Measured surface transfer impedance of multi-pin Micro-D Subminiature and LFHTM connector assemblies at frequencies up to 1 GHz

Candidate connector assemblies were examined for use in high-speed digital interconnects, such as the Fibre Channel protocol. Twelve Micro-D Subminiature connector pair and 6 Low Force Helix (LFH^TM ) connector pair with EMI backshells were measured in a triaxial test fixture over 2 frequency ranges-a low frequency range of 1 kHz to 200 MHz and a high frequency range of 300 kHz to 3 GHz. A calibration sample of known impedance was used to correct the high frequency data to mitigate effects of the test fixture parasitics and permit credible transfer impedance data to be obtained up to 1 GHz. The Micro-D connector assemblies from two manufacturers, X and Y, were measured. There was no statistical difference between the Micro-D connector plugs assembled by manufacturers X and Y. At 200 MHz, the average transfer impedance of the Micro-D connectors was 35.4 mΩ. The sample-to-sample variation of the Micro-D connector pairs was minimal (standard deviation equaled 20% of average). The high frequency transfer impedance increased at a rate less than directly proportional to frequency suggesting that the coupling mechanism was not purely aperture coupling nor contact impedance. The transfer impedance (shielding performance) of the Micro-D connector was sensitive to tightness of the jack screws. The transfer impedance increased dramatically as jack screws were loosened and removed. The LFH^TM connector exhibited transfer impedances approximately 15 dB lower than the Micro-D connector