Impulse Removal Circuit for FM Signal Noise Cancellation
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Solution Overview
Problem
Existing FM demodulation techniques face limitations in removing impulsive noise, particularly at low signal-to-noise ratios, as they often fail to completely eliminate signal components, leading to false triggers due to large frequency deviations and additive noise.
Innovation Solution
The proposed solution involves an apparatus and method that utilize a delay unit, filter, and impulse detection circuit to detect and remove impulsive noise from FM signals, using a cancellation approach that is insensitive to frequency deviation and modulation frequency, rather than relying on derivative-based methods, which includes a linear phase high pass or low pass filter to separate and subtract the impulse from the signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If derivative-based impulse detection is used, then impulsive noise can be detected, but signal components are not completely removed leading to false triggers
Solution Approach 1:
The patent segments the detection process into two independent stages: first detecting impulses using derivative-based methods, then removing them using a separate cancellation circuit that subtracts detected impulses from the original signal. This segmentation allows each stage to optimize for its specific function without interfering with the other, resolving the contradiction between detection reliability and signal preservation.
Solution Approach 2:
The patent introduces an intermediary impulse cancellation circuit that acts as a mediator between the detection stage and the output stage. This cancellation circuit uses the detected impulse information to generate correction signals that are subtracted from the original signal, thereby removing impulsive noise while preserving the underlying signal components and preventing false triggers.
2Object-affected harmful factors
If existing impulse detection methods are used, then some impulsive noise can be removed, but false triggers occur in the presence of large frequency deviation
Solution Approach 1:
The patent implements a feedback mechanism where the output of the impulse detection circuit is fed back to the impulse cancellation circuit. The cancellation circuit continuously monitors the detected impulses and adjusts its subtraction operation accordingly, creating a closed-loop system that adapts to varying signal conditions including large frequency deviations, thereby reducing false triggers while maintaining effective noise removal.
Solution Approach 2:
The patent changes the operational parameters of the detection system by separating the detection function from the removal function. The detection circuit operates with parameters optimized for impulse identification, while the cancellation circuit operates with parameters optimized for signal preservation. This parameter separation allows the system to maintain high reliability across varying frequency deviation conditions without suffering from false triggers.
Data Source
AI summary
In one example, an apparatus includes: a delay unit to delay a demodulated signal obtained from an input radio frequency (RF) frequency modulation (FM) signal; a filter to filter the demodulated signal and output a filtered demodulated signal; an impulse detection circuit to receive the filtered demodulated signal and detect presence of an impulse in the demodulated signal; and an impulse removal circuit to remove the detected impulse from the demodulated signal.