Conditional adaptation of linear filters in a system having nonlinearity

1. A method of adjusting configurable parameters of at least one filter of a communication system, the method comprising:

conditioning, by an analog front end (AFE) of a receiver in the communication system, an input signal applied to the receiver;

generating, by a sampler of the receiver, one or more sampled values of the conditioned input signal;

digitizing, by a data detector of the receiver, the one or more sampled values of the input signal;

generating, by at least one error detection module of the receiver, an error signal based on one or more of a plurality of digitized values of the input signal and at least one target value;

generating, by a decision feedback equalizer (DFE) of the receiver, an adjustment signal based on one or more of a plurality of digitized values of the input signal and one or more of a plurality of values of the error signal;

subtracting, by a summer of the receiver, the adjustment signal from the conditioned input signal, generating an adjusted input signal;

determining, by at least one adaptation module of the receiver, a conditional adaptation signal based on a comparison of one or more of a plurality of sampled values of the adjusted input signal and one or more of a plurality of values of the error signal; and

adjusting, by the at least one adaptation module, a transfer function of the at least one filter based on the determined conditional adaptation signal;

wherein the step of determining, by at least one adaptation module of the receiver, a conditional adaptation signal based on a comparison of one or more of a plurality of sampled values of the adjusted input signal and one or more of a plurality of values of the error signal further comprises:

selecting a window of N bits of the adjusted input signal, wherein N is a positive integer:

selecting a window of M bits of the error signal, wherein M is a positive integer;

determining an operating region of each of the at least one filters based on at least one of (i) the selected window of N bits of the adjusted input signal and (ii) the selected window of M bits of the error signal; and

generating the conditional adaptation signal based on the determined operating region of each of the at least one filters and at least one of (i) the N bits of the adjusted input signal and (ii) the M bits of the error signal.

2. The method of claim 1 , wherein the at least one filter comprises the AFE, the DFE and a transmit finite impulse response filter (TXFIR) of a transmitter of the communication system.

3. The method of claim 1 , wherein the step of determining an operating region of each of the at least one filters comprises:

determining a value of the error signal multiplied by the digitized data, wherein if the value is a first predefined value, the filter is in a linear operating region, and wherein if the value is a second predefined value, the filter is in a nonlinear operating region; and

if the filter is in a nonlinear operating region:

determining whether the filter is operating in a pseudo-linear operating region;

if the filter is operating in a pseudo-linear operating region:

employing the error signal to determine the conditional adaptation signal.

4. The method of claim 3 , wherein the filter is operating in a pseudo-linear operating region based on the presence of at least one of a first condition, a second condition and a third condition, wherein:

the first condition comprises presence of a transition in value between a first data bit and a subsequent data bit of the N bit window of the adjusted input signal;

the second condition comprises presence of substantially equivalent-values for substantially all the data bits of the N bit window of the adjusted input signal; and

the third condition comprises absence of a transition in value between a first data bit and a subsequent data bit of the N bit window of the adjusted input signal.

5. The method of claim 1 , wherein N is equal to 3 and M is equal to 3.

6. The method of claim 1 , wherein M is equal to 1.

7. The method of claim 1 further comprising:

delaying a data path of the error signal by yT, where T is a sampling period of the sampler, and y is a delay factor;

employing one or more future data bits in the N bit window, wherein the number of future data bits included in the N bit window is equal to y.

8. The method of claim 1 , wherein, for the method, the AFE comprises at least one of a continuous time linear equalizer (CTLE) and variable gain amplifier (VGA), and wherein the configurable parameters comprise a gain parameter of the CTLE, and a gain parameter of the VGA.

9. The method of claim 1 , further comprising:

communicating, by the adaptation module, to a finite impulse response (FIR) equalizer in the transmitter via a backchannel; and

adjusting one or more configurable parameters of the FIR equalizer based on the determined conditional adaptation signal, wherein the configurable parameters comprise a tap weight of the FIR equalizer.

10. The method of claim 1 , comprising adjusting, by the at least one adaptation module, a transfer function of the at least one filter based on the determined conditional adaptation signal, thereby improving an operating margin of an eye diagram of the communication system.

