# US 2010/0164764 A1 · Systems and Methods for Mitigating Latency in a Data Detector Feedback Loop > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2010/0164764 A1 - Document ID: US20100164764A1 - Status: Published application - Kind: A1 - Application number: 12/663,319 - Filed: 2008-05-19 - Published: 2010-07-01 - Earliest claimed: 2008-05-19 - Assignees: Agere Systems Inc. - Inventors: Ratnakar Aravind Nayak - Web page: https://patentgrep.com/patent/US20100164764A1 ## CPC - G11B 20/10009: {Improvement or modification of read or write signals} - G11B 20/10037: {A/D conversion, D/A conversion, sampling, slicing and digital quantisation or adjusting parameters thereof} - G11B 20/10046: {filtering or equalising, e.g. setting the tap weights of an FIR filter} - G11B 20/10222: {clock-related aspects, e.g. phase or frequency adjustment or bit synchronisation (dedicated sync patterns in the modulation code G11B20/1403)} - H03L 7/07: using several loops, e.g. for redundant clock signal generation - H03L 7/0807: {concerning mainly a recovery circuit for the reference signal} - H03L 7/0814: {the phase shifting device being digitally controlled} - H03L 7/0816: {the controlled phase shifter and the frequency- or phase-detection arrangement being connected to a common input} - H03L 7/091: the phase or frequency detector using a sampling device (H03L7/087 takes precedence) - G11B 2220/2516: Hard disks - H04L 7/033: using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) - H03L: AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES (generation of oscillations H03B) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract Various embodiments of the present invention provide systems and methods for mitigating latency in a data detector feedback loop. For example, a method for reducing latency in an error corrected data retrieval system is disclosed. The method includes performing an analog to digital conversion at a sampling instant to create a digital sample, and performing a data detection on the digital sample to create a detected output. The detected output is compared with the digital sample to determine a phase error. During an interim period, the digital sample is adjusted to reflect the phase error to create an adjusted digital sample. After the interim period, the sampling instant is adjusted to reflect the phase error. ## Claims ### Claim 1 A data retrieval system, the circuit comprising: an analog to digital converter, wherein the analog to digital converter is operable to receive an analog signal and to provide a first digital signal corresponding to the analog signal at a first sampling instant; a data detector, wherein the data detector is operable to perform a data detection process on the first digital signal to provide a modified data signal; an error determination circuit, wherein the error determination circuit is operable to compare the modified data signal with a derivative of the first digital signal to determine a first error indication; a first feedback loop, wherein the first feedback loop receives the first error indication and causes the analog to digital converter to provide a second digital signal corresponding to the analog signal at a second sampling instant, and wherein the second sampling instant is adjusted to reflect the first error indication; and a second feedback loop, wherein the second feedback loop receives the first error indication and adjusts the derivative of the first digital signal such that the error determination circuit determines a second error indication based at least in part on the adjusted derivative of the first digital signal. ### Claim 2 (depends on 1) The system of claim 1, wherein the second feedback loop includes an interpolator that is operable to interpolate the first digital signal in time to compensate for the first error indication during an interim period, and wherein the interpolator provides the derivative of the first digital signal. ### Claim 3 (depends on 2) The system of claim 2, wherein the second feedback loop further includes a summation element and a delay element, wherein the summation element and the delay element both receive the first error indication, and wherein the summation element is operable to subtract the first error indication from a delayed version of the first error indication. ### Claim 4 (depends on 3) The system of claim 3, wherein the output of the summation element is used to govern the amount of time interpolated by the interpolator. ### Claim 5 (depends on 3) The system of claim 3, wherein the delay applied by the delay element corresponds to a time period required for the first error indication to be reflected in the first feedback loop. ### Claim 6 (depends on 2) The system of claim 2, wherein the derivative of the first digital signal corresponds to the second digital signal after the interim period. ### Claim 7 (depends on 3) The system of claim 3, wherein the interim period reflects the time period from when the first error indication is available, until the second digital signal is available. ### Claim 8 (depends on 1) The system of claim 1, wherein the error determination circuit includes an equalization target filter that equalizes the modified data signal, wherein the error determination circuit includes a summation element that provides a difference between the derivative of the first digital signal and the equalized modified data signal, and wherein first error indication corresponds to the difference. ### Claim 9 (depends on 1) The system of claim 1, wherein the error determination circuit includes an equalization target filter that equalizes the modified data signal, wherein the error determination circuit includes a summation element that provides a difference between the derivative of the first digital signal and the equalized modified data signal, wherein the error determination circuit includes a slope detection circuit that determines a slope signal based at least in part on the modified data signal, and