# US 8,867,603 B1 · Method and system for balancing an equalizer at a receiver > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,867,603 B1 - Document ID: US8867603B1 - Status: Granted - Kind: B1 - Application number: 14/018,521 - Filed: 2013-09-05 - Granted: 2014-10-21 - Earliest claimed: 2011-05-12 - Assignees: Valens Semiconductor Ltd. - Applicants: Valens Semiconductor Ltd. - Inventors: Eyran Lida; Gaby Gur Cohen; Aviv Salamon - Web page: https://patentgrep.com/patent/US8867603B1 ## CPC - H04L 27/01: Equalisers {(baseband equalizers at the transmitter end H04L25/03343; in analogue transmission systems H04B3/04, H04B7/005)} - H04L 25/03044: {using fractionally spaced delay lines or combinations of fractionally integrally spaced taps} - H04L 25/03063: {using fractionally spaced delay lines or combinations of fractionally and integrally spaced taps} - H04L 25/03267: {with decision feedback equalisers} - H04L 2025/03356: {Baseband transmission} - H04L 2025/03732: {according to the convergence state} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A configurable analog equalizer is set to a first high-pass frequency response that is intentionally too moderate to compensate for a low-pass frequency response of a physical link coupling a transmitter and a receiver. A Feed Forward Equalizer (FFE) is activated at the receiver; the FFE includes a set of coefficients having a minimum configuration of a cursor coefficient and a first pre-cursor coefficient. A Decision Feedback Equalizer (DFE) is activated at the receiver; the DFE includes a set of coefficients having a minimum configuration of a first post-cursor coefficient. The configurable analog equalizer is then set to a high-pass frequency response that is more intense than the first high-pass frequency response, until the first post-cursor coefficient of the DFE substantially equals an absolute value of a quotient obtained by dividing the first pre-cursor coefficient of the FFE by the cursor coefficient of the FFE. ## Claims ### Claim 1 A method comprising: setting, at a receiver, a configurable analog equalizer to a first high-pass frequency response that is too moderate to compensate for a low-pass frequency response of a physical link coupling a transmitter and the receiver; activating, at the receiver, a Feed Forward Equalizer (FFE) comprising a set of coefficients having a minimum configuration of a cursor coefficient and a first pre-cursor coefficient; activating, at the receiver, a Decision Feedback Equalizer (DFE) comprising a set of coefficients having a minimum configuration of a first post-cursor coefficient; and setting the configurable analog equalizer to a high-pass frequency response that is more intense than the first high-pass frequency response until the first post-cursor coefficient of the DFE substantially equals an absolute value of a quotient obtained by dividing the first pre-cursor coefficient of the FFE by the cursor coefficient of the FFE. ### Claim 2 (depends on 1) The method of claim 1, further comprising: repeatedly increasing the high-pass frequency response of the configurable analog equalizer; allowing the DFE to substantially converge after each increment; and stop incrementing the high-pass frequency response of the configurable analog equalizer once the first post-cursor coefficient of the DFE substantially equals the absolute value of the quotient obtained by dividing the first pre-cursor coefficient of the FFE by the cursor coefficient of the FFE. ### Claim 3 (depends on 1) The method of claim 1, further comprising: repeatedly increasing the high-pass frequency response of the configurable analog equalizer; allowing the DFE to substantially converge after each increment; and stop incrementing the high-pass frequency response of the configurable analog equalizer once the first post-cursor coefficient of the DFE drops below the absolute value of the quotient obtained by dividing the first pre-cursor coefficient of the FFE by the cursor coefficient of the FFE. ### Claim 4 (depends on 3) The method of claim 3, further comprising: fine tuning the high-pass frequency response of the configurable analog equalizer, until the first post-cursor coefficient of the DFE substantially equals the absolute value of the quotient obtained by dividing the first pre-cursor coefficient of the FFE by the cursor coefficient of the FFE. ### Claim 5 (depends on 1) The method of claim 1, further comprising: repeatedly increasing the high-pass frequency response of the configurable analog equalizer; allowing the DFE to substantially converge after each increment; and stop incrementing the high-pass frequency response of the configurable analog equalizer only when the first post-cursor coefficient of the DFE substantially equals the absolute value of the quotient and the first post-cursor coefficient of the DFE is below 0.5. ### Claim 6 (depends on 1) The method of claim 1, further comprising setting the ratio between the cursor coefficient of the FFE and a first pre-cursor coefficient of the FFE to a fixed value when a timing recovery mechanism at the receiver and the FFE are in a convergence process. ### Claim 7 A system for equalizing communication signals, comprising: a configurable analog