Vehicle Bus Current Modulation for Fast Bidirectional Data Links
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Solution Overview
Problem
Existing 1:N network communication systems in vehicles face challenges in achieving fast and efficient data transmission rates from a master to slaves due to electromagnetic compatibility (EMC) standards, particularly when using non-linear impedances, where precise second-derivative bus voltage matching is difficult, leading to slower data transmission rates.
Innovation Solution
Implementing a network communication system with bidirectional current modulation using a bias voltage source, current measuring device, terminating resistor, and modulation devices to modulate data on a communication bus, allowing for direct current adjustment and simplified EMC compliance, enabling faster data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If voltage modulation encoding is used for data transmission from master to slaves, then data can be transmitted, but the data transmission rate becomes several times lower than slave to master transmission rate due to complex second-derivative voltage matching requirements
Solution Approach 1:
The patent changes the modulation parameter from voltage to current. By using current modulation instead of voltage modulation, the system avoids the complex second-derivative voltage matching requirements while achieving fast data transmission rates in both directions. The current modulation approach with first-derivative current matching simplifies the transmission characteristics.
Solution Approach 2:
The patent inverts the traditional approach by having both master and slaves use current modulation instead of the conventional voltage modulation for master-to-slave transmission. This inversion of the modulation method resolves the asymmetry in transmission rates and simplifies the matching requirements.
2Object-affected harmful factors
If precise second-derivative bus voltage matching is implemented to meet EMC standards, then electromagnetic radiation is reduced, but the system complexity increases and data transmission rate decreases
Solution Approach 1:
The patent changes the modulation parameter from voltage to current, which fundamentally alters the electromagnetic radiation characteristics. Current modulation with first-derivative matching produces different radiation profiles that can meet EMC standards more easily while maintaining high data transmission rates, avoiding the need for complex voltage matching.
3Reliability
If voltage modulation is used with non-linear impedances on the communication bus, then data transmission is possible, but precise second-derivative bus voltage matching becomes very difficult or impossible
Solution Approach 1:
The patent changes the modulation parameter from voltage to current, which resolves the issue with non-linear impedances. Current modulation is less sensitive to non-linear impedance variations on the bus, making the system more reliable and easier to implement without requiring precise matching.
4Speed
If current modulation is used from slave to master, then fast data transmission is achieved, but bidirectional fast transmission is not possible with voltage modulation from master to slaves
Solution Approach 1:
The patent makes the current modulation approach universal for both transmission directions. Both master and slaves use current modulation, enabling fast data transmission in both directions simultaneously. This multi-functional approach eliminates the asymmetry where only slave-to-master transmission could achieve high speeds.
Data Source
Figure 1~3A
Figure 3B~5
AI summary
The invention relates to a network communication system (50), in particular for a vehicle, having a communication bus (56), a first communication device (52) and a plurality of second communication devices (54), which are connected to one another via the communication bus (56), wherein the first communication device (52) comprises a bias voltage source (64) for producing a constant bias voltage on the communication bus (56), the first communication device (52) comprises a current measuring apparatus (66) for detecting the current on the communication bus (56), the network communication system (50) has a terminating resistor (60) arranged in parallel with the plurality of second communication devices (54), the first communication device (52) comprises a first modulation apparatus (72) for modulating a current produced by the bias voltage and the terminating resistor (60) on the communication bus (56), each second communication device (54) comprises a second modulation apparatus (78) for modulating the current produced by the bias voltage and the terminating resistor (60), and each second communication device (54) has a second voltage measuring apparatus (80) for detecting a voltage across the terminating resistor (60). The invention also relates to a corresponding method for communication in a network communication system (50).