Abstract:
Aspects of the disclosure provide a method for detecting marks. The method includes receiving a data signal from a channel. Further, the method includes matching the data signal to a template that corresponds to a predetermined pattern transmitted over the channel to detect marks, prior to decoding the data signal into a decoded bit stream.

Description:
INCORPORATION BY REFERENCE 
     This application claims the benefit of U.S. Provisional Application No. 61/355,489, “Detect Syncmark by Matched Filter” filed on Jun. 16, 2010, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     Generally, massive storage, such as optical storage, magnetic storage, and the like, stores user data in a bit stream that uses synchronization (sync) marks having a predetermined unique pattern to frame user data. In an example, Blu-ray standard includes a 9T9T pattern in sync marks. The 9T9T pattern has nine zeroes followed by nine ones or nine ones followed by nine zeros. When a reading device detects a 9T9T pattern in a bit stream read from a Blu-ray disc, the reading device knows a starting position of a frame of user data in the bit stream. However, when sync mark detection is based on extracted bit stream, errors in the bit detection can increase sync mark detection errors. 
     SUMMARY 
     Aspects of the disclosure provide a method for detecting marks, such as sync marks. The method includes receiving a data signal from a channel. Further, the method includes matching the data signal to a template that corresponds to a predetermined pattern transmitted over the channel to detect marks, prior to decoding the data signal into a decoded bit stream. 
     To match the data signal to the template, the method includes matching the data signal to a sync mark template that corresponds to a sync mark pattern transmitted over the channel to detect sync marks in the data signal. The sync marks are used to frame user data in the data signal. 
     Further, in an embodiment, to match the data signal to the template, the method includes matching the data signal to a non-uniformly weighted template. In an example, the method includes convolving the predetermined pattern with a partial response target that characterizes the channel to calculate a first template, and weighting the first template non-uniformly to generate a second template. 
     According to an aspect of the disclosure, the method includes calculating correlation coefficients between the data signal and the template, and detecting the marks based on the correlation coefficients. It is noted that when a calculated correlation coefficient has negative value, the method includes calculating an absolute value of the correlation coefficient. In an example, to detect the marks based on the correlation coefficients, the method includes detecting peak tops in the correlation coefficients that are larger than neighboring correlation coefficients, and comparing the peak tops to a threshold to detect the marks. In another example, to calculate the correlation coefficients between the data signal and the template, the method includes storing a pre-calculated statistical value of the template, such as Euclidean norm, standard deviation, and the like, and calculating the correlation coefficients using the stored statistical value of the template. 
     Aspects of the disclosure provide a signal processing circuit. The signal processing circuit includes a pre-decoding portion, a decoder and a mark detection module. The pre-decoding portion is configured to receive a signal corresponding to a bit stream that includes marks having a predetermined pattern, process the signal, and output a data signal for decoding. The decoder is configured to decode the data signal into a decoded bit stream. The mark detection module is configured to match the data signal to a template that corresponds to the predetermined pattern to detect the marks. 
     Aspects of the disclosure also provide an electronic system. The electronic system includes a pick-up unit, a pre-decoding portion, a decoder, and a mark detection module. The pick-up unit is configured to generate a signal corresponding to a bit stream. The bit stream includes marks having a predetermined pattern. The pre-decoding portion is configured to process the signal, and output a data signal for decoding. The decoder is configured to decode the data signal into a decoded bit stream. The mark detection module is configured to match the data signal to a template that corresponds to the predetermined pattern transmitted over a channel to detect the marks. In an example, the channel includes the pick-up unit and the pre-decoding portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of this disclosure that are proposed as examples will be described in detail with reference to the following figures, wherein like numerals reference like elements, and wherein: 
         FIG. 1  shows a block diagram of an electronic system example  100  according to an embodiment of the disclosure; 
         FIG. 2  shows a block diagram of a data read channel example  230  according to an embodiment of the disclosure; 
         FIG. 3  shows a block diagram of a synchronization (sync) mark detection module  380  according to an embodiment of the disclosure; 
         FIG. 4  shows a flow chart outlining a process example  400  for a sync mark detection module to detect sync marks according to an embodiment of the disclosure; 
         FIG. 5A  shows examples of generating sync mark templates according to an embodiment of the disclosure; 
         FIG. 5B  shows a plot of sync mark templates according to an embodiment of the disclosure; 
         FIGS. 6A-6C  show plots of sync mark detection according to an embodiment of the disclosure; 
         FIG. 7A  shows a performance example of an electronic system according to an embodiment of the disclosure; and 
         FIG. 7B  shows a performance example of a comparison electronic system. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows a block diagram of an electronic system example  100  according to an embodiment of the disclosure. The electronic system  100  includes a receiving and extracting portion  110  that receives a signal  102  corresponding to a bit stream that includes marks of a predetermined pattern. In an example, the bit stream includes synchronization (sync) marks having a predetermined pattern to frame user data. The receiving and extracting portion  110  processes the signal  102  and extracts the bit stream from the signal  102 . According to an aspect of the disclosure, the receiving and extracting portion  110  detects sync marks based on an intermediate signal during processing, instead of the extracted bit stream. 
