Methods, apparatus, and systems to synchronize Ethernet signals are disclosed. An example apparatus includes slicer circuitry having an input coupled to interface circuitry and having an output, the slicer circuitry configured to receive an analog signal corresponding to a first Analog to Digital Converter (ADC) clock in a plurality of ADC clocks and operable to determine symbols based on the analog signal; logic circuitry to determine whether there is a symbol transition in the symbols; timing error detector circuitry to update an error value in response to the determination that there is a symbol transition; timing loop circuitry to determine a frequency of voltage oscillations based on at least the error value; and phase interpolator circuitry to change a plurality of phase parameters corresponding to the plurality of ADC clocks at a rate given by the frequency of voltage oscillations.

A clock adjustment circuit includes a pattern filter circuit, a phase error detector (PED) circuit, and a phase error calculation circuit. The pattern filter circuit selects first predetermined data patterns from a plurality of consecutive data samples under an acquisition mode of the clock adjustment circuit, wherein the plurality of consecutive data samples are derived from an output of a first sampler circuit. The PED circuit detects phase errors according to an output of the pattern filter circuit and error samples derived from an output of a second sampler circuit. The phase error calculation circuit determines timing compensation of a sampling clock according to an output of the PED circuit, wherein the sampling clock is used by the first sampler circuit and the second sampler circuit.

A receiver includes a feed-forward equalizer, a first detector, a jitter estimation circuit, and a jitter mitigation circuit. The feed-forward equalizer is configured to equalize channel gain of digitized samples of a received signal and to output equalized samples. The first detector is configured to detect symbols in the equalized samples. The jitter estimation circuit is configured to estimate jitter in the equalized samples by estimating a deviation in periodicity between pairs of the equalized samples. The jitter mitigation circuit comprises a linearized FIR filter configured to receive an input including the equalized samples or the detected symbols and to compensate inter symbol interference in the equalized samples due to the jitter as a function of the estimated jitter and an estimate of the inter symbol interference.

A data receiver circuit includes a summer circuit configured to receive an input signal that encodes multiple data symbols, and combine the input signal with a feedback signal to generate an equalized input signal, which is used to generate a clock signal. The data receiver circuit also includes multiple data slicer circuits that sample, using the clock signal and multiple voltage offsets, the equalized input signal to generate multiple samples of a particular data symbol. A precursor compensation circuit included in the data receiver circuit may generate an output value for the particular data symbol using the multiple samples. The data receiver circuit also includes a post cursor compensation circuit that generates the feedback signal using at least one of the multiple samples and a value of a previously received sample.

A clock recovery circuit may include: a data slicer configured to output data values based on an input signal, a first error block, a phase adjustment loop including: a first error slicer configured to generate a first error signal based on a comparison of a threshold voltage and an input voltage, wherein the first error block is configured to selectively output the first error signal in response to a first pattern in the output data values, a second error block configured to selectively output the first error signal in response to a second pattern in the output data values, and a voltage threshold modification circuitry configured to adjust the threshold voltage based on output of the second error block, a voltage-controlled oscillator, wherein the data slicer and the first error slicer are clocked based on output of the voltage-controlled oscillator.

Embodiments of this application disclose example phase detection methods, phase detection circuits, and clock recovery apparatuses. One example method includes receiving a first signal and deciding a (2M−1) level of the first signal to obtain a decision result, where the first signal is a (2M−1)-level signal, and M is a positive integer. A response amplitude parameter of a transmission channel can then be obtained. Clock phase information in the first signal can then be extracted based on the first signal, the decision result, and the response amplitude parameter. Output clock phase information can then be determined based on at least three decision results and at least three pieces of clock phase information in at least three symbol periods.

A clock and data recovery circuit includes a phase detector that outputs phase characteristic data based on a digital data signal and an adjustment circuit that adjusts phase characteristic data. The clock and data recovery circuit sets an adjustment value in an adjustment circuit by calculating an adjustment value of phase characteristic data using a monitor circuit while changing a phase of a reference clock signal to be adjusted in a phase interpolation circuit based on offset data output from an offset output circuit in a training period before communication starts.

Disclosed retimer modules and methods enable equalizer training during link speed negotiation. One illustrative retimer module includes: an analog to digital converter that uses a sampling clock to digitize a receive signal; an equalizer that converts the digitized receive signal into an equalized signal; a decision element that derives a receive symbol stream from the equalized signal; and a clock recovery module that derives the sampling clock based at least in part on an equalization error of the equalized signal, the sampling clock having a frequency with a range including a baud rate of the receive signal at a first supported speed and including a frequency not less than twice the baud rate of the receive signal at a second supported speed.

A clock recovery circuit may include: a data slicer configured to output data values based on an input signal, a first error block, a phase adjustment loop including: a first error slicer configured to generate a first error signal based on a comparison of a threshold voltage and an input voltage, wherein the first error block is configured to selectively output the first error signal in response to a first pattern in the output data values, a second error block configured to selectively output the first error signal in response to a second pattern in the output data values, and a voltage threshold modification circuitry configured to adjust the threshold voltage based on output of the second error block, a voltage-controlled oscillator, wherein the data slicer and the first error slicer are clocked based on output of the voltage-controlled oscillator.

A receiver device implements enhanced data reception with edge-based clock and data recovery such as with a flash analog-to-digital converter architecture. In an example embodiment, the device implements a first phase adjustment control loop, with for example, a bang-bang phase detector, that detects data transitions for adjusting sampling at an optimal edge time with an edge sampler by adjusting a phase of an edge clock of the sampler. This loop may further adjust sampling in received data intervals for optimal data reception by adjusting the phase of a data clock of a data sampler such a flash ADC. The device may also implement a second phase adjustment control loop with, for example, a baud-rate phase detector, that detects data intervals for further adjusting sampling at an optimal data time with the data sampler.