11. A non-transitory machine-readable medium, having encoded thereon program code, wherein, when the program code is executed by a machine, the machine implements a method of adjusting configurable parameters of an analog front end (AFE) of a receiver in a communication system, the method comprising:

conditioning, by an analog front end (AFE) of a receiver in the communication system, an input signal applied to the receiver;

generating, by a sampler of the receiver, one or more sampled values of the conditioned input signal;

digitizing, by a data detector of the receiver, the one or more sampled values of the input signal;

generating, by at least one error detection module of the receiver, an error signal based on one or more of a plurality of digitized values of the input signal and at least one target value;

generating, by a decision feedback equalizer (DFE) of the receiver, an adjustment signal based on one or more of a plurality of digitized values of the input signal and one or more of a plurality of values of the error signal;

subtracting, by a summer of the receiver, the adjustment signal from the conditioned input signal, generating an adjusted input signal;

determining, by at least one adaptation module of the receiver, a conditional adaptation signal based on a comparison of one or more of a plurality of sampled values of the adjusted input signal and one or more of a plurality of values of the error signal; and

adjusting, by the at least one adaptation module, a transfer function of the at least one filter based on the determined conditional adaptation signal;

wherein the step of determining, by at least one adaptation module of the receiver, a conditional adaptation signal based on a comparison of one or more of a plurality of sampled values of the adjusted input signal and one or more of a plurality of values of the error signal further comprises:

selecting a window of N bits of the adjusted input signal, wherein N is a positive integer;

selecting a window of M bits of the error signal, wherein M is a positive integer;

determining an operating region of each of the at least one filters based on at least one of (i) the selected window of N bits of the adjusted input signal and (ii) the selected window of M bits of the error signal; and

generating the conditional adaptation signal based on the determined operating region of each of the at least one filters and at least one of (i) the N bits of the adjusted input signal and (ii) the M bits of the error signal.

12. The non-transitory machine-readable medium of claim 11 , wherein the at least one filter comprises the AFE, the DFE and a transmit finite impulse response filter (TXFIR) of a transmitter of the communication system.

13. The non-transitory machine-readable medium of claim 11 , wherein the step of determining an operating region of each of the at least one filters comprises:

determining a value of the error signal multiplied by the digitized data, wherein if the value is a first predefined value, the filter is in a linear operating region, and wherein if the value is a second predefined value, the filter is in a nonlinear operating region; and

if the filter is in a nonlinear operating region:

determining whether the filter is operating in a pseudo-linear operating region;

if the filter is operating in a pseudo-linear operating region;

employing the error signal to determine the conditional adaptation signal,

wherein the filter is operating in a pseudo-linear operating region based on the presence of at least one of a first condition, a second condition and a third condition, wherein:

the first condition comprises presence of a transition in value between a first data bit and a subsequent data bit of the N bit window of the adjusted input signal;

the second condition comprises presence of substantially equivalent-values for substantially all the data bits of the N bit window of the adjusted input signal; and

the third condition comprises absence of a transition in value between a first data bit and a subsequent data bit of the N bit window of the adjusted input signal.

14. The non-transitory machine-readable medium of claim 13 , wherein N is equal to 3 and M is equal to 3.

15. The non-transitory machine-readable medium of claim 11 further comprising:

delaying a data path of the error signal by yT, where T is a sampling period of the sampler, and y is a delay factor;

employing one or more future data bits in the N bit window, wherein the number of future data bits included in the N bit window is equal toy.

16. The non-transitory machine-readable medium of claim 11 , further comprising:

communicating, by the adaptation module, to a finite impulse response (FIR) equalizer in the transmitter via a backchannel; and

adjusting one or more configurable parameters of the FIR equalizer based on the determined conditional adaptation signal, wherein the configurable parameters comprise a tap weight of the FIR equalizer.

17. A communication system comprising:

a transmitting device configured to transmit an input signal over a channel to a receiver of the communication system;

an analog front end (AFE) of the receiver configured to condition the input signal;

a sampler of the receiver configured to generate one or more sampled values of the input signal;

a data detector of the receiver configured to digitize the one or more sampled values of the input signal;

at least one subtractor of the receiver configured to generate an error signal based on one or more of a plurality of digitized values of the input signal and at least one target value;

a decision feedback equalizer (DFE) of the receiver configured to generate an adjustment signal based on one or more of a plurality of digitized values of the input signal and one or more of a plurality of values of the error signal;

a summer of the receiver configured to subtract the adjustment signal from the conditioned input signal and generate an adjusted input signal; and

at least one adaptation module of the receiver configured to (i) generate a conditional adaptation signal based on a comparison of one or more of a plurality of sampled values of the adjusted input signal and one or more of a plurality of values of the error signal, and (ii) adjust a transfer function of at least one filter based on the determined conditional adaptation signal, thereby improving an operating margin of an eye diagram of the communication system,

wherein the at least one filter comprises the AFE, the DFE and a transmit finite impulse response filter (TXFIR) of the transmitter;

wherein the at least one adaptation module of the receiver is further configured to:

select a window of N bits of the adjusted input signal, wherein N is a positive integer;

select a window of M bits of the error signal, wherein M is a positive integer;

determine an operating region of the AFE for the selected window of N bits of the adjusted input signal; and

generate the conditional adaptation signal based on the determined operating region of the AFE and at least one of (i) the N bits of the adjusted input signal and (ii) the M bits of the error signal.

