Near field characterization of the electromagnetic interference for a microcontroller

Modern science is pushing Integrated circuits (IC) to higher level of integration, internal clock frequency and translation rates. In this context, the electromagnetic compatibility (EMC) of IC has gained more and more significance in the design stage, as well as the qualification. In this paper, the near field characterization is performed on a newly-built scanning system, in which a spectrum analyzer is used to detect the electromagnetic signal of the device under test. The scanning and detecting for the electromagnetic interference (EMI) is verified by a testing on the magnetic field above a microstrip. And then we apply the method to near field characterization of EMI for a microcontroller (C8051F120). The microcontroller is set to work at two different frequencies, 24.5MHz and 98MHz. The harmonic frequency is found in the range up to 500MHz. It is found that the excitation of phase lock loop module is significant for the whole electromagnetic radiation. The pins with higher EMI radiation are also identified in this paper.