Leakage from coaxial cables

Today electromagnetic compatibility plays a dominant role in the design of various parts of an electronic system. The leakage of energy into or out of coaxial cables is an important source of interference and has received considerable attention over many years. In this review, the fundamentals of cable screening and the concepts of surface transfer impedance Z_T and coupled capacitance to describe the leakage of a cable are considered. Various attempts to devise a theory of braid leakage are then discussed. The characteristics of single-braided and optimised cables are presented, those of double-braided and superscreened cables are covered, but in less detail. Methods of measuring the shielding effectiveness of coaxial cables are reviewed, and experimental and calculated values of Z_T for several types of cable are compared. It is shown that manufacturing tolerances are a very important consideration when attempting the prediction of leakage from braided cables.