CN102779531A - Closed-loop method for measuring magnetic head signal-to-noise ratio and medium signal-to-noise ratio - Google Patents

Abstract

The invention discloses a closed-loop method for measuring a magnetic head signal-to-noise ratio. The method is suitable for a recording device for recording a medium and a magnetic head. The method includes the following steps that (a) the magnetic head is loaded on the medium and a certain dynamic fly height is maintained; (b) an initial environment temperature value T1 is measured and simultaneously a signal load of a magnetic head signal is measured; (c) the magnetic head is removed from the medium; (d) the motive power for controlling the dynamic fly height is adjusted until a real-time environment temperature value T2 is identical to the initial environment temperature value T1; (e) a noise unload of a magnetic head noise value is measured; and (f) the magnetic head signal-to-noise ratio is calculated through a formula shown as follow. The method provides a fair and consistent condition for the measurement of signals and noises, and thereby the reliable and accurate magnetic head signal-to-noise ratio is obtained. Simultaneously, a closed-loop method for measuring a medium signal-to-noise ratio is further provided.

Description

Closed type is measured the magnetic head noise method of media signal to noise ratio (S/N ratio) when

Technical field

The present invention relates to the for example performance test methods of disc driver of a kind of pen recorder, relate in particular to a kind of closed type measure the magnetic head signal to noise ratio (S/N ratio) (signal to noise ratio, SNR) and the method for media (media) signal to noise ratio (S/N ratio).

Background technology

Disc drive unit is a kind of common information record carrier; It comes the stored record data through using magnetic media, and use one be positioned at said magnetic media top removable read/write head come optionally to read or the magnetropism media writes data from said magnetic media.

In order to pursue readwrite performance more accurately; Disc drive unit manufacturer is devoted to develop the disk set with higher storage capacity always; Such as increasing the density of magnetic track, and then increase the memory capacity of disk indirectly through track width or the mode of track pitch that reduces on the disk.Yet along with the increase of track density, more and more difficult becomes on the magnetic track that uses conventional art to realize faster more accurately read/write head is positioned to expect on the disk.Therefore, disc drive unit manufacturer promptly adopts voice coil motor (VCM, voice-coil motor) to improve the precision of read/write head position control on compact disk through a kind of method of effective utilization.Referring to Fig. 1, a kind of traditional magnetic disk driver element that uses voice coil motor typically has an actuating arm 104, one and is connected to and is installed in the magnetic head fold piece combination 106 on the said actuating arm 104, the Spindle Motor 102 that is suspended at the disk 101 on the said magnetic head fold piece combination 106 and rotates said disk 101.Said voice coil motor is represented with Reference numeral 105 and is connected on the said actuating arm 104; To control the motion of said actuating arm 104; And then control on the magnetic track on surface that slide block 103 on the said magnetic head fold piece combination 106 is positioned at said disk 101, make that finally the read/write heads in the said slide block 103 can or be write data on the said disk 101 from reading of data on the said disk 101.Current, (tunnel magneto resistive, TMR) sensor is commonly referred to as the TMR sensor to tunnel magneto resistance, can go up the ability of reading of data from media (magnetic disk surface) with bigger track and linear density because it has, and become the read transducer of main flow.

There are various distinctive tests to be used to measure the performance of disc driver.Wherein, signal to noise ratio (S/N ratio) is a key parameter that is used to test disc driver, because it can (bite error rate BER) has correction preferably to the bit error rate.Yet, because total signal to noise ratio (S/N ratio) of disc driver has the influence of read and write usually,, other two kinds of signal to noise ratio (S/N ratio)s have been proposed for the influence that obtains different read and writes realizes better characteristic test, therefore have: (Total_SNR) ²=(Media_SNR) ²+ (Head_SNR) ²

Particularly; Read or the magnetropism media writes the pen recorder of the magnetic head of data from magnetic media with being used for for having recording medium; Total signal to noise ratio (S/N ratio) comprises the influence of read and write; The measurement of its signal and noise all is to have certain dynamic fly height at magnetic head (dynamic fly height is carried under the condition on the media, and the magnetic head signal to noise ratio (S/N ratio) mainly includes only and reads part DFH); The measurement that is its signal is that the measurement of noise figure is to carry out under the situation after magnetic head is removed after magnetic head loads.The media signal to noise ratio (S/N ratio) has comprised that the conversion of the influence write and media is related, can calculate through following equation:

