Microwave shielding measurement method

A simple system for measuring the attenuation of microwaves in the frequency range of 700 MHz to 13 GHz is described. It has been used to test a large number of commercially available microwave shielding materials. The standard system for such measurements would require IEEE STD 299 2006. This standard requires a number of different sources and receivers depending on the frequency range and, therefore, requires a number of different physical arrangements. The simple system described here uses two microwave horns and a network analyzer to compare the signal strength for an open path between the two horns with the same path with a microwave shielding material inserted. This ratio, expressed in db, can be obtained quickly and easily for any material that can be made into a flat rectangle larger than the receiving horn. The horns used here are A. H. Systems SAS-571 with a usable range of 700 MHz to 18 GHz. The network analyzer is an hp 1397C with a high frequency limit of 13 GHz. The materials tested include conducting paints on cloth such as denim, conducting woven fabrics, and metal meshes. The typical measurements presented here to illustrate the use of the method show that conducting paints and conducting fabrics mostly show large attenuation over the quoted frequency range although almost never as high as stated by the manufacturer. When the manufacturers quote the standard used for their measurements, it is sometimes an obsolete standard that has been withdrawn.