Transparent RF Planar Transmission Lines
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Solution Overview
Problem
Existing microwave transmission lines are opaque to visible light due to thick conductive materials, making them unsuitable for applications requiring transparency, such as covert communication systems.
Innovation Solution
A microwave transmission line with a dielectric substrate and a microstrip constructed of transparent materials, where the conductive film forming the ground plane has a thickness less than one skin depth, allowing the structure to be substantially transparent to visible light while maintaining conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conductive film thickness is increased to improve electrical conductivity and signal transmission efficiency, then the transmission line becomes opaque to visible light
Solution Approach 1:
The patent changes the thickness parameter of the conductive film from conventional thick layers (greater than five skin depths) to ultrathin layers (less than one skin depth, typically 3-30 nanometers). This parameter change allows the film to remain electrically conductive while becoming substantially transparent to visible light, resolving the contradiction between signal transmission efficiency and optical transparency
Solution Approach 2:
The patent employs composite material structures combining ultrathin conductive films with dielectric substrates and protective overcoats. The conductive film is integrated into a multi-layer composite structure that maintains electrical functionality while achieving optical transparency, allowing the transmission line to satisfy both electrical and optical requirements simultaneously
2Illumination intensity
If the conductive film thickness is reduced to achieve optical transparency, then the electrical conductivity and transmission efficiency deteriorate
Solution Approach 1:
The patent optimizes the thickness parameter to be greater than zero but less than one skin depth (typically 3-30 nm), which is counterintuitive compared to conventional practice. This precise parameter control enables the ultrathin film to maintain sufficient electrical conductivity for microwave transmission while achieving substantial optical transparency, thus resolving the contradiction between transparency and electrical performance
Solution Approach 2:
The patent replaces conventional thick metal ground planes with ultrathin conductive films deposited on dielectric substrates. This substitution fundamentally changes the structural approach from bulk metal to thin-film technology, enabling both optical transparency and adequate electrical conductivity to be achieved simultaneously
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 enables the use of microwave transmission lines in applications requiring transparency, such as covert antennas and circuits, with minimal visual interference despite reduced efficiency.
Implementation Method 1
the thickness of the microstrip typically is greater than five skin depths corresponding to the operating frequency of the transmission line and in which one skin depth is the distance penetrating into a signal conductor at which the alternating current density has exponentially decayed to 1/e of the value at the surface
Implementation Method 2
a dielectric substrate having two spaced apart, planar and parallel upper and lower sides... The substrate itself is constructed of a material that is transparent to visible light
Data Source
AI summary
A high radio frequency transmission line having a dielectric substrate with two sides and constructed of a transparent material. An electrically conductive strip extends along at least a portion of one side of the substrate. An electrically conductive film is deposited on one of the sides of the substrate at a position spaced from the conductive strip. This conductive film has a thickness sufficiently small so that the film is substantially transparent.