# US 10,312,920 B2 · Baseline wander compensation

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- Number: US 10,312,920 B2
- Document ID: US10312920B2
- Status: Granted
- Kind: B2
- Application number: 15/719,973
- Filed: 2017-09-29
- Published: 2019-04-04
- Granted: 2019-06-04
- Earliest claimed: 2017-09-29
- Assignees: Cavium, Inc.
- Applicants: Cavium, LLC
- Inventors: Ethan Crain; Lu Wang
- Web page: https://patentgrep.com/patent/US10312920B2

## CPC

- H03L 7/0807: {concerning mainly a recovery circuit for the reference signal}
- H03L 5/00: Automatic control of voltage, current, or power
- H04L 7/0087: {Preprocessing of received signal for synchronisation, e.g. by code conversion, pulse generation or edge detection}
- H04L 7/048: {using the properties of error detecting or error correcting codes, e.g. parity as synchronisation signal}
- H04L 25/03057: {with a recursive structure (H04L25/03031 takes precedence)}
- H04L 7/0331: {with a digital phase-locked loop [PLL] processing binary samples, e.g. add/subtract logic for correction of receiver clock (H04L7/0337 takes precedence)}
- 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

A data recovery circuit provides compensation for baseline wander exhibited by a data signal. An adaptive equalizer generates a recovered data signal from a data input. A level shifter and low-pass filter provide a compensation signal as a function of the recovered data signal. An adaptation engine adjusts the level of the compensation signal to compensate for baseline wander. The adaptive equalizer generates the recovered data signal as a function of the data input and the compensation signal, thereby providing accurate recovery of the data signal.

## Claims

### Claim 1

A circuit comprising:
an AC-coupling network configured to receive a data input signal and output a high-pass filtered data signal;
an adaptive equalizer configured to output a recovered data signal;
a level shifter configured to output a level-shifted signal as a function of the recovered data signal;
a low-pass filter configured to output a low-pass filtered signal as a function of the level-shifted signal, the low-pass filtered signal corresponding to a low-frequency component of the data input signal, the adaptive equalizer generating the recovered data signal as a function of the low-pass filtered signal and the high-pass filtered data signal;
an adaptation engine configured to control the level shifter to adjust an amplitude of the level-shifted signal as a function of the recovered data signal; and
a comparator configured to receive a first input, the first input being a combination of the low-pass filtered signal and high-pass filtered data signal, the comparator outputting an error signal to the adaptation engine.

### Claim 2 (depends on 1)

The circuit of claim 1, wherein the comparator is further configured to receive a second input corresponding to the recovered data signal, the comparator outputting the error signal as a function of a difference between the first and second inputs.

### Claim 3 (depends on 1)

The circuit of claim 1, wherein the adaptation engine is further configured to adjust the amplitude of the level-shifted signal as a function of the error signal.

### Claim 4 (depends on 1)

The circuit of claim 1, further comprising a deserializer configured to convert the error signal to a parallel error signal.

### Claim 5 (depends on 4)

The circuit of claim 4, wherein the adaptation engine is further configured to receive the parallel error signal.

### Claim 6 (depends on 1)

The circuit of claim 1, further comprising a combiner configured to combine the high-pass filtered data signal and low-pass filtered signal and output a combined data signal.

### Claim 7 (depends on 6)

The circuit of claim 6, wherein the adaptive equalizer is further configured to output the recovered data signal as a function of the combined data signal.

### Claim 8 (depends on 1)

The circuit of claim 1, wherein the adaptive equalizer includes a decision feedback equalizer (DFE).

### Claim 9

A circuit comprising:
an AC-coupling network configured to receive a data input signal and output a high-pass filtered data signal;
an adaptive equalizer configured to output a recovered data signal;
a level shifter configured to output a level-shifted signal as a function of the recovered data signal;
a low-pass filter configured to output a low-pass filtered signal as a function of the level-shifted signal, the low-pass filtered signal corresponding to a low-frequency component of the data input signal, the adaptive equalizer generating the recovered data signal as a function of the low-pass filtered signal and the high-pass filtered data signal;
an adaptation engine configured to control the level shifter to adjust an amplitude of the level-shifted signal as a function of the recovered data signal; and
a deserializer configured to convert the recovered data signal to a parallel data signal.

### Claim 10 (depends on 9)

The circuit of claim 9, wherein the adaptation engine is further configured to receive the parallel data signal.

### Claim 11

A method of recovering a data signal, comprising:
filtering a data input signal at an AC-coupling network to generate a high-pass filtered data signal;
level-shifting a recovered data signal to generate a level-shifted signal;
filtering the level-shifted signal to output a low-pass filtered signal, the low-pass filtered signal corresponding to a low-frequency component of the data input signal;
generating the recovered data signal as a function of the low-pass filtered signal and the high-pass filtered data signal;
adjusting an amplitude of the level-shifted signal as a function of the recovered data signal; and
comparing a first input, the first input being a combination of the low-pass filtered signal and high-pass filtered data signal and outputting an error signal.

### Claim 12 (depends on 11)

The method of claim 11, further comprising receiving a second input corresponding to the recovered data signal and outputting the error signal as a function of a difference between the first and second inputs.

### Claim 13 (depends on 11)

The method of claim 11, further comprising adjusting the amplitude of the level-shifted signal as a function of the error signal.

### Claim 14 (depends on 11)

The method of claim 11, further comprising converting the error signal to a parallel error signal.

### Claim 15 (depends on 11)

The method of claim 11, further comprising combining the high-pass filtered data signal and low-pass filtered signal and outputting a combined data signal.

### Claim 16 (depends on 15)

The method of claim 15, further comprising outputting the recovered data signal as a function of the combined data signal.

### Claim 17

A method of recovering a data signal, comprising:
filtering a data input signal at an AC-coupling network to generate a high-pass filtered data signal;
level-shifting a recovered data signal to generate a level-shifted signal;
filtering the level-shifted signal to output a low-pass filtered signal, the low-pass filtered signal corresponding to a low-frequency component of the data input signal;
generating the recovered data signal as a function of the low-pass filtered signal and the high-pass filtered data signal;
adjusting an amplitude of the level-shifted signal as a function of the recovered data signal; and
converting the recovered data signal to a parallel data signal.