Flat RF Transmission Line for Thin Profile Installation
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Solution Overview
Problem
Conventional RF cables are too thick to fit under energy-efficient windows or doors, and they struggle to efficiently transmit both RF signals and DC power without causing thermal issues due to current limitations, which can lead to installation challenges and safety hazards.
Innovation Solution
A thin, flat RF cable design featuring a stripline configuration with conductive layers and a center conductor, incorporating an RF choke element to separate DC and RF signals, allowing for high current capacity while maintaining a thin profile, and utilizing capacitive coupling for shielding to prevent electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional RF cables are used, then RF signal transmission is achieved, but the cable thickness prevents installation under energy-efficient windows or doors
Solution Approach 1:
The patent transitions from conventional round cable geometry to a flat planar geometry, effectively changing the dimensional orientation of the cable cross-section. This allows the cable to fit in spaces where traditional radial symmetry would fail, enabling installation under thin window panes while maintaining all necessary conductive and dielectric layers for RF transmission.
Solution Approach 2:
The cable is segmented into distinct functional layers including center conductor, dielectric material, shield layers, and outer jacket, with each layer optimized for its specific function. This segmentation allows precise control over cable thickness while maintaining RF performance characteristics and enabling the flat profile necessary for installation under energy-efficient windows.
2Power
If high current capacity is achieved for DC power transmission, then power delivery is improved, but thermal issues and safety hazards increase
Solution Approach 1:
The patent introduces an RF choke element as an intermediary component that separates DC power transmission from RF signal transmission pathways. This choke allows DC current to pass through the center conductor to the outdoor unit while blocking RF signals from entering the DC power line, preventing interference and enabling independent optimization of both power and signal paths for thermal management.
Solution Approach 2:
Different sections of the cable are assigned different functional qualities: the center conductor is optimized for DC power carrying with appropriate gauge and material, while the shield layers are optimized for RF shielding, and the dielectric material provides both electrical isolation and thermal management. This local optimization allows high current capacity in the power path while managing thermal distribution across the cable structure.
3Reliability
If RF signals are transmitted through the cable, then communication functionality is achieved, but electromagnetic interference increases without proper shielding
Solution Approach 1:
The cable employs composite construction with multiple shield layers (including braided shield and foil shield) combined with dielectric materials of specific permittivity values. This composite structure creates effective electromagnetic shielding that contains RF signals within the cable, preventing interference with external devices while maintaining signal integrity for reliable communication.
4Volume of moving object
If a thin profile is achieved for the cable, then installation flexibility is improved, but current-carrying capability may be reduced
Solution Approach 1:
The patent redistributes the current-carrying cross-sectional area from a radial configuration to a planar configuration. The flat cable maintains adequate current capacity by spreading conductive materials across the width of the cable rather than concentrating them in a circular cross-section, achieving both thin profile and sufficient power transmission capability.
Solution Approach 2:
The patent specifies particular parameter ranges for conductor width, dielectric thickness, and shield layer configuration to optimize the balance between cable thickness and current capacity. By carefully controlling these parameters, the cable achieves a thin profile suitable for installation under windows while maintaining the current-carrying capability necessary for DC power transmission to outdoor units.
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
Enables efficient transmission of RF signals and DC power with high current capacity in a thin profile, reducing installation damage and thermal risks, and providing improved electromagnetic interference immunity.
Implementation Method 1
an RF choke element that conducts a direct current signal between the center conductor and the second conductive layer
Implementation Method 2
dielectric material disposed between the first conducive layer and the second conductive layer
Implementation Method 3
capacitive coupling for shielding to prevent electromagnetic interference
Data Source
AI summary
A radio frequency (RF) transmission line includes a first conductive layer, a second conductive layer conductively isolated from the first conductive layer, a center conductor disposed between the first conductive layer and the second conductive layer, dielectric material disposed between the first conducive layer and the second conductive layer and at least partially surrounding the center conductor, and an RF choke element that conducts a direct current signal between the center conductor and the second conductive layer.