Abstract: A wireless receiver comprises a band-pass filter module that includes an input for receiving a first pilot signal, an output that generates a first signal based on the first pilot signal, and a control input for adjusting a center frequency of the band-pass filter module. A control module determines the energy of the first signal, generates a control signal based on the energy, and communicates the control signal to the control input of the band-pass filter module.

Abstract: In some implementations, an apparatus includes an echo canceller that generates an echo interference compensation signal that compensates for an echo interference signal in a communication signal, a crosstalk canceller that generates a crosstalk interference compensation signal that compensates for a crosstalk interference signal in the communication signal, and a combiner that generates a combined interference compensation signal based on the echo interference compensation signal and the crosstalk interference compensation signal.

Abstract: The present disclosure includes apparatus, systems, and techniques relating to receiver image cancellation. A described technique includes receiving a downconverted signal in a digital domain, the downconverted signal including an in-phase signal and a quadrature signal; generating a first signal of a signal channel based on the downconverted signal; generating a second signal of an image channel based on the downconverted signal; filtering the second signal using first weights to produce a pilot training signal; filtering the second signal using second weights to produce an image cancellation signal; generating an output signal by subtracting the image cancellation signal from the first signal to resolve the desired signal; updating the first weights based on the first weights, the second signal, the pilot training signal, and a pilot signal; and updating the second weights based on the second weights, the output signal, and the pilot training signal.

Abstract: A circuit comprises an analog to digital converter (ADC) that samples a received signal based on a sampling clock. A feed forward filter communicates with the ADC and does not remove first precursor intersymbol interference from the received signal. An adaptive timing loop circuit that adjusts a timing phase of the sampling clock of said ADC to remove the first precursor intersymbol interference from the received signal. The adaptive timing loop circuit adjusts the timing phase based on at least one of an estimate signal and a loop gain control constant.

Abstract: A transceiver including an equalizer configured to receive an input signal. A control circuit selects a predetermined coefficient, maintains the predetermined coefficient at a fixed value, and based on the predetermined coefficient, selects first coefficients and second coefficients. The control circuit that, while maintaining the predetermined coefficient at the fixed value and while the equalizer is receiving the input signal, adjusts a coefficient of one of the first or second coefficients. The equalizer includes: first taps configured to, based on the first coefficients, filter the input signal to generate a first filtered signal; a unity tap configured to, based on the predetermined coefficient, filter the first filtered signal to generate a second filtered signal; and second taps configured to, based on the second coefficients, filter the second filtered signal to generate a third filtered signal. An output transmits the third filtered signal.

Abstract: A nonlinear echo compensator comprises a mapping circuit that includes a weighting circuit that generates a weighted signal based on a current symbol and a prior symbol and a function generating circuit that selects one of N functions based on the weighted signal, where N is an integer greater than one. The mapping circuit generates a driving signal based on the selected one of the N functions and the weighted signal. A canceling circuit generates a nonlinear echo compensation signal based on the driving signal.

Abstract: Systems, apparatus and methods are provided for detecting the mode of a received OFDM signal. A received signal may be correlated with one or more time-delayed version of itself resulting in a set of correlation signals. Each correlation signal may be analyzed for one or more characteristics that can be used to determine the symbol length of the received signal. In order to minimize the number of correlations performed, one or more correlations can be used with varying symbol lengths and a fixed guard interval length. The correlation signals can be processed by filters, and the characteristics of the filtered correlation signals can be analyzed to determine the guard interval length of the received signal. In addition to detecting symbol length, the present invention can be used to detect receiver impairment and perform any appropriate compensations.

Abstract: An adaptive analog echo/near-end crosstalk (NEXT) cancellation system includes a processor configured to receive a first digital signal corresponding to a first signal received by the system, receive a second digital signal corresponding to a second signal transmitted by the system, and generate a first error control signal based on each of the first digital signal and the second digital signal. A cancellation device is configured to generate a second error control signal based on a first analog signal corresponding to the first signal. The cancellation device selectively outputs the second error control signal or the first error control signal based on whether the system is operating in a first mode or a second mode, respectively. The cancellation device selectively outputs a cancellation signal according to one of the second error control signal and the first error control signal, and a second analog signal corresponding to the second signal.

Abstract: A system including a filter circuit, an error module, and a measurement module. The filter circuit receives, from a network device, an analog signal having jitter, generates an equalized signal based on digital feedback signals and the analog signal, and generates a recovered data signal based on the equalized signal. The recovered data signal includes data transmitted by the network device to the system. The error module generates an error signal based on the equalized signal and a threshold signal. The measurement module generates a multiple signals based on the recovered data signal, and the error signal. The multiple signals include the digital feedback signals and eye characteristic signals. The eye characteristic signals indicate characteristics of an eye diagram of the recovered data signal. The measurement module generates the digital feedback signals such that the eye diagram of the recovered data signal does not include the jitter.

Abstract: A decision-feedback equalizer (DFE) can be operated at higher frequencies when parallelization and pre-computation techniques are employed. Disclosed herein is a DFE design suitable for equalizing receive signals with bit rates above 10 GHz, making it feasible to employ decision feedback equalization in silicon-based optical transceiver modules.

