# US 2008/0304557 A1 · Self-calibrating continuous-time equalization

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- Number: US 2008/0304557 A1
- Document ID: US20080304557A1
- Status: Published application
- Kind: A1
- Application number: 11/759,072
- Filed: 2007-06-06
- Published: 2008-12-11
- Earliest claimed: 2007-06-06
- Assignees: Micron Technology, Inc.
- Inventors: Timothy M. Hollis
- Web page: https://patentgrep.com/patent/US20080304557A1

## CPC

- H04L 27/01: Equalisers {(baseband equalizers at the transmitter end H04L25/03343; in analogue transmission systems H04B3/04, H04B7/005)}
- H04L 25/03885: {adaptive}
- H04L 2025/03617: {Time recursive algorithms (H04L2025/03643 takes precedence)}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

Embodiments of the invention comprise a continuous-time equalizer for reducing ISI in data received from a communication channel, and methods and circuitry for tuning or calibrating that equalizer. Selected coefficients for a transfer function of the equalizer circuit are fixed, while other coefficients are tuned by an adaptive algorithm. The adaptive algorithm minimizes errors associated with the tunable coefficients based on one or more training signals sent by the transmitter and received by the equalizer circuit at the receiver. The training signals allow for a variety of error terms to be calculated, from which the tunable coefficients are updated so as to iteratively minimize the error terms and simultaneously tune the equalizer to more accurately compensate for the degrading effects of the channel.

## Claims

### Claim 1

A method for tuning an equalizer coupled to a channel, the channel having a frequency response, comprising:
receiving at least one training signal at the equalizer, wherein the at least one training signal is sent through the channel;
assessing the at least one training signal to deduce at least one error term;
tuning the equalizer using the at least one error term; and
repeating the above steps to minimize the error term.

### Claim 2 (depends on 1)

The method of claim 1, wherein the equalizer comprises a transfer function comprising a plurality of variables, and wherein tuning the equalizer comprises tuning at least one variable of the transfer function while other variables of the transfer function are fixed.

### Claim 3 (depends on 2)

The method of claim 2, wherein tuning the equalizer comprises simultaneously tuning two variables of the transfer function while other variables of the transfer function are fixed.

### Claim 4 (depends on 2)

The method of claim 2, wherein the transfer function comprises a second-order filter having a single zero and a complex pole.

### Claim 5 (depends on 4)

The method of claim 4, wherein the variables of the transfer function comprise a quality factor, a zero frequency, and a peaking frequency.

### Claim 6 (depends on 1)

The method of claim 1, wherein the error term comprises a difference between an actual magnitude of the received training signal and its ideal magnitude.

### Claim 7 (depends on 6)

The method of claim 6, wherein the ideal magnitude comprises an ideal magnitude for a logic ‘1’ pulse.

### Claim 8 (depends on 6)

The method of claim 6, wherein the ideal magnitude comprises an ideal magnitude for a logic ‘0’ pulse.

### Claim 9 (depends on 1)

The method of claim 1, wherein the error term comprises a difference indicative of asymmetry in the received training signal.

### Claim 10 (depends on 1)

The method of claim 1, wherein the error term is scaled before tuning the equalizer.

### Claim 11 (depends on 1)

The method of claim 1, wherein the method is performed prior to actual operation of the equalizer.

### Claim 12 (depends on 1)

The method of claim 1, wherein the method is performed during actual operation of the equalizer.

### Claim 13 (depends on 1)

The method of claim 1, wherein the training signal comprises a single pulse.

### Claim 14 (depends on 1)

The method of claim 1, wherein the training signal comprises a double pulse.

### Claim 15 (depends on 1)

The method of claim 1, wherein the training signal comprises single and double pulses.

### Claim 16 (depends on 1)

The method of claim 1, wherein the training signal comprises a single pulse and a plurality of consecutive pulses.

### Claim 17 (depends on 1)

The method of claim 1, wherein repeating the above steps to minimize the error term comprises repeating the above steps to a limit.

### Claim 18

A method for tuning an equalizer coupled to a channel, the channel having a frequency response, comprising:
receiving at least one training signal at the equalizer, wherein the at least one training signal is sent through the channel;
assessing the at least one training signal to deduce a first error term and a second error term;
tuning the equalizer using the first and second error terms; and
repeating the above steps to minimize the first and second error terms.

### Claim 19 (depends on 18)

The method of claim 18, wherein the equalizer comprises a transfer function comprising a plurality of variables, and wherein tuning the equalizer comprises tuning two of the variables of the transfer function while other variables of the transfer function are fixed.

### Claim 20 (depends on 19)

The method of claim 19, wherein tuning the equalizer comprises simultaneously tuning the two variables using the first and second error terms.

