# US 9,436,209 B2 · Method and system for clock recovery with adaptive loop gain control > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,436,209 B2 - Document ID: US9436209B2 - Status: Granted - Kind: B2 - Application number: 13/824,551 - Filed: 2011-09-16 - Published: 2014-04-24 - Granted: 2016-09-06 - Earliest claimed: 2010-09-17 - Assignees: Xieon Networks S.a.r.l. - Applicants: Bernhard Spinnler; Christina Hebebrand; Stefano Calabro - Inventors: Bernhard Spinnler; Christina Hebebrand; Stefano Calabro - Web page: https://patentgrep.com/patent/US9436209B2 ## CPC - H03L 7/07: using several loops, e.g. for redundant clock signal generation - G06F 1/04: Generating or distributing clock signals or signals derived directly therefrom - H03L 7/0807: {concerning mainly a recovery circuit for the reference signal} - H04L 7/0029: {interpolation of received data signal} - H03L 7/0814: {the phase shifting device being digitally controlled} - H04J 14/06: Polarisation multiplex systems - H04L 7/0335: {Gardner detector} - H03L: AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES (generation of oscillations H03B) - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S) ## Abstract A method for phase recovery in a system that includes a clock recovery unit and an estimation unit. The clock recovery unit of the system has a first phase detector unit. The estimation unit has a second phase detector unit and it is configured to estimate a gain of the second phase detector unit. The estimation unit and the clock recovery unit are configured to operate in parallel. ## Claims ### Claim 1 A system, comprising: a clock recovery unit having a gain adjustment unit, a first phase detector unit, a filter and a numerically controlled oscillator coupled in a closed loop, wherein an output of the first phase detector unit is coupled to the filter, an output of the filter is coupled to the numerically controlled oscillator, and wherein a signal provided by the output of the filter controls the numerically controlled oscillator based on a signal provided by the output of the first phase detector unit; an estimation unit having a second phase detector unit and a gain estimation unit coupled in series, said gain estimation unit being configured to estimate a gain of said second phase detector unit; wherein the estimated gain of said second phase detector unit includes a variable part; and wherein said estimation unit and said clock recovery unit are configured to operate in parallel, wherein the clock recovery unit is coupled to an output of the estimation unit, and the gain adjustment unit of the clock recovery unit is adapted to adaptively adjust loop gain of the closed control loop including the first phase detector unit based on the estimated gain of the second phase detector unit to achieve a constant loop gain. ### Claim 2 (depends on 1) The system according to claim 1, wherein the estimated gain of said second phase detector unit is configured to feed said first phase detector unit. ### Claim 3 (depends on 1) The system according to claim 1, wherein the system is adjustable such that the variable part of the estimated gain can be reduced to zero substantially canceled out. ### Claim 4 (depends on 1) The system according to claim 1, wherein said clock recovery unit comprises a phase-locked-loop system. ### Claim 5 (depends on 4) The system according to claim 4, wherein said phase-locked-loop system includes said filter, and the filter has perfect integrator path. ### Claim 6 (depends on 1) The system according to claim 1, wherein said first phase detector unit and said second phase detector unit are Gardner phase detectors. ### Claim 7 (depends on 1) The system according to claim 1, wherein the system is a communication system. ### Claim 8 (depends on 7) The system according to claim 7, wherein the communication system is an optical communication system. ### Claim 9 A method for phase recovery for a system, the system having a clock recovery unit and an estimation unit wherein the clock recovery unit is coupled to an output of the estimation unit, the clock recovery unit including a gain adjustment unit, a first phase detector unit a filter and a numerically controlled oscillator coupled in a closed loop, and the estimation unit including second phase detector unit and a gain estimation unit coupled in series, the method comprising: receiving at the filter of the clock recovery unit a signal provided by an output of the first phase detector unit, controlling the numerically controlled oscillator of the clock recovery unit by a signal provided by an output of the filter and based on the signal provided by the output of the first phase detector unit; estimating a gain of the second phase detector unit by the gain estimation unit, wherein the estimated gain of the second phase detector unit includes a variable part; and adaptively adjusting loop gain of the closed control loop including the first phase detector unit by the gain adjustment unit and based on the estimated gain of the second phase detector unit to achieve a constant loop gain. ### Claim 10 (depends on 9) The method according to claim 9, wherein the estimated gain of the second phase detector unit feeds the first phase detector unit.