     In an embodiment, the receiving and extracting portion  110  includes a pick-up unit  120  and a signal processing circuit  130 . The pick-up unit  120  receives the signal  102  and suitably generates an electrical signal  135  in response to the signal  102 . The signal processing circuit  130  processes the electrical signal  135 , and extracts the bit stream. 
     It is noted that the signal  102  can be any suitable signal. In an embodiment, the signal  102  is generated in response to a bit stream stored on a storage medium  101 . It is noted that the storage medium  101  can be any suitable storage medium. In an example, the storage medium  101  is a hard disk drive that stores the bit stream as magnetic field changes. The pick-up unit  120  includes a magnetic head that generates the electrical signal  135  in response to the magnetic field changes on the storage medium  101 . The signal processing circuit  130  processes the electrical signal  135  and extracts the bit stream. 
     In another example, the storage medium  101  is an optical disc, such as compact disc (CD), digital versatile disc (DVD), Blu-ray disc, and the like, that stores the bit stream as optical property changes. The pick-up unit  120  is an optical pick-up unit that generates the electrical signal  135  in response to the optical property changes. Specifically, the pick-up unit  120  directs a light beam to the storage medium  101 . The light beam is reflected from the storage medium  101 . The signal  102 , which is the reflected light beam, has light properties that correspond to the optical property changes on the storage medium  101 . The pick-up unit  120  generates the electrical signal  135  in response to the light properties of the signal  102 . The signal processing circuit  130  processes the electrical signal  135  and extracts the bit stream. 
     In another embodiment, the signal  102  is an electromagnetic signal transmitted in the air, for example, from a base station (not shown). The pick-up unit  120  includes an antenna that suitably generates the electrical signal  135  in response to the electromagnetic signal  102 . The signal processing circuit  130  processes the electrical signal  135  and extracts the bit stream. 
     In the  FIG. 1  example, the signal processing circuit  130  includes a pre-decoding portion  131 , a decoder  170  and a sync mark detection module  180 . The pre-decoding portion  131  processes the electrical signal  135  to prepare the electrical signal  135  for decoding. The pre-decoding portion  131  outputs a data signal  165 . The decoder  170  makes bit decisions based on the data signal  165  to extract the bit stream. The sync mark detection module  180  detects sync marks based on the data signal  165 . 
     According to an aspect of the disclosure, the decoder  170  may make wrong bit decisions and throw out useful information for sync mark detection. When sync mark detection is based on the data signal  165  prior to the bit decisions, the sync mark detection can use suitable information in the data signal  165  to reduce detection errors. 
     It is noted that the electronic system  100  can include other suitable components (not shown), such as processor, user input module, audio/video module, and the like. 
       FIG. 2  shows a block diagram of a signal processing circuit example  230  according to an embodiment of the disclosure. The signal processing circuit  230  includes a pre-decoding portion  231 , a decoder  270 , and a sync mark detection module  280 . The pre-decoding portion  231  receives an electrical signal  235 , processes the electrical signal  235 , and provides a processed electrical signal, such as a data signal  265 , to the decoder  270  and the sync mark detection module  280 . The decoder  270  makes bit decisions based on the data signal  265  to extract a bit stream. The sync mark detection module  280  detects sync marks based on the data signal  265 . These elements are coupled together as shown in  FIG. 2 . 
     The pre-decoding portion  231  includes any suitable elements to process the electrical signal  235 . In an embodiment, the pre-decoding portion  231  includes a front-end analog portion  240 , an analog to digital converter (ADC)  250 , a timing module  252 , and an equalizer  260 . These elements are coupled together as shown in  FIG. 2 . 
