Patent Application
20080062549
A system and method for determining the F-BER and BER of a disk is described herein. The system and method may be implemented with components or modules. The components and modules may include hardware (including electronic and/or computer circuitry), firmware and/or software (collectively referred to herein as “logic”). A component or module can be implemented to capture any of the logic described herein. The F-BER is a method for understanding and determining the BER of a disk by analyzing parametric data of a disk based on an idealized E2PRML channel. The F-BER projects the error rate performance of a recording system.
During testing, data including read back signals, used to determine F-BER is collected by a module such as PCCRWA. The F-BER data to determine F-BER includes PW50, signal at low frequency (LF TAA), media noise Nm, head and electronic noise (Nhe), band width. Further the F-BER test uses an ideal E2PRML channel, which mimics an optimized real channel with parametric data as input. This data is then provided to a computer to determine the F-BER. Specifically, in addition to typical spin-stand operation, the method calls for adding a head unload operation to obtain head and electronic noise. In this way, one can separate the media noise from total noise by subtracting the head and electronic noise.
The method for determining the F-BER of a longitudinal disk is as follows and may be performed by a module to determine F-BER. Such a module includes a data processing device that receives F-BER data as described above. The data processing device then determines BW. From BW and the other data, FOM0 and FOM1 may be calculated. The FOM0 and FOM1 calculations are used to determine CSNR. In turn, ψ is determined from CSNR. Finally, the F-BER is determined from ψ. These steps are described in equations (1)-(6).
FOM0=(S0/Nm)2/(PW50/T) (1)
BW=1/(2T) (3)
CSNR=1/+√{square root over (d/π/FOM0+e/FOM1)} (4)
ω=0.5*CSNR (5)
FBER=0.5*[1−erf(ψ)] (6)
where:
The parameters of a, b, c, d, e in equations (1)-(6) are determined from an E2PRML channel. a is preferably 10.8 and ranges from 10 to 12; b is preferably 6.56 and ranges from 6 to 7; c is preferably 1.935 and ranges from 1.75 to 2.25; d is preferably 4.7452 and ranges from 4.5 to 5; e is preferably 0.65685 and ranges from 0.4 to 0.8.
In addition, two extensions to the algorithm allow F-BER to be calculated for a perpendicular disk. The first extension is measure the T50 of the perpendicular disk on a spinstand. The readback signal from perpendicular media is a square-type waveform. The transition width of a written bit on perpendicular media is called T50, which defines the signal range from 25% to 75% of peak value. From this test, PW50 can be obtained with the use of equation (7).
PW50=2.77×T50, (7)
The PW50 value is then incorporated in the F-BER module via the math conversion of equation (7).
The second possible extension is to add hardware into the spinstand to perform waveform differential. The waveform differentiator allows PW50 of the perpendicular recording to be directly measured.
The method for determining F-BER can be constructed based on E2PRML equalization. Equalization forms generally are described in “Bit Cell Aspect Ratio: An SNR and Detection Perspective”, T. C. Amoldussen, IEEE Trans. Magn. Vol. 34, pp1851-1853 (1998).
The F-BER method can be a module of a program to perform media testing. Further the F-BER module can be embedded in a spinstand or outside a spinstand. In addition, the module can be made part of a suite or GUI designed to test media as shown in
While the present invention has been particularly shown and described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit and scope of the invention. Accordingly, the disclosed invention is to be considered merely as illustrative and limited in scope only as specified in the appended claims.