$\mathrm{Media}\_\mathrm{SNR}=\sqrt{{(\mathrm{Total}\_\mathrm{SNR})}^2-{(\mathrm{head}\_\mathrm{SNR})}^2}.$

In disk note driver, the magnetic recording medium on the disk is the granulated metal alloy, routine CoPt alloy, and the media intrinsic noise increases along with the increase of linear recording density.Owing to the irregular media noise that occurs of the magnetic conversion of record, and cause the random drift of readback signal peak value.Higher media noise causes higher bit error rate, so in disc driver, obtain higher area density, must reduce the media intrinsic noise, promptly improves the signal to noise ratio (S/N ratio) of recording medium.Therefore the estimation that is necessary for the media signal to noise ratio (S/N ratio) provides accurate magnetic head signal to noise ratio (S/N ratio) parameter.

Traditional method that is used to measure the magnetic head signal to noise ratio (S/N ratio) is through utilizing dynamic property (dynamic performance; DP) signal is under the condition that magnetic head does not have to load, to measure noise figure, and magnetic head load with situation about removing under; The power of its control dynamic fly height all exists; Therefore, owing to be the measuring condition that power is being opened and magnetic head is removed from media, will cause estimating the value of little magnetic head signal to noise ratio (S/N ratio) at the control dynamic fly height; Because the temperature of the environment when measuring noise causes noise figure higher than high under the actual conditions.

Therefore, be badly in need of providing a kind of closed type method to improve the measuring accuracy of magnetic head signal to noise ratio (S/N ratio) and the measuring accuracy of media signal to noise ratio (S/N ratio).

Summary of the invention

One of the object of the invention is to provide for pen recorder a kind of method of closed type measurement magnetic head signal to noise ratio (S/N ratio), and this method can be the fair measuring condition that signal and noise keep, thereby improves the measuring accuracy of magnetic head signal to noise ratio (S/N ratio).

Another object of the present invention is to provide for pen recorder a kind of method of closed type measurement media signal to noise ratio (S/N ratio), this method can be the fair measuring condition that signal and noise keep, thereby improves the measuring accuracy of media signal to noise ratio (S/N ratio).

In order to achieve the above object; The present invention provides a kind of closed type to measure the method for magnetic head signal to noise ratio (S/N ratio); Be applicable to pen recorder, said method comprising the steps of: (a) be loaded into magnetic head on the media and keep certain dynamic fly height with recording medium and magnetic head; (b) measure original ambient temperature value T1, and measure magnetic head signal signal simultaneously _Load(c) magnetic head is removed from media; (d) adjustment is used to control the power of dynamic fly height, and T2 equals original ambient temperature T1 up to the real time environment temperature value; (e) measure magnetic head noise figure noise _Unload(f) calculate the magnetic head signal to noise ratio (S/N ratio) through following equation:

$\mathrm{Head}\_\mathrm{SNR}=20\×\log \left(\frac{{\mathrm{signal}}_{\mathrm{load}}}{{\mathrm{noise}}_{\mathrm{unload}}}\right).$

Preferably, said environment temperature is detected by temperature sensor, and said temperature sensor is embedded in the said magnetic head, and said environment temperature is characterized by the impedance of said temperature sensor.

Preferably, said step (b) is for measuring the initial impedance value TSR1 of temperature sensor.Preferably, said step (d) equals the initial impedance TSR1 of temperature sensor for adjusting the power that is used to control dynamic fly height up to the real-time resistance value TSR2 of temperature sensor.

Preferably, said step (d) may further comprise the steps: (d1) increase the power that is used to control dynamic fly height; (d2) T2 of measurement under corresponding dynamic action; (d3) judge whether T2=T1 sets up, if not, execution in step (d1)-(d2) is if forward step (e) to.Preferably, the said power that is used to control dynamic fly height is by zero beginning increase gradually.

