This paper shows quantitative evaluation of coupling between a monopole antenna outside a shield case and a strip line inside that for a portable telephone. The amount of the coupling is calculated using FDTD method together width EMF method. This combination of methods can raise the calculation efficiency. Dependence of the coupling on the length of gaps, the height of the strip line and the length of the antenna is clarified. The correspondence between calculated and measured results shows the validity of the calculation.

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.

In this paper, a balance-unbalance conversion factor (TCTL: Transverse Conversion Transfer Loss, TCL: Transverse Conversion Loss) and a radiated emission for differential type microstrip lines with a partial unbalance on a PCB (Printed Circuit Board) are investigated. As the result, after inserting an unbalance element, it can be seen that a radiated emission increased according to the deterioration of TCL. The calculated results of the TCTL and TCL by using 4-terminal pair network chain matrix agreed with the measured results very well. In order to calculate radiated emission from the differential type microstrip lines, a common mode current on differential type microstrip lines with a partial unbalance was calculated by using 4-terminal pair network chain matrix. The calculated results of the radiated emission also agreed with the measured results.