Transmission of infrared and visible wavelengths through energy-saving glass due to etching of frequency-selective surfaces

The transmission of infrared (IR) and visible frequencies through modern energy-saving glass, due to etching of bandpass frequency-selective surfaces (FSSs), is analysed. Energy-saving glass panels employ a very thin layer of metallic oxide on one side of the ordinary glass. Due to the presence of this layer, IR waves are attenuated whereas visible wavelengths can pass through, providing good see-through effect. However, one drawback with such energy-saving glass panels is that they also attenuate useful radio frequency (RF)/ microwave (MW) signals such as those used for mobile (e.g. global system for mobile communication (GSM)), global positioning system (GPS) and personal communication systems, due to the resistance of metallic oxide coating. To overcome this problem, an aperture-type bandpass FSS may be etched in the glass coating to selectively improve the transmission of useful signals. However, such an FSS also leads to an increase in overall IR transmission through energy-saving glass which is unwanted. In this study the authors analyse the effect of etching an FSS on the transmission of RF/MW, IR and light waves, for two types of commercial energy-saving glass panels. For example, an FSS with 8 mm aperture designed to improve MW transmission by 20 dB (from about -30 to -10 dB) at 1.3 GHz causes an increase in overall IR transmission from 23.8% to 33.8% (10%), which may be acceptable. An FSS with a narrower (4 mm) aperture improves MW transmission by 16 dB with 6.2% increase in IR transmission. Theoretical and measured results are presented.