《全套电磁兼容资料8.》.pdf

Coupling Outline • Capacitive coupling: – frequency domain – time domain • Inductive coupling: – frequency domain – time domain 1 Capacitive Coupling • Wherever there are two circuits, there is mutual capacitance. Voltages in one circuit create electric fields which affect the second circuit. • A mutual capacitive coupling between two circuits 1 and 2 is simply a parasitic capacitor C12 connected from circuit 1 to circuit 2. • A mutual capacitance C12 injects a current into circuit 2 proportional to the rate of change of voltage in circuit 1 2 Capacitive Coupling: Frequency Domain C12 = parasitic capacitance between conductors 1 and 2 Conductor 2 Conductor 1 U C R 2N 12 U 1 C 2G 3 Capacitive Coupling: Frequency Domain Equivalent circuit C 12 + U 1 C2G R U2N Voltage noise U2N induced in conductor 2 U jω C 2N 12 =