In order to reach above-mentioned another purpose, the present invention provides a kind of closed type to measure the method for media signal to noise ratio (S/N ratio) simultaneously, said method comprising the steps of: (a) be loaded into magnetic head on the media and keep certain dynamic fly height; (b) measure original ambient temperature T1, and measure magnetic head signal signal simultaneously _Load(c) magnetic head is removed from media; (d) adjustment is used to control the power of dynamic fly height, equals original ambient temperature T1 up to real time environment temperature T 2; (e) measure magnetic head noise figure noise _Unload(f) calculate the magnetic head signal to noise ratio (S/N ratio) through following equation: (g) calculate the media signal to noise ratio (S/N ratio) through following equation:

Preferably, said step (b) further comprises measurement magnetic head noise figure noise _LoadSaid total signal to noise ratio (S/N ratio) is calculated through following equation:

Preferably, said environment temperature is detected by temperature sensor, and said temperature sensor is embedded in the said magnetic head, and said environment temperature is characterized by the impedance of said temperature sensor.

Preferably, said step (b) is for measuring the initial impedance TSR1 of temperature sensor.Said step (d) equals the initial impedance TSR1 of temperature sensor for adjusting the power that is used to control dynamic fly height up to the real-time impedance TSR2 of temperature sensor.

Preferably, said step (d) may further comprise the steps: (d1) increase the power that is used to control dynamic fly height; (d2) T2 of measurement under corresponding dynamic action; (d3) judge whether T2=T1 sets up, if not, execution in step (d1)-(d2) is if forward step (e) to.Preferably, the said power that is used to control dynamic fly height is by zero beginning increase gradually.

Compared with prior art, thus closed type provided by the invention measure the method for magnetic head signal to noise ratio (S/N ratio) and provide the condition of justice to have higher measuring accuracy through measurement for signal and noise.Said magnetic head signal to noise ratio (S/N ratio) is passed through equation:

Calculate, wherein, magnetic head signal signal _LoadMeasurement be to be carried on the media and to keep under the condition of certain flying height at magnetic head, and the measurement of noise is under the condition that magnetic head is removed from media, magnetic head signal signal _LoadWith noise figure noise _UnloadMeasurement all be under the condition that the motive use that is used to control dynamic fly height, to carry out.Because the power that is used to control dynamic fly height is still in application, environment temperature is high more a lot of than actual conditions when magnetic head is removed, and influences noise figure noise _UnloadAnd cause over-evaluating of noise figure.Method provided by the present invention is attempted " control " temperature after magnetic head is removed makes it near actual conditions.Therefore, measuring magnetic head signal signal _LoadThe time; Initial environment temperature T1 is simultaneously measured to be used as comparison; Then after magnetic head is removed, the power that is used to control dynamic fly height through adjustment influences real-time environment temperature and equals T1 up to corresponding real time environment temperature T 2, is under fair consistent condition, to accomplish thereby make the measurement of noise; Obtain reliable, accurate magnetic head signal to noise ratio (S/N ratio) thus, further obtained reliable, accurate media signal to noise ratio (S/N ratio) thus equally.

Through following description and combine accompanying drawing, technology contents of the present invention, structural attitude, institute reaches purpose and effect will become more clear, and these accompanying drawings are used to explain embodiments of the invention.

Description of drawings

Fig. 1 writes and/or the structural representation of the traditional record device of the magnetic head of reading of data from media with being used for for the recording medium that has according to prior art.

Fig. 2 is a process flow diagram of measuring the method for magnetic head signal to noise ratio (S/N ratio) according to the closed type of one embodiment of the invention.

Fig. 3 is the sub-process figure of the step (S104) of method shown in Figure 2.

Fig. 4 is for the impedance of showing temperature sensor and be used to control the chart of the relation between the power of dynamic fly height.

Fig. 5 is a process flow diagram of measuring the method for media signal to noise ratio (S/N ratio) according to the closed type of one embodiment of the invention.

