Directional Coupler With Variable Capacitor For Stable Coupling
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Solution Overview
Problem
Directional couplers in wireless communication devices face challenges in maintaining a stable degree of coupling due to variations in frequency and mounting state, leading to reduced directivity and inconsistent performance.
Innovation Solution
Incorporating a variable capacitor between the main line and sub-line, with a control terminal to adjust capacitance based on external signals, and positioning it close to both lines to minimize parasitic inductance and wiring length, allowing for stable coupling adjustment while maintaining a compact size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed magnitude capacitor is used between the main line and sub-line, then the directivity is improved by canceling capacitive coupling components, but the degree of coupling becomes unstable due to wiring resistance variations and frequency changes
Solution Approach 1:
The patent applies the dynamics principle by replacing the fixed capacitor with a variable capacitor that can dynamically adjust its capacitance value. The variable capacitor is controlled by a control circuit that receives feedback about the actual coupling degree, allowing the system to adapt to frequency changes and wiring variations to maintain stable coupling performance.
Solution Approach 2:
The patent implements feedback by using a control circuit that monitors the coupling degree between the main line and sub-line, compares it with a target value, and adjusts the variable capacitor's capacitance accordingly. This closed-loop control system ensures that the coupling degree remains stable despite external variations.
2Power
If the distance between the main line and sub-line is reduced to increase capacitance, then the coupling is enhanced, but the directivity degrades due to excessive capacitive coupling
Solution Approach 1:
The patent applies parameter changes by using a variable capacitor that can adjust its capacitance value to optimize the balance between coupling strength and directivity. Instead of fixing the distance between lines, the system dynamically adjusts the capacitance parameter to achieve the desired coupling level while maintaining high directivity.
3Adaptability or versatility
If the variable capacitor is positioned far from the main line and sub-line, then the adjustment range is larger, but parasitic inductance increases and coupling stability decreases
Solution Approach 1:
The patent applies local quality by positioning the variable capacitor in a specific location close to both the main line and sub-line, where it can effectively influence the coupling without introducing excessive parasitic inductance. This optimal positioning ensures both coupling stability and sufficient adjustment range.
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 achieves a stable degree of coupling between the main and sub-lines, even with varying factors, by reducing parasitic inductance and allowing for precise adjustment of coupling, thereby maintaining high directivity and compact size.
Implementation Method 1
a variable capacitor whose capacitance is varied in accordance with a control signal
Implementation Method 2
by way of magnetic coupling and capacitive coupling between the main line and the sub-line, part of a radio-frequency signal transmitted through the main line can be coupled with the sub-line
Implementation Method 3
by way of magnetic coupling and capacitive coupling between the main line and the sub-line
Data Source
AI summary
A directional coupler (10) includes a main line (20), a sub-line (40), and a variable capacitor (60). At least part of the sub-line (40) is disposed along the main line (20). The variable capacitor (60) is connected between the main line (20) and the sub-line (40). The directional coupler (10) achieves a stable degree of coupling between the main line (20) and the sub-line (40).