PWM Decoder Threshold Adaptation for Node Timing Variations
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Solution Overview
Problem
In in-vehicle communications systems, the variation in electrical characteristics among nodes leads to inconsistent timing of trailing edges in PWM signals, causing decoding issues when a common sampling timing is used, especially at higher transmission rates.
Innovation Solution
A decoder that measures the duty duration of input signals and determines the corresponding output signal based on this measurement, using a decoding threshold value set according to the measured duty duration and an allowable margin, allowing each node to adjust its decoding threshold appropriately for its circuit characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common sampling timing is used in each node for PWM code decoding, then the decoding process is simplified, but decoding accuracy deteriorates due to variation in electrical characteristics among nodes
Solution Approach 1:
The patent changes the parameter being measured from a fixed time interval to a variable duty duration. Instead of sampling at a predetermined time after the leading edge, the system measures the actual duty duration of the PWM signal and uses this measured value as the basis for decoding. This parameter change accommodates variations in electrical characteristics among different nodes while maintaining decoding accuracy.
2Productivity
If the transmission rate is increased to improve communication efficiency, then productivity is improved, but decoding reliability deteriorates due to insufficient time difference between trailing edges
Solution Approach 1:
The patent introduces feedback by measuring the actual duty duration of the received PWM signal and using this measured value to determine the decoded output. This feedback mechanism allows the decoder to adapt to variations caused by high transmission rates and electrical characteristic differences, ensuring reliable decoding even when the time difference between trailing edges is small.
3Device complexity
If fixed sampling time is used in the decoder, then the decoder structure is simplified, but it cannot accommodate variations in trailing edge timing due to electrical characteristic differences
Solution Approach 1:
The patent enables the decoder to serve itself by automatically measuring the duty duration of the input signal and using this self-measured value for decoding. This self-service approach eliminates the need for external calibration or adjustment, allowing the decoder to adapt to its own electrical characteristics while maintaining a relatively simple structure.
Data Source
AI summary
A decoder for decoding an input signal coded with a pulse width modulation code as a line code to an output signal in a binary code, has a first memory, a first timer, a determination circuit and a first controller. The information on a duty duration of the PWM code, corresponding to at least one kind of the output signals, is stored on the first memory. The first timer has a capacity to measure the duty duration of the input signal. The determination circuit has a capacity to determining which kind of the output signals corresponds to the input signal, on the basis of the information stored on the first memory and the duty duration measured with the first timer. The first controller has a capacity to updating the information stored on the first memory, on the basis of the determination result and the measured duty duration.