Developments in the electronics industry have led to the widespread use of radio-frequency (RF) devices in various areas, including telecommunication, radio and television broadcasting, radar, industrial processing, medical applications and consumer products. Electromagnetic fields extend over large areas when generated for communication, broadcasting and radar devices, but generally spread only over small areas when used in industrial, medical and consumer devices. In many modern applications leakage of low amounts of RF and microwave radiation is very harmful. Keeping exposure levels at the allowed range calls for RF and microwave shielding around radiation emitting sources. These are usually conductive metal enclosed volumes. However, for visible light admitting windows in these volumes a different solution is needed in the sort of a transparent RF, IR and microwave shielding.
Electromagnetic radiation used for modern communications (wireless LAN, mobile phones) may contain sensitive information which is prone to potential interception by third parties because radiation spatially extends over the office building area where it is generated. Typically the office windows are the weak link in communication protection i.e. against IR-laser based directional microphones and poor RF shielding. There is a demand for sensitive compartmented information facilities that include measures to protect information from leaking through windows. A transparent spectrally selective window foil will prevent sensitive information from leaking and interception by third parties.
The goal of this project is the development of an RF shielding window film, which is not only transparent but also spectrally selective. It allows visible light into the room while blocking other specific wavelengths of the electromagnetic spectrum (i.e. infrared part of the solar spectrum, thus making it energy efficient). We propose a dedicated design to overcome the conflict between the transparency requirement of a window and thick conductive metal layer (opaque) providing a good RF shielding.
The project outcome will be a prototype film with the following preliminary specifications:
UV Transmission (<380nm) < 1%
IR Transmission (800-1500nm) < 1%
RF (30MHz …) > 46dB
VLT (400-780nm) > 53%
Visible Light Reflectance ~13%
Total Solar Energy Rejected ~70%
Shading coefficient ~0.32
Solar Heat Gain Coefficient ~0.27
Proposed work plan:
1. Design of a prototype film according to the specifications above (new product):
The design phase will include, as a first phase, utilization of existing simulations developed in KiloLambda Ltd. for the spectrally selective window film. The second step will be an adaptation of those simulations for the designing of the RF shielding properties. The next phase will include definition of the layers structure, according to material types and layers thicknesses. Design parameters will refer to roll-to-roll production process.
2. Prototype manufacturing (new process):
Manufacturing processes of the prototype configurations will be developed by KiloLambda and Haverkamp GmbH, utilizing small-scale roll-to-roll process. Application of layers by dry and\or wet coating techniques will be considered, in terms of film performances and production cost. Finally, films will be laminated for coating protection to increase environmental resistance.
3. Tests and analysis:
Each prototype configuration will be tested for functionality, regarding spectrally selective characterization, using spectrophotometer in transmission and reflection. Tests of RF shielding performances will be performed as well. All configurations will be submitted to environmental tests.
Analysis of tests results will refer to the overall performances of prototype optical, RF and environmental characteristics.
- Spectrally selective window film with RF shielding prototype with the above specifications.
- Simulation of spectrally selective coating with adaptation for RF shielding.
- Roll-to-roll production process in moderate cost development and testing.
- Lamination procedure development for increasing environmental resistance.