     The front-end analog portion  240  receives the electrical signal  235 , regulates the electrical signal, and outputs an analog data signal  245 . The front-end analog portion  240  regulates the electrical signal  235  using analog techniques, such as amplification, compensation for offsets, adjusting an appropriate dynamic range, and the like. Thus, the analog data signal  245  is suitable for subsequent circuit components to handle. 
     The ADC  250  receives the analog data signal  245  and samples the analog data signal  245  based on a sampling clock  256  provided by the timing module  252 . Further, the ADC  250  converts the sampled signal into a digital signal  255 . In an embodiment, the timing module  252  and the ADC  250  forms a timing loop. The timing module  252  generates the sampling clock  256  based on the digital signal  255 . It is noted that, in another embodiment, the timing loop includes other elements, such as the equalizer  260 . 
     The equalizer  260  receives the digital signal  255 , shapes the digital signal  255 , and outputs a shaped digital signal, such as the data signal  265 . In an embodiment, the equalizer  260  is a finite impulse response (FIR) digital filter that is configured to shape the digital signal  255  according to a partial response target to reduce noises from the digital signal  255  and control inter-symbol interferences. In an example, the partial response target characterizes a channel for conveying the bit stream. For example, the partial response target collectively characterizes a channel that includes the pick-up unit  120  for generating the electrical signal  135  in response to the bit stream read from the storage medium  101  and the pre-decoding portion  165  for processing the electrical signal  135 . It is noted that the partial response target can be fixed, programmable or adaptive. 
     The decoder  270  extracts the bit stream from the data signal  265 . The decoder  270  can use any suitable technique to extract the bit stream. In an embodiment, the detector  270  includes a Viterbi detector  275  that makes bit decisions according to a Viterbi algorithm. 
     The sync mark detection module  280  detects sync marks based on the data signal  265  instead of the extracted bit stream. In an embodiment, the sync mark detection module  280  uses a matched filter to match the data signal  265  with a template that characterizes a sync mark pattern in a channel that conveys the bit stream to detect sync marks from the data signal  265 . Specifically, in an embodiment, the sync mark detection module  280  includes a template module  282 , a correlation module  284  and a detector  286 . These elements are coupled together as shown in  FIG. 2 . 
     The template module  282  provides a template that characterizes the sync mark pattern in the channel. In an embodiment, the template is predetermined and stored in a memory (not shown) associated with the template module  282 . During operation, the memory provides the stored template. 
     It is noted that sync marks for different storage media may include different patterns. The template module  282  may store templates in association with corresponding storage mediums. Based on a storage medium, the template module  282  provides the corresponding template for the storage medium. 
     In another embodiment, the template module  282  includes a partial response target  283  that characterizes the channel for conveying the bit stream. During operation, based on a storage medium, the template module  282  calculates the template for the storage medium by convolving a sync mark for the storage medium with the partial response target  283 . It is noted that the partial response target  283  can be programmable or adaptively updated. 
     It is also noted that the template can be further adjusted to improve sync mark detection accuracy. In an embodiment, the template is weighed according to weight windows to emphasize or deemphasize different portions of the template. 
     The correlation module  284  calculates correlation coefficients between the data signal  265  and the template. In an example, the template is in a form of a N-tuple vector (N is a positive integer), and the data signal  265  is in a form of a discrete-time signal. At each time point, the most recent N time points of the data signal  265  form a N-tuple data vector, and the correlation module  284  calculates a correlation coefficient between the data vector and the template vector for the time point. 
     It is noted that the correlation module  284  can use any suitable techniques to reduce calculation complexity. In an example, a correlation coefficient is calculated using Eq. 1: 
                     C   ⁡     (     X   ,   Y     )       =       ∑       x   i     ⁢     y   i               (     ∑     x   i   2       )     ⁢     (     ∑     y   i   2       )                   Eq   .           ⁢   1               
where X denotes the template vector, and Y denotes the data vector. In an example, the correlation module  284  pre-calculates a Euclidean norm of the template vector (Σx i   2 ) and stores the Euclidean norm in a memory. Thus, the correlation module  284  uses the stored Euclidean norm of the template vector to calculate the correlation coefficients between the data signal  265  and the template.
 
     The detector  286  compares the correlation coefficients with a threshold  287  to detect sync marks. For example, when an absolute value of a correlation coefficient is larger than the threshold  287 , the sync mark detection module  280  detects a sync mark. It is noted that, in an embodiment, the threshold  287  is pre-calibrated to have a reduced number of detection errors. 
