Abstract: A post-processing method and circuit (30) for correcting media noise errors and producing a corrected recovered data output signal (49) is disclosed for use in a sampled data read channel of a mass data storage device. The mass data storage device has a Viterbi detector (34) that receives actual sampled partial response target data (32) from a data medium of a mass data storage device. A recovered partial response target signal derived from the recovered data output signal and the sampled partial response target data is filtered to produce a filtered output signal (51). A threshold circuit (64) provides a threshold against which the filtered output signal is compared, and a predetermined value (60) is added to the filtered output signal when a predetermined error event pattern due to media noise or other transition jitter occurs in the recovered data output signal (35). The recovered data output signal is modified (70) when the filtered output signal exceeds the threshold of said threshold circuit (64).

Abstract: Methods and apparatus are disclosed for detecting PR4 equalized Gray codes, providing phase tolerant Gray codes and detection thereof. A Gray code detector is provided, which receives a PR4 equalized Gray code input signal and provides a binary detector output. The detector comprises a plurality of filters providing Euclidean distance values based on the input signal. A logic component selectively provides the detector output based on one or more of the Euclidean distance values from the matched filters, according to one or more criteria, such as the detector mode.

Abstract: A detector (55) and method for detecting a synchronization servo mark (SSM) in a data stream of mass data storage device (10) has a matched filter (56) to receive the data stream. The filter (56) produces a maximum output when the SSM is applied. A delay element receives (64) the matched filter output to produce a delay element output (72). When the delay element output (72) is greater than a predetermined threshold value (Vth) and is larger than the output value (74), the (SSM) is in a current time location. When the “D” element output (72) is greater than the predetermined threshold value (Vth) and less than the output value, the SSM is in the next time location. The threshold may be established to be less than maximum if the phase of the SSM is within a predetermined phase range.

Abstract: A post-processing method and circuit (30) for correcting media noise errors and producing a corrected recovered data output signal (49) is disclosed for use in a sampled data read channel of a mass data storage device. The mass data storage device has a Viterbi detector (34) that receives actual sampled partial response target data (32) from a data medium of a mass data storage device. A recovered partial response target signal derived from said recovered data output signal and said sampled partial response target data is filtered to produce a filtered output signal (51). A threshold circuit (64) provides a threshold against which said filtered output signal is compared, and a predetermined value (60) is added to the filtered output signal when a predetermined error event pattern due to media noise or other transition jitter occurs in said recovered data output signal (35). The recovered data output signal is modified (70) when said filtered output signal exceeds the threshold of said threshold circuit (64).

Abstract: A post-processor (10) is added to a PRML read channel in a mass data storage device for improving the error rate performance. The post-processor (10) includes dominant error pattern detection filters, which include a noise-whitening filter (32) and an error pattern matched filter (34). The post-processor improves performance by whitening the colored noise which bring the noise correlation loss, and by generating an error signal when one of the dominant error patterns is detected to enable the data output to be properly corrected.

Abstract: A detector (55) and method for detecting a synchronization servo mark (SSM) in a data stream of mass data storage device (10) has a matched filter (56) to receive the data stream. The filter (56) produces a maximum output when the SSM is applied. A delay element receives (64) the matched filter output to produce a delay element output (72). When the delay element output (72) is greater than a predetermined threshold value (Vth) and is larger than the output value (74), the (SSM) is in a current time location. When the “D” element output (72) is greater than the predetermined threshold value (Vth) and less than the output value (73), the SSM is in the next time location. The threshold may be established to be less than maximum if the phase of the SSM is within a predetermined phase range.

Abstract: Methods and apparatus are disclosed for detecting PR4 equalized Gray codes, providing phase tolerant Gray codes and detection thereof. A Gray code detector is provided, which receives a PR4 equalized Gray code input signal and provides a binary detector output. The detector comprises a plurality of filters providing Euclidean distance values based on the input signal. A logic component selectively provides the detector output based on one or more of the Euclidean distance values from the matched filters, according to one or more criteria, such as the detector mode.

Abstract: The present invention implements a maximum likelihood detector for optical disk drive without using a Viterbi detector. The detection algorithm that includes y0+y1 detection is very simple by requiring only one adder and one comparator, and not survival path memories.

Abstract: This invention relates to improvements in servo Gray code detection techniques in rotating data storage drives such as hard disk drives, or the like. The detection technique uses a rate ¼ Gray code servo signals equalized to a PR4 target, and a matched filter detector, and can realize a servo Gray code detector having high speed and performance. The Gray code detector (30) has an input (44) for receiving an input signal containing a Gray code that has been equalized to a PR4 target and a circuit (40-42, 46) for processing said input signal to determine a maximum Euclidean distance from zero to a value of the Gray code. The construction of the detector (30) depends upon the particular Gray code that is employed.

Abstract: A magnetic recording system with a rate 16/17(0,6/8) encoder/decoder modulation code. This modulation code has a low k constraint for synchronization of a road clock of the magnetic recording system. Furthermore, this magnetic recording system has a low hard error rate due to low 3- and 4-byte error propagation. The digital logic circuit for the encoder/decoder system is elegantly simple. Such simplicity reduces propagational delays and circuit size, as measured in number of logic gates. The modulation code is implemented with a decoder that includes a lower byte decoder and an upper byte decoder. An input of the upper byte decoder is in part coupled to and in part decoupled from the lower byte decoder. Similarly, an input of the lower byte decoder is in part coupled to and in part decoupled from the upper byte decoder.

Abstract: A method and apparatus for reducing noise correlation in a partial response channel through optimization of a look-ahead maximum likelihood (ML) detector. In the method of the present invention, the ML detector is optimized in light of the noise correlation generated by the partial response channel. The improved ML detector provides comparable performance to, or better performance than, a Viterbi detector in the presence of colored noise. In the present invention, a set of finite impulse response (FIR) transversal filters are used as the ML estimator for the look-ahead detector. The weighted sum outputs of the FIR filters are compared to a set of thresholds based on previously detected data to make the decision for current detection. The present invention improves the ML detector's performance and reduces its complexity by optimizing the coefficients of the FIR filters in the presence of the correlated or colored noise.