Granted Patent B2

US 8,098,451 · App. 12/669,483 · Granted Jan 17, 2012

Abstract

Claims (64)

1. A system for determining fly height, the system comprising:

a head assembly disposed in relation to a storage medium;

a write channel;

a read circuit, wherein the read circuit is operable to receive information from both the head assembly and the write channel;

a frequency determination circuit, wherein the frequency determination circuit is operable to receive a first signal from the read circuit corresponding to information received from the write channel and to provide a first fundamental frequency and a first higher order frequency based on the first signal, and wherein the frequency determination circuit is operable to receive a second signal from the read circuit corresponding to information received from the head assembly and to provide a second fundamental frequency and a second higher order frequency based on the second signal;

a compensation variable calculation module, wherein the compensation variable calculation module is operable to divide the first fundamental frequency by the first higher order harmonic to yield a compensation variable; and

a fly height calculation module, wherein the fly height calculation module is operable to divide the second fundamental frequency by the second higher order harmonic and the compensation variable to yield an indication of a distance between the head assembly and the storage medium.

2. The system of claim 1 , wherein the information received from the write channel and the information received from the head assembly correspond to a pattern selected from a group consisting of: a 6T pattern and a 12T pattern.

3. The system of claim 1 , wherein the first higher order harmonic and the second higher order harmonic are selected from a group consisting of: a third order harmonic, a fourth order harmonic, and a sixth order harmonic.

4. The system of claim 1 , wherein the frequency determination circuit implements a discrete Fourier transform.

5. The system of claim 1 , wherein the system further comprises a memory, and wherein the memory is operable to receive the compensation variable from the compensation variable calculation module, and wherein the memory is operable to provide the compensation variable to the fly height calculation module.

6. The system of claim 5 , wherein the compensation variable is a first compensation variable specific to a first zone of the storage medium, wherein the frequency determination circuit is operable to receive a third signal from the read circuit corresponding to information received from the write channel and to provide a third fundamental frequency and a third higher order frequency based on the third signal, wherein the third fundamental frequency is specific to a second zone of the storage medium, and wherein the compensation variable calculation module is operable to divide the third fundamental frequency by the third higher order harmonic to yield a second compensation variable specific to the second zone of the storage medium.

7. The system of claim 6 , wherein the fly height calculation module receives an indication that the second information is derived from the second zone of the storage medium, and wherein the fly height calculation module is operable to divide the second fundamental frequency by the second higher order harmonic and the second compensation variable to yield an indication of a distance between the head assembly and the storage medium.

8. The system of claim 5 , wherein the system is implemented as part of a storage device.

9. A method for calculating relative fly height, the method comprising:

disposing a head assembly a fly height distance from a storage medium;

writing a first pattern from a write circuit;

receiving the first pattern at the read circuit;

based at least on the first pattern, calculating a compensation variable;

storing the compensation variable;

receiving a second pattern from the storage medium;

based at least on the second pattern and the compensation variable, calculating an indication of the fly height distance.

10. The method of claim 9 , wherein the first pattern and the second pattern are 6T patterns.

11. The method of claim 9 , wherein calculating the compensation variable includes:

determining a fundamental frequency of a signal corresponding to the received first pattern;

determining a higher order harmonic of the signal corresponding to the received first pattern; and

dividing the fundamental frequency by the higher order harmonic to create the compensation variable.

12. The method of claim 11 , wherein the higher order harmonic is selected from a group consisting of: a third order harmonic, a fourth order harmonic, and a sixth order harmonic.

13. The method of claim 11 , wherein determining the fundamental frequency and determining the higher order harmonic is done by performing a discrete Fourier transform.

14. The method of claim 9 , wherein calculating the indication of the fly height distance includes:

determining a fundamental frequency of a signal corresponding to the received second pattern;

determining a higher order harmonic of the signal corresponding to the received second pattern; and

dividing the fundamental frequency by the higher order harmonic and the compensation variable to create the indication of the fly height distance.

15. The method of claim 14 , wherein the higher order harmonic is selected from a group consisting of: a third order harmonic, a fourth order harmonic, and a sixth order harmonic.

16. The method of claim 14 , wherein determining the fundamental frequency and determining the higher order harmonic is done by performing a discrete Fourier transform.

17. The method of claim 9 , wherein the read circuit includes an analog front end, and wherein the compensation variable compensates for one or more variables of the analog front end selected from a group consisting of: temperature, supply voltage, and disk zone.

18. The method of claim 9 ,

wherein the read circuit includes an analog front end, and wherein the compensation variable compensates for one or more variables of the analog front end selected from a group consisting of: temperature and supply voltage; and

wherein calculating the compensation variable includes calculating a first compensation variable for a first combination including one or more of temperature and supply voltage, and calculating a second compensation variable for a second combination including one or more of temperature and supply voltage;

selecting one of the first compensation variable and the second compensation variable; and

wherein calculating the indication of the fly height distance includes:

determining a fundamental frequency of a signal corresponding to the received second pattern;

determining a higher order harmonic of the signal corresponding to the received second pattern; and

dividing the fundamental frequency by the higher order harmonic and the selected compensation variable to create the indication of the fly height distance.

19. The method of claim 18 , wherein selecting the one of the first compensation variable and the second compensation variable includes:

measuring at least one of temperature and supply voltage; and

selecting one of the first compensation variable and the second compensation variable based on a combination of one or more of a measured temperature and a measured supply voltage.

20. The method of claim 9 , wherein the storage medium includes at least a first disk zone and a second disk zone; wherein the first pattern exhibits a fundamental frequency specific to the first disk zone; wherein the compensation variable is specific to the first disk zone; and wherein the method further comprises:

determining that the second pattern is derived from the first disk zone;

based at least in part on the determination that the second pattern is derived from the first disk zone, selecting the compensation variable;

wherein calculating the indication of the fly height distance includes:

determining a fundamental frequency of a signal corresponding to the received second pattern;

determining a higher order harmonic of the signal corresponding to the received second pattern; and

dividing the fundamental frequency by the higher order harmonic and the selected compensation variable to create the indication of the fly height distance.

21. A storage system, the storage system comprising:

a storage medium;

a head assembly disposed a distance from the storage medium;

a write circuit;

a read circuit, wherein the read circuit is operable to receive information from both the head assembly and the write channel, wherein the read circuit includes at least an amplifier operable to amplify a received signal, and wherein the amplifier is susceptible to temperature variation and supply voltage variation;

a frequency determination module; wherein the frequency determination module is operable to receive a first signal from the read circuit corresponding to information received from the write channel at a defined amplifier temperature and amplifier supply voltage, and to provide a first fundamental frequency and a first higher order frequency based on the first signal, and wherein the frequency determination circuit is operable to receive a second signal from the read circuit corresponding to information received from the head assembly and to provide a second fundamental frequency and a second higher order frequency based on the second signal;

a compensation variable calculation module, wherein the compensation variable calculation module is operable to divide the first fundamental frequency by the first higher order harmonic to yield a compensation variable specific to the defined amplifier temperature and defined amplifier supply voltage;

a temperature sensor operable to provide a measured amplifier temperature;

a supply voltage sensor operable to provide a measured amplifier supply voltage; and

a fly height calculation module, wherein the fly height calculation module is operable select the compensation variable based at least in part on the measured amplifier temperature and the measured amplifier supply voltage, and to divide the second fundamental frequency by the second higher order harmonic and the compensation variable to yield an indication of the distance.

Assignments (11)