Charge Domain Filter Bandwidth Compensation With SCN Mode Control
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Solution Overview
Problem
Conventional charge domain filters (CDFs) have narrow bandwidths and suffer from Sinc-function distortion due to the lack of bandwidth compensation circuits, limiting their effectiveness in signal processing.
Innovation Solution
The proposed CDF incorporates multiple switch-capacitor networks (SCNs) with amplifier stages and mode control signals to mitigate Sinc-function distortion, enabling bandwidth compensation through time-interleaving operations and impulse response mode settings, allowing for X-axis and Y-axis compensation in frequency response graphs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional charge domain filters are used without bandwidth compensation circuits, then the device complexity is reduced, but the bandwidth is narrow and Sinc-function distortion occurs
Solution Approach 1:
The filter is divided into multiple parallel SCN branches (first SCN, second SCN, third SCN, fourth SCN) with different impulse response modes. Each branch processes signals independently and their outputs are combined, allowing bandwidth expansion through parallel operation while maintaining manageable complexity in each individual branch
Solution Approach 2:
The patent introduces a new dimension of impulse response mode selection (FIR/IIR modes) for each SCN branch. By controlling mode signals to switch between different impulse response modes, the system achieves bandwidth compensation without significantly increasing the basic circuit structure, effectively adding a control dimension rather than purely structural complexity
2Speed
If multiple SCNs with different impulse response modes are used for bandwidth compensation, then the bandwidth is enhanced and Sinc-function distortion is mitigated, but the device complexity increases
Solution Approach 1:
Each SCN branch is designed to be multi-functional by incorporating mode control terminals that can switch between FIR and IIR impulse response modes. This universality allows the same hardware structure to perform different filtering functions, reducing the need for separate dedicated circuits for each mode and thereby limiting the increase in overall device complexity
Solution Approach 2:
The patent merges multiple SCN branches with different impulse response characteristics into a unified filter structure. The outputs of the first, second, third, and fourth SCNs are combined through summation to achieve bandwidth compensation. This merging approach allows the system to leverage the strengths of different SCN configurations without requiring entirely separate circuit implementations
3Manufacturing precision
If SCN capacitor areas are changed due to process variations, then manufacturing precision is affected, but the size ratios remain constant and filtering effect is preserved
Solution Approach 1:
The patent utilizes process variation itself as a design parameter by intentionally designing SCNs with different impulse response modes (FIR and IIR) that have complementary characteristics. Instead of trying to maintain exact capacitor values, the system changes the operational parameters (impulse response modes) to compensate for variations, allowing the filter to maintain stable performance across different manufacturing conditions
Data Source
AI summary
A charge domain filter (CDF) and a method thereof are provided. The CDF includes an amplifier, a first switch-capacitor network (SCN), a second SCN, a third SCN and a fourth SCN. Input terminals of the first and the second SCNs are coupled to first and second output terminals of the amplifier, respectively. Input and output terminals of the third SCN are coupled to output terminals of the first and the second SCNs, respectively. Input and output terminals of the fourth SCN are coupled to output terminals of the second and the first SCNs, respectively. A mode control terminal of the third SCN receives a first mode signal to set an impulse response mode of the third SCN. A mode control terminal of the fourth SCN receives a second mode signal to set an impulse response mode of the fourth SCN.