High-Order Filter Circuit With Feedback Frequency Correction
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Solution Overview
Problem
Conventional telemedical care systems face signal distortion due to noise interference, causing center frequency deviations in notch and band-pass filters, leading to ineffective noise filtration and signal attenuation.
Innovation Solution
A low order filter circuit with a frequency correction function, comprising a second order filter unit, an analog-to-digital converter with dual working statuses, and a digital correction unit, which adjusts the filter's working frequency and ADC status to maintain signal integrity by comparing digitalized peaks with default values and generating feedback signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional notch filter or band-pass filter is used in the sensing channel, then noise filtration and signal retrieval functions are provided, but the center frequency deviates due to process, voltage, temperature and usage time, causing ineffective filtering and signal attenuation
Solution Approach 1:
The patent implements an automatic frequency tracking system where the ADC detects peak frequencies of the filtered signal and feeds this information back to a digital correction unit. This correction unit generates control signals to adjust the filter's center frequency dynamically, ensuring it remains accurately aligned with the target frequency despite environmental variations. This closed-loop feedback mechanism resolves the contradiction by continuously correcting frequency deviations while maintaining effective noise filtration.
Solution Approach 2:
The patent employs dynamic parameter adjustment by changing the operating parameters of the filter based on detected peak frequencies. The system monitors the center frequency deviation and adjusts capacitance or resistance values in the filter circuit to compensate for drift caused by temperature, voltage, and aging effects. This parameter adaptation allows the filter to maintain accurate center frequency alignment while preserving its noise rejection capabilities.
2Reliability
If the center frequency of the filter deviates, then the filter cannot effectively filter off interfering noises or retrieve desired signals, but adding frequency correction functionality increases device complexity
Solution Approach 1:
The patent integrates multiple functions into a unified system where the ADC serves dual purposes: converting the filtered signal for output and simultaneously detecting peak frequencies for correction. The digital correction unit processes both the signal data and frequency detection data, generating control signals that adjust the filter. This multi-functional integration achieves frequency correction without proportionally increasing circuit complexity, as shared components perform multiple roles.
Solution Approach 2:
The system implements self-correction by automatically detecting its own frequency deviations and adjusting its parameters without external intervention. The ADC continuously monitors the output signal and identifies peak frequencies, feeding this information back to the correction unit which automatically adjusts the filter's center frequency. This self-service mechanism maintains signal quality while minimizing the need for external calibration equipment or manual adjustment circuits.
3Object-affected harmful factors
If a low-pass filter and notch filter are added to the sensing channel, then noise interference is reduced, but the circuit complexity increases and signal attenuation may occur
Solution Approach 1:
The patent combines multiple filtering functions into an integrated filter circuit that performs both low-pass filtering and notch filtering simultaneously. By merging these functions into a single coordinated system with shared components and a unified control mechanism, the circuit achieves effective noise reduction across multiple frequency ranges without proportionally increasing complexity. The automatic frequency tracking further optimizes performance by ensuring the combined filters work together efficiently.
Data Source
AI summary
A high order filter circuit is integrated by a plurality of the low order filter circuits. Before correcting the high order filter circuit, switch units may restore the high order filter circuit to the low order filter circuits for correction, and then combine the corrected low order filter circuits to form the original high order filter circuit.