Gm-C Filter Capacitance Tuning via Integrator-Based Voltage Comparison
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Solution Overview
Problem
The existing Gm-C filter tuning methods, particularly those using a Phase-Locked Loop (PLL) structure, face challenges in precision due to the linearity changes with tail current variations, affecting the filter's performance.
Innovation Solution
A method and system that generate a current to charge an integrator, simulate a capacitor within a given time, compare integral voltage with a reference voltage, and adjust a control code to determine the tuning capacitance, ensuring linear discrete tuning without affecting the filter's linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a PLL structure is used to regulate the tail current for frequency tuning, then the filter frequency can be tuned, but the linearity of the filter changes with the tail current variations, affecting tuning precision
Solution Approach 1:
The patent introduces an integrator as an intermediary component between the tail current and the capacitor array. The integrator converts the current signal into a voltage signal that linearly controls the capacitance selection, eliminating the non-linear relationship between tail current and filter frequency. This mediator (integrator) transforms the control mechanism from direct current modulation to integrated voltage control, achieving linear tuning.
Solution Approach 2:
The patent replaces the direct electrical control mechanism (tail current modulation) with an integrated control mechanism (integrator output voltage). By substituting the direct current control with an integration-based voltage control system, the non-linear electrical relationship is transformed into a linear control relationship, improving tuning precision.
2Adaptability or versatility
If the tail current is varied for frequency tuning, then the filter frequency can be adjusted, but the linearity changes and filter performance is affected
Solution Approach 1:
The integrator serves as a mediator that decouples the direct relationship between tail current variations and filter frequency. By introducing this intermediate integration stage, the system achieves frequency adjustability while maintaining stable filter performance, as the integrator output provides linear control independent of tail current non-linearities.
3Device complexity
If discrete currents are used to control Gm value, then the circuit can be simplified, but it is hard to control the cut-off frequency precisely due to non-proportional relationship
Solution Approach 1:
The patent replaces the direct discrete current control of Gm with an integrated voltage control system. The integrator converts the current input into a linear voltage output that precisely controls the capacitor array selection, maintaining circuit simplicity while achieving precise cut-off frequency control through the integration mechanism.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the precision of Gm-C filter tuning without altering the filter's performance by maintaining linearity, allowing for precise capacitance adjustment.
Implementation Method 1
integrating a simulated capacitor of the Gm-C filter within a given time when the integrator is charged wherein the simulated capacitor simulates the capacitor of the Gm-C filter which is set to a capacitor array
Implementation Method 2
comparing the integral voltage obtained by integrating the simulated capacitor with a preset reference voltage, finding a simulated capacitance of the simulated capacitor that makes the integral voltage equal to the reference voltage via gradual approaching by adjusting a control code
Data Source
AI summary
The present invention discloses a method, apparatus and system for obtaining the tuning capacitance of a Gm-C filter. The method includes: integrating a simulated capacitor within a given time via a current, where the simulated capacitor simulates the capacitor of the Gm-C filter which is set to an even capacitor array; and comparing the integral voltage obtained by the integration with the reference voltage, finding a simulated capacitance that makes the integral voltage equal to the reference voltage via gradual approaching by adjusting a control code, and determining the simulated capacitance as the tuning capacitance. The present invention improves the performance of a Gm-C filter without affecting the performance of the Gm-C filter.