18. The communication system of claim 17 , wherein the at least one adaptation module is further configured to:

determine a value of the error signal multiplied by the digitized data, wherein if the value is positive, the AFE is in a linear operating region, and wherein if the value is negative, the AFE is in a nonlinear operating region; and

if the AFE is in a nonlinear operating region:

determine whether the AFE is operating in a pseudo-linear operating region;

if the AFE is operating in a pseudo-linear operating region:

employ the error signal to determine the conditional adaptation signal,

wherein the AFE is operating in a pseudo-linear operating region based on the presence of at least one of a first condition, a second condition and a third condition, wherein:

the first condition comprises presence of a transition in value between a first data bit and a subsequent data bit of the N bit window of the adjusted input signal;

the second condition comprises presence of substantially equivalent-values for substantially all the data bits of the N bit window of the adjusted input signal; and

the third condition comprises absence of a transition in value between a first data bit and a subsequent data bit of the N bit window of the adjusted input signal.

19. The communication system claim 17 further comprising:

at least one delay module configured to delay a data path of the error signal by yT, where T is a sampling period of the sampler, and y is a delay factor, whereby the at least one adaptation module is configured to employ one or more future data bits in the N bit window, wherein the number of future data bits included in the N bit window is equal to y.

20. The communication system of claim 17 , wherein

the transmitter is implemented as a first integrated circuit chip; and

the receiver is implemented as a second integrated circuit chip.

21. A transmitter for encoding data for transmission over a communication channel, the transmitter comprising:

a finite impulse response (FIR) filter, the FIR filter coupled to the communication channel, wherein the FIR filter is configured to (i) equalize data for transmission over the communication channel, and (ii) adjust one or more configurable parameters of the FIR filter based on a conditional adaptation signal;

wherein the FIR filter is further configured to:

receive the conditional adaptation signal from a receiver coupled to the communication channel, wherein the receiver is configured to decode the transmitted data, and wherein the conditional adaptation signal is based on a determined operating region of the AFE and at least one of (i) a selected window of N bits of an adjusted input signal and (ii) a selected window of M bits of an error signal, wherein:

the adjusted input signal is based on one or more digitized samples of the decoded data and one or more of a plurality of values of an error signal; and

the error signal is based on one or more digitized samples of the decoded data and at least one target value.

22. The transmitter of claim 21 , wherein the transmitter is coupled to a backchannel configured to communicate the conditional adaptation signal from the receiver.

23. The transmitter of claim 21 , wherein the one or more configurable parameters comprise a tap weight of the FIR equalizer.

24. A receiver for decoding received data from a communication channel, the receiver comprising:

an analog front end (AFE) of the receiver configured to condition an input signal;

a sampler of the receiver configured to generate one or more sampled values of the input signal;

a data detector of the receiver configured to digitize the one or more sampled values of the input signal;

at least one subtractor of the receiver, an error signal based on one or more of a plurality of digitized values of the input signal and at least one target value;

a decision feedback equalizer (DFE) of the receiver configured to generate an adjustment signal based on one or more of a plurality of digitized values of the input signal and one or more of a plurality of values of the error signal;

a summer of the receiver configured to subtract the adjustment signal from the conditioned input signal and generate an adjusted input signal; and

at least one adaptation module of the receiver configured to (i) generate a conditional adaptation signal based on a comparison of one or more of a plurality of sampled values of the adjusted input signal and one or more of a plurality of values of the error signal, and (ii) adjust a transfer function of at least one filter based on the determined conditional adaptation signal, thereby improving an operating margin of an eye diagram of the receiver,

wherein the at least one filter comprises the AFE, the DFE and a transmit finite impulse response filter (TXFIR) of a transmitter of the communication system; and

wherein the at least one adaptation module of the receiver is further configured to:

select a window of N bits of the adjusted input signal, wherein N is a positive integer;

select a window of M bits of the error signal, wherein M is a positive integer;

determine an operating region of the AFE for the selected window of N bits of the adjusted input signal; and

generate the conditional adaptation signal based on the determined operating region of the AFE and at least one of (i) the N bits of the adjusted input signal and (ii) the M bits of the error signal.

25. The receiver of claim 24 , wherein the adaptation module is further configured to communicate the conditional adaptation signal to a finite impulse response (FIR) equalizer in a transmitter, wherein the transmitter is configured to adjust one or more configurable parameters of the FIR equalizer based on the determined conditional adaptation signal.

26. The receiver of claim 25 , wherein the configurable parameters comprise a tap weight of the FIR equalizer.

27. The receiver of claim 25 , wherein the receiver is coupled to a backchannel configured to communicate the conditional adaptation signal to the transmitter.