# US 9,001,943 B2 · Digital equalizer adaptation using on-die instrument

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- Number: US 9,001,943 B2
- Document ID: US9001943B2
- Status: Granted
- Kind: B2
- Application number: 13/974,297
- Filed: 2013-08-23
- Published: 2014-09-18
- Granted: 2015-04-07
- Earliest claimed: 2013-03-14
- Assignees: Altera Corporation
- Applicants: Altera Corporation
- Inventors: Tim Tri Hoang; Nam V. Nguyen
- Web page: https://patentgrep.com/patent/US9001943B2

## CPC

- H04L 25/03885: {adaptive}
- H03G 3/002: {Control of digital or coded signals (H03G3/3089 take precedence)}
- H04B 1/16: Circuits
- H04B 3/143: {using amplitude-frequency equalisers}
- H04L 25/03: Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L 25/03019: {adaptive, i.e. capable of adjustment during data reception}
- H04L 25/03057: {with a recursive structure (H04L25/03031 takes precedence)}
- H04L 5/006: {Quality of the received signal, e.g. BER, SNR, water filling}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H03G: CONTROL OF AMPLIFICATION
- H04B: TRANSMISSION

## Abstract

Systems and methods are provided for adjusting gain of a receiver. Adaptation circuitry is operable to identify, based on a matrix representation of a receiver's output generated from horizontal and vertical sweeps of the receiver's output, an eye opening of the receiver's output. The adaptation circuitry is also operable to determine whether a size of the eye opening needs to be changed. When it is determined that the size of the eye opening needs to be changed, the adaptation circuitry is operable to generate a digital signal to change a gain setting of the receiver. When the signal at the receiver's output is under-equalized, the AC gain of the receiver is increased. When the signal at the receiver's output is over-equalized, the AC gain of the receiver is decreased.

## Claims

### Claim 1

A method for adjusting gain of a receiver having an output, the method comprising:
generating, based on horizontal and vertical sweeps of the receiver's output, a matrix representation of the receiver's output;
identifying, based on the generated matrix representation, an eye opening of the receiver's output;
determining, using on-die instrument (ODI) circuitry, whether a vertical height of the eye opening needs to be changed; and
when it is determined that the vertical height of the eye opening needs to be changed, generating, using adaptation circuitry coupled to the ODI circuitry, a digital signal to change an AC gain setting and a DC gain setting of the receiver.

### Claim 2 (depends on 1)

The method of claim 1, further comprising calculating the vertical height of the identified eye opening.

### Claim 3 (depends on 2)

The method of claim 2, wherein determining whether the vertical height of the eye opening needs to be changed comprises comparing the calculated vertical height to a pre-defined vertical envelope.

### Claim 4 (depends on 2)

The method of claim 2, wherein determining whether the vertical height of the eye opening needs to be changed comprises comparing the calculated vertical height to an optimum vertical eye opening.

### Claim 5 (depends on 1)

The method of claim 1, wherein elements of the generated matrix representation have a first value where an eye opening exists and a second value where an eye opening does not exist.

### Claim 6 (depends on 1)

The method of claim 1, further comprising finding envelope limits of the receiver's output before identifying the eye opening of the receiver's output.

### Claim 7 (depends on 1)

The method of claim 1, further comprising determining whether the receiver's output is under-equalized or over-equalized, and wherein generating the digital signal to change the AC gain setting and the DC gain setting of the receiver comprises:
when it is determined that the receiver's output is under-equalized, generating a digital signal to increase the AC gain of the receiver if the AC gain of the receiver is not at a maximum setting; and
when it is determined that the receiver's output is over-equalized, generating a digital signal to decrease the AC gain of the receiver if the AC gain of the receiver is not at a minimum setting.

