Directional Coupler Impedance Segmentation for Directivity
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Solution Overview
Problem
Conventional directional couplers experience degradation in isolation characteristics and directivity when bent, and when coupled line impedance is lower than terminal impedance due to manufacturing constraints.
Innovation Solution
A directional coupler design with a first coupler having a lower coupled line impedance and a second coupler with higher coupled line impedance, where the isolations of both couplers have equal amplitudes and nearly opposite phases, canceling each other out to maintain isolation characteristics and improve directivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the coupled line impedance is lower than the terminal impedance due to manufacturing constraints, then the coupling amount is maximized, but the passing phase at even mode operation leads against that at odd mode operation, causing directivity degradation
Solution Approach 1:
The directional coupler is divided into two separate coupled lines: a first coupled line with impedance lower than terminal impedance and a second coupled line with impedance higher than terminal impedance. This segmentation allows each coupled line to have different impedance characteristics, enabling the system to achieve both high coupling amount and good directivity by combining their effects.
Solution Approach 2:
Different coupled lines are assigned different impedance characteristics tailored to their specific functions. The first coupled line uses lower impedance to maximize coupling amount, while the second coupled line uses higher impedance to compensate for phase differences and maintain directivity. This local differentiation of properties resolves the contradiction between coupling efficiency and directivity.
2Volume of moving object
If the two coupled lines are bent for downsizing, then the size is reduced, but a difference occurs between the passing phase in the bent portion at even mode operation and that at odd mode operation, causing directivity degradation
Solution Approach 1:
The directional coupler structure is segmented into two coupled lines with different impedance characteristics. When bending is required for downsizing, the second coupled line with higher impedance serves as a compensation mechanism that counteracts the phase differences introduced by the bent structure, thereby maintaining directivity despite the size reduction.
Solution Approach 2:
The impedance parameter of the coupled lines is changed to achieve different functional effects. By setting the second coupled line's impedance higher than the terminal impedance, the system compensates for phase shifts caused by bending, allowing the directional coupler to maintain good directivity even in a compact, bent configuration.
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 design effectively avoids degradation of isolation characteristics and maintains good directivity even with a bending structure and lower coupled line impedance relative to terminal impedance, enhancing the performance of the directional coupler.
Implementation Method 1
a first coupler provided with a first main signal line conductor and a first secondary signal line conductor arranged in parallel with the first main signal line conductor
Data Source
AI summary
Disclosed is a directional coupler including a broadside coupled line 1031 provided with a main signal line conductor 1001 and a secondary signal line conductor 1011 arranged in parallel with the main signal line conductor 1001, and an offset broadside coupled line 1032 provided with a main signal line conductor 1002 having an end portion connected to an end portion of the main signal line conductor 1001 and a second secondary signal line conductor 1012 having an end portion connected to an end portion of the secondary signal line conductor 1011, and arranged in parallel with the main signal line conductor 1002, in which a coupled line impedance in the broadside coupled line 1031 is lower than a terminal impedance and a coupled line impedance in the offset broadside coupled line 1032 is higher than the terminal impedance.