       FIG. 3  shows a block diagram of a synchronization (sync) mark detection module  380  according to an embodiment of the disclosure. The sync mark detection module  380  includes a window template module  382 , a correlation module  384 , and a detector  386 . These elements are coupled together as shown in  FIG. 3 . 
     The window template module  382  stores a partial response target  383  that characterizes a channel for conveying the bit stream and a weight window  381  that defines weights for emphasizing or de-emphasizing different portions of a template. In an embodiment, the window template module  382  convolves the partial response target  383  with a sync mark to calculate a template. Further, the window template module  382  weights the template according to the weight window  381  to determine a windowed template. 
     The correlation module  384  receives a data signal  365 , and calculates correlation coefficients between the data signal  365  and the windowed template. 
     The detector  386  includes a peak top detector  388  and a threshold  387 . The peak top detector  388  detects peak tops in the correlation coefficients that are larger than neighbor correlation coefficients. Then, the detector  386  compares the peak tops with the threshold  387  to detect sync marks. 
     It is noted that the weighting operation can be performed using other suitable techniques. In an example, the template is not weighted, however, the correlation module  384  is configured to weight different portions differently. For example, the correlation module  384  is configured to heavily weight transition portions, and lightly weight flat portions. 
       FIG. 4  shows a flow chart outlining a process example  400  for a sync mark detection module, such as the sync mark detection modules  180 ,  280  and  380 , to detect sync marks according to an embodiment of the disclosure. The process starts from S 401  and proceeds to S 410 . 
     At S 410 , the sync mark detection module determines a template for sync mark detection. In an example, the sync mark detection module stores predetermined templates in association with storage media in a memory. Then, a storage medium is identified. Based on the identified storage medium, the sync mark detection module reads the stored template in association with the storage medium. For example, an optical disc stores disc and format information, such as disc category, version number, and the like, in a control data zone on the optical disc. The disc and format information can be read to identify the optical disc. Based on the identified optical disc, the sync mark detection module reads the stored template in association with the optical disc. 
     In another example, the sync mark detection module stores a partial response target that characterizes a channel for conveying a bit stream that includes the sync marks. Further, the sync mark detection module convolves the partial response target with a sync mark for a storage medium to determine a template for the storage medium. In another example, the sync mark detection module weights the template according to weight windows to determine a weighed template. 
     At S 420 , the sync mark detection module receives a data signal prior to decoding. The data signal corresponds to a bit stream that uses sync marks to frame user data. In an embodiment, the data signal is output from a pre-decoding portion, such as the pre-decoding portions  131 ,  231  and the like, that prepares the data signal for decoding. Then, the data signal is input to a decoder, such as a Viterbi decoder, that makes bit decisions to extract the bit stream. Thus, the data signal is an intermediate signal prior to decoding. Information in the data signal can be suitable used to increase sync mark detection accuracy. 
     At S 430 , the sync mark detection module calculates correlation coefficients between the data signal and the template. In an example, the template is in the form of a N-tuple vector. The data signal is in the form of a discrete-time signal. At each time point, the data signal of the most recent N time points form a N-tuple data vector, and the sync mark detection module calculates a correlation coefficient between the template vector and the data vector for the time point. 
     At S 440 , the sync mark detection module detects sync marks based on the correlation coefficients. In an embodiment, the sync mark detection module detects peak tops in the correlation coefficients. The peak tops are those correlation coefficients that are larger than their neighbor correlation coefficients. Then, the sync mark detection module compares peak tops with a threshold to detect sync marks. For example, the sync mark detection module compares absolute values of the peak tops with the threshold. When an absolute value of a peak top is larger than the threshold, the sync mark detection module detects a sync mark. Then, the process proceeds to S 499  and terminates. 
       FIG. 5A  shows an example  500 A of generating a windowed template according to an embodiment of the disclosure. In the example, a sync mark  510 A includes a 9T9T (nine zeros followed by nine ones or nine ones followed by nine zeros) pattern. The sync mark  510 A forms a vector  530 A by changing zeros to negative ones. Further, the vector  530 A is convolved with a partial response target  520 A to determine a template  540 A. The template  540 A is weighted according to a weight window  550 A to calculate the weighted template  560 A. 
