Switched Capacitor Notch Filter for Precise High-Frequency Attenuation
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Solution Overview
Problem
Traditional notch filters face challenges in precision and power consumption when implementing high-frequency notching, and they are difficult to integrate with other circuits due to variations in components, leading to noise and inefficiencies.
Innovation Solution
A switched capacitor notch filter circuit that reduces frequency location errors by sampling and filtering stages, uses clock-controlled switches to minimize power consumption, and introduces a switch to isolate the output, allowing for high-frequency notching with reduced noise performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional notch filters are implemented with precision amplifiers to reduce offsets, then frequency precision is improved, but power consumption increases and chip area requirements increase
Solution Approach 1:
The patent replaces traditional voltage-mode operational amplifiers with a current-mode switched capacitor implementation. This substitution eliminates the need for precision amplifiers, thereby reducing power consumption and chip area while maintaining frequency precision through the switched capacitor mechanism controlled by clock signals.
Solution Approach 2:
The patent employs periodic clock signals to control the switching of capacitors, creating a time-based filtering mechanism. This periodic action allows the circuit to achieve frequency-selective notching without requiring precision amplifiers, thus reducing power consumption while maintaining accurate frequency control through the clock signal parameters.
2Reliability
If traditional notch filters are implemented with precision amplifiers, then offset reduction is achieved, but device complexity increases
Solution Approach 1:
The patent replaces complex precision amplifiers with a simpler switched capacitor network controlled by clock signals. This substitution reduces device complexity by eliminating the need for high-precision analog components while maintaining offset reduction through the periodic switching mechanism that inherently rejects DC offsets.
Solution Approach 2:
The patent extracts and removes the precision amplifier component from the traditional notch filter architecture. By taking out this complex element and replacing it with a switched capacitor implementation, the device complexity is reduced while the essential function of offset reduction is maintained through the switching mechanism.
3Measurement precision
If traditional notch filters are implemented, then frequency attenuation is achieved, but integration with other circuits is difficult due to component variations
Solution Approach 1:
The patent changes the fundamental operating parameters from voltage-mode to current-mode operation with switched capacitors. This parameter change makes the filter characteristics dependent on clock frequency and capacitor ratios rather than absolute component values, thereby improving integration compatibility and reducing sensitivity to component variations while maintaining accurate frequency attenuation.
Solution Approach 2:
The patent introduces dynamic switching control through clock signals, making the filter characteristics adjustable and adaptable. This dynamic approach allows the filter to be integrated with other circuits with varying requirements, as the switching frequency and capacitor configurations can be adjusted to match different system requirements without being constrained by fixed component values.
4Speed
If traditional notch filters are implemented, then frequency notching is achieved, but noise performance deteriorates at high frequencies
Solution Approach 1:
The patent uses periodic clocked switching to achieve high-frequency operation with improved noise performance. The periodic action synchronizes the switching with the signal frequency, allowing for effective notching at high frequencies while the switched capacitor mechanism inherently filters out broadband noise, thereby improving noise performance at high frequency ranges.
Data Source
AI summary
Switched capacitor notch filter circuits are disclosed. An example switched capacitor notch filter circuit described herein includes a switched capacitor amplifier to receive an input signal and a first feedback signal, to amplify the input signal and the first feedback signal, and to output an output signal, a first integrator to receive the output signal and a second feedback signal, to integrate the output signal and the second feedback signal, and to output the first feedback signal, a second integrator to receive the first feedback signal, to integrate the first feedback signal, and to output the second feedback signal, a sample and hold to receive the output signal, to periodically store a value of the output signal, and to output the value of the output signal, and a first switch to couple the sample and hold to the output signal when the sample and hold is to store the value of the output signal and to isolate the sample and hold from the output signal when the sample and hold is to output the value of the output signal.