PLC Modem Dynamic Frequency Notching for Impedance Interference
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Solution Overview
Problem
Power line communication systems face interference from impedance modulating devices connected to the same electrical power wiring, leading to reduced transmission quality and effectiveness of frequency notching, as these devices cause frequency intermodulations and increase signal levels in unused frequency bands.
Innovation Solution
A method to detect and mitigate interferences by selecting specific frequencies to be notched from power line communication and avoiding transmission during time periods when impedance modulating devices switch, using a PLC modem device with a detecting unit to monitor signals and a selecting unit to adjust transmission parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frequency notching is performed to protect external radio services, then interference to external services is reduced, but transmission quality within PLC system is degraded due to inter-carrier interferences from impedance modulating devices
Solution Approach 1:
The PLC system dynamically adjusts its operation by detecting impedance modulations caused by external devices and adapting frequency notching in real-time. The system monitors the power line for impedance changes and modifies the notched frequencies dynamically to avoid inter-carrier interferences while maintaining protection for external radio services.
Solution Approach 2:
The system changes operational parameters by identifying frequencies affected by impedance modulating devices and adjusting the notching configuration accordingly. Instead of using fixed notching frequencies, the system modifies the notched frequency parameters based on detected interference sources, thereby resolving the contradiction between external service protection and internal transmission quality.
2Device complexity
If impedance modulating devices are not controlled, then device complexity remains low, but transmission spectrum is degraded with increased signal levels in unused frequency bands
Solution Approach 1:
The PLC system implements a feedback mechanism by monitoring the power line for impedance modulations and frequency intermodulations caused by external devices. Based on this feedback, the system automatically adjusts its transmission parameters and frequency notching to mitigate signal leakage into unused bands, maintaining low device complexity while reducing harmful emissions.
Solution Approach 2:
The system performs self-diagnosis and self-adjustment by detecting impedance changes on the power line and autonomously modifying its frequency notching configuration. This self-service capability allows the PLC system to combat frequency intermodulations and signal leakage without requiring complex external control systems.
3Object-affected harmful factors
If traditional frequency notching is used, then amateur radio bands are protected, but notching effectiveness is reduced due to impedance modulating devices causing inter-carrier interferences
Solution Approach 1:
The system transitions from static frequency notching to dynamic notching by continuously monitoring for impedance modulations. When impedance modulating devices are detected, the system dynamically adjusts the notched frequencies to precisely target the frequencies causing inter-carrier interferences, thereby restoring and enhancing the effectiveness of frequency notching for protecting amateur radio services.
Data Source
AI summary
A method for operating a PLC system including at least one PLC modem device, in which interferences on transmission signals of the PLC system and/or on a transmission spectrum of the PLC system are detected, the interferences are caused by influences of an impedance modulating device connected to a mains used by the PLC system for communication, and, in a case such interferences are detected, frequencies on which the impedance modulating device causes interferences are selected to be notched from power line communication and/or time periods when the impedance modulating device is in a switching mode are selected to be avoided for transmitting PLC signals. A PLC modem device and a PLC system can implement the method.