JPH0696404A - Noise removal circuit for floppy disk drive - Google Patents

Abstract

(57) [Abstract] [Purpose] Effectively removing main noise from the detection signal of the magnetic head of a floppy disk drive. [Structure] A magnetic head 11 for recording or reproducing magnetic data on or from a rotating floppy disk is provided.
A noise removal circuit used for a floppy disk drive configured to obtain
A comb filter 13 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for eliminating external noise in a detection signal from a magnetic head of a floppy disk drive, particularly for eliminating horizontal scanning signal leakage from a cathode ray tube (hereinafter referred to as CRT). The present invention relates to a noise elimination circuit for a floppy disk drive.

[0002]

2. Description of the Related Art A conventional floppy disk drive is
It is configured as shown in FIG. That is, the floppy disk drive 1 has a magnetic head 2 that comes into contact with a magnetic track of the floppy disk, and a signal detector that detects a signal from the magnetic head 2. This signal detection unit is an amplifier (Amp) that amplifies the signal of the magnetic head 2.
3 and a detection circuit 4 for extracting a desired detection signal S from the output signal of the amplifier 3.

Generally, various devices are arranged around the floppy disk drive. External noise generated from these devices comes into the detection signal S transmitted between the magnetic head 2 of the floppy disk drive 1 and the detection circuit 4, in particular. This detection signal S is a signal of a relatively small level. In this case, the largest external noise is C near the floppy disk drive.
It is a horizontal scanning signal leaking from the flyback transformer of the RT. External noise due to the leakage of the horizontal scanning signal is
For example, as shown in the spectrum of FIG. 4, it is an integral multiple of the frequency of 15.75 kHz of the normal horizontal scanning frequency.
Other than this largest external noise, the other noises are very low.

In order to remove this external noise, the entire floppy disk drive 1 of FIG. 1 is shielded with a metal plate, or the magnetic head 2 is surrounded by a metal plate or ferrite. This prevents external noise from entering as much as possible.

[0005]

However, if the magnetic head or the entire drive is magnetically shielded as described above, the number of parts is increased and the manufacturing cost is increased. Further, by making the floppy disk drive itself smaller and thinner, and also making the CRT smaller, when a floppy disk drive and a CRT are integrated to form a small computer, the CRT is placed closer to the floppy disk drive. It is provided. Therefore, there is a problem that the horizontal scanning signal of the CRT jumps into the detection signal S from the magnetic head as main noise.

The present invention has been made to solve the above problems, and can effectively remove the main noise due to the leakage of the horizontal scanning signal of the CRT from the detection signal from the magnetic head of the floppy disk drive. It is an object of the present invention to provide a noise elimination circuit for a floppy disk drive that can be used.

[0007]

According to the present invention, the above object is provided with a magnetic head for recording or reproducing magnetic data on a rotating floppy disk, and a detection signal from this magnetic head via a signal detection section. A noise elimination circuit used for a floppy disk drive configured so as to obtain a noise elimination circuit for a floppy disk drive, characterized in that a comb filter is provided in the signal detecting section. It

In the noise elimination circuit of the floppy disk drive according to the present invention, preferably, the signal detection section has a first amplifier and a second amplifier, and the comb filter includes the first amplifier and the second amplifier. It is provided between the amplifiers.

In the noise elimination circuit of the floppy disk drive according to the present invention, the peak of the absorption frequency of the comb filter is preferably an integral multiple of the horizontal scanning frequency of the cathode ray tube.

In the noise elimination circuit of the floppy disk drive according to the present invention, preferably, the peak of the absorption frequency of the comb filter is at an integral multiple of 15.75 kHz which is the horizontal scanning frequency of the cathode ray tube.

[0011]

According to the above construction, the comb filter capable of absorbing a frequency that is an integral multiple of the horizontal scanning frequency of the CRT is inserted in the transmission path from the magnetic head to the detection circuit. Therefore, the CRT around the floppy disk drive
Even if a horizontal scanning signal leaking from the intrusion of a noise signal having a frequency and an integral multiple thereof, the noise signal is removed by the comb filter.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to FIGS. It should be noted that the examples described below are suitable specific examples of the present invention, and therefore, various technically preferable limitations are given, but the scope of the present invention particularly limits the present invention in the following description. Unless otherwise stated, the present invention is not limited to these modes.