equalizer; a Feed Forward Equalizer (FFE) comprising set of coefficients having a minimum configuration of a cursor coefficient and a first pre-cursor coefficient; and a Decision Feedback Equalizer (DFE) comprising set of coefficients having a minimum configuration of a first post-cursor coefficient; wherein the system is configured to: set the configurable analog equalizer to a first high-pass frequency response that is too moderate to compensate for a low-pass frequency response of a physical link coupling a transmitter and the system; activate the FFE; activate the DFE; and set the configurable analog equalizer to a high-pass frequency response that is more intense than the first high-pass frequency response, until the first post-cursor coefficient of the DFE substantially equals an absolute value of a quotient obtained by dividing the first pre-cursor coefficient of the FFE by the cursor coefficient of the FFE. ### Claim 8 (depends on 7) The system of claim 7, further configured to: repeatedly increase the high-pass frequency response of the configurable analog equalizer; allow the DFE to substantially converge after each increment; and stop incrementing the high-pass frequency response of the configurable analog equalizer once the first post-cursor coefficient of the DFE substantially equals the absolute value of the quotient obtained by dividing the first pre-cursor coefficient of the FFE by the cursor coefficient of the FFE. ### Claim 9 (depends on 7) The system of claim 7, further configured to: repeatedly increase the high-pass frequency response of the configurable analog equalizer; allow the DFE to substantially converge after each increment; and stop incrementing the high-pass frequency response of the configurable analog equalizer once the first post-cursor coefficient of the DFE drops below the absolute value of the quotient obtained by dividing the first pre-cursor coefficient of the FFE by the cursor coefficient of the FFE. ### Claim 10 (depends on 9) The system of claim 9, further configured to: fine tune the high-pass frequency response of the configurable analog equalizer, until the first post-cursor coefficient of the DFE substantially equals the absolute value of the quotient obtained by dividing the first pre-cursor coefficient of the FFE by the cursor coefficient of the FFE. ### Claim 11 (depends on 7) The system of claim 7, further configured to: repeatedly increase the high-pass frequency response of the configurable analog equalizer; allow the DFE to substantially converge after each increment; and stop incrementing the high-pass frequency response of the configurable analog equalizer only when the first post-cursor coefficient of the DFE substantially equals the absolute value of the quotient and the first post-cursor coefficient of the DFE is below 0.5. ### Claim 12 (depends on 11) The system of claim 11, wherein when the first post-cursor coefficient of the DFE is below 0.5, noise propagation from a previous symbol estimator error is eliminated. ### Claim 13 (depends on 7) The system of claim 7, wherein when the first post-cursor coefficient of the DFE substantially equals the absolute value of the quotient, a total frequency response of the FFE and the DFE is substantially equally partitioned between the FFE and the DFE, resulting in substantially total linear phase. ### Claim 14 (depends on 7) The system of claim 7, further configured to: set ratio between the cursor coefficient of the FFE and a first pre-cursor coefficient of the FFE to a fixed value when a timing recovery mechanism and the FFE are in a convergence process. ### Claim 15 (depends on 14) The system of claim 14, wherein the ratio between the cursor coefficient of the FFE and a first pre-cursor coefficient of the FFE is set to a value expected to result in substantially best frequency compensation to an expected frequency response of the physical link coupling the transmitter and the system. ### Claim 16 (depends on 14) The system of claim 14, wherein the ratio between the cursor coefficient of the FFE and a first pre-cursor coefficient of the FFE is set to a value expected to result in substantially best frequency compensation to an expected combined frequency response of the physical link coupling the transmitter to the system and the configurable analog equalizer. ### Claim 17 (depends on 16) The system of claim 16, wherein setting to a fixed value the ratio between the cursor coefficient of the FFE and a first pre-cursor coefficient of the FFE results in decoupled correct convergence of the timing recovery mechanism and of FFE coefficients. ### Claim 18 (depends on 17) The system of claim 17, wherein the fixed value of the ratio between the cursor coefficient of the FFE and the first pre-cursor coefficient of the FFE is set once after setting the configurable analog equalizer to the first high-pass frequency response that is too moderate to compensate for a low-pass frequency response of a physical link coupling the transmitter and a receiver. ### Claim 19 (depends on 14) The system of claim 14, wherein the fixed value of the ratio between the cursor coefficient of the FFE and the first pre-cursor coefficient of the FFE is set once before receiving signals at the receiver.