JPH01134708A - Magnetic medium reading signal pseudo-waveform preparing circuit for magnetic recording device - Google Patents

Abstract

PURPOSE:To obtain a pseudo-waveform approximate to a reading signal waveform and without a noise by providing a filter circuit and a differentiation circuit between an input circuit and an output circuit to execute an impedance conversion and an amplitude conversion. CONSTITUTION:A digital signal is made to pass an input circuit 9 to execute the impedance conversion and amplitude conversion, thereafter, filter-processed by a filter circuit 10, and next, differentiated by a differentiation circuit 11. A differentiation output is extracted from an output circuit 12 to have impedance conversion and amplitude conversion function. Since a step response filter output is differentiated in such a way, an impulse response in the changing point of a digital input signal can be obtained, and the signal of a waveform approximate to the waveform of an actual reading signal and without the noise can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a circuit for creating a pseudo waveform of a read signal of an electromagnetic conversion system used for circuit testing of a magnetic disk drive or the like.

[Conventional technology]

Figures 24 and 25 show part of the data circuit system and servo drive of a magnetic disk drive described in the Silicon Systems product low-resolution memory device general catalog (Internics Corporation, published in March 1986). A part of the circuit system is summarized and shown. 1 is a magnetic disk, 2 is a magnetic head, 3 is an amplifier, 4 is an automatic gain control circuit (AGC circuit), 5 is a pulse detection circuit, and 6 is a data discrimination circuit. The circuit 7 is a position detection circuit.

The magnetic data recorded on the magnetic disk l is read out through the magnetic head 2, amplified by the amplifier 3, and then
It is converted into a signal of constant amplitude by the GC circuit 4, and the 24th
In the data circuit system shown in the figure, after phase information of the signal is detected by a pulse detection circuit 5, the signal is discriminated into a data signal and a clock signal by a data discrimination circuit 6. On the other hand, in the servo circuit system shown in FIG. 25, the output of the AGC 4 is converted into a position signal by the position detection circuit 7.

[Problem that the invention seeks to solve]

By the way, since noise is superimposed on the read signal (digital signal) sent out from the magnetic head 2, the performance of the data circuit system and servo circuit system described above was evaluated using the output of this magnetic head 2. In this case, there was a problem in that the problem location could not be found due to the noise, and the results of the performance evaluation could not be 100% reliable.

This invention was made to solve the above problem.
It is an object of the present invention to provide a pseudo waveform creation circuit for a magnetic medium read signal of a magnetic recording device, which can create a pseudo waveform of a read signal from a magnetic medium to improve the reliability of the performance evaluation described above.

[Means for solving problems]

In order to achieve the above object, the present invention converts digital signals into
After passing through an input circuit that performs impedance conversion and amplitude conversion, it is filtered in a filter circuit, then differentiated in a differentiation circuit, and the differential output is taken out through an output circuit that has impedance conversion and amplitude conversion functions. .

[Effect]

In this invention, since the step response filter output is differentiated, an impulse response at a change point of the digital input signal can be obtained, and a signal with a pseudo waveform that approximates the waveform of the actual readout signal and is free of noise can be obtained.

〔Example〕

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

In FIG. 1, 8 is a digital input signal, 9 is an input circuit, 10 is a filter circuit, 11 is a differentiation circuit, 12 is an output circuit, and 13 is an analog output signal. The generation circuit 29 for the digital input signal 8 uses a write circuit of a magnetic disk device or a commercially available data generator, and the analog output signal 13 is generated by the amplifier 3 shown in FIG. 24 or 25.
given to.

The input circuit 9 performs impedance conversion and amplitude conversion of the TTL level digital input signal 8 as shown in FIG. 3 using, for example, the circuits shown in FIGS. 2 and 12, and performs ECL
It is converted into a level differential signal of 15.16. 9a is a voltage dividing resistor having a grounded center tap, 9b is a differential amplifier, and 9C is a matching resistor.

The filter circuit 10 is a low-pass filter circuit with linear phase characteristics, and as shown in FIG. 4, it includes an impedance conversion section 17 whose characteristic impedance is a matching resistor 18 on the input side, a filter section 19, and an output side. The line potential difference signal waveform 24 of the differential signals 15 and 16
In response, as shown in FIG. 7, an output signal 21 that responds in a step manner is sent out. Tr is a transistor, R is a resistor,
L is an impedance and C is a capacitor.

Note that if the value of the matching resistor 18 is determined in consideration of the output impedance of the input circuit 9, the circuit shown in FIG. 13 may be used. Moreover, any order can be used as the order of the filter section 19.

