Cable Termination Resistance Layout for Low-Reflection FlexRay Networks
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Solution Overview
Problem
High-speed communication networks, such as those using FlexRay, face significant challenges due to reflections caused by impedance discontinuities at cable ends, leading to communication failures and excessive power dissipation in traditional termination methods, while existing solutions often only address the main cable ends, neglecting the impact on other cable ends.
Innovation Solution
A method to determine termination resistances for all cable ends in a communication network by calculating cable lengths, assigning weights based on length, and using a common constant of proportionality to determine termination resistances, ensuring minimal reflection effects across the network topology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional termination methods are used at main cable ends, then reflections are reduced at those ends, but power dissipation increases and other cable ends still cause reflections
Solution Approach 1:
The patent divides the termination problem into segments by applying different termination resistances to different cable ends based on their position and cable length. Instead of uniform termination, each cable end is individually optimized with a specific termination resistance value calculated from its distance to other cable ends, thereby reducing both reflections and power dissipation in a distributed manner.
Solution Approach 2:
The patent implements local quality by assigning different termination resistance values to different cable ends based on their specific characteristics (cable length, position in the network). Each cable end receives a customized termination resistance calculated locally from its distance to other cable ends, rather than applying a global termination scheme to all ends uniformly.
2Reliability
If termination resistors are connected at both main cable ends, then signal fidelity improves, but power dissipation in termination resistors increases
Solution Approach 1:
The patent changes the parameter of termination resistance from fixed standard values to dynamically calculated values based on cable length and position. By adjusting the termination resistance parameter for each cable end according to its specific characteristics, the system optimizes the balance between signal fidelity and power dissipation, achieving high signal quality with reduced power consumption.
3Device complexity
If only main cable ends are terminated, then implementation complexity is reduced, but communication reliability deteriorates due to reflections at other cable ends
Solution Approach 1:
The patent creates a universal termination solution that can be applied to all cable ends in the network using a standardized calculation method. The same termination resistance calculation formula applies universally to every cable end based on its distance to other ends, providing a multi-functional approach that simultaneously addresses reflections at all cable ends while maintaining implementation simplicity through a unified methodology.
Data Source
AI summary
The invention relates in general to a method for determining cable termination resistances in communication networks and a corresponding communication network, and is applicable especially to high-speed communication networks in automobiles, which uses dual-wire harnesses like FlexRay e.g. For this purpose a method for determining cable termination resistances in communication networks is proposed, where a termination resistance is assigned to at least a part of the cable ends of the network in accordance with the following steps determining for each cable end the cable length to any other cable end, assigning a weight value to each length where lengths with greater values are combined with higher weights than lengths with smaller values, for all cable ends: summing up the weights assigned to all lengths starting from a specific cable end and assigning this sum to the respective cable end as the weight of this cable end, determining the termination resistance of a specific cable end by multiplying the cable impedance Z with a constant of proportionality and the sum of the weights of all cable ends divided by the weight of the specific cable end.