EMI Cancellation Circuitry for Wireline Receivers
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Solution Overview
Problem
Wireline communication systems face challenges in mitigating electromagnetic interference (EMI) due to signal attenuation and mode conversions, especially at high data rates, which can lead to bit errors and safety issues in applications like autonomous driving, and existing solutions like high-quality cables and common mode chokes are costly or ineffective.
Innovation Solution
A receiver chip with integrated EMI cancellation circuitry that regenerates a replica of RFI noise and subtracts it from the equalizer output, eliminating the need for expensive cables and reducing signal degradation, while also providing EMI detection for enhanced safety features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high quality cable is used to mitigate EMI, then EMI resistance is improved, but system cost increases
Solution Approach 1:
The patent creates a copy of the EMI signal by extracting common-mode noise from the differential signal and using an adaptive filter to generate a replica of the EMI. This copied EMI signal is then subtracted from the received signal to cancel the interference, eliminating the need for expensive shielded cables while maintaining EMI resistance.
Solution Approach 2:
The patent replaces the mechanical/physical solution of using high-quality shielded cables with a digital signal processing approach. By using adaptive equalization and EMI cancellation algorithms in the receiver, the system achieves EMI mitigation through software/firmware processing rather than relying on expensive physical infrastructure.
2Object-affected harmful factors
If common mode choke is used to reduce common mode signal, then common mode noise is reduced, but EMI converted to differential signal is not reduced
Solution Approach 1:
The patent implements feedback by continuously monitoring the received signal for EMI characteristics and using an adaptive filter to adjust the EMI cancellation signal in real-time. The system detects common-mode noise, generates a corresponding differential EMI replica through adaptive filtering, and subtracts it from the received signal, creating a closed-loop feedback mechanism that effectively mitigates EMI.
Solution Approach 2:
The patent changes the parameter approach by transforming the EMI cancellation from a static common-mode filtering operation to a dynamic adaptive process. The adaptive filter continuously adjusts its coefficients based on the detected EMI characteristics, allowing the system to adapt to varying EMI conditions and effectively cancel EMI across different frequency and amplitude conditions.
3Object-affected harmful factors
If notch filter is used to attenuate RFI noise, then RFI noise is reduced, but signal at same frequency is also attenuated
Solution Approach 1:
The patent extracts the EMI component from the received signal by first detecting common-mode noise and then generating a separate EMI cancellation signal through adaptive filtering. This extracted EMI signal is then subtracted from the received signal, effectively removing only the harmful EMI component while preserving the original data signal, avoiding the signal degradation that would occur with broadband notch filtering.
Data Source
AI summary
Embodiments of the present disclosure utilizes the natural properties of RFI noise on a wireline link. Since differential RFI noise in the system has some correlation with the common mode noise on the cable, a replica of RFI noise can be regenerated by an adaptive filter based on information about the common mode noise. The replica RFI is subtracted from the equalizer output prior to the data decision circuitry or slicer. In this method, the system does not require expensive cable, nor does the equalizer suffer additional loss due to an RFI notch filter. Since RFI can be detected and mitigated, this information can also be coupled to safety systems to increase functional safety under high EMI conditions.