wherein the error determination circuit includes a timing error detection circuit that generates the first error indication based at least in part on the difference and the slope signal. ### Claim 10 (depends on 1) The system of claim 1, wherein the first error indication includes a phase error indication and a frequency error indication, and wherein a sum of the phase error indication and the frequency error indication is used as the first error indication in the first feedback loop, and wherein on the phase error indication is used as the first error indication in the second feedback loop. ### Claim 11 A method for reducing latency in an error corrected data retrieval system, the method comprising: performing an analog to digital conversion at a sampling instant to create a digital sample; performing a data detection on the digital sample to create a detected output; comparing the detected output with the digital sample to determine a phase error; during an interim period, adjusting the digital sample to reflect the phase error to create an adjusted digital sample; and after the interim period, adjusting the sampling instant to reflect the phase error. ### Claim 12 (depends on 11) The method of claim 11, wherein the method further comprises: receiving an analog input signal, wherein the analog input signal includes a data stream incorporated therein. ### Claim 13 (depends on 11) The method of claim 11, wherein comparing the detected output with the digital sample includes comparing the detected output with the adjusted digital sample during the interim period, and comparing the detected output directly with the digital sample after the interim period. ### Claim 14 (depends on 11) The method of claim 11, wherein the analog to digital conversion is a first analog to digital conversion, wherein the sampling instant is a first sampling instant, wherein the digital sample is a first digital sample, wherein adjusting the sampling instant to reflect the phase error provides a second sampling instant, wherein the data detection is a first data detection, wherein the detected output is a first detected output, wherein the phase error is a first phase error, wherein the interim period is a first interim period, wherein the adjusted digital sample is a first adjusted digital sample, and wherein the method further comprises: performing a second analog to digital conversion at a second sampling instant to create a second digital sample; performing a second data detection on the second digital sample to create a second detected output; comparing the second detected output with the second digital sample to determine a second phase error; during a second interim period, adjusting the second digital sample to reflect the second phase error to create a second adjusted digital sample; and after the second interim period, adjusting the sampling instant to reflect the second phase error. ### Claim 15 (depends on 14) The method of claim 14, wherein the first interim period precedes the second interim period, and wherein a non-zero time period is disposed between the first interim period and the second interim period. ### Claim 16 (depends on 14) The method of claim 14, wherein comparing the second detected output with the second digital sample includes comparing the second detected output with the second adjusted digital sample during the second interim period, and comparing the second detected output directly with the second digital sample after the second interim period. ### Claim 17 A data processing system, the data processing system comprising: a data receiving device, wherein the data receiving device derives an analog signal from a medium, and wherein the data receiving device further includes: an analog to digital converter, wherein the analog to digital converter is operable to receive the analog signal and to provide a first digital signal corresponding to the analog signal at a first sampling instant; a data detector, wherein the data detector is operable to perform a data detection process on the first digital signal to provide a modified data signal; an error determination circuit, wherein the error determination circuit is operable to compare the modified data signal with a derivative of the first digital signal to determine a first error indication; a first feedback loop, wherein the first feedback loop receives the first error indication and causes the analog to digital converter to provide a second digital signal corresponding to the analog signal at a second sampling instant, and wherein the second sampling instant is adjusted to reflect the first error indication; and a second feedback loop, wherein the second feedback loop receives the first error indication and adjusts the derivative of the first digital signal such that the error determination circuit determines a second error indication based at least in part on the adjusted derivative of the first digital signal. ### Claim 18 (depends on 17) The data processing system of claim 17, wherein the second feedback loop includes an interpolator, a summation element and a delay element; wherein the derivative of the first digital signal corresponds to the first digital signal interpolated in time to compensate for the first error indication during an interim period; wherein the summation element and the delay element both receive the first error indication, wherein the summation element is operable to subtract the first error indication from a delayed version of the first error indication; and wherein the output of the summation element is used to govern the amount of time interpolated by the interpolator. ### Claim 19 (depends on 17) The data processing system of claim 17, wherein the data receiving device is a wireless receiver, and wherein the medium is a wireless transmission medium. ### Claim 20 (depends on 17) The data processing device of claim 17, wherein the data processing system is a hard disk drive system, and wherein the medium is a magnetic storage medium.