Embodiment

Below will combine accompanying drawing to describe each embodiment of the present invention, wherein, mark identical in each accompanying drawing is represented components identical.As stated; The invention provides a kind of closed type and measure the method for magnetic head signal to noise ratio (S/N ratio); Be applicable to that having recording medium writes and/or the pen recorder of the magnetic head of reading of data from media with being used for, this method is attempted " control " temperature after magnetic head is removed makes it near actual conditions.Measuring magnetic head signal signal _LoadThe time; Initial environment temperature T1 is simultaneously measured to be used as comparison; Then after magnetic head is removed, the power that is used to control dynamic fly height through adjustment influences real-time environment temperature and equals T1 up to corresponding real time environment temperature T 2, is under fair consistent condition, to accomplish thereby make the measurement of noise; Obtain reliable, accurate magnetic head signal to noise ratio (S/N ratio) thus, further can obtain reliable, accurate media signal to noise ratio (S/N ratio) thus.

With reference to figure 2, as shown in the figure, the method for measuring the magnetic head signal to noise ratio (S/N ratio) according to the closed type of one embodiment of the invention may further comprise the steps: (step S101) is loaded into magnetic head on the media and keeps certain dynamic fly height; (step S102) measures original ambient temperature T1, and measures magnetic head signal signal simultaneously _Load(step S103) removes magnetic head from media; (step S104) adjustment is used to control the power of dynamic fly height, equals original ambient temperature T1 up to real time environment temperature T 2; (step S105) measures magnetic head noise figure noise _Unload(step S106) calculates the magnetic head signal to noise ratio (S/N ratio) through following equation:

$\mathrm{Head}\_\mathrm{SNR}=20\×\log \left(\frac{{\mathrm{signal}}_{\mathrm{load}}}{{\mathrm{noise}}_{\mathrm{unload}}}\right).$

Particularly, the environment temperature in the step (S102) is detected by temperature sensor, and said temperature sensor is embedded in the said magnetic head, and said environment temperature is characterized by the impedance of said temperature sensor.Said temperature sensor is additional being embedded in the magnetic head, especially near the TMR sensor, but different with the TMR sensor.Through said temperature sensor, thereby obtain real-time environment temperature.Preferably, in order to compare more easily, said step (S102) replaces measures the initial impedance TSR1 that original ambient temperature T1 becomes the measurement temperature sensor.Correspondingly, said step (S104) becomes the power that adjustment is used to control dynamic fly height, equals the initial impedance TSR1 of temperature sensor up to the real-time impedance TSR2 of temperature sensor.

The power that being used in the said step (S104) controlled dynamic fly height is to be used for influencing real-time environment temperature.When magnetic head is loaded on the media, one be used to control dynamic fly height power will be applied to make this magnetic head to float in media surface with having certain flying height.Because this power that is used to control dynamic fly height is removed the back just as a well heater at magnetic head, makes environment temperature become higher, thereby causes the unfairness of noise measurement condition.Therefore, the control temperature is essential when magnetic head is removed back measurement noise.With reference to figure 3, step (S104) further may further comprise the steps: (S401) increase the power that is used to control dynamic fly height; (S402) T2 of measurement under corresponding dynamic action; (S403) judge whether T2=T1 sets up, if not, execution in step (S401)-(S402) is if forward step (S105) to.Under the application of temperature sensor, can come the variation of representative of ambient temperature through the real-time change that obtains a temperature sensor impedance.When TSR2=TSR1, actual environment temperature T2 equals initial environment temperature T1.Through this determining step, closed circuit method of adjustment is achieved, thereby guarantees to obtain fair condition.

Fig. 4 is for showing that (fly height, when FH) being 1.5nm, the chart of the relation between the power of dynamic fly height is controlled in the impedance of temperature sensor and being used to when initial flying height.Said Initial Flight Level can be adjusted into suitable value according to actual needs, that is, this Initial Flight Level can not impact the method for raising snr measurement precision of the present invention.With reference to figure 4, to have drawn among the figure under the condition that magnetic head loads or removes, the variation under the effect of power of dynamic fly height is controlled in the impedance of temperature sensor in different being used to.Through increasing the power that is used to control dynamic fly height gradually by zero beginning; When the voltage of power resources reaches 24mW; Corresponding TSR2 value equals the value of TSR1; Explanation is used to control under the adjustment and condition that magnetic head is removed of power of dynamic fly height at this, the real time environment temperature T of this moment 2 basic with measuring magnetic head signal signal _LoadThe time original ambient temperature value T1 identical, therefore can obtain fair relatively condition, under this condition, measure noise figure noise _UnloadCan obtain accurate magnetic head signal to noise ratio (S/N ratio).In this adjustment process, the power that is used to control dynamic fly height is that the real-time impedance TSR2 that increases gradually up to temperature sensor equals TSR1.Preferable, under the situation that magnetic head is removed, this power that is used to control dynamic fly height can realize that self-adaptation regulates through closed circuit detecting device.

