Charge-Domain Filter Bandwidth Compensation for Folding Noise
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Solution Overview
Problem
Charge-domain filters (CDFs) face issues with folding noise and narrower bandwidth due to decimation and lack of bandwidth compensation, leading to sinc-function distortion.
Innovation Solution
Incorporating a bandwidth compensation network (BCN) that senses signals from the switched-capacitor network (SCN) and output-signal combination network (OSCN) to generate feedback or forward signals for bandwidth compensation, improving frequency and power response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If decimation and sampling are performed in the average CDF, then the filtering function is achieved, but folding noise is generated and system performance is reduced
Solution Approach 1:
The patent implements feedback paths that feed back a portion of the output signal to the input stage. This feedback mechanism allows the system to compensate for the folding noise generated by decimation and sampling, thereby maintaining system performance while achieving the filtering function.
Solution Approach 2:
The patent changes the parameter of bandwidth by introducing a bandwidth compensation network that adjusts the frequency response. This parameter change allows the system to operate effectively despite the folding noise introduced by decimation.
2Device complexity
If no bandwidth compensation circuit is used in the average CDF, then the circuit complexity is reduced, but the bandwidth becomes narrower and sinc-function distortion occurs
Solution Approach 1:
The patent introduces a bandwidth compensation network that dynamically adjusts the bandwidth parameter of the filter. By changing the bandwidth parameter through feedback paths and adjustable components, the system achieves wider bandwidth and reduced sinc-function distortion while maintaining reasonable circuit complexity.
Solution Approach 2:
The patent makes the bandwidth compensation dynamic by using feedback paths that continuously adjust the filter characteristics based on the input and output signals. This dynamic adjustment allows the bandwidth to be optimized for different operating conditions.
3Manufacturing precision
If the SCN filters the input signal by controlling capacitor charge storage, then the filtering effect is determined by capacitor size ratio which is process-independent, but the bandwidth is limited and sinc-function distortion occurs
Solution Approach 1:
The patent changes the bandwidth parameter by adding a bandwidth compensation network that works in conjunction with the fixed capacitor ratio filter. This allows the filtering effect to remain process-independent while the bandwidth is dynamically adjusted to compensate for limitations.
Solution Approach 2:
The patent introduces an intermediary bandwidth compensation network that mediates between the fixed capacitor ratio filter and the output. This intermediary stage adjusts the frequency response to widen the bandwidth and reduce distortion without affecting the process-independent filtering characteristics of the SCN.
Data Source
AI summary
A charge-domain filter (CDF) apparatus and an operation method thereof are provided. The CDF apparatus includes an input-signal combination network (ISCN), a switch-capacitor network (SCN) module, an output-signal combination network (OSCN), and a bandwidth compensation network (BCN). The input terminal of the ISCN receives an input signal. The SCN module is connected between the ISCN and the OSCN. The OSCN outputs an output signal of the CDF apparatus. The BCN senses the signal of the SCN module, senses the signal of the OSCN, or senses the signal of each of the SCN module and the OSCN, and correspondingly generates a forward signal or a feedback signal for the ISCN or the OSCN according to the sensing result to perform bandwidth compensation.