Adjustable Capacitor Control Circuit with Feedback Loop
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Solution Overview
Problem
BST capacitors used in radiofrequency applications face inaccuracies in capacitance control due to manufacturing tolerances, temperature variations, and hysteresis, which affect their performance in adapting to external environments.
Innovation Solution
A device comprising two paired capacitors with identical temperature variations and manufacturing dispersions, along with a control circuit that generates a bias voltage based on the capacitance of one capacitor to adjust the other, using a feedback loop to synchronize frequencies and reduce inaccuracies, includes an adjustable resistor and a temperature-stable reference capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a BST capacitor is used with adjustable capacitance, then adaptability to external environment is improved, but manufacturing precision and control accuracy deteriorate due to tolerances, temperature variations, and hysteresis
Solution Approach 1:
The patent implements a feedback mechanism where the control circuit monitors the actual capacitance value and adjusts the bias voltage accordingly to achieve the desired capacitance. This closed-loop control compensates for manufacturing tolerances, temperature variations, and hysteresis effects, resolving the contradiction between adaptability and manufacturing precision.
Solution Approach 2:
The patent changes the bias voltage parameter dynamically to adjust the capacitance value of the BST capacitor. By controlling the bias voltage within a specific range (2-20 volts), the system achieves adaptability while the control circuit ensures precision by compensating for variations through feedback.
2Adaptability or versatility
If a dedicated control circuit performs high voltage digital-to-analog conversion, then capacitance adjustment capability is improved, but control accuracy deteriorates due to manufacturing tolerances and temperature variations
Solution Approach 1:
The control circuit incorporates feedback from the actual capacitance measurement to adjust the digital-to-analog conversion process. This ensures that despite manufacturing tolerances and temperature variations in the DAC components, the final capacitance control accuracy is maintained through continuous correction.
Solution Approach 2:
The patent replaces traditional mechanical adjustment methods with electronic digital-to-analog conversion controlled by a microcontroller. This substitution improves adjustability while the embedded feedback mechanism compensates for the reduced precision of electronic components.
3Adaptability or versatility
If BST capacitors are used in mobile telephony applications, then communication functionality is improved, but performance deteriorates due to inaccuracies in capacitance control
Solution Approach 1:
The feedback mechanism continuously monitors and corrects capacitance deviations, ensuring reliable performance in mobile telephony applications. This resolves the contradiction by maintaining communication functionality while compensating for control inaccuracies that would otherwise degrade reliability.
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 solution achieves precise control of capacitance, reducing inaccuracies to the order of a percent, enabling efficient use in multi-standard mobile telephony terminals with smaller, more precise radio frequency filters.
Implementation Method 1
a first capacitance capacitor adjustable to a set value by application of a bias voltage; a second capacitance capacitor adjustable to a setpoint value by application of a bias voltage
Implementation Method 2
a feedback loop adapted to adjust the bias voltage to slaving the first frequency to a second reference frequency
Data Source
Figure 1~2
AI summary
The invention relates to a device comprising: a first capacitor (CV) with adjustable capacitance set to a reference value by application of a bias voltage (VBIAS); a second capacitor (CV') with adjustable capacitance set to a reference value by application of a bias voltage, the second capacitor (CV') being arranged to receive the same bias voltage (VBIAS) as the first capacitor (CV); and a control circuit (121) adapted to receive said reference value and to generate said bias voltage (VBIAS) taking into account a quantity representative of the capacitance of the second capacitor (CV').