JPS645267B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the detection of defects on the storage surface of a storage medium that uses the hysteresis effect of a magnetic material to read and write information, and particularly to a modulation error detection circuit.

A magnetic material is coated or plated on the surface of storage media such as magnetic disks and magnetic tapes.
Due to variations in coating conditions, adhesion conditions, and mechanical surface finish conditions, voltages higher than the standard, i.e., positive modulation errors, and voltages lower than the standards, i.e., negative modulation errors, may occur over a wide range. There is.

In conventional inspection equipment, the read signal is full-wave rectified or half-wave rectified and passed through a low-pass filter in order to determine the peak value variation, or envelope, of the read signal from the head, but there is a limit to the frequency characteristics of the rectifier circuit. In particular, waveform distortion occurs at frequencies above 10-odd megahertz, and there is a fear that accurate envelope waveforms cannot be obtained. Furthermore, since a voltage drop occurs in the low-pass filter, it is necessary to correct the voltage drop. Furthermore, the amount of voltage drop correction changes depending on the frequency and waveform of the read signal, and it is impossible to obtain an envelope with the same correction circuit, especially when the frequency of the solitary wave, which is an output waveform unique to magnetic materials, differs. It was hot. Therefore, in order to obtain the envelope waveforms of signals of magnetic storage media with different read frequencies and to detect modulation errors, detection circuits corresponding to each are required, which leads to high equipment investment and is uneconomical. It was hot.

The purpose of the present invention is to eliminate the above-mentioned drawbacks and to simplify modulation errors in magnetic storage media with different read frequencies by obtaining accurate envelope waveforms over a wide range of frequencies ranging from several hundred kilohertz to more than ten megahertz. and can be obtained using the same circuit.

According to the present invention, there is provided a comparator in which a read signal from a head is connected to a non-inverting input and an output is fed back to an inverting input via a low-pass filter, and an output of the low-pass filter is set to a predetermined upper limit value or a predetermined lower limit value. There is obtained a magnetic storage medium error detection circuit characterized in that it is constituted by two comparators that each output an error pulse when it exceeds the threshold.

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention. A read signal input to an input terminal 101 is connected to a non-inverting input terminal 12 of a comparator 1. In FIG. Comparator 1
The output 13 of is connected to the inverting input terminal 11 of the comparator 1 via the low-pass filter 2, as well as to the non-inverting input terminal 17 of the comparator 3 and the inverting input terminal 18 of the comparator 4. The positive modulation error reference value Eb is input to the inverting input terminal 16 of the comparator 3, and the non-inverting input terminal 19 of the comparator 4 is input.
Input the negative modulation error reference value Ea. The output of comparator 3 is connected to terminal 102, and the output of comparator 4 is connected to terminal 103.

The operation will be explained below. A signal e(t) as shown in FIG. 2A is now input to the read signal input terminal 101.
is input, the input signal of the inverting input terminal 11 of the comparator 1 immediately after the input is at zero level, so the output terminal 13 of the comparator 1 has e(t)≧E.
Since the time period (t) is long, the output pulse width immediately after inputting e(t) becomes large, as shown in FIG. 2B.
When the high frequency component of the pulse is removed by the low-pass filter 2, the pulse is sent to the output terminal 15 of the low-pass filter 2.
As shown in Figure 2C, the waveform E(t) immediately after inputting the input signal e(t) becomes a waveform obtained by integrating the pulses in Figure 2B, and gradually becomes the envelope voltage of the input signal e(t). rises to. On the other hand, since the output signal E(t) of the low-pass filter 2 is fed back to the inverting input terminal 11 of the comparator 1, the time for e(t)≧E(t) in the comparator 1 becomes shorter. The output pulse width at the output terminal 15 of the comparator 1 also becomes smaller. For the output signal E(t) of the output terminal 15 of the low-pass filter 2, the input signal e
When (t) increases, the output pulse width of comparator 1 increases in the direction of increasing E(t), and when the input signal e(t) decreases, no pulse is output from comparator 1 and E(t) descends. That is, E
(t) will be output following the envelope of the input signal e(t).

Furthermore, the signal E(t) shown in FIG.
Criterion value for positive modulation error in
When E(t)≧Eb, a positive modulation error pulse as shown in FIG. 2D is output to the output terminal 102. Similarly, E(t) is compared with a negative modulation error reference value Ea in the comparator 4, and when E(t)≦Ea, a negative modulation error as shown in FIG. 2E is detected. It is output to the output terminal 103 as a pulse. Immediately after the input signal e(t) is input, as shown in FIG. 2E, it is mistakenly recognized as a negative modulation error, so error detection is not performed for a certain period h.

As explained above, according to the present invention, the feedback circuit works in the direction of reducing the error between the peak value of the input signal and the obtained envelope signal, so the influence of the frequency and waveform of the input signal is small, and the readout frequency is In addition to being able to test different magnetic storage media with the same circuit, it is possible to create an inexpensive testing device because the number of elements used is small.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, in which 1 is a comparator, 2 is a low-pass filter, 3 and 4 are
indicates a comparator. Figure 2 shows the waveforms of each part in Figure 1, and
(t) is the signal input to the input terminal 101, E of A
(t) is the same as E(t) of C, low pass filter 2
signal at output terminal 15, B is terminal 13, D is terminal 1
02 and E indicate the signals at the terminal 103, respectively, the horizontal axis indicates time, and the vertical axis indicates voltage.

Claims (1)

[Claims] 1 In a device for testing the output characteristics of a storage medium that uses the hysteresis effect of a magnetic material to read and write information, the read signal from the head is connected to a non-inverting input, and the output is fed back to the inverting input via a low-pass filter. A magnetic storage medium error detection circuit comprising: a comparator; and two comparators each outputting an error pulse when the output of the low-pass filter exceeds a specified upper limit value or a specified lower limit value.