Evaluation of Emission from a PCB by Using Crosstalk between a Low Frequency Signal Trace and a Digital Signal Trace

Naoto OKA  Chiharu MIYAZAKI  Shuichi NITTA  

IEICE TRANSACTIONS on Communications   Vol.E83-B   No.3   pp.586-592
Publication Date: 2000/03/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Recent Progress in Electromagnetic Compatibility Technology)
Category: EMC Design of PCB
EMI,  radiated emission,  printed circuit board,  coupling,  crosstalk,  

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In this paper, the evaluation of emission from a PCB by using crosstalk between a low frequency signal trace and a digital signal trace is investigated. These signal traces are closely routed in parallel to each other on the different several signal planes in the PCB. It is shown experimentally that the coupled signal trace with a cable section causes drastic increase of emission from the PCB. From the measurement results of current distribution on the cable section, it is shown that this current distribution contributes to the increase of emission from the PCB. Therefore, emission increasing by coupling between signal traces is evaluated by crosstalk between them. The measurement results of radiation and the calculation results of crosstalk on the PCB (deviation from results of the PCB which is referred, respectively) agree with each other within 2 dB range or 3.5 dB range. This result shows that reduction effect of emission from the PCB can be predicted by calculation results of crosstalk. Moreover, it is shown that evaluation of emission level by using crosstalk is useful to decide PCB's structure for reduction of emission from a high-density assembled PCB. From the viewpoint of practical application, it is effective for the reduction of emission from a PCB to separate a low frequency signal trace from a high-speed digital signal trace by ground plane of a PCB.