Electromagnetic shielding effectiveness of braided shields surrounding two-wire lines

Includes bibliographical references (pages 37-38)An experimental study was made of the relative effectiveness of braid-type electrostatic shields surrounding a twisted-pair transmission line at ultrahigh frequencies. The experiment involved the immersion of each of five samples of cable of differing shield configurations into a TEM field supported by parallel-plate transmission lines. Each sample was fed through a hole drilled through both plates of the transmission line with the axis of the sample parallel to the electric vector within the parallel-plate transmission line. The relative signal levels coupled to the samples were compared. Results of the experiments indicated the following trends: A single braid-type shield reduces coupled energy by approximately 40 decibels at 400 MHz, decreasing to approximately 20 decibels at 1000 MHz. A double shield further reduces coupled energy by approximately 15 decibels over the range tested