The Influence of Electromagnetic Absorber on Crosstalk and Signal Integrity of Coupled Transmission Lines

The paper investigates the effect of an electromagnetic absorber on the useful signal integrity in a two-conductor coupled transmission line. The absorber in PCB design is intended to reduce emission from PCBs, to reduce their susceptibility to emission, or to improve the performance of filters on distributed-element circuits. We measured the S-parameters of lines coated and uncoated with the absorber using a vector circuit analyzer in the 0-10 GHz frequency range. The results show that absorber coating can increase the far end crosstalk amplitude up to 1.5 times and its duration up to 2 times. The high loss in the absorber reduces the transmission coefficient and increases the jitter of the signal. Thus, the coating reduces the SNR by in 2 times, but it still remains at an acceptable level for properly matched transmission line. In general, absorber coating can significantly affect the useful signal integrity with a speed greater than 1 Gbps.