Baseline Signal Subtraction in Impedance Measurement Circuits
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Solution Overview
Problem
Current impedance measurement technologies face challenges in accurately measuring small changes in impedance due to the dominance of baseline signals, leading to noise and reduced resolution, especially when dealing with high-performance amplifiers and analog-to-digital converters.
Innovation Solution
The impedance measuring apparatus generates a sinusoidal or pseudo-sinusoidal baseline signal and subtracts it from the amplitude modulated signal, using an amplitude estimation circuit and phase extraction circuit to accurately match phases and amplitudes, thereby enhancing resolution and reducing noise from harmonic frequency components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high-performance amplifier and analog-to-digital converter are used to amplify the amplitude modulated signal, then the signal amplification capability is improved, but the baseline signal dominates and reduces measurement resolution
Solution Approach 1:
The patent extracts and removes the baseline signal component from the amplified amplitude modulated signal. By separating the baseline signal (which contains no impedance information) from the modulated signal, the system prevents the baseline from dominating the measurement, thereby maintaining both high amplification capability and measurement resolution.
Solution Approach 2:
The patent segments the amplified signal into distinct components: the baseline signal and the amplitude modulated signal containing impedance information. This segmentation allows independent processing of each component, enabling the system to utilize the full amplification capability while focusing measurement resources on the relevant impedance signal portion.
2Device complexity
If the baseline signal is not subtracted, then the amplification process is simpler, but noise from harmonic frequency components increases
Solution Approach 1:
The patent converts the harmful baseline signal (which causes noise and reduces resolution) into a useful reference component. By generating a baseline signal with matched amplitude and phase, the system can subtract it cleanly from the modulated signal, transforming what was previously a source of noise into a tool for achieving precise impedance measurement.
3Device complexity
If the amplitude and phase of the baseline signal are not accurately matched, then the signal processing is simpler, but measurement accuracy decreases
Solution Approach 1:
The patent employs feedback mechanisms through amplitude estimation circuits and phase extraction circuits that continuously monitor the amplified signal and adjust the baseline signal parameters accordingly. This feedback ensures that the baseline signal's amplitude and phase are accurately matched to the actual signal conditions, maintaining high measurement accuracy while automating the complex adjustment process.
Data Source
AI summary
An impedance measuring apparatus is disclosed. The impedance measuring apparatus includes an input current generator configured to generate a sinusoidal input signal of a carrier frequency, a first electrode configured to apply the sinusoidal input signal to an object which has an impedance, a second electrode configured to receive an amplitude modulated signal from the object, a first amplifier configured to amplify the received amplitude modulated signal and output a first amplified signal, a baseline signal subtractor configured to subtract a baseline signal generated based on the first amplified signal from the amplitude modulated signal and output a subtraction modulated signal, an analog-to-digital converter (ADC) configured to convert the subtraction modulated signal to a digital modulated signal, and an impedance measurer configured to measure the impedance based on the digital modulated signal.