# US 11,115,251 B1 · PAM4 equalization DSM

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- Number: US 11,115,251 B1
- Document ID: US11115251B1
- Status: Granted
- Kind: B1
- Application number: 17/156,346
- Filed: 2021-01-22
- Granted: 2021-09-07
- Earliest claimed: 2021-01-22
- Assignees: Litrinium, Inc.
- Applicants: Litrinium, Inc.
- Inventors: Sebastien Douyere
- Web page: https://patentgrep.com/patent/US11115251B1

## CPC

- H04L 25/4917: {using multilevel codes}
- H04L 25/03146: {with a recursive structure (H04L25/03127 takes precedence)}
- H04L 27/01: Equalisers {(baseband equalizers at the transmitter end H04L25/03343; in analogue transmission systems H04B3/04, H04B7/005)}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

In a system for calibrating PAM4 signals, an equalizer determines a first signal amplitude measurement of the PAM4 signal. The equalizer determines a first signal boost measurement of the PAM4 signal. The equalizer determines whether the first signal boost measurement and the signal amplitude measurement are substantially consistent with each other. Responsive to determining that the signal boost and the signal amplitude are not substantially consistent with each other, the equalizer determines a reference amplification modification and calibrates a PAM4 signal according to the determined reference amplification modification.

## Claims

### Claim 1

A method of automatically equalizing a PAM4 signal, comprising:
generating a reference signal for the PAM4 signal by slicing the PAM4 signal into a first level and a second level;
determining a constant coefficient;
amplifying the reference signal by the constant coefficient, wherein the amplified reference signal is used to modulate the PAM4 signal;
determining a first signal amplitude measurement of the PAM4 signal;
determining a first signal boost measurement of the PAM4 signal;
determining whether the first signal boost measurement and the signal amplitude measurement are substantially consistent with each other;
responsive to determining that the signal boost and the signal amplitude are not substantially consistent with each other, determining a reference amplification modification; and
calibrating a PAM4 signal according to the determined reference amplification modification.

### Claim 2 (depends on 1)

The method of claim 1, further comprising;
responsive to determining that the first signal boost measurement and the first signal amplitude measurement are substantially consistent with each other, initiating a sleep period using a sleep timer;
determining whether the sleep period has elapsed; and
responsive to determining that the sleep period has elapsed, determining a second signal amplitude measurement of the PAM4 signal; and
determining a second signal boost measurement of the PAM4 signal.

### Claim 3 (depends on 1)

The method of claim 1, further comprising, responsive to determining that the sleep period has not elapsed, initiating a second sleep period.

### Claim 4

A system for equalizing a PAM4 signal, comprising;
an PAM4 signal equalizer configured to:
generate a reference signal for the PAM4 signal by slicing the PAM4 signal into a first level and a second level;
determine a constant coefficient;
amplify the reference signal by the constant coefficient, wherein the amplified reference signal is used to modulate the PAM4 signal;
determine a first signal amplitude measurement of the PAM4 signal;
determine a first signal boost measurement of the PAM4 signal;
determine whether the first signal boost measurement and the signal amplitude measurement are substantially consistent with each other; and
responsive to determining that the signal boost and the signal amplitude are not substantially consistent with each other, determine a reference amplification modification; and
calibrate a PAM4 signal according to the determined reference amplification modification.

### Claim 5 (depends on 4)

The system of claim 4, wherein the PAM4 signal equalizer is further configured to;
responsive to determining that the first signal boost measurement and the first signal amplitude measurement are substantially consistent with each other, initiate a sleep period using a sleep timer;
determine whether the sleep period has elapsed; and
responsive to determining that the sleep period has elapsed, determine a second signal amplitude measurement of the PAM4 signal; and
determine a second signal boost measurement of the PAM4 signal.

### Claim 6 (depends on 4)

The system of claim 4, wherein the PAM4 signal equalizer is further configured to, responsive to determining that the sleep period has not elapsed, initiate a second sleep period.