Patent Issued for Method and Circuit for Decoding a Sample of a Signal Read from a Storage Medium to Obtain a Physical Address of Data on the Storage Medium
The patent's assignee for patent number 8724440 is
News editors obtained the following quote from the background information supplied by the inventors: "Certain optical disc standards, such as HD DVD and DVD+(R and RW), employ BPSK to encode address or location data in the form of bits 0 and 1 on a wobble of an optical disc. During mastering or recording of a disc, this addressing data may be stored as phase modulated data, which is known in the art as Address-in-Pregroove (ADIP). The wobble is a continuous sinusoidal deviation of a track from an average centerline. A wobble signal also may be read from the wobble by a recording drive to precisely rotate the disc according to the frequency of the wobble signal. Using the frequency of the wobble signal, a timing signal may be generated to be used when writing data to the disc. An exemplary embodiment of a disc using BPSK encoding may have data bit 0 represented by a wobble with a first phase (i.e., a normal phase) and data bit 1 represented by a wobble with a second phase 180 degrees apart from the first phase (i.e., an inverted phase). During the mastering process, phase change transitions from a wobble having a normal phase to a wobble having an inverted phase may not be perfect. The inverted phase may extend to its neighboring normal phase wobble or vice versa.
"FIG. 1 illustrates an example of a phase change transition problem using a captured HD DVD wobble signal waveform. FIG. 1 shows a captured wobble signal 110 in relation to a wobble clock signal 105. Four arrows 115, 120, 125, 130 point to imperfect phase change transitions from a wobble signal with a normal phase to a wobble signal with an inverted phase. The imperfect phase transitions degrade the performance of wobble signal detection, thereby hampering detection of addressing or ADIP data stored on the wobble of the disc.
"Therefore, it would be desirable to have an apparatus that can detect and correct phase transition imperfections associated with optical disc wobble, particularly optical discs storing signals using BPSK."
As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventors' summary information for this patent: "A circuit is provided and includes a converter, a timing control device, a first scaling device, a first multiplier, a first integrator, a comparator, and a decoder. The converter is configured to sample a signal read from a storage medium to generate a sample. The signal includes a physical address of data read from a track on the storage medium. The timing control device is configured to generate a clock signal based on a deviation of the track from a reference line. The first scaling device is configured to generate a first scale factor based on the clock signal. The first multiplier is configured to multiply the sample by the first scale factor to generate a first scaled sample. The first integrator is configured to integrate the first scaled sample over a period of the clock signal to generate a first resultant value. The comparator is configured to compare the first resultant value to a threshold to generate an output. The output indicates whether no phase imperfection exists in the first scaled sample. The decoder is configured to, based on the output of the comparator, decode the first resultant value to obtain the physical address of the data.
"In other features, a method is provided and includes: sampling, via a converter, a signal read from a storage medium to generate a sample, where the signal includes a physical address of data read from a track on the storage medium; generating a clock signal based on a deviation of the track from a reference line; and generating a first scale factor based on the clock signal. The method further includes: multiplying the sample by the first scale factor to generate a first scaled sample; integrating the first scaled sample over a period of the clock signal to generate a first resultant value; and comparing the first resultant value to a threshold to generate an output, where the output indicates whether no phase imperfection exists in the first scaled sample. The method further includes, based on the output of the comparator, decoding the first resultant value to obtain the physical address of the data.
"To address the stated need and fulfill other desired objectives, in accordance with one embodiment of the invention, a wobble detector may detect a wobble signal and a synchronization signal based on the wobble signal and may provide a wobble clock signal. A wobble signal phase imperfection detector may detect and correct a phase transition imperfection in the wobble signal. The imperfection detector may integrate a first scaled wobble signal sample over substantially a half period portion of the wobble clock signal; compare the first scaled wobble signal sample integrated over substantially one period of the wobble clock signal to a variable threshold value; and based on the comparison, output either the half period integrated and scaled wobble sample or the first scaled wobble sample integrated over one period of the wobble clock signal. The imperfection detector further may decode the output to obtain wobble address period data. In one embodiment, the imperfection detector may include a half-period integrator, a comparator, a selector, and a decoder to perform the indicated functions."
For additional information on this patent, see: Liu, Jingfeng; Lee, Wooi-Kean. Method and Circuit for Decoding a Sample of a Signal Read from a Storage Medium to Obtain a Physical Address of Data on the Storage Medium. U.S. Patent Number 8724440, filed
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