Experimental Study on Common Mode Choke for Conducted Noise Reduction from Differential Line to Ground Plane

Communication capacity is increasing in various markets, and it is desired to increase data transmission speed. Therefore, the use of shielded cables with high frequency characteristics as transmission cables has been studied. However, even in the shielded cable, noise is conducted to the shield layer, which causes a radiation noise problem. Therefore, in this study, the noise conducted to the ground from the differential line is measured, the cause of the noise increase is observed, and the mounting of a countermeasure component for noise reduction is discussed. As a result, it was confirmed that the amount of conducted noise to the ground changed depending on the amount of common mode transmitted to the differential line. Furthermore, the common mode choke (CMC) is mounted, and the conducted noise can be reduced by reducing the common mode. However, it was confirmed that depending on the common mode amount of the differential line, the noise may not be reduced or may be increased depending on the mode conversion characteristics of the CMC.