FIG. 1 shows a preferred embodiment of a floppy disk drive to which the present invention is applied. In FIG. 1, the floppy disk drive 10 is a magnetic head 1.
1 and a signal detector 20. The magnetic head 11 is
By contacting a rotating floppy disk, magnetic data is recorded on or reproduced from a magnetic track.
The signal detection unit 20 includes a first amplifier (Amp) 12 that amplifies an electric signal generated in the magnetic head 11, and a comb filter 13 that removes a noise signal from an output signal of the first amplifier 12 as described later. A second amplifier 14 for amplifying the signal from the comb filter 13, and a second amplifier 14
And a detection circuit 15 for extracting a desired detection signal SS from the output signal of.

In the comb filter 13, the delay circuit 13
The signal delayed by 1H by a is amplified by the amplifier (Amp) 13
After amplification via b, it is fed back and subtracted. That is, the delay circuit 13a
Is usually composed of a glass delay line or CCD delay element,
The delay circuit delays the signal by H (horizontal scanning period). This 1H (horizontal scanning period) is 1 / 15,75KH
There is a delay of z, that is, 63.5 μS. 15,75
If KHz is fH, 1H is 1 / fH.

The amplitude characteristic obtained by using only the delay circuit 13a is represented by the equation 1 assuming that a 1H delay line is ideal.

[Equation 1]

In Equation 1, the maximum value is obtained in Equation 2 and the characteristic is obtained in Equation 3 to be 0, and a comb filter for removing a signal of an integral multiple of fH is obtained. As a result, as shown in FIG.
Has a filter characteristic such that the horizontal scanning frequency of the reference CRT, for example, a frequency that is an integral multiple of the frequency of 15.75 kHz is set as the peak of the absorption frequency. In reality, since there is attenuation, the amplifier 13b is inserted in the feedback system as shown in FIG.

[Equation 2]

[Equation 3]

In this way, the floppy disk drive 10
The horizontal scanning signal leaking from the CRT around the floppy disk drive 10 enters the transmission path from the magnetic head 11 to the amplifier 12, so that the horizontal scanning frequency of the CRT is 15.75 kHz and its integral multiple. Even if a noise signal of a frequency enters the transmission line of the signal detecting section 20, this noise signal is removed by the comb filter 13.

[0018]

As described above, according to the present invention, C
CRT with a simple configuration that only has a comb filter that absorbs an integer multiple of the horizontal scanning frequency of RT
The main noise due to the horizontal scanning signal can be effectively removed. Therefore, the main noise due to the scanning signal leaked from the CRT, which is the largest noise signal among the detection signals of the magnetic head, is removed by the comb filter. Therefore, the S / N ratio of the detection signal can be significantly improved and the sensitivity can be increased. This eliminates the need for a shield plate or the like that has conventionally been used to remove external noise, thus reducing costs. Then, as the floppy disk drive becomes smaller and thinner,
The integration of the floppy disk drive and CRT is C
This can be easily performed without considering the main noise due to the RT scanning signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing a preferred embodiment of a floppy disk drive to which the present invention is applied.

FIG. 2 is a graph showing an example of characteristics of the comb filter in the embodiment of FIG.

FIG. 3 is a block diagram showing a conventional floppy disk drive.

FIG. 4 is a diagram showing a noise characteristic that penetrates into a detection signal of a magnetic head in the conventional floppy disk drive of FIG.

[Explanation of symbols]

 10 Floppy Disk Drive 11 Magnetic Head 12 First Amplifier 13 Comb Filter 13a Delay Circuit 13b Amplifier 14 Second Amplifier 15 Detection Circuit 20 Signal Detection Circuit

Claims (4)

[Claims] 1. A floppy disk drive comprising a magnetic head for recording or reproducing magnetic data on a rotating floppy disk, and a detection signal is obtained from the magnetic head via a signal detecting section. A noise elimination circuit for a floppy disk drive, characterized in that a comb filter is provided in the signal detection section. 2. The signal detector includes a first amplifier and a second amplifier.
2. The noise elimination circuit for a floppy disk drive according to claim 1, further comprising: an amplifier, wherein the comb filter is provided between the first amplifier and the second amplifier. 3. The noise of a floppy disk drive according to claim 1, wherein the peak of the absorption frequency of the comb filter is at a frequency that is an integral multiple of the horizontal scanning frequency of the cathode ray tube. Removal circuit. 4. The peak of the absorption frequency of the comb filter is 15.75 k, which is the horizontal scanning frequency of the cathode ray tube.
3. The noise elimination circuit for a floppy disk drive according to claim 1, wherein the noise elimination circuit is at an integral multiple of Hz.