An N-tap feedforward equalizer (FFE) comprises a set of N FFE taps coupled together in parallel, a filter coupled between the (N−1)th FFE tap and the Nth FFE tap, and a summer coupled to an output of the set of N FFE taps. Each FFE tap includes a unique sample-an-hold (S/H) circuit that generates a unique time-delayed signal and a unique transconductance stage that generates a unique transconductance output based on the unique time-delayed signal. The filter causes the N-tap FFE to have the behavior of greater than N taps. In some examples, the filter is a first order high pass filter that causes coefficients greater than N to have an opposite polarity of the Nth coefficient. In some examples, the filter is a first order low pass filter that causes coefficients greater than N to have the same polarity as the Nth coefficient.

Decision feedback equalization (DFE) is used to help reduce inter-symbol interference (ISI) from a data signal received via a band-limited (or otherwise non-ideal) channel. A first PAM-4 DFE architecture has low latency from the output of the samplers to the application of the first DFE tap feedback to the input signal. This is accomplished by not decoding the sampler outputs in order to generate the feedback signal for the first DFE tap. Rather, weighted versions of the raw sampler outputs are applied directly to the input signal without further analog or digital processing. Additional PAM-4 DFE architectures use the current symbol in addition to previous symbol(s) to determine the DFE feedback signal. Another architecture transmits PAM-4 signaling using non-uniform pre-emphasis. The non-uniform pre-emphasis allows a speculative DFE receiver to resolve the transmitted PAM-4 signals with fewer comparators/samplers.

A transmission device includes a receiver configured to receive a frame signal including synchronization data, main signal data, and an error correction code, a compensator configured to compensate for distortion of the frame signal based on a compensation coefficient, a detector configured to detect synchronization timing of the frame signal from the synchronization data; a corrector configured to correct an error of the frame signal after the distortion is compensated, based on the error correction code according to the synchronization timing, a generator configured to generate a replica signal from the frame signal after the error is corrected by the corrector, based on the synchronization timing, the replica signal corresponding to the frame signal before the distortion is compensated, and an update processor configured to update the compensation coefficient based on the replica signal and the frame signal before the distortion is compensated.

Decision feedback equalization (DFE) is used to help reduce inter-symbol interference (ISI) from a data signal received via a band-limited (or otherwise non-ideal) channel. A first PAM-4 DFE architecture has low latency from the output of the samplers to the application of the first DFE tap feedback to the input signal. This is accomplished by not decoding the sampler outputs in order to generate the feedback signal for the first DFE tap. Rather, weighted versions of the raw sampler outputs are applied directly to the input signal without further analog or digital processing. Additional PAM-4 DFE architectures use the current symbol in addition to previous symbol(s) to determine the DFE feedback signal. Another architecture transmits PAM-4 signaling using non-uniform pre-emphasis. The non-uniform pre-emphasis allows a speculative DFE receiver to resolve the transmitted PAM-4 signals with fewer comparators/samplers.

Embodiments of the disclosure include signal processing methods to reduce crosstalk between signal lines of a channel bus using feed forward equalizers (FFEs) configured smear pulse response energy transmitted on signal lines of the channel to reduce pulse edge rates. The coefficients for the FFE may be based on crosstalk interference characteristics. Smearing or spreading pulse response energy across a longer time period using a FFE increases inter-symbol interference (ISI). To counter increased inter-symbol interference caused by smearing pulse response energy, receivers configured to recover symbol data transmitted on the channel bus may each include respective decision-feedback equalizers (DFEs) that are configured to filter ISI from transmitted symbols based on previous symbol decisions of the channel. The combination of the FFE configured to smear pulse responses and the DFE to filter ISI may improve data eye quality for recovery of transmitted data on a channel bus when crosstalk dominates noise.

Decision feedback equalization (DFE) is used to help reduce inter-symbol interference (ISI) from a data signal received via a band-limited (or otherwise non-ideal) channel. A first PAM-4 DFE architecture has low latency from the output of the samplers to the application of the first DFE tap feedback to the input signal. This is accomplished by not decoding the sampler outputs in order to generate the feedback signal for the first DFE tap. Rather, weighted versions of the raw sampler outputs are applied directly to the input signal without further analog or digital processing. Additional PAM-4 DFE architectures use the current symbol in addition to previous symbol(s) to determine the DFE feedback signal. Another architecture transmits PAM-4 signaling using non-uniform pre-emphasis. The non-uniform pre-emphasis allows a speculative DFE receiver to resolve the transmitted PAM-4 signals with fewer comparators/samplers.

An equalizer includes a first feed-forward stage that provides a measure of low-frequency IS I and a second feed-forward stage that includes a cascade of stages each making an IS I estimate. The IS I estimate from each stage is further equalized by application of the measures of low-frequency IS I from the first feed-forward stage and fed to the next in the cascade of stages. The IS I estimate from the stages thus become progressively more accurate. The number of stages applied to a given signal can be optimized to achieve a suitably low bit-error rate. Power is saved by disabling stages which are not required to meet that goal.

A transmission device includes a receiver configured to receive a frame signal including synchronization data, main signal data, and an error correction code, a compensator configured to compensate for distortion of the frame signal based on a compensation coefficient, a detector configured to detect synchronization timing of the frame signal from the synchronization data; a corrector configured to correct an error of the frame signal after the distortion is compensated, based on the error correction code according to the synchronization timing, a generator configured to generate a replica signal from the frame signal after the error is corrected by the corrector, based on the synchronization timing, the replica signal corresponding to the frame signal before the distortion is compensated, and an update processor configured to update the compensation coefficient based on the replica signal and the frame signal before the distortion is compensated.

Methods and systems are described for sampling a data signal using a data sampler operating in a data signal processing path having a decision threshold associated with a decision feedback equalization (DFE) correction factor, measuring an eye opening of the data signal by adjusting a decision threshold of a spare sampler operating outside of the data signal processing path to determine a center-of-eye value for the decision threshold of the spare sampler, initializing the decision threshold of the spare sampler based on the center-of-eye value and the DFE correction factor, generating respective sets of phase-error signals for the spare sampler and the data sampler responsive to a detection of a predetermined data pattern, and updating the decision threshold of the data sampler based on an accumulation of differences in phase-error signals of the respective sets of phase-error signals.

Decision feedback equalization (DFE) is used to help reduce inter-symbol interference (ISI) from a data signal received via a band-limited (or otherwise non-ideal) channel. A first PAM-4 DFE architecture has low latency from the output of the samplers to the application of the first DFE tap feedback to the input signal. This is accomplished by not decoding the sampler outputs in order to generate the feedback signal for the first DFE tap. Rather, weighted versions of the raw sampler outputs are applied directly to the input signal without further analog or digital processing. Additional PAM-4 DFE architectures use the current symbol in addition to previous symbol(s) to determine the DFE feedback signal. Another architecture transmits PAM-4 signaling using non-uniform pre-emphasis. The non-uniform pre-emphasis allows a speculative DFE receiver to resolve the transmitted PAM-4 signals with fewer comparators/samplers.