Implementing spin-torque oscillator sensing with enhanced delay control feedback circuit for hard disk drives

• US 8,553,346 B2
• Filed: 12/09/2011
• Issued: 10/08/2013
• Est. Priority Date: 12/09/2011
• Status: Active Grant

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co)
• Original Assignee: HGST Netherlands B.V. (Western Digital Corporation)
• Inventors: Braganca, Patrick Mesquita, Galbraith, Richard Leo, Gurney, Bruce Alvin, Smith, Neil, Wilson, Bruce, Zakai, Rehan Ahmed
• Primary Examiner(s): HOLDER, REGINA NEAL
• Application Number:
  US13/316,407
• Publication Number:
  US 20130148229A1
• Time in Patent Office: 669 Days
• Field of Search: None
• US Class Current: 360/30
• CPC Class Codes: G11B 2005/0016 of magnetoresistive transducers
• CPC Class Codes: G11B 5/02 Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
• CPC Class Codes: G11B 5/3903 using magnetic thin film layers or their effects, the films being part of integrated structures

Abstract

A method, apparatus, and system for implementing spin-torque oscillator (STO) sensing with an enhanced delay control feedback circuit for hard disk drives. A detector receives an input signal from a STO read sensor having an oscillation frequency related to the strength of the detected magnetic signal field. The received input signal is mixed with a time delayed input signal for providing a detector output signal. A low frequency component signal of the detector output signal is monitored and a delay control feedback is applied to an adjustable time delay to bias the DC signal of the detector output signal.

Claims

1. A method for implementing data detection with spin-torque oscillator (STO) sensing for hard disk drives comprising:

receiving an input signal from a STO read sensor having an oscillation frequency related to detected magnetic signal field strength;

mixing said received input signal with a time delayed input signal of an adjustable time delay and providing a detector output signal;

monitoring a low frequency component signal of said detector output signal; and

applying a delay control feedback signal to said adjustable time delay responsive to said monitored low frequency component signal to bias a level of said monitored DC signal of said detector output signal.

2. The method for implementing data detection with STO sensing as recited in claim 1 wherein receiving an input signal from a STO read sensor includes providing a preamplifier and limiter circuit and applying a readback signal from a STO read sensor to said preamplifier and limiter circuit compensating for amplitude fluctuations in said readback signal.

3. The method for implementing data detection with STO sensing as recited in claim 1 wherein mixing said readback signal with said time delayed input signal includes providing a mixer for mixing said readback signal with said time delayed input signal and providing a lowpass filter coupled to said mixer, said mixer producing a resulting modulated signal, and said lowpass filter lowpass filtering said resulting modulated signal.

4. The method for implementing data detection with STO sensing as recited in claim 3 includes providing a baseband amplifier coupled to said lowpass filter and applying said filtered modulated signal to said baseband amplifier, providing said detector output signal.

5. The method for implementing data detection with STO sensing as recited in claim 1 includes providing a lowpass filter receiving said detector output signal and providing a filtered detector output signal input to a delay control function providing said delay control feedback signal.

6. The method for implementing data detection with STO sensing as recited in claim 1 wherein applying a delay control feedback signal to said adjustable time delay responsive to said monitored low frequency component signal to bias a level of said monitored low frequency component signal includes providing bias to zero said monitored low frequency component signal of said detector output signal.

7. The method for implementing data detection with STO sensing as recited in claim 6 includes providing bias for a selected level of said monitored low frequency component signal of said detector output signal.

8. The method for implementing data detection with STO sensing as recited in claim 1 wherein applying a delay control feedback signal to said adjustable time delay responsive to said monitored DC signal includes switching delay lines of said adjustable time delay responsive to said monitored low frequency component signal.

9. The method for implementing data detection with STO sensing as recited in claim 1 wherein applying a delay control feedback signal to said adjustable time delay responsive to said monitored DC signal includes switching capacitors of said adjustable time delay responsive to said monitored low frequency component signal.

10. An apparatus for implementing data detection with spin-torque oscillator (STO) sensing for hard disk drives comprising:

a spin-torque oscillator (STO) read sensor sensing a signal magnetic field and producing a readback signal;

a delay line detector including

a mixer receiving an input signal from said STO read sensor, said mixer coupled to an adjustable time delay for mixing said received input signal with a time delayed input signal and providing a detector output signal;

a delay control feedback circuit monitoring a low frequency component signal of said detector output signal including a delay control function applying a delay control feedback signal to said adjustable time delay responsive to said monitored low frequency component signal to bias a level of said monitored low frequency component signal of said detector output signal;

detector output signal being used for processing by data detection electronics.

11. The apparatus for implementing data detection as recited in claim 10 includes a preamplifier and limiter circuit coupled to said mixer, and said STO signal being applied to said preamplifier and limiter circuit for compensating for amplitude fluctuations in said readback signal.

12. The apparatus for implementing data detection as recited in claim 11 wherein said delay control feedback circuit includes a lowpass filter receiving said detector output signal and providing a filtered detector output signal input to said delay control function providing said delay control feedback signal.

13. The apparatus for implementing data detection as recited in claim 10 includes a lowpass filter coupled to said mixer, said mixer producing a resulting modulated signal, and said lowpass filter lowpass filtering said resulting modulated signal.

14. The apparatus for implementing data detection as recited in claim 13 includes a baseband amplifier coupled to said lowpass filter and said filtered modulated signal being applied to said baseband amplifier for providing said detector output signal.

15. The apparatus for implementing data detection as recited in claim 10 wherein adjustment of said adjustable time delay includes switching capacitors of said adjustable time delay responsive to said monitored low frequency component signal.

16. The apparatus for implementing data detection as recited in claim 10 wherein adjustment of said adjustable time delay includes switching delay lines of said adjustable time delay responsive to said monitored low frequency component signal.

17. The apparatus for implementing data detection as recited in claim 10 includes said delay control function applying said delay control feedback signal to said adjustable time delay responsive to said monitored low frequency component signal for zeroing said monitored low frequency component signal of said detector output signal.

18. A system for implementing data detection with spin-torque oscillator (STO) sensing for hard disk drives comprising:

a media generating a magnetic signal having an amplitude determined by media field strength;

a spin-torque oscillator (STO) read sensor sensing said magnetic signal generated by said media and producing a readback signal;

a delay line detector including

a mixer receiving an input signal from a STO read sensor, said mixer coupled to an adjustable time delay for mixing said received input signal with a time delayed input signal and providing a detector output signal;

a delay control feedback circuit monitoring a low frequency component signal of said detector output signal including a delay control function applying a delay control feedback signal to said adjustable time delay responsive to said monitored low frequency component signal to bias a level of said monitored low frequency component signal of said detector output signal;

detector output signal being used for processing by data detection electronics.

19. The system for implementing data detection as recited in claim 18 includes a preamplifier and limiter circuit coupled to said mixer, and said STO signal being applied to said preamplifier and limiter circuit for compensating for amplitude fluctuations in said readback signal.

20. The system for implementing data detection as recited in claim 19 includes a lowpass filter coupled to said mixer and lowpass filtering a resulting modulated signal from said mixer and a baseband amplifier coupled to said lowpass filter receiving a lowpass filtered output of said lowpass filter and said baseband amplifier providing said detector output signal.