AM Radio Signal Filtering via Dynamic Modulation Measurement
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Solution Overview
Problem
Existing amplitude-modulated radio signal filtering techniques inadequately filter audio signals of 'voice' type, leading to residual noise when the speaker stops talking, as they primarily target high frequencies and fail to effectively distinguish between voice and music signals.
Innovation Solution
A method involving dynamic selectivity and standardized modulation level measurement in the frequency range close to the center frequency of the AM radio signal, allowing for optimized filtering by selecting narrow filters when low modulation is detected, thereby reducing background noise playback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If high-frequency filters are applied to AM radio signals, then music-type audio signals are filtered effectively, but voice-type audio signals are insufficiently filtered and residual noise remains
Solution Approach 1:
The patent implements dynamic filter selection based on real-time modulation level detection. The system automatically adjusts between narrow and wide filter configurations depending on whether the detected audio signal is voice-type (low modulation) or music-type (high modulation), making the filtering process adaptive rather than static
Solution Approach 2:
The system changes the filter parameters (bandwidth, center frequency) based on the detected modulation characteristics of the audio signal. For voice-type signals with low modulation, a narrow filter centered at the carrier frequency is applied, while for music-type signals with high modulation, a wide filter is used
2Object-affected harmful factors
If narrow filters are applied to voice-type signals, then noise is effectively filtered during speech pauses, but the system complexity increases due to dynamic selectivity requirements
Solution Approach 1:
The system performs preliminary detection of the modulation level before applying the filter. By detecting whether the signal is voice-type or music-type in advance, the system can pre-select the appropriate filter configuration, avoiding the need for complex real-time adjustments during signal processing
Solution Approach 2:
The patent replaces complex mechanical or hardware-based dynamic filter mechanisms with a software-based modulation level detection and filter selection system, reducing physical complexity while maintaining filtering effectiveness
3Quantity of substance
If wide filters are applied to music-type signals, then the full audio bandwidth is preserved, but voice-type signals contain unnecessary noise that should be filtered
Solution Approach 1:
The patent applies different filter characteristics to different types of audio signals based on their local characteristics. Voice-type signals receive narrow filtering targeted at the carrier frequency, while music-type signals receive wide filtering that preserves the full audio bandwidth, optimizing the filtering for each signal type's specific needs
Data Source
AI summary
A method for filtering an amplitude-modulated radio signal, the radio signal having a bandwidth, the method including: transforming the radio signal into baseband, determining a frequency range close to the center frequency, measuring the level of the radio signal, by frequency steps, in the frequency range, determining a standardized modulation level in the radio signal, corresponding to the sum of the level measurements by frequency steps, in the frequency range under consideration, divided by the measurement of the level of the radio signal in baseband calculated around the center frequency, comparing the standardized noise level thus determined with a predetermined threshold, on the basis of the comparison, choosing a first filter applied to the amplitude-modulated radio signal.