Variable Capacitance Element With Ferroelectric Film And Resistor Network
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Solution Overview
Problem
Existing NFC module antenna circuits face challenges in adjusting resonant frequency due to size constraints and reliability issues, particularly with active elements causing distortion and increased IC size, as well as complexity and mechanical reliability concerns with trimmer capacitors.
Innovation Solution
A high-frequency device incorporating a variable capacitance element with ferroelectric capacitors and a control voltage application circuit using resistance voltage dividers, eliminating the need for active switches and simplifying circuit architecture, while ensuring reliable frequency adjustment without mechanical control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable-capacitance diodes and switching circuits are provided to adjust resonant frequency, then frequency adjustment capability is improved, but circuit complexity and IC size increase
Solution Approach 1:
The patent extracts and eliminates the switching circuit component from the frequency adjustment mechanism. Instead of using active switches to select different capacitance values, the invention uses a passive resistor network that directly divides the control voltage to achieve continuous capacitance variation in the variable capacitance element, thereby removing the complexity of switching control logic.
Solution Approach 2:
The patent replaces the mechanical/electronic switching system with an electrical voltage division system. The resistor network passively divides the control voltage according to predetermined ratios, eliminating the need for active switching elements and their associated control circuits, thus reducing overall device complexity.
2Measurement precision
If multiple capacitors and switches are used to adjust capacitance in fine steps, then frequency adjustment precision is improved, but IC size increases
Solution Approach 1:
The patent changes the control parameter from discrete capacitor selection to continuous voltage division. By varying the control voltage applied to the variable capacitance element through different resistor ratio combinations, the system achieves fine frequency adjustment steps without requiring multiple discrete capacitor components, thus reducing IC area.
Solution Approach 2:
The resistor network serves multiple functions simultaneously: it divides control voltage into multiple predetermined ratios, provides impedance matching, and eliminates the need for separate switching circuits. This multi-functionality reduces the total component count and IC size while maintaining frequency adjustment precision.
3Adaptability or versatility
If active elements are used for frequency adjustment, then frequency adaptability is improved, but signal distortion increases
Solution Approach 1:
The patent uses passive resistor elements instead of active switching elements. These passive components do not introduce the non-linear effects and signal distortion associated with active elements like transistors or diodes in switching mode. The resistors simply divide voltage linearly, maintaining signal integrity while providing frequency adjustment capability.
4Adaptability or versatility
If trimmer capacitors are used for mechanical capacitance adjustment, then frequency adjustment is achieved, but device reliability under mechanical stress decreases
Solution Approach 1:
The patent completely replaces the mechanical trimmer capacitor adjustment mechanism with an electrical voltage division system. The resistor network electronically controls the capacitance of the variable capacitance element through voltage division, eliminating all moving parts and mechanical components that would be vulnerable to impact and mechanical stress, thereby significantly improving device 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
The solution provides stable and reliable frequency adjustment without distortion, reduces IC size, and simplifies circuit architecture, ensuring robustness against mechanical stress and size constraints.
Implementation Method 1
a capacitance value changes according to a value of a control voltage applied between the capacitor electrodes
Implementation Method 2
a control voltage application circuit including a resistance voltage divider circuit including a plurality of resistance elements having different resistance values
Data Source
AI summary
A high-frequency device includes an antenna coil, a variable capacitance element, and an RFIC. The variable capacitance element is configured by capacitor units in each of which a ferroelectric film is sandwiched between capacitor electrodes, and a capacitance value changes according to a control voltage applied between the capacitor electrodes. A control voltage application circuit configured by a plurality of resistance elements of different resistance values, and a resistance element of the variable capacitance element unit configured to apply a control voltage to the variable capacitance element are arranged in a layered manner above the capacitor unit. Thus, a variable capacitance element and a high-frequency device that includes a control voltage application circuit eliminating problems such as distortion due to active elements and growing IC size along with complication of circuit architecture, and ensuring reliability on impact due to falling or the like, are provided.