Passive Star Node Network With Reflection-Canceling Current Source
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Solution Overview
Problem
Existing data networks with three or more line branches connected via a common star node face interference issues due to signal reflections, which are difficult to manage with passive star nodes, especially at high bit rates, leading to signal distortions and information loss.
Innovation Solution
A data network design that employs a passive star node with bus-user devices equipped with a current source circuit, which maintains a high impedance to prevent further signal reflections, and compensation filters to manage reflections, allowing for interference-free operation at higher bit rates without complex circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a passive star node is used to connect three or more line branches, then the device complexity is reduced, but signal reflections occur causing interference and information loss
Solution Approach 1:
The invention converts the harmful signal reflection at the passive star node into a beneficial effect by having the transmitting bus-user device send a compensation signal that cancels out the reflection. The reflection, which was previously causing interference, is now used as a basis for generating a counter-signal that eliminates the interference entirely, enabling interference-free operation at high bit rates with simple passive star nodes
Solution Approach 2:
The system implements feedback by having the transmitting bus-user device measure or calculate the reflected signal from the passive star node and generate a compensation signal based on this feedback. This closed-loop approach allows the system to actively cancel the harmful reflections while maintaining the simplicity of passive star nodes
2Reliability
If active star nodes are used to prevent signal reflections, then signal quality is improved, but the device complexity and circuit requirements increase
Solution Approach 1:
The invention extracts the active signal processing function from the star node itself and relocates it to the bus-user devices. Instead of requiring the star node to actively terminate or protect against reflections, the bus-user devices perform the compensation function, thereby simplifying the star node to a passive component while maintaining high signal quality
3Loss of information
If slide-on ferrite cores are used to transform line segment impedances, then reflections are reduced within a limited frequency band, but higher symbol rates cannot be achieved
Solution Approach 1:
The invention changes the approach from passive impedance transformation with ferrite cores to active parameter compensation through signal processing. By dynamically generating compensation signals that adapt to the reflection characteristics, the system achieves broad frequency effectiveness and supports high symbol rates without being constrained by the limited frequency band of ferrite core transformations
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
The solution enables interference-free operation with low technical complexity by minimizing signal reflections, allowing for the connection of multiple line branches via a passive star node, supporting high bit rates and secure communication.
Implementation Method 1
the transmit unit has a current source circuit which, in order to generate the message signal, is configured to generate or to inject an electric current into the electrical lines of the circuit branch to which the bus-user device is connected. A current source circuit can be embodied, as is known per se from the prior art, for instance by LVDS... the transmit unit is connected by its current source circuit between the lines of the line branch constantly 'as a high impedance' even in transmit mode
Implementation Method 2
The star node is passive, which means that in distributing the message signal, a reflection occurs at the star node, which is reflected back to the transmitting bus-user device
Data Source
AI summary
A data network has at least three line branches connected via a common star node to distribute message signals from one of the line branches onto the other line branches, wherein connected to at least one of the line branches is at least one bus-user device is configured to generate in a corresponding transmit mode by a corresponding transmit unit at least one of the message signals, wherein in the corresponding bus-user device, the transmit unit has a current source circuit which, in generating the message signal (16), is configured to inject an electric current into electrical lines of the line branch to which the bus-user device is connected, and via the current source circuit the lines are connected to an internal impedance value of the current source circuit that in transmit mode is constantly greater than 10 times the value of the characteristic impedance, for example greater than 500 Ohms.