Feedback-Filtered Sensor Circuit for Interference Rejection
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Solution Overview
Problem
Sensitive sensors face challenges in dynamic range due to large interference signals, particularly from mains-related frequencies, which can lead to saturation and require high gain, making it difficult to amplify small signals effectively without exceeding noise floors.
Innovation Solution
The use of band-pass or band-stop filters in a feedback network to tailor the sensor's frequency response, increasing sensitivity to desired frequencies and reducing interference, thereby reducing the dynamic range requirement and improving signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high gain is used to amplify small signals, then signal-to-noise ratio is improved, but saturation occurs from large interference signals
Solution Approach 1:
The patent applies parameter changes by modifying the frequency response characteristics of the sensor system through feedback filtering. By adjusting the frequency-dependent gain and phase parameters, the system achieves high gain at signal frequencies while maintaining low gain at interference frequencies, thereby resolving the contradiction between amplifying small signals and avoiding saturation from large interference signals.
Solution Approach 2:
The patent employs feedback mechanisms where the output signal is fed back through a filter network that selectively attenuates interference frequencies. This feedback loop dynamically adjusts the system response to maintain stability while achieving the desired frequency-selective gain, allowing high amplification of weak signals without saturation from strong interference.
2Measurement precision
If sensor sensitivity is increased to detect extremely small signals, then detection capability is improved, but dynamic range requirement increases due to large interference signals
Solution Approach 1:
The patent changes the frequency response parameters of the sensor system to create a selective sensitivity profile. By modifying the gain and phase parameters across different frequencies through feedback filtering, the system achieves high sensitivity to small signals at specific frequencies while simultaneously reducing sensitivity to large interference signals at other frequencies, thereby reducing the overall dynamic range requirement.
Solution Approach 2:
The patent applies local quality by making the sensor response non-uniform across the frequency spectrum. Instead of uniform high sensitivity across all frequencies, the system creates localized high sensitivity regions at signal frequencies and localized low sensitivity regions at interference frequencies, achieving high detection capability without requiring extreme dynamic range.
3Object-affected harmful factors
If analogue filtering is used to remove interference frequencies, then interference signals are attenuated, but signal processing precision may be reduced
Solution Approach 1:
The patent uses feedback-based filtering where the filtering action is applied in a closed-loop configuration. This allows the system to attenuate interference frequencies while maintaining signal integrity through the feedback mechanism, which compensates for any signal degradation and preserves processing precision while achieving interference rejection.
Solution Approach 2:
The patent introduces a feedback filter network as an intermediary element between the sensor output and the final signal processing stage. This intermediary selectively attenuates interference frequencies while allowing signal frequencies to pass with minimal distortion, thereby reducing interference amplitude without compromising signal processing precision.
Data Source
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AI summary
The present invention provides a sensor system and a corresponding sensing method employing the sensor system. The sensor system comprises a sensor (12) having an input (20) and an output (22), a feedback path (16) from the output to the input, and a filter (14; 92) in the feedback path. The filter comprises a narrow band filter, which is tuned or tunable to a respective one of signals that are wanted signals and signals that represent interference signals. The sensor and the filter are arranged so as to alter the relative amplitudes of the wanted signals and the interference signals in order to increase the relative amplitude of the wanted signals and reduce the relative amplitude of the interference signals.