JPH0192962A - Magnetic recording read system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording reading system, and relates to an improvement of a magnetic recording reading system that reads signals recorded by FM modulation.

[Conventional technology]

The conventional device is as described in Magnetic Recording Technology Volume 3-5.
Variation in reading speed and order of reading signal.

At the same time, no consideration was given to the phase shift.

[Problem that the invention seeks to solve]

One of the common methods of configuring signals recorded on magnetic media is to place a magnetic head on the medium, move either the magnetic head or the medium m1, and amplify the signal from the magnetic head. . At this time, if the reading speed is unstable, it is difficult to accurately FM demodulate the regenerated signal.

As one of the above-mentioned measures, the standard timing for FM demodulation may be always determined based on the length of data one bit before. In this way, even if the reading speed changes and the length of 1 bit changes, FM demodulation becomes possible while following the change.

However, there is another problem here. The problem is that the phase of the regenerated signal shifts depending on the data reading pattern. For example, in the case of FIG. 3, when the center and trailing edge signals of data "1" are shifted backwards, when FM demodulation is performed using the above method, the data changes from "0100" to "011".

The purpose of the present invention is to solve the above two problems.

[Means for solving problems]

The above object is achieved by determining the reference timing for FM demodulation not by the length of data one bit before, but by the average of the data lengths of a plurality of bits up to one bit before.

[Effect]

Since the phase shift of the signal occurs locally, if the reference timing is shifted by averaging the lengths of a plurality of bits, the variation in the reference timing due to the phase shift will be further reduced.

However, when using the average value of many bits, it is necessary to use a weighted average that reduces the influence of the bit length of temporally distant bits in order to prevent the standard timing from degrading the ability to follow fluctuations in reading speed. There is.

[Example] An example of the present invention will be described below with reference to FIGS. 1 and 2.

1 is a counter, 2 to 4 are registers, 5.6 is a multiplier, 7
8 is an adder; 8 is a counter that counts down by a block (CLK2); 9. IU+1 flip-flop,
15 is a waveform converter, 10 is EXCLUS IVg-OR
The gate 11 is an inverter. Waveform 15 is an FM modulated configurable waveform, waveform 16 is the output of counter 8, waveform 17 is the output of waveform converter 13, and waveform 18 is the FM demodulated output of flip-flop 12.

Waveform 15 is “1” from rOJ or from “1” to “0”
, the output of the gate 8 becomes "1" and is converted into a positive pulse by the waveform converter.

Since the output signal of the waveform converter serves as a trigger for register 2, the count value of counter 1 is transferred to register 2, and the value of register 2 is transferred to register 5 through multiplier 5. Since register 1 is reset bit by bit by waveform 17, the multiplication coefficients of multipliers 5 to 60 are set to 1/1.
2, register 2 is set to the count value 1 bit before, register 5 is set to 172, the count value 2 bits ago, and register 4 is set to 1/4 of the count value 6 bits ago. is set.

Therefore, the output value of the adder 7 is (count value 1 bit before x 1/2) + (count value 2 bits before x).

1/q) + (3 bits previous count value x1/4)
becomes. On the other hand, since the waveform 17 is the load input of the counter 8, the output value of the adder 7 is used as the initial value, and the CL
By K2, the force 9 counter 8 starts a countdown.

Here, if the frequency ratio of 2 to CLKI and CI is set to 0.75:1, the pollo output of the counter 8 (corresponding to waveform 16) can be used as the reference timing for FM demodulation.

A portion 14 surrounded by a dashed line in FIG. 1 is an FM demodulator.

According to this embodiment, there is an effect that reading errors can be reduced with respect to fluctuations in reading speed and phase shifts of configurable waveforms.

〔Effect of the invention〕

According to the present invention, since the reference timing of FM demodulation is determined by the average value of a plurality of bit lengths, it is effective to reduce reading errors due to fluctuations in reading speed and locally generated phase shifts of the read signal. There is.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a signal waveform diagram of FIG. 1, and FIG. 3 is a waveform diagram when the read signal is out of phase. 1... Counter, 2-4... Register, 5, 6... Multiplier, 7... Adder,
14...-FM demodulator.

Claims (1)

[Claims] 1. In the magnetic recording reading method that reads magnetic records recorded by FM modulation, there is a counter that measures the length of 1 bit from the regenerated signal, a register that stores the counter value, and the values of the counter and register are added together. and a demodulator to demodulate the regenerated signal.
A magnetic recording reading method characterized in that a reference timing for demodulating an M signal is generated using an average value of the lengths of a plurality of bits up to one bit before.