       FIG. 5B  shows a plot  500 B of the templates in  FIG. 5A . The plot  500 B includes a first curve  540 B corresponding to the template  540 A, and a second curve  56013  corresponding to the windowed template  560 A. The windowed template weights transition portions  570 B heavier than the flat portions  580 B. Thus, the transition portions  570 B are emphasized and the flat portions  580 B are de-emphasized. 
     It is noted that the partial response target  520 A is merely an example. Other suitable partial response target is contemplated. It is also noted that the weight window  550 A is merely an example. Other suitable weight window is contemplated. 
       FIGS. 6A-6C  show plots for a sync mark detection example according to an embodiment of the disclosure.  FIG. 6A  shows a data signal  610  in the form of discrete-time signal. In an example, the data signal  610  corresponds to a bit stream read from a Blu-ray disc, and is output from a pre-decoding portion, such as the pre-decoding portion  231 . According to a Blu-ray standard, the sync mark includes a 9T9T pattern. In addition, an 8T8T pattern is legal for user data according to the Blu-ray standard. In  FIG. 6A , the data signal  610  includes a first portion  611  corresponding to a 8T8T pattern, and a second portion  612  corresponding to a 9T9T pattern. 
       FIG. 6B  shows correlation coefficients between the data signal  610  and the template  540 A. The first portion  611  of the data signal  610  has a first correlation coefficient  621  to the template  540 A. The second portion  612  of the data signal  610  has a second correlation coefficient  622  to the template  540 A. It is noted that a difference between the first correlation coefficient  621  and the second correlation coefficient  622  is relatively small. It is also noted that neighbor coefficients  623  of the second correlation coefficient  622  also has relatively large values. In an embodiment, a threshold is suitably determined to discriminate the first correlation coefficient  621  or the neighbor coefficients  623  from being detected as sync marks. 
       FIG. 6C  shows correlation coefficients between the data signal  610  and the windowed template  560 A according to an embodiment of the disclosure. The first portion  611  of the data signal  610  has a third correlation coefficient  631  to the windowed template  560 A. The second portion  612  of the data signal  610  has a fourth correlation coefficient  632  to the windowed template  560 A. 
     Due to the reason that the weight window  550 A emphasizes the transition portions of template and de-emphasizes the flat portions of the template, the third correlation coefficient  631  is reduced from the first correlation coefficient  621 , and a difference between the third correlation coefficient  631  and the fourth correlation coefficient  632  is relatively larger. In an embodiment, a threshold is suitably determined to discriminate the third correlation coefficient  631  from being detected as sync marks. 
       FIG. 6C  also shows peak tops in the correlation coefficients that are larger than neighbor correlation coefficients. The peak tops can be used to discriminate neighbor coefficients from being considered as sync marks. 
       FIG. 7A  shows a performance table  700 A of a Blu-ray system example according to an embodiment of the disclosure. The Blu-ray system matches an intermediate signal, such as the data signal  365 , with a windowed template of a sync mark having 9T9T pattern to detect sync marks. According to an embodiment of the disclosure, a threshold can be suitably selected to reduce detection errors. Generally, the detection errors include both false detection errors and miss sync errors. When a portion of the data signal  365  does not include a sync mark, and the Blu-ray system detects a sync mark, the Blu-ray system has a false detection error. When a portion of the data signal  365  has a sync mark, and the Blu-ray system doesn&#39;t detect the sync mark, the Blu-ray system has a miss sync error. 
     The numbers of the false detection errors and the miss sync errors depend on the threshold used for sync mark detection. For example, increasing the threshold reduces false detection errors but increases miss sync errors, and reducing the threshold reduces miss sync errors but increases false detection errors. The threshold can be suitably selected to reduce the total number of the detection errors. 
     The performance table  700 A shows total detection errors in association with thresholds using a same input signal to the Bin-ray system. The threshold 0.94 is selected to achieve 13 detection errors in total. 
       FIG. 7B  shows a performance table  700 B of a comparison Blu-ray system. The comparison Blu-ray system matches an extracted bit stream with a sync mark pattern, such as 9T9T, to detect sync marks. The performance table  700 B shows total detection errors in association with thresholds. It is noted that the same input signal is provided to the Blu-ray system in  FIG. 7A  and the comparison Blu-ray system in  FIG. 7B . According to the performance table  700 B, the threshold 21 is selected to achieve 29 detection errors in total. 
     While the invention has been described in conjunction with the specific embodiments thereof that are proposed as examples, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, embodiments of the invention as set forth herein are intended to be illustrative, not limiting. There are changes that may be made without departing from the scope of the invention.