reproduces an accurate FSK data signal using a high-gain amplifier that can obtain a nearly accurate data signal with level fluctuation removed and a saturated output from a data signal with a predetermined level drop, and no recording of magnetic tape during playback The present invention provides a data recorder which, when reaching the portion, reduces the gain of the preceding high gain amplifier and prevents the supply of erroneous data due to noise.

The present invention will be described in detail below based on the illustrated embodiments.

FIG. 3 shows a data recorder reproduction signal transmission system of the present invention, in which 1 is a reproduction head, 2 is a reproduction preamplifier, 3 is a differentiating circuit, and 4 is a variable gain amplifier. A signal level detection circuit 5 detects the sine wave data signal level picked up by the magnetic head 1 and amplified by the preamplifier 2. Reference numeral 6 denotes a transistor switch that is ON-OFF controlled by the detection output from the detection circuit 5. In the ON state, one end of one negative feedback resistor R2 of the negative feedback circuit 7 of the variable gain amplifier 4 is grounded, and the negative feedback The amplifier has an amplification degree obtained by the ratio β = R2 / R1 + R2. The gain in this case is set so that a saturated output can be obtained even if a data signal whose level has been lowered by a predetermined level with respect to the normal signal level of the data signal is input. Considering the dropout and noise level in commercially available data tapes, the gain is set so that even a data signal that is 20dB lower than the normal data signal level can be corrected. As a result, all the data signals having a level higher than that of the data signal to be level-corrected are shaped into pulse signals of a constant level.

On the other hand, when the transistor switch 6 is OFF, the gain of the variable gain amplifier 4 is 1 because 100% negative feedback is added.

The state where the transistor switch 6 is ON is during reproduction of the data recording portion of the magnetic tape, and the OFF state is during reproduction of the last recorded portion of the magnetic tape.

The circuit configuration is as described above, and its operation will be described next.

FIG. 4 shows a reproduced waveform of the data signal in each part of the above circuit, and FIG. 4a shows a recorded waveform (original signal), which is picked up by the reproducing head 1 and amplified by the preamplifier 2 to be shown in FIG. 4b. A sinusoidal data signal S is obtained. The zero level of the data signal S fluctuates during the period t1 (dotted line Q in FIG. 4b), and the signal level drops extremely during the period t2. By applying this data signal to the differentiating circuit 3 and processing it, a pulse-shaped data signal T having a zero level at adjacent positive and negative peak points can be obtained as shown in FIG. 4c. Although the phase of the data signal T is advanced by 90 ° with respect to the original signal, the pulse width is almost the same as the original signal. That is, the data signal S obtained from the preamplifier is a derivative of the original signal, and the interval between the positive and negative differential pulses obtained at the rising portion and the falling portion of the original signal matches the pulse width of the original signal. Therefore, the adjacent positive and negative peaks of the data signal S obtained by differentiating the original signal are equal to the pulse width of the original signal regardless of the fluctuation of the zero level. That is, the zero level interval of the data signal T obtained by differentiating the data signal S almost indicates the pulse width of the original signal.

Next, the data signal T is supplied to the variable gain amplifier 4.
At this time, the variable gain amplifier 4 is in the high gain state because the transistor switch 6 is ON due to the detection output from the level detection circuit 5, and a sufficient saturation output is obtained even from the signal whose level has decreased in the t2 period of the data signal S. Can be obtained (FIG. 4d), and a data signal U almost equal to that obtained by amplifying the original signal can be obtained.

Therefore, at the time of data reproduction, even if there is a data signal whose level is extremely lowered with respect to the normal signal level in the data recorder, data loss or data error does not occur.

Next, in the reproducing state, when the non-recorded portion of the data signal existing between the programs is reached, no output is obtained from the reproducing preamplifier, and the transistor switch 6 is turned on by the level detection circuit detecting the non-signal state. It turns off, and the gain of the variable gain amplifier drops to 1.

This is because when a high gain amplifier is simply used without using a variable gain amplifier, if noise is mixed during playback of the data unrecorded portion of the magnetic tape, there is a risk of amplifying this and outputting a signal equivalent to the data. Therefore, the variable gain amplifier is used and the gain is set to 1 except when necessary. It is also possible to prevent the residual noise including the tape and hiss noise from being enlarged by the speaker of the data recorder during the reproduction of the non-recorded portion of the data and causing annoyance.

Although one embodiment of the present invention has been described above, various other modifications are possible. For example, in the above embodiment, the presence or absence of a data signal was detected at the input side of the variable cane amplifier. It is also possible to detect on the output side of the gain amplifier.

As described above, in the present invention, in the data recorder using the magnetic tape, the data signal picked up by the magnetic head is applied to the differentiating circuit, and the data signal from the differentiating circuit is reproduced in the data recording portion of the magnetic tape. There is no data error due to zero level fluctuations in the reproduced data signal, and the level drops such as dropout because the data processing is performed in addition to the variable gain amplifier which becomes high gain when the data is not recorded on the magnetic tape and low gain when reproducing the data unrecorded part of the magnetic tape. It is possible to correct the error and prevent the malfunction due to the mixing of noise during the reproduction of the non-recorded portion of the data.

[Brief description of drawings]

FIG. 1 is a reproduced data signal waveform diagram for explaining a reproducing operation of a conventional data recorder, FIG. 2 is a reproduced data signal waveform diagram for explaining a defect of the conventional data recorder, and FIG. 3 is an example of a data recorder of the present invention. FIG. 4 is a block diagram showing an embodiment, and FIG. 4 is a reproduced data signal waveform diagram for explaining the embodiment of the present invention. Explanation of symbols 1 ... Magnetic head, 2 ... Playback preamplifier 3 ... Differentiation circuit, 4 ... Variable gain amplifier 5 ... Level detection circuit 6 ... Transistor switch

Claims (1)

[Scope of utility model registration request] 1. A data recorder for recording / reproducing data on / from a magnetic tape, and a differentiating circuit for obtaining a pulse-shaped data signal having rising and falling points of adjacent positive and negative peaks of a data signal picked up by a magnetic head. , A variable gain amplifier for switching the output from the differentiating circuit, a level detection circuit for detecting the presence or absence of the data signal, and for switching the variable gain amplifier to high or low according to the output from the level detection circuit When the presence of a data signal is detected by the detection circuit, the detection output puts the variable gain amplifier into a high gain state via the control circuit and detects the absence of a data signal. When it does, the detection output from the detection circuit through the control circuit Data recorder being characterized in that the variable gain amplifier so as to form a low state.