The differentiating circuit 11, as shown in FIG. 5, includes an impedance converting section 22 and a differentiating section 23, and produces a differential output 25 shown in FIG. 7 with respect to the output signal 21 of the filter circuit 10. The impedance conversion section 22 is provided so as not to affect the filter circuit side 10. This differential circuit 1
1 may have a differential function, and other examples are shown in FIGS. 16 to 18. A is a differential amplifier.

As shown in FIG. 6, the output circuit 12 consists of a differential amplifier 27 for impedance conversion and a resistor 28 for arbitrarily setting the amplitude.
5 to amplifier 3 in FIG. This output circuit 12 only needs to have the functions of impedance conversion and amplitude conversion, and other examples are shown in FIGS. 19 and 20.

In this way, in this embodiment, after converting the digital human input signal 8 into the differential signal 15.16, it is passed through the filter circuit 10 and the output of this filter circuit 10 is differentiated.
As is clear from the comparison between the waveform 25 in the figure and the average waveform 26 of the actual read signal waveform sent out from the magnetic head 2 of the magnetic disk drive shown in FIG. 11, it is very close to the actual read signal waveform 26. A signal 25 having a waveform can be created.

Since this pseudo waveform 25 has no noise, the output circuit 12
If the pseudo waveform 25 is used in a performance evaluation test of the data circuit system or servo circuit system after adjusting the amplitude etc. through the servo circuit, highly reliable evaluation results can be obtained.

8 to 10 show the waveform of the output 21 of the filter circuit 10 with respect to the output (line potential difference signal waveform) of the input circuit 9 when the digital input signal 8 is continuously input,
The waveform of the differential output 25 of the differential circuit 11 is shown.

The input circuit 9 is provided with a signal conversion circuit for converting the digital input signal 8 into the modulation signal 8A shown in FIG. 23 or the NRZI signal 8B, for example, a flip-flop circuit shown in FIGS. 21 and 22. You may.

In order to improve the phase characteristics of the filter section 19, a phase compensation circuit as shown in FIGS. 14 and 15 may be inserted into the filter circuit 10.

The output circuit 12 may have a function of adding a plurality of other signals to the output signal 25.

In the above embodiment, it goes without saying that the positions of the filter circuit 10 and the differentiating circuit 11 may be reversed.

Although the above embodiment uses a differential circuit system, the present invention can obtain similar effects even when a single-end system is used.

〔Effect of the invention〕

As explained above, this invention has a configuration in which a filter circuit and a differentiation circuit are provided between an input circuit and an output circuit that can perform impedance conversion and amplitude conversion. Since it is possible to obtain a noise-free pseudo waveform that approximates the read signal waveform, by using this pseudo waveform signal, it is possible to accurately evaluate the performance of the magnetic recording device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the invention, FIGS. 2 and 12 are circuit diagrams showing the specific configuration of the input circuit in the above embodiment, and FIG. 3 is an input/output waveform diagram of the input circuit.
4 and 13 are circuit diagrams showing the specific configuration of the filter circuit in the above embodiment, and FIGS. 5 and 16 to 1
Figure 8 is a circuit diagram of the differential circuit in the above embodiment; Figure 6;
19 and 20 are circuit diagrams showing the specific configuration of the output circuit in the above embodiment, and FIGS. 7 to 10 are output waveform diagrams of the filter circuit and the differentiation circuit corresponding to the input of the filter circuit. , FIG. 11 is an average output waveform diagram of the magnetic head output, FIGS. 14 and 15 are diagrams showing an example of a phase compensation circuit, and FIGS. 21 and 22 are diagrams showing a signal conversion circuit incorporated in the input circuit. , FIG. 23 is an output waveform diagram of the signal conversion circuit, and FIGS. 24 and 25 are diagrams showing examples of circuits to be subjected to performance evaluation. In the figure, 9--input circuit, 10--filter circuit, 11--differentiating circuit, 12--output circuit, 17--impedance conversion section, 18--input end matching resistor, 19--filter section, 20--output side matching resistor, 22 - impedance conversion section, 23 - differentiation section, 29 - digital input signal generation circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] An input circuit that inputs a digital signal and performs impedance conversion, a low-pass filter circuit that has a linear phase characteristic and filters the output of the input circuit, and a differential processing of the output of the filter circuit. A magnetic medium read signal pseudo waveform creation circuit for a magnetic recording device, comprising a differentiating circuit and an output circuit that takes in the output of the differentiating circuit and performs impedance conversion. (2) A magnetic medium read signal pseudo waveform generation circuit for a magnetic recording device according to claim 1, wherein the impedance conversion is accompanied by amplitude conversion. (3) A magnetic medium read signal pseudo waveform generation circuit for a magnetic recording device according to claim 1 or 2, wherein the filter has a phase compensation circuit.