Application of curve fitting in EMS test of CRT display

The video graphics array (VGA) interface is a standard interface for display. The exposed interconnection cables of VGA interface are often the introducers of electromagnetic interference (EMI). The test method of bulk current injection (BCI) was used in the electromagnetic susceptibility (EMS) of cathode ray tube (CRT) display for compute. In order to acquire the quantization relation between coupled signal of VGA interface cable and interference phenomena, the amplitude of coupled sinusoidal signal along the VGA interface cable needed to be picked up accurately. For the horizontal synchronization (HS) and vertical synchronization (VS) signals were digital ones, the coupled level was hard to acquire directly because of the effect of noise signal of theirselves. The method of curve fitting was introduced. Thus the amplitude and initial phase of the coupled sinusoidal signal could be gotten accurately, which provided solid foundation for quantizing the relation between coupled signal and interference phenomena.