Adaptive AM Radio Signal Filtering for Noise Reduction
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Solution Overview
Problem
Existing radio receivers in automotive vehicles face challenges in effectively filtering noise from amplitude-modulated (AM) radio signals, as conventional filtering methods adulterate the data after demodulation and do not adaptively address noise and adjacent signal interference.
Innovation Solution
Implementing an adaptive filtering method using dynamic selectivity, where filters are applied on both sides of the passband based on noise level and adjacent signal detection, with sensors determining the appropriate filters to minimize noise impact before demodulation, and incorporating a hysteresis mechanism to stabilize filter changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If filtering is applied to the demodulated radio signal, then noise and disruptive interference are eliminated or limited, but the data contained in the radio signal is adulterated
Solution Approach 1:
The patent applies filtering before demodulation rather than after. The filter is applied to the modulated signal in the frequency domain, extracting the message signal before the demodulation process. This preliminary filtering action eliminates noise and interference from the modulated signal while preserving the integrity of the message data, as the filtering occurs on the carrier signal rather than on the extracted audio data.
2Adaptability or versatility
If dynamic selectivity is deactivated when no adjacent radio signal is detected, then device complexity is reduced, but adaptability to noise conditions is lost
Solution Approach 1:
The patent implements dynamic selectivity by changing the filter parameters (cutoff frequencies, filter order) based on detected signal conditions. When adjacent signals or noise are detected, the system adjusts the filtering parameters adaptively. This allows the system to maintain simplicity when no adjustment is needed while providing full adaptability when conditions require it, resolving the contradiction between adaptability and complexity.
3Object-affected harmful factors
If filtering is applied after demodulation, then noise limitation is achieved, but the audio signal quality is degraded
Solution Approach 1:
The patent performs filtering as a preliminary action before demodulation and audio processing. By applying the filter to the modulated radio signal in the frequency domain before the message is extracted, the system removes noise and interference from the carrier signal itself. This preserves the quality of the message signal during demodulation, whereas post-demodulation filtering would have to work with already extracted audio data that may have already suffered quality degradation.
Data Source
AI summary
The present invention relates to an adaptive filtering method for an amplitude-modulated radio signal (AM), the radio signal having a bandwidth, the method comprising: ⋅ transforming the radio signal into baseband, ⋅ measuring the level of noise and/or detecting the presence of an adjacent radio signal (A), of a first side of the bandwidth, ⋅ selecting or not selecting a first filter (F) numbered X, from among N first filters capable of cutting the amplitude-modulated radio signal of the first side of the bandwidth, ⋅ if a first filter numbered X is selected and applied to the amplitude-modulated radio signal transformed into baseband, the automatic selection of a second filter (F′) numbered Y, Y being greater than or equal to X, from among N second filters, capable of cutting the amplitude-modulated radio signal from the opposite side to the first side of the bandwidth.