Chopper Amplifier Sampling to Shift Spectral Aggressors
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Solution Overview
Problem
Medical devices face challenges in amplifying low-frequency physiological signals, such as brain signals, due to the introduction of spectral aggressors by chopper amplifiers, which can cause noise in the target frequency band of interest, especially in implantable devices with limited power resources.
Innovation Solution
The technique involves selecting a chopper frequency and sampling rate for the analog-to-digital converter (ADC) such that spectral aggressors generated by the chopper amplifier occur outside the target frequency band of interest, reducing noise and improving signal analysis by moving these aggressors to frequencies outside the band of analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a chopper amplifier is used to amplify low-frequency physiological signals, then the amplification capability and low-power characteristics are improved, but spectral aggressors are introduced that cause noise in the target frequency band
Solution Approach 1:
The patent changes the chopper frequency parameter to a specific value or range that moves the spectral aggressors outside the target frequency band of interest. By carefully selecting the chopper frequency, the system maintains the low-power amplification benefits while avoiding the introduction of noise within the physiological signal frequency range.
Solution Approach 2:
The patent converts the harmful spectral aggressors generated by the chopper amplifier into a beneficial situation by positioning them outside the target frequency band. The spectral aggressors still exist but no longer interfere with the physiological signal analysis, effectively transforming a harmful effect into an acceptable byproduct.
2Object-affected harmful factors
If the chopper frequency is increased to move spectral aggressors outside the target frequency band, then the noise in the target band is reduced, but the power consumption and potential introduction of new aggressors may increase
Solution Approach 1:
The patent optimizes the chopper frequency parameter to achieve the minimum necessary value that moves spectral aggressors outside the target band. This avoids excessive power consumption while still achieving the goal of reducing noise in the physiological signal frequency range.
3Object-affected harmful factors
If the sampling rate is adjusted to control spectral aggressors, then the noise distribution is improved, but the device complexity and computational requirements increase
Solution Approach 1:
The patent selects specific sampling rate values that naturally position spectral aggressors outside the target frequency band when combined with the chosen chopper frequency. This parameter selection approach simplifies the overall system design by avoiding the need for complex filtering or additional processing stages.
Data Source
AI summary
This disclosure describes techniques for controlling spectral aggressors in a sensing device that uses a chopper amplifier to amplify an input signal prior to sampling the signal. In some examples, the techniques for controlling spectral aggressors may include generating a chopper-stabilized amplified version of an input signal based on a chopper frequency, sampling the chopper-stabilized amplified version of the input signal at a sampling rate to generate a sampled signal, and analyzing a target frequency band of the sampled signal. The chopper frequency and the sampling rate may cause spectral interference that is generated due to the chopper frequency to occur in the sampled signal at one or more frequencies that are outside of the target frequency band of the sampled signal. The techniques for controlling spectral aggressors may reduce the noise caused by the chopper frequency in the resulting sampled signal, thereby improving the quality of the signal.