Reverberation Chamber Testing of Noise Coupling to Category Cabling

摘要

Cables with interrupted shields are a topic of current interest: in particular, the possibility of presenting some shielding without the need for shields terminated at connects is a commercially very attractive proposition. Non-continuous and unterminated shields do 'violate' good practice for electromagnetic compatibility (EMC). However, as in all engineering solutions, a cost-benefit trade-off may be involved. The general principles of discontinuous shields are investigated in this paper through the use of a reverberation chamber, allowing shielding for electrically long lengths of cable to be tested. The shield was implemented by using foil wrap around UTP cable with regular 'gaps' being introduced in the cable on successive iterations. The test was performed by subjecting the cable to an external electromagnetic field and calculating the shielding effectiveness by measuring the peak signal over one stepped rotation of the stirrer. Unshielded cable and 'terminated' full shields were used as benchmarks for the tests. The results indicate that only marginal benefit can be obtained from discontinuous shielding when compared to fully terminated shielding as a general principle.