System and method for filtering electromagnetic transmissions

Abstract

A combination of filters for filtering selected wavelengths of electromagnetic radiation is provided on a transparent substrate such as a plastic film or glazing of a window. The combination of filters prevents or attenuates the passage of wavelengths through the substrate into a building, where the passage of the wavelengths into the building could adversely affect people or machinery within the building. The combination of filters is useful improve wireless networks performance by blocking or attenuating undesired electromagnetic interference, and radio frequency interference.

1 . A method for reducing electromagnetic interference, and radio frequency interference within an enclosure having transparent areas, the method comprising the step of applying a optically transparent filter to said transparent areas, said filter comprising an electrically conductive metal layer, said combination of filters being configured to prevent or attenuate the passage of the electromagnetic interference and radio frequency interference through the transparent areas. 
   
   
       2 . The method of  claim 1 , wherein the filter is attached to the transparent areas using an electrically conductive adhesive. 
   
   
       3 . The method of  claim 1 , wherein said electrically conductive metal layer of the filter has at least the electrical conductivity of aluminum. 
   
   
       4 . The method of  claim 1 , wherein the filter comprises an IR reflecting metal layer and one or more dielectric layers, each of said dielectric layers having an index of refraction of substantially 1.35 to 2.6. 
   
   
       5 . The method of  claim 1 , wherein dielectric layer comprises a metal oxide having an index of refraction of substantially 1.7-2.6 and, wherein the IR reflecting metal layer comprises silver. 
   
   
       6 . The method of  claim 1 , wherein said filter comprises an Ag/Ti sputtered stack, wherein said Ag/Ti sputtered stack has a sheet resistance less than 4 ohms/square. 
   
   
       7 . The method of  claim 6 , wherein said Ag/Ti sputtered stack is made by sputter coating the following sequence of layers onto said substrate or onto a transparent plastic sheet: 1) a layer of metal oxide, 2) a silver IR reflecting layer, 3) a protective sacrificial layer of titanium, 4) a layer of metal oxide, 5) a silver IR reflecting layer, 6) a protective sacrificial layer of titanium, 7) a metal oxide layer, 8) a silver IR reflecting layer, 9) a protective sacrificial layer of titanium, 10) a layer of metal oxide. 
   
   
       8 . The method of  claim 6 , wherein said Ag/Ti sputtered stack is made by coating the following sequence of layers onto said transparent plastic sheet: 1) a layer of indium tin oxide about 30 nm thick, 2) a silver IR reflecting layer about 9 nm thick, 3) a protective sacrificial layer of titanium about 1 nm thick, 4) a layer of indium tin oxide about 70 nm thick, 5) a silver IR reflecting layer about 9 nm thick, 6) a protective sacrificial layer of titanium about 1 nm thick, 7) an indium tin oxide layer about 70 nm thick, 8) a silver IR reflecting layer about 9 nm thick, 9) a protective sacrificial layer of titanium about 1 nm thick, and 10) a layer of indium tin oxide about 30 nm thick. 
   
   
       9 . The method of  claim 1 , wherein said filter comprises an Ag/Au sputtered stack, wherein said Ag/Au sputtered stack has a sheet resistance less than 4 ohms/square. 
   
   
       10 . The method of  claim 9 , wherein said Ag/Au sputtered stack is made by sputter coating the following sequence of layers onto said substrate or onto a transparent plastic sheet: 1) a layer of metal oxide, 2) a silver IR reflecting layer, 3) a layer of gold, 4) a layer of metal oxide, 5) a silver IR reflecting layer, 6) a layer of gold, 7) a layer of metal oxide, 8) a silver IR reflecting layer, 9) a gold layer, and 10) a layer of metal oxide. 
   
   
       11 . The method of  claim 9 , wherein said Ag/Au sputtered stack comprises the following sequence of layers coated onto said transparent plastic sheet: 1) a layer of indium tin oxide about 30 nm thick, 2) a silver IR reflecting layer about 9 nm thick, 3) a layer of gold about 1 nm thick, 4) an ITO layer about 70 nm thick, 5) a silver IR reflecting layer about 9 nm thick, 6) a layer of gold about 1 nm thick, 7) an ITO layer about 70 nm thick, 8) a silver IR reflecting layer about 9 nm thick, 9) a gold layer about 1 nm thick, and 10) an ITO layer about 30 nm thick; and, wherein: said second light filter comprises one or two PET films with UV absorbers dyed therein in an amount to produce at least 2.4 optical density absorbance in each PET film; and, wherein: said copper layer is sandwiched between two corrosion protection metal or metal alloy layers which protect said copper layer from corrosion. 
   
   
       12 . The method of  claim 1 , wherein said filter comprises a film made by sputter coating the following sequence of layers onto a transparent plastic film with UV absorbers dyed therein at 2.4 optical density absorbance: 1) a layer of indium tin oxide about 30 nm thick, 2) a layer of Ag/Cu alloy about 9 nm thick, 3) a layer of indium metal about 3 nm thick, 4) a layer of titanium metal about 1 nm thick, 5) a layer of indium tin oxide about 80 nm thick, 6) a layer of Ag/Cu alloy about 9 nm thick, 7) a layer of indium metal about 2 nm thick, 8) a layer of titanium metal about 1 nm thick, and 9) a layer of indium tin oxide about 30 nm thick.