# US 2019/0173695 A1 · Linear feedback equalization > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0173695 A1 - Document ID: US20190173695A1 - Status: Published application - Kind: A1 - Application number: 15/831,092 - Filed: 2017-12-04 - Published: 2019-06-06 - Earliest claimed: 2017-12-04 - Assignees: Credo Technology Group Limited - Applicants: Credo Technology Group Limited - Inventors: Haoli QIAN; Haihui LUO - Web page: https://patentgrep.com/patent/US20190173695A1 ## CPC - H04L 25/03019: {adaptive, i.e. capable of adjustment during data reception} - H04L 25/03057: {with a recursive structure (H04L25/03031 takes precedence)} - H03L 7/0807: {concerning mainly a recovery circuit for the reference signal} - H04B 1/1027: {assessing signal quality or detecting noise/interference for the received signal} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H03L: AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES (generation of oscillations H03B) - H04B: TRANSMISSION ## Abstract A linear feedback equalizer includes comparators that digitize incoming analog signals. The equalizer further includes digital-to-analog converters (“DACs”) that transform a current digitized signal into one or more feedback analog signals. The equalizer further includes a subtractor that subtracts the feedback analog signals from the output of a continuous-time linear equalizer (“CTLE”) and provides the difference to the comparators as incoming analog signals. ## Claims ### Claim 1 A linear feedback equalizer comprising: comparators that digitize an incoming analog signal to provide a multi-bit thermometer-coded digital signal; one or more digital-to-analog converters (“DACs”) that transform the thermometer-coded digital signal into one or more feedback analog signals each having a corresponding tap delay; and a subtractor that subtracts the one or more feedback analog signals from an output of a continuous-time linear equalizer (“CTLE”) and provides the difference to the comparators as said incoming analog signals. ### Claim at position 2 -21. (canceled) ### Claim 22 (depends on 1) The linear feedback equalizer of claim 1, wherein the comparators slice the incoming analog signal into a number of bins that is one greater than a number of bits used by the multi-bit thermometer-coded digital signal, and wherein the number of bins is also greater than a number of symbols in a signal constellation used by the incoming analog signal. ### Claim 23 (depends on 22) The linear feedback equalizer of claim 22, wherein the number of symbols in the signal constellation is two and the number of bins is five. ### Claim 24 (depends on 22) The linear feedback equalizer of claim 22, wherein the number of symbols in the signal constellation is four and the number of bins is five. ### Claim 25 (depends on 1) The linear feedback equalizer of claim 1, wherein a transmitted data stream is reconstructed from the multi-bit thermometer-coded digital signal. ### Claim 26 (depends on 1) The linear feedback equalizer of claim 1, wherein the comparators use evenly-spaced reference voltages to generate bits of the multi-bit thermometer-coded digital signal. ### Claim 27 (depends on 1) The linear feedback equalizer of claim 1, wherein the comparators use unevenly-spaced reference voltages to generate bits of the multi-bit thermometer-coded digital signal. ### Claim 28 (depends on 27) The linear feedback equalizer of claim 27, wherein at least one of the one or more DACs weights the bits of the multi-bit thermometer coded digital signal unevenly when transforming the digital signal into a feedback analog signal. ### Claim 29 A linear feedback equalization method that comprises: comparing an incoming analog signal to multiple thresholds to obtain a multi-bit thermometer-coded digital signal; transforming the multi-bit thermometer-coded digital signal into one or more feedback analog signals each having a corresponding tap delay; filtering a receive signal with a continuous time linear equalizer (“CTLE”) to obtain a filtered analog signal; and combining the one or more feedback analog signals with the filtered analog signal to provide said incoming analog signal, said incoming analog signal having reduced intersymbol interference relative to the filtered analog signal. ### Claim 30 (depends on 29) The method of claim 29, wherein said receive signal carries a transmitted data stream encoded with a constellation having a given number of symbols, and wherein said comparing digitizes the incoming analog signal into one of a number of bins that is greater than said given number of symbols. ### Claim 31 (depends on 30) The method of claim 30, wherein the given number of symbols in the signal constellation is two and the number of bins is five. ### Claim 32 (depends on 30) The method of claim 30, wherein the given number of symbols in the signal constellation is four and the number of bins is five. ### Claim 33 (depends on 30) The method of claim 30, further comprising: reconstructing the transmitted data stream from the multi-bit thermometer-coded digital signal. ### Claim 34 (depends on 29) The method of claim 29, wherein the multiple thresholds are evenly-spaced. ### Claim 35 (depends on 29) The method of claim 29, wherein the multiple thresholds are unevenly-spaced. ### Claim 36 (depends on 35) The method of claim 35, wherein said transforming includes weighting the bits of the multi-bit thermometer coded digital signal unevenly when transforming the digital signal into a feedback analog signal. ### Claim 37 An integrated circuit having a serializer/deserializer interface with a receiver that comprises a linear feedback equalizer, the linear feedback equalizer including: comparators that compare an incoming analog signal to multiple thresholds to obtain a multi-bit thermometer-coded digital signal; one or more digital analog converters (“DACs”) that transform the multi-bit thermometer-coded digital signal into one or more feedback analog signals each having a corresponding tap delay; a continuous time linear equalizer (“CTLE”) that filters a receive signal to obtain a filtered analog signal; and a combiner that subtracts the one or more feedback analog signals from the filtered analog signal to provide said incoming analog signal, said incoming analog signal having reduced intersymbol interference relative to the filtered analog signal. ### Claim 38 (depends on 37) The integrated circuit of claim 37, wherein said receive signal carries a transmitted data stream encoded with a constellation having a given number of symbols, and wherein said comparators digitize the incoming analog signal into a number of discrete values that is greater than said given number of symbols.