Electromagnetic shielding provided by selected DB-25 subminiature connectors

The surface transfer impedance of a variety of DB-25 subminiature connectors, such as are used on personal computer peripherals, was measured over the frequency range of 1 kHz to 100 MHz. The test samples included die cast and metallized plastic backshells, receptacles with and without gaskets, circumferential (dual cones or compression insert) and single point (strain relief devices, compression set screw or pigtail) braid terminations. All samples included several centimeters of braid beyond the point where the backshell made contact to the braid. The measured results are presented along with a discussion of the electromagnetic significance of each of the design features. The electromagnetic performance of these samples is compared to that of circular connectors