### Claim 21 (depends on 19)

The method of claim 19, wherein the transfer function comprises a second-order filter having a single zero and a complex pole.

### Claim 22 (depends on 21)

The method of claim 21, wherein the variables of the transfer function comprise a quality factor, a zero frequency, and a peaking frequency.

### Claim 23 (depends on 18)

The method of claim 18, wherein repeating the above steps to minimize the first and second error terms comprises repeating the above steps to a limit.

### Claim 24

A receiver for receiving digital data sent through a channel having a frequency response, comprising:
an equalizer coupled to the channel, the equalizer for producing an output to other circuitry in the receiver; and
a tuning circuit coupled to the output of the equalizer for continually assessing at least one error for each of a continuous sequence of training signals received by the equalizer, wherein the tuning circuit continually converges the at least one error to tune the equalizer.

### Claim 25 (depends on 24)

The receiver of claim 24, wherein the equalizer, the tuning circuit and the other circuitry are integrated in an integrated circuit.

### Claim 26 (depends on 24)

The receiver of claim 24, wherein the equalizer comprises a transfer function comprising a plurality of variables, and wherein tuning the equalizer comprises tuning at least one variable of the transfer function while other variables of the transfer function are fixed.

### Claim 27 (depends on 26)

The receiver of claim 26, wherein the variables of the transfer function comprise a quality factor, a zero frequency, and a peaking frequency.

### Claim 28 (depends on 26)

The receiver of claim 26, wherein the transfer function comprises a second-order filter having a single zero and a complex pole.

### Claim 29 (depends on 24)

The receiver of claim 24, wherein the error comprises a difference between an actual magnitude of the received training signals and their ideal magnitudes.

### Claim 30 (depends on 24)

The receiver of claim 24, wherein the error comprises a difference indicative of asymmetry in the received training signals.

### Claim 31 (depends on 24)

The receiver of claim 24, wherein the training signals comprise single pulses.

### Claim 32 (depends on 24)

The receiver of claim 24, wherein the training signals comprise double pulses.

### Claim 33 (depends on 24)

The receiver of claim 24, wherein the training signals comprise single and double pulses.

### Claim 34 (depends on 24)

The receiver of claim 24, wherein each training signal comprises a single pulse and a plurality of consecutive pulses.

### Claim 35 (depends on 24)

The receiver of claim 24, wherein the tuning circuit is only operable during initialization of the receiver.

### Claim 36 (depends on 24)

The receiver of claim 24, wherein the tuning circuit is operable during on-going operation of the receiver.

### Claim 37 (depends on 24)

The receiver of claim 24, wherein the tuning circuit continually converges the at least one error until a limit is reached to tune the equalizer.

### Claim 38

A system, comprising:
a transmitter, the transmitter for sending digital data to a receiver across a channel having a frequency response; and
a receiver for receiving the digital data, the receiver comprising:
an equalizer coupled to the channel, the equalizer for producing an output to other circuitry in the receiver;
a tuning circuit coupled to the output of the equalizer for continually assessing the digital data received by the equalizer, wherein the tuning circuit continually tunes the equalizer.

### Claim 39 (depends on 38)

The system of claim 38, wherein the transmitter comprises a training signal circuit for sending training signals across the channel to the receiver.

### Claim 40 (depends on 38)

The system of claim 38, wherein the transmitter and receiver comprise integrated circuits on a printed circuit board, and wherein the channel comprises a trace on the printed circuit board.

### Claim 41 (depends on 38)

The system of claim 38, wherein the transmitter, the receiver, and the channel are integrated on a semiconductor device.

### Claim 42 (depends on 38)

The system of claim 38, wherein the equalizer comprises a transfer function comprising a plurality of variables, and wherein tuning the equalizer comprises tuning at least one variable of the transfer function while other variables of the transfer function are fixed.

### Claim 43 (depends on 42)

The system of claim 42, wherein the variables of the transfer function comprise a quality factor, a zero frequency, and a peaking frequency.

### Claim 44 (depends on 38)

The system of claim 38, wherein the tuning circuit continually determines at least one error for each training signals received by the equalizer, and wherein the tuning circuit continually converges the at least one error toward a nominal value to tune the equalizer.

### Claim 45 (depends on 44)

The receiver of claim 44, wherein the error comprises a difference between an actual magnitude of the received training signals and their ideal magnitudes.

### Claim 46 (depends on 44)

The receiver of claim 44, wherein the error comprises a difference indicative of asymmetry in the received training signals.

### Claim 47 (depends on 38)

The system of claim 38, wherein the training signal circuit and tuning circuit are only operable during initialization of the system.

### Claim 48 (depends on 38)

The system of claim 38, wherein the tuning circuit continually tunes the equalizer to a suitable point.