CAN Bus Emission Compensation Circuit for Harmonic Cancellation
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Solution Overview
Problem
CAN devices often fail to comply with electromagnetic compatibility (EMC) requirements in the automotive sector, leading to costly redesigns, particularly due to excessive harmonic components in the frequency range of 0.6 MHz to 10 MHz, and existing solutions like filtering capacitors may not provide sufficient EMC performance.
Innovation Solution
A method and circuit for compensating electromagnetic noise in CAN buses by transmitting a test signal, performing frequency analysis to detect harmonic components exceeding a threshold, and generating anti-phase sinusoidal compensation signals to be transmitted over the bus, which are adjusted in amplitude and phase to effectively reduce harmonic amplitudes and comply with EMC standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If filtering capacitors are coupled at the output of the CAN transceiver, then electromagnetic emissions are reduced, but EMC performance requirements are still not sufficiently met
Solution Approach 1:
The patent applies preliminary anti-action by generating compensation signals that are in anti-phase with the harmful harmonic components before they propagate through the CAN bus. The system detects harmonic components exceeding the 55 dB threshold and generates counter-phase sinusoidal signals to cancel them out, thereby preemptively neutralizing the electromagnetic emissions rather than merely filtering them after generation
Solution Approach 2:
The patent converts the harmful harmonic emissions into a beneficial solution by using the detected harmonic components themselves to generate the compensation signals. The system takes the harmful electromagnetic emissions, analyzes their frequency characteristics through frequency analysis processing, and transforms them into anti-phase compensation signals that actively cancel the original harmonics, thereby turning the harmful factor into the means of its own elimination
2Device complexity
If CAN devices are designed without EMC compensation, then device complexity is low, but electromagnetic emissions exceed EMC thresholds
Solution Approach 1:
The patent implements preliminary action by performing frequency analysis processing to detect harmonic components during the design and testing phase, before the device is deployed. The system identifies which harmonic frequencies exceed the 55 dB threshold and pre-configures the compensation signal generation parameters, allowing the device to be properly tuned for EMC compliance before actual operation
Solution Approach 2:
The patent applies dynamics by making the compensation signal characteristics adaptive rather than fixed. The system dynamically adjusts the amplitude and phase of compensation signals based on real-time detection of harmonic components, and the compensation mechanism can be selectively activated only for specific frequency ranges where harmonics exceed thresholds, optimizing both EMC performance and resource utilization
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
This approach improves the electromagnetic compatibility of CAN devices, reducing the risk of non-compliance with automotive EMC requirements by continuously generating and adjusting compensation signals, thereby ensuring compliance without the need for extensive redesigns.
Implementation Method 1
generating and transmitting over the CAN bus a set of compensation signals, each compensation signal in the set of compensation signals being a sinusoidal signal having a respective frequency equal to one of the frequencies stored, and being in anti-phase with respect to the harmonic component of the test signal received having the respective frequency
Data Source
AI summary
A method of compensating electromagnetic emissions of a device for use in a communication bus, the method including: transmitting a test signal over the communication bus; receiving, at the device, the test signal after propagation over the communication bus; performing frequency analysis processing of the test signal received to detect a set of harmonic components of the test signal received having an amplitude exceeding a certain threshold; storing respective values of frequency of harmonic components in the set of harmonic components having an amplitude exceeding the certain threshold; and generating and transmitting over the communication bus a set of compensation signals, each compensation signal in the set of compensation signals being a sinusoidal signal having a respective frequency equal to one of the frequencies stored, and being in anti-phase with respect to the harmonic component of the test signal received having the respective frequency.