Frequency-Selective Glazing Coating for RF-Transparent Solar Control
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Solution Overview
Problem
Conventional glazing units, particularly in automotive and building applications, suffer from high reflectance for RF radiation due to solar control coatings, which impedes the transmission and reception of radio frequency signals, especially at higher frequencies, limiting indoor and outdoor coverage and posing health risks due to increased peak field exposure.
Innovation Solution
A glazing unit with a low RF reflectance coating system featuring frequency-selective decoated portions that create a dual band bandpass filter, allowing electromagnetic waves with different wavelength ranges to pass through, reducing loss attenuation for both horizontal and vertical polarizations, while maintaining the energy conserving properties of the coating system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a solar control coating system is applied to the glazing unit to reduce heat accumulation, then energy conservation is improved, but RF radiation reflectance increases causing signal transmission degradation
Solution Approach 1:
The coating system is segmented into multiple functional layers: a solar control coating layer for heat reduction and a frequency selective surface layer with conductive elements arranged in specific patterns. This segmentation allows each layer to perform its dedicated function - the solar control layer manages thermal energy while the FSS layer manages RF signal transmission, resolving the contradiction between heat rejection and RF transparency
Solution Approach 2:
The frequency selective surface introduces local variations in electrical properties through strategically placed conductive elements (patches, dipoles, or gratings) within the coating system. These localized conductive structures create frequency-dependent impedance characteristics that allow selective transmission of RF signals while maintaining overall solar control functionality, thus improving RF signal transmission without sacrificing heat reduction capabilities
2Temperature
If the coating system is made highly reflective for RF radiation to improve solar control, then heat reduction is improved, but antenna reception and transmission capability deteriorates
Solution Approach 1:
The coating system utilizes frequency-selective surfaces that change their electromagnetic response parameters based on incident wave frequency. By designing conductive elements with specific geometries, sizes, and spacing, the coating achieves high reflectance for solar frequencies (thermal control) while maintaining high transmittance for RF frequencies (antenna functionality), thus resolving the contradiction between temperature control and antenna operation
Solution Approach 2:
The coating system combines dissimilar materials with complementary properties: transparent conducting oxides or metal films for solar control, and patterned conductive elements (patches, dipoles, gratings) for frequency selection. This composite structure integrates thermal management and RF transmission functions into a single multi-functional coating layer, eliminating the need to choose between heat reduction and antenna performance
3Use of energy by stationary object
If conventional solar control coatings are used to block solar energy, then energy savings are improved, but RF signal penetration into buildings deteriorates
Solution Approach 1:
The frequency selective surface introduces dynamic electromagnetic interaction with incident waves through its patterned conductive elements. The structure's effective electrical properties change with frequency, allowing the coating to dynamically adapt its response - blocking solar/thermal radiation while permitting RF signal penetration. This dynamic frequency-dependent behavior resolves the contradiction between energy savings and indoor RF coverage
Solution Approach 2:
The frequency selective surface acts as an intermediary layer between the solar control coating and the interior space. It mediates the electromagnetic environment by selectively transmitting desired RF frequencies while blocking unwanted solar and thermal radiation, thus enabling both energy savings and reliable indoor RF coverage simultaneously
4Speed
If high-frequency electromagnetic waves are used to increase communication speed, then data transmission rate is improved, but transmission through coated glazing deteriorates due to broadband reflectance
Solution Approach 1:
The frequency selective surface is designed with conductive element dimensions and spacing parameters optimized for specific high-frequency bands including 5G and mmWave frequencies. By adjusting these geometric parameters, the coating maintains low reflectance and high transmittance for targeted high-frequency communication bands, enabling fast wireless communication through the glazing without suffering from broadband reflectance effects
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 enhances the transmission of waves with lower frequencies below 6 GHz and mmWave frequencies above 15 GHz, reducing loss attenuation by up to -10 decibels, thereby improving RF coverage and minimizing health risks associated with peak field exposure while maintaining the glazing unit's energy conserving properties.
Implementation Method 1
The FSS is a periodic structure that has been designed to reflect or transmit electromagnetic waves in a frequency selective manner
Implementation Method 2
allowing electromagnetic waves with different wavelength ranges to pass through
Implementation Method 3
a glazing unit may be coated with a coating system, for example a solar control coating system, that absorbs or reflects solar energy
Implementation Method 4
reduce the accumulation of heat in the interior of a building or vehicle
Implementation Method 5
Such coating systems, however, are typically electrically conductive and are high in reflectance for RF radiation
Data Source
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Figure 5~6
AI summary
The present invention discloses an improved a glazing unit comprising a glass panel which is low in reflectance for RF radiation, a coating system which is high in reflectance for RF radiation disposed on the said glass panel and creating onto the glazing unit a dual band bandpass filter. The glazing unit further comprises at least one frequencies selective decoated portion of the coating system extending along a plane, P, defined by a longitudinal axis, X, and a vertical axis, Z; having a width, DW, measured along the longitudinal axis, X, and a length, DL, measured along the vertical axis, Z. The at least one frequencies selective decoated portion comprising a first decoated element (31) comprising a plurality of unit cells (34) forming a regular grid of n rows by m columns unit cells, Um,n, m and n are positive integer higher than 5 (n > 5 and m > 5) forming three zones, zone A from U1,n to Ux,n, zone B from Ux+1,n to Uy,n and zone C from Uy+1,n to Um,n, x and y are positive integer respectively higher than 1 and x (x > 1 and y > x). The at least one frequencies selective decoated portion further comprises a plurality of second decoated elements wherein a second decoated element is placed in a unit cell of the first decoated element, wherein no second decoated element is in contact with the first decoated element and at least one unit cell of the first decoated element has no second decoated element. Zone A and zone C each have more second decoated elements than zone B.