Rambus Inc.

Cadence Design Systems, Inc.

Nanyan Wang

Marcus Van Ierssel

Prashant Choudhary

Vadim Moshinsky

Prabhnoor Singh Kainth

A receiver may sample an amplitude-modulated input signal expressed as a series of symbols using a clock signal with edges aligned to the symbols. Repeated symbols and the level transitions between them may form signal eyes. The receiver may detect the inner signal eyes and aligns the phase of the clock signal relative to the symbols responsive to the detected timing center of signal eyes and corresponding symbol patterns.

Methods and circuits for inner-eye timing center detection and clock phase alignment

An integrated circuit that includes a feedback loop to adapt receiver parameters. The feedback loop includes a receiver to sample a signal and produce a sampled signal sequence. The feedback loop also includes a first pattern counter to detect and count occurrences of a first pattern in the sampled signal sequence, and a second pattern counter to detect and count occurrences of a second pattern in the sampled signal sequence. Control circuitry coupled to the receiver adapts a parameter value of the receiver to minimize a difference between a first ratio and a second ratio. The first ratio is a target ratio. The second ratio is between a first counted number of occurrences of the first pattern in the sampled signal sequence and a second counted number of occurrences of the second pattern in the sample signal sequence.

Pattern detection based parameter adaptation

A decision-feedback equalizer (DFE) samples an input signal with respect to a gamut of p reference-voltage levels to place the symbol represented by the input signal within a voltage region. The DFE derives a set of tentative decisions for the voltage region, the set excluding at least one of the possible values for the symbol under consideration. A feedback stage then selects a final decision from among the tentative decisions.

Methods and circuits for decision-feedback equalization using compensated decision regions

A clock-and-data recovery circuit for serial receiver includes a jitter meter and an adaptive loop gain adjustment circuitry. The clock-recovery circuitry phase aligns a clock signal to the incoming data. A jitter meter provides a measure of jitter, while adaptation circuitry uses the measure to adjust the clock-recovery circuitry in a manner that reduces clock jitter. The jitter measure can be a ratio of errors associated with different inter-symbol slew rates.

Methods and circuits for reducing clock jitter

Optimized continuous time linear equalization (CTLE) circuit parameters for a received signal are found using an iterative search process. The received signal is repeatedly sampled by an analog-to-digital converter (ADC). Certain samples containing interference that cannot be cancelled by a CTLE in the sampled series are filtered out (discarded). The remaining samples are used to generate, over a selected evaluation window, a histogram of the sampled values. This histogram is used to calculate a figure of merit for the current CTLE parameter settings. The figures of merit for various CTLE parameter settings are compared to find the set of CTLE parameter settings that optimize the figure of merit and by extension, optimize the CTLE circuitry's performance at equalizing the received signal.

CTLE adaptation based on statistical analysis

A receiver samples an analog, multi-level, pulse-amplitude-modulated signal using a clock-and-data recovery circuit (CDR) that samples the signal against adaptively calibrated symbol-decision thresholds in time with a clock signal that is phased aligned with and locked to the signal. The CDR can erroneously align the clock signal to inter-symbol edges of the signal, a condition called 'edge lock,' rather than on the symbols themselves. A transition-type detector senses the edge-lock condition and unlocks the CDR, which can then realign the clock signal, this time on the symbols rather than the inter-symbol edges. The receiver can also respond to the edge-lock condition by kick-starting a shift of symbol-decision threshold that helps the CDR settle more quickly on correct symbol-decision thresholds.

Circuits and methods for detecting and unlocking edge-phase lock

In a PAM-N receiver, sampler reference levels, DC offset and AFE gain may be jointly adapted to achieve optimal or near-optimal boundaries for the symbol decisions of the PAM-N signal. For reference level adaptation, the hamming distances between two consecutive data samples and their in-between edge sample are evaluated. Reference levels for symbol decisions are adjusted accordingly such that on a data transition, an edge sample has on average, equal hamming distance to its adjacent data samples. DC offset may be compensated to ensure detectable data transitions for reference level adaptation. AFE gains may be jointly adapted with sampler reference levels such that the difference between a reference level and a pre-determined target voltage is minimized.

Sampler reference level, DC offset, and AFE gain adaptation for PAM-N receiver

In a PAM-N receiver, sampler reference levels, DC offset and AFE gain may be jointly adapted to achieve optimal or near-optimal boundaries for the symbol decisions of the PAM-N signal. For reference level adaptation, the hamming distances between two consecutive data samples and their in-between edge sample are evaluated. Reference levels for symbol decisions are adjusted accordingly such that on a data transition, an edge sample has on average, equal hamming distance to its adjacent data samples. DC offset may be compensated to ensure detectable data transitions for reference level adaptation. AFE gains may be jointly adapted with sampler reference levels such that the difference between a reference level and a pre-determined target voltage is minimized

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Cupertino, CA, United States of America

Nanyan Wang