At magnetic head signal signal _LoadWith noise figure noise _UnloadAfter having measured respectively under the same conditions, an accurate magnetic head signal to noise ratio (S/N ratio) can be calculated acquisition through following equation:

$\mathrm{Head}\_\mathrm{SNR}=20\×\log \left(\frac{{\mathrm{signal}}_{\mathrm{load}}}{{\mathrm{noise}}_{\mathrm{unload}}}\right)$

Same, a kind of closed type is used to improve the method for measuring media signal to noise ratio (S/N ratio) precision and can obtains through identical mode.With reference to figure 5, the method that a kind of closed type according to the present invention is measured the media signal to noise ratio (S/N ratio) may further comprise the steps: (step S201) is loaded into magnetic head on the media and keeps certain dynamic fly height; (step S202) measures original ambient temperature T1, and measures magnetic head signal signal simultaneously _Load(step S203) removes magnetic head from media; (step S204) adjustment is used to control the power of dynamic fly height, equals original ambient temperature T1 up to real time environment temperature T 2; (step S205) measures magnetic head noise figure noise _Unload(step S206) calculates the magnetic head signal to noise ratio (S/N ratio) through following equation:

(step S207) through the following equation media SNR:

Particularly, the measurements and calculations method of said magnetic head signal to noise ratio (S/N ratio) and above-mentioned mention the same.In order to calculate total signal to noise ratio (S/N ratio), step (S202) further comprises measures magnetic head noise figure noise _Load, the signal signal of total signal to noise ratio (S/N ratio) _LoadWith noise figure noise _LoadMeasurement all be under the condition that magnetic head loads, after this, said total signal to noise ratio (S/N ratio) is calculated through following equation:

Afterwards, the media signal to noise ratio (S/N ratio) can be through recently calculating acquisition according to magnetic head signal to noise ratio (S/N ratio) and total noise.

Compared with prior art, thus closed type provided by the invention measure the method for magnetic head signal to noise ratio (S/N ratio) and provide the condition of justice to have higher measuring accuracy through measurement for signal and noise.Said magnetic head signal to noise ratio (S/N ratio) is passed through equation:

Calculate, wherein, magnetic head signal signal _LoadMeasurement be to be carried on the media and to keep under the condition of certain flying height at magnetic head, and the measurement of noise is under the condition that magnetic head is removed from media, magnetic head signal signal _LoadWith noise figure noise _UnloadMeasurement all be under the condition that the motive use that is used to control dynamic fly height, to carry out.Because the power that is used to control dynamic fly height is still in application, environment temperature is high more a lot of than actual conditions when magnetic head is removed, and influences noise figure noise _UnloadAnd cause over-evaluating of noise figure.Method provided by the present invention is attempted " control " temperature after magnetic head is removed makes it near actual conditions.Therefore, measuring magnetic head signal signal _LoadThe time; Initial environment temperature T1 is simultaneously measured to be used as comparison; Then after magnetic head is removed, the power that is used to control dynamic fly height through adjustment influences real-time environment temperature and equals T1 up to corresponding real time environment temperature T 2, is under fair consistent condition, to accomplish thereby make the measurement of noise; Obtain reliable, accurate magnetic head signal to noise ratio (S/N ratio) thus, further obtained reliable, accurate media signal to noise ratio (S/N ratio) thus equally.

Invention has been described more than to combine most preferred embodiment, but the present invention is not limited to the embodiment of above announcement, and should contain various modification, equivalent combinations of carrying out according to essence of the present invention.

