Non-Uniform TEM-Mode Directional Coupler for Constant Impedance
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Solution Overview
Problem
Traditional transverse electromagnetic mode directional couplers with longer coupling sections than a quarter wavelength at the center frequency do not maintain constant even-mode and odd-mode impedances along the length, leading to aperiodic high-pass properties and non-uniform coupling, which affects phase properties and coupling consistency across ports.
Innovation Solution
The directional coupler features inner and outer electrical conductors that are electromagnetically coupled via transverse electromagnetic mode radiation, with varying cross-sectional dimensions and tapered shapes to maintain constant even-mode and odd-mode impedances, allowing for uniform electrical properties despite physical non-uniformity, enabling seamless transitions and cascaded connections without additional decoupling means.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the coupling section length is increased beyond quarter wavelength at center frequency, then the coupling bandwidth is extended, but the even-mode and odd-mode impedances become non-constant along the length, causing aperiodic high-pass properties and non-uniform coupling
Solution Approach 1:
The patent applies local quality by varying the cross-sectional dimensions of conductors at different positions along the coupling section. Specifically, the width of center conductors and/or the spacing between them are adjusted locally to compensate for the natural impedance variations that occur in longer coupling sections, thereby maintaining constant even-mode and odd-mode impedances throughout the structure while achieving extended bandwidth
Solution Approach 2:
The patent changes physical parameters (cross-sectional dimensions of conductors) along the length of the coupling section to maintain electrical uniformity. By continuously or discretely adjusting conductor widths and/or spacings, the design compensates for the frequency-dependent impedance variations that would otherwise occur in longer coupling sections, enabling both extended bandwidth and constant impedance characteristics
2Stability of the object's composition
If the cross-sectional dimensions of conductors are varied along the length, then the physical uniformity is reduced, but the electrical uniformity (constant even-mode and odd-mode impedances) is maintained
Solution Approach 1:
The patent deliberately introduces local variations in conductor cross-sectional dimensions (width and/or spacing) at specific positions along the coupling section. These localized geometric modifications are designed to compensate for electromagnetic field distribution changes, thereby maintaining constant even-mode and odd-mode impedances despite the overall physical non-uniformity of the structure
3Ease of manufacture
If traditional uniform geometry is used, then the manufacturing is simpler, but the coupling properties become non-uniform in longer sections, affecting phase properties and coupling consistency
Solution Approach 1:
The patent implements local variations in conductor dimensions (width and/or spacing) at strategically positioned sections along the coupling structure. These localized geometric adjustments are designed to maintain constant even-mode and odd-mode impedances throughout the coupling section, ensuring uniform coupling properties and consistent phase characteristics across the entire structure, while the variations are sufficient to achieve this goal without requiring completely complex geometries
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 design ensures constant coupling properties and near-ideal electrical performance by maintaining even-mode and odd-mode impedances, preventing abrupt coupling interruptions and enabling wideband performance in cascaded arrangements without electrical or mechanical complexity.
Implementation Method 1
The first and the second inner electrical conductor and the outer electrical conductor are adapted to be electromagnetically coupled via transverse electromagnetic mode radiation
Data Source
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AI summary
The invention relates to a Directional coupler (100) with at least a first (102) and a second (104) inner electrical conductor and one outer electrical conductor (106), the outer electrical conductor surrounding the first and the second inner electrical conductor, wherein the first and the second inner electrical conductor and the outer electrical conductor are adapted to be electromagnetically coupled via transverse-electromagnetic-mode radiation, wherein an even-mode impedance and an odd-mode impedance are constant along the length of the first and the second inner and the outer electrical conductor, and wherein the cross-sectional dimensions of the first and the second inner and the outer electrical conductor vary over the length of the first and the second inner and the outer electrical conductor.