Waveguide Phase Stability via Rotating Invar Ribs
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Solution Overview
Problem
Waveguides in multiplexer-demultiplexers, especially those made of aluminum, experience significant phase shifts due to temperature variations, leading to equipment malfunctions like channel mismatches, as existing compensation methods require heavy Invar plates increasing device mass.
Innovation Solution
A mechanical compensation device with offset, cut longitudinal ribs made of low thermal expansion materials like Invar, which rotate to deform the short sides of the waveguide, ensuring phase stability without the need for extensive Invar plates, using bimetallic strips or straps to manage thermal expansion differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Invar plates are used to compensate thermal expansion, then phase stability is improved, but device mass increases
Solution Approach 1:
The waveguide structure is segmented by introducing longitudinal ribs that are offset from the median axis of the short sides. These ribs act as independent deformation elements that can rotate on their own axes, allowing localized compensation of thermal expansion effects without requiring a complete Invar plate structure.
Solution Approach 2:
The invention changes the physical state and configuration of the waveguide by allowing the longitudinal ribs to rotate on themselves. This rotation parameter change enables the ribs to deform the short sides of the waveguide, compensating for thermal expansion-induced phase shifts without adding significant mass.
2Weight of stationary object
If aluminum waveguides are used to reduce device mass, then device mass is reduced, but phase stability deteriorates due to thermal expansion
Solution Approach 1:
The aluminum waveguide structure incorporates longitudinal ribs that automatically compensate for its own thermal expansion. The ribs, made of low thermal expansion material, rotate on themselves in response to temperature changes, self-correcting the phase shifts caused by aluminum's high coefficient of thermal expansion without external intervention.
Solution Approach 2:
The waveguide structure combines aluminum (high thermal expansion) with Invar or other low thermal expansion materials for the longitudinal ribs and rotating elements. This composite approach allows the majority of the structure to be lightweight aluminum while the critical compensation elements use low-expansion materials to maintain phase stability.
3Stress or pressure
If the coefficient of thermal expansion of the manifold is homogenized with the equipment, then mechanical stress is reduced, but phase compensation capability is limited
Solution Approach 1:
The longitudinal ribs are designed to rotate dynamically on their own axes in response to temperature changes. This dynamic rotation allows the ribs to actively compensate for thermal expansion effects on the waveguide phase, providing adaptability to temperature variations while maintaining structural integration with the aluminum manifold.
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 solution effectively compensates for thermal expansion-induced phase shifts in waveguides, maintaining stability and reducing mechanical stress without increasing the device's mass, by adjusting the electrical lengths of the waveguide to correct phase shifts.
Implementation Method 1
the means for rotating the longitudinal rib consist of a bimetallic strip comprising at least the little thermodeformable element, having the second coefficient of thermal expansion, and an additional element having a third coefficient of thermal expansion greater than the second coefficient of thermal expansion
Implementation Method 2
the temperature variations can be significant. As these manifolds can typically be made of aluminium, whose coefficient of thermal expansion (or CTE for Coefficient of Thermal Expansion) is 23 ppm, the deformations induced by these temperature variations are such that phase shifts are introduced into the guided waves
Data Source
Figure 1
Figure 2a~2b
Figure 3a
AI summary
A compensated waveguide device comprises waveguide having first coefficient of thermal expansion (CTE) comprising long sides (6, 7), short sides (4, 5) having median axis and longitudinal ribs (2, 3) having surface common with over 1/2 width of short side and being off-axis relative to median axis to cut in body of waveguide, and rotation unit in contact with longitudinal rib to deform short side. The rotation unit comprises prongs (8, 9, 10, 11) of low thermal deformability having second CTE smaller than first CTE by a factor >= 5 and a brace and frame (12) having CTE larger than second CTE.