Apparatus and method for providing pre-emphasis to a signal

• US 8,937,975 B1
• Filed: 12/10/2013
• Issued: 01/20/2015
• Est. Priority Date: 10/22/2002
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Wu, Lei, Hu, Timothy
• Primary Examiner(s): Qureshi, Afsar M
• Application Number:
  US14/101,502
• Time in Patent Office: 406 Days
• Field of Search: 370395- 62, 370532-539, 375/224, 375/233, 375/259, 375/295, 375/354
• US Class Current: 370/532
• CPC Class Codes: G06F 13/4072 Drivers or receivers G06F13/4086 takes precedence; for multistate logic circuits H03K19/0002
• CPC Class Codes: H04L 25/0292 Arrangements specific to the receiver end
• CPC Class Codes: H04L 25/03025 using a two-tap delay line

Abstract

A circuit including delay stages, gain stages, and a summer. The delay stages are configured to provide delayed versions of a first signal. The gain stages are configured to receive the delayed versions of the first signal. Each of the gain stages provides an amount of gain for a corresponding one of the delayed versions of the first signal. The delay stages and the gain stages are configured to provide pre-emphasis to the first signal. The summer is configured to output a second signal based on the delayed versions of the first signal. The second signal includes the pre-emphasis.

Claims

1. A circuit comprising:

a plurality of delay stages configured to provide a plurality of delayed versions of a first signal;

a plurality of gain stages configured to receive the plurality of delayed versions of the first signal, wherein each of the plurality of gain stages provides an amount of gain for a corresponding one of the plurality of delayed versions of the first signal, and wherein the plurality of delay stages and the plurality of gain stages are configured to provide pre-emphasis to the first signal; and

a first summer configured to output a second signal based on the plurality of delayed versions of the first signal, wherein the second signal includes the pre-emphasis.

2. The circuit of claim 1, wherein:

the first signal comprises serial data; and

the second signal comprises pre-emphasized serial data.

3. The circuit of claim 1, wherein the plurality of delay stages are connected in series, such that each successive one of the plurality of delay stages provides additional delay to the first signal.

4. The circuit of claim 1, wherein:

the plurality of delay stages comprise respective outputs; and

the plurality of gain stages are configured to respectively receive the outputs of the plurality of delay stages.

5. The circuit of claim 1, wherein each of the plurality of gain stages comprises a respective one of a plurality of amplifiers, wherein each of the plurality of amplifiers is configured to amplify a corresponding one of the plurality of delayed versions of the first signal to provide the amount of gain for the corresponding one of the plurality of gain stages.

6. The circuit of claim 1, further comprising an amplifier configured to generate a third signal based on the first signal,

the first summer is configured to output the second signal based on the third signal.

7. The circuit of claim 1, wherein the first summer is configured to output the second signal based on (i) the first signal, and (ii) the plurality of delayed versions of the first signal.

8. The circuit of claim 1, wherein each of the delayed versions of the first signal has a different amount of delay than other ones of the delayed versions of the first signal.

9. The circuit of claim 1, further comprising a second summer, wherein:

the plurality of delay stages comprise a first delay stage and a second delay stage;

the plurality of gain stages comprise a first gain stage, a second gain stage and a third gain stage;

the first signal includes serial data;

the serial data includes first data, second data and third data;

the first delay stage delays the second data;

the second delay stage delays the third data;

the first gain stage provides gain for the first data;

the second gain stage provides gain for the second data;

the third gain stage provides gain for the third data;

the second summer sums (i) an output of the second gain stage, and (ii) an output of the third gain stage; and

the first summer sums (i) an output of the first gain stage, and (ii) an output of the second summer.

10. The circuit of claim 1, wherein the plurality of gain stages are configured to amplify the delayed versions of the first signal such that (i) signal magnitudes at certain frequencies are amplified, and (ii) signal magnitudes at other frequencies are attenuated.

11. The circuit of claim 1, further comprising a multiplexer configured to (i) receive a plurality of signals, and (ii) output the first signal based on a selected one of the plurality of signals, wherein:

the first signal comprises a plurality of frequencies and has a respective signal magnitude at each of the plurality of frequencies,

the plurality of gain stages amplify the plurality of delayed versions of the first signal such that (i) signal magnitudes at certain ones of the plurality of frequencies are amplified, and (ii) signal magnitudes at other ones of the plurality of frequencies are attenuated.

12. The circuit of claim 1, further comprising a selector configured to adjust the amounts of gain for the plurality of gain stages.

13. The circuit of claim 12, further comprising a transmitter, wherein:

the transmitter comprises the plurality of delay stages, the plurality of gain stages and the first summer; and

the selector is preprogrammed based on at least (i) data stored in memory, or (ii) data input to a physical layer of the transmitter.

14. The circuit of claim 1, wherein:

the plurality of delay stages and the plurality of gain stages provide the pre-emphasis to offset a characteristic of a channel; and

the characteristic of the channel includes frequency dependent noise.

15. The circuit of claim 1, further comprising a selector configured to, based on a characteristic of a channel, select a first gain value and a second gain value, wherein:

the plurality of delay stages comprise a first delay stage;

the plurality of gain stages comprise a first amplifier and a second amplifier;

the first amplifier is configured to, based on the first gain value, amplify the first signal to generate a first amplified signal;

the first delay stage is configured to delay the first signal to generate a first delayed version of the first signal; and

the second amplifier configured to, based on the second gain value, amplify the first delayed version of the first signal to generate a second amplified signal,

wherein the first summer is configured to sum the first amplified signal and the second amplified signal to generate the second signal output from the first summer.

16. A method comprising:

providing a plurality of delayed versions of a first signal via a plurality of delay stages;

providing pre-emphasis to the first signal including receiving the plurality of delayed versions of the first signal via a plurality of gain stages, wherein each of the plurality of gain stages provides an amount of gain for a corresponding one of the plurality of delayed versions of the first signal; and

outputting a second signal based on the plurality of delayed versions of the first signal, wherein the second signal includes the pre-emphasis.

17. The method of claim 16, wherein:

the first signal comprises serial data; and

the second signal comprises pre-emphasized serial data.

18. The method of claim 16, wherein each of the delayed versions of the first signal has a different amount of delay than other ones of the delayed versions of the first signal.

19. The method of claim 16, further comprising amplifying each of the plurality of delayed versions of the first signal to provide the amounts of gain for the plurality of gain stages.

20. The method of claim 16, further comprising:

receiving a plurality of signals;

outputting the first signal based on a selected one of the plurality of signals,

wherein the first signal comprises a plurality of frequencies and has a respective signal magnitude at each of the plurality of frequencies; and

amplifying the plurality of delayed versions of the first signal such that (i) signal magnitudes at certain ones of the plurality of frequencies are amplified, and (ii) signal magnitudes at other ones of the plurality of frequencies are attenuated.