Abstract: A parallel implementation of the Viterbi decoder becomes more efficient when it employs end-state information passing as disclosed herein. The improved efficiency enables the usage of less area and/or provides the capacity to handle higher data rates within a given heat budget. In at least some embodiments, a decoder chip employs multiple decoders that operate in parallel on a stream of overlapping data blocks, using add-compare-select operations, to obtain a sequence of state metrics representing a most likely path to each state. Each decoder passes information indicative of a selected end-state for a decoder operating on a preceding data block. Each decoder in turn receives, from a decoder operating on a subsequent data block, the information indicative of the selected end-state. The end-state information eliminates any need for post-data processing, thereby abbreviating the decoding process.

Abstract: A system and method of determining an unbalanced current condition in Power over Ethernet applications are disclosed. In some implementations, a user or network administrator may be notified of potential impairments due to unbalanced current.

Abstract: Embodiments of the present invention include communication systems and methods using channel estimation based on cumulants. In one embodiment, the present invention includes a receiver comprising a sampler coupled to a communication channel for receiving an input signal and providing samples of the input signal at a first sample rate, a channel estimation circuit coupled to receive the sampled input signal, the channel estimation circuit estimating the amplitude response of the communication channel by autocorrelating the input signal, estimating the phase response of the communication channel using a fourth order cumulant of the input signal, and generating an estimated impulse response of the communication channel using the estimated amplitude response and the estimated phase response, and a channel initialization circuit coupled to the channel estimation circuit for configuring the receiver using the estimated impulse response.

Abstract: The present disclosure includes apparatus, systems, and techniques relating to receiver image cancellation. A described technique includes receiving a downconverted signal in a digital domain, the downconverted signal including an in-phase signal and a quadrature signal; generating a first signal of a signal channel based on the downconverted signal; generating a second signal of an image channel based on the downconverted signal; filtering the second signal using first weights to produce a pilot training signal; filtering the second signal using second weights to produce an image cancellation signal; generating an output signal by subtracting the image cancellation signal from the first signal to resolve the desired signal; updating the first weights based on the first weights, the second signal, the pilot training signal, and a pilot signal; and updating the second weights based on the second weights, the output signal, and the pilot training signal.

Abstract: A system including a summer, a comparator, a zero-crossing module, and a control module. The summer is configured to (i) receive a data input signal, and (ii) generate an equalized signal in response to the data input signal. The comparator is configured to generate a recovered data signal in response to the equalized signal. The zero-crossing module is configured to generate a zero-crossing signal in response to the equalized signal. The control module is configured to generate eye information in response to i) the recovered data signal and ii) the zero-crossing signal. The eye information includes characteristic data associated with the recovered data signal, and the characteristic data when plotted provides an eye diagram.

Abstract: A transceiver including an equalizer, and a control circuit. The equalizer includes i) a unity tap comprising a coefficient input configured to receive a coefficient equal to 1, ii) a first plurality of taps including a first plurality of coefficient inputs—each configured to receive a respective one of first coefficients, wherein the first plurality of taps generate a first output signal based on an input, iii) a second plurality of taps including a second plurality of coefficient inputs—each configured to receive a respective one of second coefficients, wherein the second plurality of taps are configured to filter the first output signal to generate a second output signal. The control circuit is configured to limit a sum of the first coefficients and the second coefficients to a first predetermined range based on the coefficient of the unity tap.

Abstract: A decision-feedback equalizer (DFE) can be operated at higher frequencies when parallelization and pre-computation techniques are employed. Disclosed herein is a DFE design that operates at frequencies above 10 GHz, making it feasible to employ decision feedback equalization in optical transceiver modules. An adaptation technique is also disclosed to maximize communications reliability. The adaptation module can be treated as a straightforward extension of the pre-computation unit. At least some method embodiments include, in each time interval: sampling a signal that is partially compensated by a feedback signal; comparing the sampled signal to a set of thresholds to determine multiple speculative decisions; selecting and outputting one of the speculative decisions based on preceding decisions; and updating a counter if the sampled signal falls within a window proximate to a given threshold. Once a predetermined interval has elapsed, the value accumulated by the counter is used to adjust the given threshold.

Abstract: Methods and apparatus describe techniques for reducing interference signals in a communication signal. An apparatus includes, in at least one aspect, a transceiver circuit to receive a communication signal that includes one or more interference signals and a compensation circuit to generate a compensation signal to compensate for the one or more interference signals in the communication signal based on one or more cancellation coefficients and one or more data symbols.

Abstract: A transceiver includes an analog front end (AFE) device and first, second, third, and fourth transmitters. A digital signal processor (DSP) receives digital receive signal and digital transmit signals and generates a shared error control signal and first, second, third, and fourth individual error control signals. An echo canceller system generates an estimated echo signal. First, second, and third NEXT canceller systems generate first, second, and third estimated NEXT signals, respectively, each based on the second analog receive signal and respective ones of the analog transmit signals from the second, third, and fourth transmitters during the first mode and each based on the shared error control signal, respective ones of the second, third, and fourth individual error control signals, and the respective ones of the analog transmit signals from the second, third, and fourth transmitters during the second mode.

Abstract: An adaptive analog echo/near-end crosstalk (NEXT) cancellation system includes a bit slicer that receives a first analog receive signal and that generates a first error control signal. A digital signal processor (DSP) receives a digital receive signal and a digital transmit signal and generates second and third error control signals. A first summing module generates a fourth error control signal by summing the second and third error control signals. A selector outputs the first error control signal during a first mode and the fourth error control signal during a second mode. An echo/NEXT cancellation module communicates with the selector and generates an estimated echo/NEXT signal based on the first error control signal and an analog transmit signal during the first mode and based on the fourth error control signal and the analog transmit signal during the second mode.