Radiation from differential type microstrip lines with common mode choke coil

Measurements and calculations were performed for radiations from differential type microstrip lines (DML) with a common mode choke coil (CMC). Radiations from DML can be calculated by a common mode current on DML. In order to calculate a common mode current distribution, DML with CMC was divided into minute sections and represented by 4-terminal pair network chain matrix. F parameter of CMC was converted from measurement values of S parameter. The calculated results of radiations from DML agreed with the measured results. It was confirmed that 4-terminal pair network chain matrix theory for radiations from DML with CMC was valid.