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Differentiate between radiated Common-Mode Coupling and Differential-Mode Coupling
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written 2.5 years ago by | • modified 2.5 years ago |
Common Mode Coupling | Differential Mode Coupling | |||
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It is defined as the unwanted electrical potential difference between any current carrying conductor and the reference ground. | It is defined as the unwanted potential difference between two current carrying conductor. | |||
This type of EMI coupling occurs when the noise appears in the same phase on the two conductors, e.g. +ve and -ve for power cables. | This occurs when the noise is out of phase on the two conductors. | |||
It is defined as Vc = (VPG + VNG)/2 | It is defined as Vd = (VPG - VNG)/2 | |||
A common-mode EMI signal appears on the two signal lines simultaneously in the same direction and phase. | Differential-mode interference is a signal that appears on two lines of a closed loop but current flow is in opposite directions. | |||
The solution to prevent this coupling is a common-mode choke, produces equal and opposite magnetic fields that cancel one another. A capacitor from each line to ground is also used. | The solution to prevent this coupling is an inductor in series with the high side (and/or low side) of the line and a shunt capacitor across the lines. |