Charge-Domain Filter Bandwidth Compensation for Sinc Distortion
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Solution Overview
Problem
Switch-capacitor networks used in charge-domain filters face challenges in maintaining consistent filtering effects due to fabrication process variations, leading to issues with bandwidth compensation and Sinc-function distortion.
Innovation Solution
A charge-domain filter (CDF) with a bandwidth compensation circuit that includes a configurable power-reference cell (CPC) and a programmable-delay cell (PDC), which perform power sensing and delay adjustments to compensate for frequency and power variations, allowing for flexible X-axis and Y-axis compensation in the frequency response diagram.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If switch-capacitor networks are used in charge-domain filters, then filtering effects are determined by capacitor area ratios which remain stable against fabrication variations, but bandwidth compensation and Sinc-function distortion removal become difficult
Solution Approach 1:
The patent introduces dynamic elements including a bandwidth compensation circuit with variable capacitors that can adjust capacitance values, and a delay element with programmable delay time. These dynamic components allow the filter to adapt its frequency response and compensate for bandwidth variations while maintaining the stable filtering effect provided by the switch-capacitor networks.
Solution Approach 2:
The patent changes key parameters of the system by introducing variable capacitors whose capacitance can be adjusted, and a delay element with programmable delay time. These parameter changes enable the filter to achieve bandwidth compensation and remove Sinc-function distortion while preserving the manufacturing precision benefits of the original switch-capacitor architecture.
2Stability of the object's composition
If fixed switch-capacitor networks are used, then fabrication process variations do not affect capacitor size ratios and filtering effect, but flexibility in adjusting frequency response and bandwidth is limited
Solution Approach 1:
The patent maintains the stable capacitor size ratios of the fixed switch-capacitor networks while adding dynamic adjustment capabilities through variable capacitors in the bandwidth compensation circuit and a programmable delay element. This combination preserves the manufacturing stability while enabling frequency response adjustment.
Solution Approach 2:
The patent segments the filter into distinct functional modules: the fixed switch-capacitor networks for stable filtering, variable capacitors for bandwidth compensation, and a programmable delay element for frequency adjustment. This segmentation allows each component to perform its specialized function while working together to achieve both stability and adaptability.
3Device complexity
If no bandwidth compensation circuit is used, then the filter structure remains simple, but Sinc-function distortion cannot be removed and bandwidth varies with fabrication processes
Solution Approach 1:
The patent implements a bandwidth compensation circuit that provides feedback to adjust and stabilize the filter's frequency response. The circuit monitors the actual frequency response and uses variable capacitors to compensate for deviations, ensuring consistent bandwidth performance across different fabrication processes while maintaining reasonable structural complexity.
Data Source
AI summary
A charge domain filter (CDF) and a bandwidth compensation circuit of the CDF are provided. The CDF includes an amplifier, a plurality of switch-capacitor networks (SCNs), a connector, a current adder (CA) and a bandwidth compensation circuit. A first input terminal of the amplifier receives an input signal, and an output terminal thereof is connected to input terminals of the SCNs. The connector is connected between the output terminal of the SCNs and the CA for configuring coupling status of the output terminals of the SCNs and input terminals of the CA. The bandwidth compensation circuit senses a portion of or all of the output terminals of the SCNs and the CA, and outputs the sensing result to a second input terminal of the amplifier.