Transmission Line Electric Length Detection Using Capacitance
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Solution Overview
Problem
Existing methods, such as TDR, struggle to accurately measure the electric length of transmission lines with branches, as multiple reflected waves complicate the identification of usable reflected waves for calculation.
Innovation Solution
A transmission line length detection device comprising a first capacitance calculation unit to determine total capacitance, a second capacitance calculation unit to measure characteristic impedance, and an electric length calculation unit to calculate electric length by dividing total capacitance by capacitance per unit length, allowing for accurate measurement regardless of branch points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the TDR method is used to measure the electric length of a transmission line, then the measurement is simple and quick, but it becomes impossible to measure accurately when the communication network has branches in the middle of the line due to multiple reflected waves
Solution Approach 1:
The patent replaces the TDR method (which relies on time-domain reflection analysis) with an electrostatic capacitance-based measurement method. By measuring the total capacitance of the transmission line and dividing by the known capacitance per unit length, the system can determine electric length without being affected by reflected waves from branch points. This substitution of measurement principle resolves the contradiction by making the measurement independent of the network topology.
2Adaptability or versatility
If the TDR method is applied to transmission lines with multiple branch points, then the measurement process becomes complex due to the need to identify and distinguish multiple reflected waves, but the basic measurement capability remains
Solution Approach 1:
The patent eliminates the complexity of reflected wave analysis by substituting the TDR method with a capacitance measurement approach. The system measures the total capacitance of the transmission line using an LCR meter or similar device, then calculates the electric length by dividing the total capacitance by the known capacitance per unit length. This method completely avoids the need to analyze multiple reflected waves from branch points, thereby resolving the contradiction between adaptability and device complexity.
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
Enables precise measurement of electric length in communication networks with branches, determining transmission speed and handling networks as lumped constant lines.
Implementation Method 1
a first capacitance calculation unit to observe a voltage change in a transmission line in a communication network, and to calculate the total capacitance which is the capacitance of the whole of the transmission line on the basis of the voltage change
Implementation Method 2
a second capacitance calculation unit to measure the characteristic impedance of the transmission line and to calculate the capacitance per unit length of the transmission line from the characteristic impedance
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A transmission line length detection device (3) is configured in such a way as to include: a first capacitance calculation unit (21) to observe a voltage change in a transmission line (2) in a communication network, and to calculate the total capacitance which is the capacitance of the whole of the transmission line (2) on the basis of the voltage change; a second capacitance calculation unit (22) to measure the characteristic impedance of the transmission line (1) and to calculate the capacitance per unit length of the transmission line (2) from the characteristic impedance; and an electric length calculation unit (23) to calculate the electric length of the transmission line (2) by dividing the total capacitance calculated by the first capacitance calculation unit (21) by the capacitance per unit length calculated by the second capacitance calculation unit (22).