Measurement and Analysis of Shielding Effectiveness and Transfer Impedance of High Speed Data Cables

摘要

Common mode noise and its implications on both EMI and signal integrity are becoming a significant concern with ever-increasing data transmission rates due to the potential for failing radiated emission limits as well as functional problems. Prior work illustrated the causes and potential impact of common mode noise. There are two primary approaches used to measure the quality of shielding of high speed cables: a "tube" fixture, which actually measures transfer impedance, and a reverberation chamber, which directly measures shielding effectiveness. This paper describes both measurement setups and methods for processing and interpreting the data, and presents data for some sample cables with varying degrees of deliberate shield damage to evaluate the effects on transfer impedance and therefore radiated emissions.