Measurements of screening effectiveness of multi-pin and coaxial connectors to 300 and 1000 MHz

Abstract

The measurement of transfer impedance as a guide to the screening effectiveness of coaxial cables and connectors is well established, but only recently has a serious effort been made to extend the technique to multi-pin connectors used at frequencies up to 1 GHz. Among the many connectors in common use, the D-connector is one family whose widespread use keeps them inexpensive. If only for this reason this paper is written round testing of D-connectors, though its conclusions are applicable to most ranges of multi-pin connectors used in the digital instrument industry. Quite apart from the cost of components to be tested, if adequate screening is needed, it is important that the means of assessing this should not be costly. The test method described is being discussed and modified by a Working Group of IEC Technical Committee 46 and, to cover the frequency range deemed necessary, uses test equipment which might be thought expensive, though the test itself is simple. An alternative test is also suggested which is easier to use but is limited to frequencies where the test sample is electrically small. It is particularly useful in investigating the fundamental problems of using such connectors at high frequencies without the need for special test jig. It can be carried out with commonly available and inexpensive laboratory equipment, and may be made in the time domain, with the diagnostic benefits this brings.