Instantaneous Impedance Determination in PLC Analog Front-Ends
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Solution Overview
Problem
Existing methods for determining the input impedance of AC power lines used in Power Line Communication (PLC) require separate electrical signals, which can cause interference and are intrusive, and often necessitate additional hardware like Characteristic Impedance Meters (CIMs).
Innovation Solution
The method utilizes the preamble portion of data packets in Narrow Band PLC standards to determine instantaneous input impedance by measuring current and voltage at the analog-front-end (AFE) of the transmission line, eliminating the need for separate signal injection and allowing for integration with existing AFEs, using algorithms that can be incorporated into software for real-time impedance calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate electrical signals are transmitted to determine impedance, then impedance measurement is possible, but interference and intrusiveness occur
Solution Approach 1:
The system uses its own data transmission signals (preamble portions) to perform impedance measurements, eliminating the need for separate measurement signals. The preamble signals already present in the communication channel are repurposed for impedance determination, making the system self-serving and avoiding additional interference
Solution Approach 2:
The preamble signals serve dual functions: communication synchronization and impedance measurement. By making the communication signals multi-functional, the system eliminates the need for separate measurement signals, thereby reducing interference and intrusiveness while maintaining measurement capability
2Measurement precision
If Characteristic Impedance Meters are connected to the transmission line, then impedance determination is possible, but additional hardware and complexity are required
Solution Approach 1:
The analog-front-end circuitry is designed to perform both communication signal processing and impedance measurement functions. By integrating impedance measurement capabilities into the existing communication hardware, the system eliminates the need for separate Characteristic Impedance Meters, reducing hardware complexity while maintaining measurement accuracy
Solution Approach 2:
The measurement function is merged with the communication function by using the same analog-front-end components for both purposes. The voltage and current measurements needed for impedance calculation are obtained through the existing communication signal path, combining multiple functions into a single integrated system
3Adaptability or versatility
If impedance measurements are performed in real-time, then dynamic adaptation is improved, but processing complexity increases
Solution Approach 1:
Impedance measurements are performed during the preamble portion of data packets, which occurs before the main communication data is processed. This preliminary measurement approach allows the system to obtain impedance information in advance, enabling dynamic adaptation without adding complexity to the main data processing path
Solution Approach 2:
Impedance measurements are conducted periodically at regular intervals using the preamble signals of transmitted data packets. This periodic measurement approach provides real-time impedance information for dynamic adaptation while distributing the processing load over time, avoiding excessive instantaneous complexity
Data Source
AI summary
There is provided a method and apparatus for determining the input impedance (ZL) of an AC transmission line used for Power Line Communications (PLC), using a transmitted data packet having a preamble portion. The method comprises, at the analog-front-end (AFE) of the AC transmission line, determining the current through the AFE and the AC transmission line during transmission of the preamble portion of the data packet and determining the voltage during transmission of the preamble portion of the data packet. The method further comprises calculating the total impedance (Zt) from the determined current and voltage. The total impedance (Zt) includes the input impedance (ZL) of the AC transmission line and the AFE impedance (ZAFE). Finally, the method includes determining the input impedance (ZL) of the AC transmission line from the total impedance (Zt).