Glass Characterization for Designing Frequency Selective Surfaces to Improve Transmission through Energy Saving Glass Windows

This paper reports initial work on creating frequency selective surfaces (FSS) on modern day glass windows to improve the transmission of wireless/mobile/cellular communication signals through the glass. The manufacturers of these glass windows apply very thin layers of metallic oxides on one side of glass to provide extra thermal insulation. These coatings block the infrared and ultraviolet waves to provide thermal insulation, but they also attenuate communication signlas such as GSM 900, GSM 1800/1900, UMTS and 3G mobile signals. This creates a major communication problem when buildings are constructed using mostly such type of glass. A bandpass FSS can provide a solution to increase the transmission of useful bands through the coated glass. In order to design an appropriate FSS, the relative permittivity and conductivity of glass should be measured accurately. Moreover, electrical properties of the coated layer must also be known in order to obtain a resonance in the desired band. In this work, we used two different methods of measuring the permittivity and conductivity of glass. Electrical properties of one of the common glass windows (Optithermtrade SN) are presented. Simulations of Optitherm glass shows about 35 dB transmission loss over 900-2200 MHz frequency band.