Adaptive Notch Filtering for CAN Receiver Ringing Suppression
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Solution Overview
Problem
CAN bus communication is limited by signal ringing due to unterminated stubs and lower characteristic cable impedance, which affects reliable communication at higher frequencies, and existing solutions are costly and topology-dependent.
Innovation Solution
A circuit with an adaptive notch filter and feedback loop that dynamically tunes its frequency response to match the ringing frequency, using a time-to-digital converter and digital control circuit to precisely adjust the notch filter parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the data rate is increased by increasing the data frame length and throughput, then the productivity is improved, but signal ringing occurs due to unterminated stubs and lower characteristic cable impedance which limits reliable communication at frequencies higher than 2.5 MHz
Solution Approach 1:
The patent implements a feedback mechanism where the receiver detects ringing on the CAN bus and sends feedback information to the transmitter. The transmitter then adjusts its transmission parameters based on this feedback, creating a closed-loop system that adapts to bus conditions and maintains reliable communication at high data rates.
Solution Approach 2:
The system dynamically changes transmission parameters including data frame length, bit rate, and termination resistance based on detected ringing conditions. This allows the system to optimize for high productivity when conditions permit while maintaining reliability by adjusting parameters when ringing is detected.
2Object-affected harmful factors
If existing solutions to reduce ringing by modifying the network topology and transmitter are implemented, then the signal ringing is reduced, but the device complexity and cost increase due to topology-specific adaptations
Solution Approach 1:
The patent creates a universal solution that works across different CAN bus topologies without requiring topology-specific hardware modifications. The ringing detection and feedback mechanism is topology-agnostic, making the system adaptable to various network configurations while maintaining simplicity.
Solution Approach 2:
The system performs self-diagnosis by having the receiver detect ringing conditions and automatically generate feedback to the transmitter. This self-service approach eliminates the need for external configuration or complex control systems, reducing device complexity while effectively reducing ringing.
3Object-affected harmful factors
If existing solutions to reduce ringing are implemented, then the signal ringing is reduced, but the loss of time and cost occur due to the need to adapt to each particular topology
Solution Approach 1:
The system performs preliminary ringing detection and characterization during system initialization or during idle periods. This preliminary action allows the system to pre-adjust transmission parameters before high-speed communication begins, eliminating the need for time-consuming adaptations during operation.
Solution Approach 2:
The system dynamically adjusts transmission parameters in real-time based on continuous ringing detection. This dynamic adaptation allows the system to respond to changing bus conditions without requiring time-consuming reconfiguration, maintaining both speed and effectiveness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively removes ringing on the CAN bus, allowing for increased data rates and reliable communication without topology-specific adaptations, ensuring quick and efficient suppression of signal interference.
Implementation Method 1
an adaptive notch filter that is coupled to the CAN bus line and configured to filter a CAN signal received from the CAN bus line
Implementation Method 2
a feedback circuit that is configured to estimate a frequency of the ringing on the CAN lines and to tune a frequency response of the notch filter based on the determined ringing frequency
Implementation Method 3
The time-to-digital converter coupled to the first comparator circuit and configured to convert the output signal of the first comparator circuit into a digital word representing a frequency of the ringing
Data Source
AI summary
A circuit comprises a CAN bus line with two wires, an adaptive notch filter that is coupled to the CAN bus line and configured to filter a CAN signal received from the CAN bus line, and a CAN receiver. The circuit further comprises a first comparator circuit, a time-to-digital converter, and a digital control circuit. The first comparator circuit is coupled to the CAN bus line and configured to generate an output signal representing a ringing of the CAN signal. The time-to-digital converter is coupled to the first comparator circuit and configured to convert the output signal of the first comparator circuit into a digital word representing a frequency of the ringing. The digital control circuit is connected to the time-to-digital converter and configured to digitally control a frequency response of an adaptive notch filter based on the digital word.