eLORAN RF Interference Cancellation for Reliable Navigation
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Solution Overview
Problem
eLORAN navigation systems are prone to electromagnetic interference (EMI) from man-made sources and natural noise, which can compromise their reliability in critical applications such as navigation at sea, in the air, and on land.
Innovation Solution
A LORAN device with an ambient RF interference canceller that includes a sensor and cancellation circuitry to generate a cancellation signal based on sensed interference, using adaptive filtering and channel weights to mitigate EMI, and incorporates power supply line sensing for comprehensive interference cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If eLORAN systems use 100 kHz frequency for ground wave propagation, then navigation reliability is improved, but susceptibility to electromagnetic interference from man-made sources increases
Solution Approach 1:
The patent employs adaptive interference cancellation that converts the harmful EMI signals into useful information by sensing them with dedicated sensors, characterizing their properties through adaptive filtering, and then generating cancellation signals that transform the harmful interference into a beneficial noise-reduction mechanism, effectively converting the harm into a benefit for maintaining navigation reliability
2Object-affected harmful factors
If ambient RF interference cancellation is implemented in eLORAN receivers, then interference mitigation is improved, but device complexity increases
Solution Approach 1:
The patent segments the interference cancellation function into distinct modular components: RF interference sensors separate from the main receiver, dedicated cancellation circuitry with adaptive filters, and weight calculation units. This segmentation allows each component to perform its specific function independently, making the overall complex system more manageable and maintainable while achieving effective interference mitigation
Solution Approach 2:
The patent introduces an intermediary ambient RF interference canceller that acts as a mediator between the LORAN antenna/receiver and the processing system. This intermediary component senses interference, generates cancellation signals, and injects them into the signal path, isolating the main receiver from direct exposure to interference while adding complexity only where needed for cancellation functionality
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 effectively reduces EMI, enhancing LORAN receiver performance in challenging environments, maintaining reliable navigation and communication systems.
Implementation Method 1
an ambient RF interference sensor configured to generate a sensed ambient RF interference signal based on the ambient RF interference
Implementation Method 2
cancellation circuitry configured to cooperate with the ambient RF interference sensor to generate an ambient RF interference cancellation signal based upon the sensed ambient RF interference signal, and add the ambient RF interference cancellation signal to the RF signal path
Data Source
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AI summary
A LORAN device may include a LORAN antenna, a LORAN receiver, an RF signal path extending between the LORAN antenna and the LORAN receiver and being subject to ambient RF interference, and an ambient RF interference canceller coupled in the RF signal path. The ambient RF interference canceller may include an ambient RF interference sensor configured to generate an estimated ambient RF interference signal based on the sensed ambient RF interference, and cancellation circuitry configured to cooperate with the ambient RF interference sensor to generate an ambient RF interference cancellation signal based upon the sensed ambient RF interference signal, and add the ambient RF interference cancellation signal to the RF signal path.