Claims (14)

1. the method for a closed type measurement magnetic head signal to noise ratio (S/N ratio) is applicable to the pen recorder with recording medium and magnetic head, it is characterized in that, said method comprising the steps of:

(a) be loaded into magnetic head on the media and keep certain dynamic fly height;

(b) measure original ambient temperature value T1, and measure magnetic head signal signal simultaneously _Load

(c) magnetic head is removed from media;

(d) adjustment is used to control the power of dynamic fly height, and T2 equals original ambient temperature T1 up to the real time environment temperature value;

(e) measure magnetic head noise figure noise _Unload

(f) calculate the magnetic head signal to noise ratio (S/N ratio) through following equation:

$\mathrm{Head}\_\mathrm{SNR}=20\×\log \left(\frac{{\mathrm{signal}}_{\mathrm{load}}}{{\mathrm{noise}}_{\mathrm{unload}}}\right).$

2. the method for claim 1 is characterized in that, said environment temperature is detected by temperature sensor, and said temperature sensor is embedded in the said magnetic head, and said environment temperature is characterized by the impedance of said temperature sensor.

3. method as claimed in claim 2 is characterized in that, said step (b) is for measuring the initial impedance value TSR1 of temperature sensor.

4. method as claimed in claim 3 is characterized in that, said step (d) equals the initial impedance TSR1 of temperature sensor for adjusting the power that is used to control dynamic fly height up to the real-time resistance value TSR2 of temperature sensor.

5. the method for claim 1 is characterized in that, said step (d) may further comprise the steps:

(d1) increase the power that is used to control dynamic fly height;

(d2) T2 of measurement under corresponding dynamic action;

(d3) judge whether T2=T1 sets up, if not, execution in step (d1)-(d2) is if forward step (e) to.

6. method as claimed in claim 5 is characterized in that, the said power that is used to control dynamic fly height is by zero beginning increase gradually.

7. the method for a closed type measurement media signal to noise ratio (S/N ratio) is applicable to the pen recorder with recording medium and magnetic head, it is characterized in that, said method comprising the steps of:

(a) be loaded into magnetic head on the media and keep certain dynamic fly height;

(b) measure original ambient temperature value T1, and measure magnetic head signal signal simultaneously _Load

(c) magnetic head is removed from media;

(d) adjustment is used to control the power of dynamic fly height, and T2 equals original ambient temperature T1 up to the real time environment temperature value;

(e) measure magnetic head noise figure noise _Unload

(f) calculate the magnetic head signal to noise ratio (S/N ratio) through following equation:

$\mathrm{Head}\_\mathrm{SNR}=20\×\log \left(\frac{{\mathrm{signal}}_{\mathrm{load}}}{{\mathrm{noise}}_{\mathrm{unload}}}\right);$

(g) calculate the media signal to noise ratio (S/N ratio) through following equation:

$\mathrm{Media}\_\mathrm{SNR}=\sqrt{{(\mathrm{Total}\_\mathrm{SNR})}^2-{(\mathrm{head}\_\mathrm{SNR})}^2}.$

8. method as claimed in claim 7 is characterized in that, said step (b) further comprises measures magnetic head noise figure noise _Load

9. method as claimed in claim 8; It is characterized in that said total signal to noise ratio (S/N ratio) is calculated through following equation:

10. method as claimed in claim 7 is characterized in that said environment temperature is detected by temperature sensor, and said temperature sensor is embedded in the said magnetic head, and said environment temperature is characterized by the impedance of said temperature sensor.

11. method as claimed in claim 10 is characterized in that, said step (b) is for measuring the initial impedance value TSR1 of temperature sensor.

12. method as claimed in claim 11 is characterized in that, said step (d) equals the initial impedance TSR1 of temperature sensor for adjusting the power that is used to control dynamic fly height up to the real-time resistance value TSR2 of temperature sensor.

13. method as claimed in claim 7 is characterized in that, said step (d) may further comprise the steps:

(d1) increase the power that is used to control dynamic fly height;

(d2) T2 of measurement under corresponding dynamic action;

(d3) judge whether T2=T1 sets up, if not, execution in step (d1)-(d2) is if forward step (e) to.

14. method as claimed in claim 13 is characterized in that, the said power that is used to control dynamic fly height is by zero beginning increase gradually.

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