### Claim 8 (depends on 7)

The method of claim 7, wherein generating the digital signal to change the AC gain setting and the DC gain setting of the receiver comprises:
when it is determined that the receiver's output is under-equalized and the AC gain of the receiver is at the maximum setting, generating a digital signal to decrease the DC gain of the receiver and set the AC gain of the receiver substantially equal to zero; and
when it is determined that the receiver's output is over-equalized and the AC gain of the receiver is at the minimum setting, generating a digital signal to increase the DC gain of the receiver and set the AC gain of the receiver substantially equal to zero.

### Claim 9

Adaptation circuitry in an integrated circuit, said circuitry comprising:
circuitry that identifies, based on a matrix representation of a receiver's output generated from horizontal and vertical sweeps of the receiver's output, an eye opening of the receiver's output;
circuitry that determines whether a vertical height of the eye opening needs to be changed; and
circuitry that, when it is determined that the vertical height of the eye opening needs to be changed, generates a digital signal to change an AC gain setting and a DC gain setting of the receiver.

### Claim 10 (depends on 9)

The adaptation circuitry of claim 9, further comprising:
circuitry that calculates the vertical height of the identified eye opening; and
circuitry that compares the calculated vertical height to a pre-defined vertical envelope.

### Claim 11 (depends on 9)

The adaptation circuitry of claim 9, further comprising:
calculate the vertical height of the identified eye opening; and
compare the calculated vertical height to an optimum vertical eye opening.

### Claim 12 (depends on 9)

The adaptation circuitry of claim 9, further comprising circuitry that controls the horizontal and the vertical sweeps of the receiver's output.

### Claim 13 (depends on 9)

The adaptation circuitry of claim 9, further comprising circuitry that finds envelope limits of the receiver's output.

### Claim 14 (depends on 9)

The adaptation circuitry of claim 9, further comprising:
circuitry that determines whether the receiver's output is under-equalized or over-equalized;
circuitry that, when it is determined that the receiver's output is under-equalized:
generates a digital signal to increase the AC gain of the receiver if the AC gain of the receiver is not at a maximum setting, and
circuitry that, if the AC gain of the receiver is at the maximum setting, generates a digital signal to decrease the DC gain of the receiver and set the AC gain of the receiver substantially equal to zero; and
circuitry that, when it is determined that the receiver's output is over-equalized:
generates a digital signal to decrease the AC gain of the receiver if the AC gain of the receiver is not at a minimum setting, and
circuitry that, if the AC gain of the receiver is at the minimum setting, generate a digital signal to increase the DC gain of the receiver and set the AC gain of the receiver substantially equal to zero.

### Claim 15

A communications system comprising:
a receiver having at least one amplifier;
an on-die instrument (ODI) configured to sample an output of the receiver;
a first digital adaptation unit configured to:
analyze outputs of the ODI;
control horizontal and vertical sweeps of the receiver's output that are used to generate a matrix representation of the receiver's output; and
generate a first set of digital signals for adjusting a gain setting of at least one amplifier in the receiver;
a decision feedback equalizer (DFE) configured to amplify the output of the receiver; and
a clock-data recovery (CDR) unit coupled to an output of the DFE and configured to send data to the ODI.

### Claim 16 (depends on 15)

The system of claim 15, further comprising a second digital adaptation unit configured to generate a second set of digital signals for adjusting a gain setting of the DFE.

### Claim 17 (depends on 15)

The system of claim 15, further comprising circuitry for bypassing the DFE such that the CDR unit is coupled to the output of the receiver.

### Claim 18 (depends on 15)

The system of claim 15, further comprising a digital-to-analog converter configured to generate, based on the first set of digital signals, a bias signal that sets the gain setting of at least one amplifier in the receiver.

### Claim 19 (depends on 18)

The system of claim 18, wherein:
the receiver has a plurality of amplifiers;
the digital-to-analog converter generates, based on the first set of digital signals, a first plurality of bias signals for setting AC gains of the plurality of amplifiers; and
the digital-to-analog converter generates, based on the first set of digital signals, a second plurality of bias signals for setting DC gains of the plurality of amplifiers.