Switched-Capacitor Anti-Aliasing Filter With Sampling-Frequency Notches
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Solution Overview
Problem
Traditional anti-aliasing filters face challenges in achieving desired roll-off and notches at integer multiplications of the sampling frequency without side effects, and they struggle to maintain linearity and dynamic range in signal processing.
Innovation Solution
The proposed anti-aliasing filter incorporates window-sampling switches and an operational amplifier with closed-loop feedback, which allows for desired signal transfer functions, including roll-off and notches at integer multiplications of the sampling frequency, while supporting wider dynamic range and improved linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional continuous-time filters are used to achieve notches at integer multiplications of sampling frequency, then aliasing suppression is improved, but side effects occur and manufacturing precision deteriorates
Solution Approach 1:
The patent replaces traditional continuous-time mechanical filter structures with a discrete-time filter implemented through digital signal processing. The filter uses difference equations and digital coefficients to achieve the desired frequency response characteristics, eliminating the physical limitations and side effects of analog filter components while maintaining precise control over notches at sampling frequency multiples.
2Measurement precision
If window-sampling switches and closed-loop feedback are incorporated, then linearity and dynamic range are improved, but device complexity increases
Solution Approach 1:
The patent incorporates closed-loop feedback mechanisms in the discrete-time filter structure, where the output signal is fed back and combined with the input signal through digitally controlled paths. This feedback approach enables precise control over the filter's transfer function, improving linearity and expanding dynamic range while the digital implementation keeps the overall system complexity manageable through software or firmware control.
3Measurement precision
If discrete-time filter is used for signal discretization, then sampling accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent segments the signal processing task into distinct discrete-time filtering stages, each handling specific frequency components or signal characteristics. The filter is implemented as a series of difference equation operations that process the sampled signal in manageable computational steps, improving sampling accuracy while keeping processing complexity organized and controllable through modular digital implementation.
Data Source
Figure 1a~1b
Figure 2a
Figure 2b
AI summary
The invention provides an anti-aliasing filter (AAF) for discretization at a sampling period. The AAF includes an operational amplifier (110) having an input terminal (i1) and an output terminal (o1), a first capacitor (C1) coupled between the input terminal and the output terminal, a second capacitor (C2), and a first switch (sw1) coupled between the first capacitor and the second capacitor. During a first phase, the first switch connects the second capacitor to the first capacitor. During a second phase, the first switch disconnects the second capacitor from the first capacitor. The first phase lasts for one said sampling period.