GLENAIR
Filtered EMI connectors effectively shield individual contacts / circuits For discrete signal connector applications, an EMI filter package may be incorporated into the insert stack. This will in effect put a fine ground-mesh around every contact and prevent certain EMI events from disturbing the circuits in the box. The filter value should be selected so as to allow the desired signals that pass through, but block unwanted higher frequencies. The ceramic materials used in Glenair filtered connectors can be exposed to high doses of radiation without adverse effects. Transient Voltage Suppression (TVS)-equipped connectors prevent voltage spikes from discharge events from damaging delicate circuits inside electronic boxes. A correctly designed TVS diode can take millions of discharge events without damage. This is important because in space, discharge events may happen at regular and frequent intervals.
Aluminum wrapping versus braided shielding Electrical cables exterior to the sealed/protected zone of a satellite need to be shielded—typically with wrapped foils or conductive braid materials—to extend the protective Faraday cage that is routinely established for electronic boxes and enclosures to interconnecting wires and cables. Elimination of apertures or gaps in braided wire shielding is critical, especially for high-frequency (short wavelength) EMI. In addition, the termination of wire shielding at the connector interface must be accomplished with good ground connections. As conductive adhesives on foil are notoriously bad,
such materials should not be relied on for effective EMI/RFI shielding for critical systems in space flight applications.
Flexible braided shielding (left) is far less likely to develop gaps and apertures that can lead to entry/exit points for electromagnetic interference as compared to foil-wrapped assemblies
Ground fingers and springs on connectors enhance shielding effectiveness, reduce shell-to-shell resistance, and improve ground path The use of robust connector ground springs and/or fingers can markedly reduce connector shell-to-shell resistance, and improve the ground path to eliminate surface conducted EMI. An EMI spring can be located on a plug or receptacle. Many types and approaches are employed, from simple dimpling on shells, such as found on inexpensive D-subminiature connectors (mystifyingly still specified in many satellite applications), to more sophisticated recessed springs in high-performance circulars. Ground fingers such as are used on the gold-plated D-Sub in the picture are particularly effective for critical space-flight applications.
QwikConnect • January 2021
11
Powered by FlippingBook