Directional Coupler Impedance Tuning for Stable Directivity
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Solution Overview
Problem
Directional couplers with termination resistors connected to one end of the sub-line face instability in directivity and return loss due to varying resistance values and frequency-dependent performance.
Innovation Solution
A directional coupler with a variable termination circuit and a variable matching circuit connected to the sub-line, along with a control circuit using non-volatile memory to adjust impedance and attenuation, ensuring stable directivity and return loss across different frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a termination resistor is connected to one end of the sub-line, then the directional coupler can extract power of traveling waves, but the resistance value varies causing unstable directivity
Solution Approach 1:
The patent applies dynamics by replacing the fixed termination resistor with a variable termination circuit whose impedance can be adjusted. This allows the system to adapt to variations in resistance value and maintain stable directivity across different operating conditions and frequencies.
Solution Approach 2:
The patent changes the impedance parameter of the termination circuit from fixed to variable. By controlling the impedance value dynamically, the system compensates for manufacturing variations and maintains consistent directivity performance.
2Reliability
If correction of impedance is applied to each directional coupler, then directivity stabilizes, but the amount of correction varies causing return loss instability
Solution Approach 1:
The patent makes the matching circuit universal by designing it to handle both directivity correction and return loss stabilization functions. The same variable matching circuit and control mechanism address both issues, reducing overall system complexity.
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 more stable directivity and return loss compared to traditional directional couplers by dynamically adjusting impedance and attenuation, maintaining consistent performance across varying frequencies.
Implementation Method 1
a main line and a sub-line that are electromagnetically coupled to each other
Data Source
AI summary
A directional coupler includes a main line and a sub-line electromagnetically coupled to each other, a variable termination circuit that is connected to one end of the sub-line and that has a variable impedance, a variable matching circuit that is connected to the other end of the sub-line and that has a variable impedance or a variable attenuator that has a variable attenuation, and a control circuit that controls the impedance of the variable termination circuit and that controls the impedance of the variable matching circuit or the attenuation of the variable attenuator. The control circuit includes a non-volatile memory and controls the impedance of the variable termination circuit in accordance with data stored in the memory.