Adaptive Resampling for SerDes Near-End Crosstalk Mitigation
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Solution Overview
Problem
Serializer/Deserializer (SerDes) devices face challenges in canceling near-end crosstalk (NEXT) interference due to asynchronous clocks between transmitters and receivers, making it difficult to filter out the interference using static digital filtering schemes and obtaining real-time phase difference information.
Innovation Solution
An adaptive resampling scheme using a Farrow filter tracks the phase difference between transmitter and receiver clocks, dynamically adjusting resampling coefficients, and a NEXT cancellation filter applies a Hadamard transform to efficiently implement crosstalk cancellation by decomposing a finite impulse response (FIR) filter into sub-filters, reducing residual crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If static digital filtering schemes are used to cancel NEXT interference, then device complexity is reduced, but crosstalk cancellation effectiveness deteriorates due to asynchronous clocks between transmitter and receiver
Solution Approach 1:
The patent implements dynamic resampling of the aggressor data stream using adaptive phase shift compensation. The resampler dynamically adjusts sampling phases based on estimated phase differences between asynchronous transmitter and receiver clocks, allowing effective NEXT cancellation despite clock asymmetry. This dynamic approach replaces static filtering with adaptive time-domain resampling that tracks phase variations in real-time.
Solution Approach 2:
The system changes the temporal parameters of the aggressor data by applying time-varying phase shifts during resampling. By dynamically adjusting the phase alignment between transmitter and receiver clocks through parameter modulation, the system achieves effective crosstalk cancellation without requiring identical clock synchronization, thus resolving the contradiction between simplicity and effectiveness.
2Measurement precision
If real-time phase difference information is obtained between asynchronous clocks, then crosstalk cancellation precision is improved, but measurement and detection difficulty increases
Solution Approach 1:
The patent introduces an intermediary phase detector that estimates phase differences between asynchronous clocks by processing training sequences. This intermediary component translates the difficult direct measurement of phase differences into a more manageable estimation process using known training data, enabling precise phase tracking without direct complex synchronization.
Solution Approach 2:
The system performs preliminary phase alignment by processing training sequences before main data transmission. The phase detector uses known training data to pre-establish phase relationship estimates, which are then used to guide the resampling process during actual data communication. This preliminary action simplifies real-time phase measurement by preparing phase compensation parameters in advance.
Data Source
AI summary
A communication apparatus includes a receiver disposed in proximity to a transmitter, and a crosstalk cancellation circuit. The receiver includes an input buffer, a front end, and an adaptive resampling circuit. The input buffer receives from the transmitter aggressor data, the aggressor data being timed by a transmitter clock clocking the transmitter. The front end receives data over a communication link, the data being serialized according to a receiver clock clocking the receiver, the receiver clock operating independently of the transmitter clock. The front end further generates a stream of data samples corresponding to the received data. The adaptive resampling circuit resamples the aggressor data, and generates resampled data timed by the receiver clock. The crosstalk cancellation circuit estimates, based on the resampled data, a crosstalk error signal related to the aggressor data, and subtracts the estimated crosstalk error signal from the stream of data samples.