Design007 Magazine

PCBD-Mar2014

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64 The PCB Design Magazine • March 2014 A poorly-shielded cable was connected to the DUT port to serve as the aggressor. Sever- al different victim cables were connected, in turn, to the DET port. The aggressor and victim cables lay loosely near each other, as shown in Figure 3. The results measured for each victim con- figuration are shown in Figure 4: • Red trace: High-quality, well-shielded vic- tim cable, with both cables open-ended. • Blue trace: Poorly-shielded victim cable, with both cables open-ended. • Green trace: Poorly-shielded victim cable, with both cables terminated. • Grey trace: Poorly-shielded victim cable, with both cables terminated, with ferrite-ab- sorbers on the victim cable. The upper photo in Figure 3 shows both cables open-ended, and the lower photo shows both cables terminated and with ferrite absorb- ers on the victim. The VNA was set to measure transmission (S 21 ), which in this case represents the crosstalk between the two cables through the cable braid quiet power CHECKING CABLE PERFORMANCE WITH VNA continues Figure 4: Crosstalk through the cable braid and air for four different cable combinations.

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