Fast Diagnosis, Prediction and Signal Characterization of Radiated Electromagnetic Interference (EMI) Noise * Zhao Yang 1 See Kye Yak 2 Li Shijin 1 Luo Yongchao 1 1 College of Electrical Engineering, Nanjing Normal University, China 2 School of EEE, Nanyang Technological University, Singapore * This work is supported by the Open Research Fund of State Key Lab. of Millimeter Waves, Southeast University, China (#K200603) Abstract- Usually the analysis and solution scheme for radiated EMI noise is trouble and difficult, since it is concerned with EM field or EM wave model and analysis. In order to ease the radiated EMI problem solved more efficiently, in this paper an approach of fast diagnosis , prediction and signal characterization for radiated EMI noise is presented. In the approach the EMI noise diagnosis technique is based on the near-field measurement and comparison, EM field prediction technique is based on the RF circuit measurement instead of EM field measurement and the noise identification is based on signal processing. It is seen that by using this fast modeling technique, the radiated EMI noise analysis can be simplified somewhere. Key Words: radiated EMI noise, noise diagnosis, EM field prediction, signal identification I. Introduction Though research in the field of radiated EMI noise analysis and noise modeling has been done by many authors and much progress has been achieved [1]-[3] , however, these analysis methods are either very complicated needing verbose mathematical deduction or very time-consuming and the methods are limited in use because of strict conditions and assumption for methods application. This is because the radiated EMI noise analysis mostly regarded as electromagnetic field or electromagnetic wave problem, thus both employed measurement and theoretic modeling techniques become hard to understand and difficult in implementation. Up now it is still lack of easily doing and fast realization way for efficient radiated EMI noise analysis. For this reason, a fast modeling is described in this paper. First the mechanism of radiated EMI is diagnosed by near- field electrical field/ magnetic field measurement and comparison. Then, the radiated EMI field strength in the far- field is predicted by circuit parameter measurement with frequency range up to 1GHz, i.e. the common mode(CM) current measurement and ground voltage potential measurement at some special points for rough estimation of EM field performance at 3m-distance or 10m-distance regulated by EMC standards. Finally some signal characterizations are introduced to further identify the radiated EMI noise so as for noise suppression. II. Fast Diagnosing of Radiated EMI Mechanism At the present time, the EMC compliance test for radiated EMI noise can only tells whether the total EMC performance of product meets EMC regulation, but can not provide any additional information what reason makes the product not satisfied with the regulation and how these radiated EMI noise generation. Similar to conducted EMI noise analysis, the radiated EMI noise also consists two components, one is common mode (CM) radiation component which is mainly generated by the electric dipole radiation because of not well-grounded circuit or ground potential bounce and forming a rod antenna, the other is differential mode (DM) radiation component which is mainly generated by the magnetic dipole radiation because of not well-looped circuit or large loop area forming a loop antenna. Since different component generation of EMI radiation is of different mechanism and also is suppressed in different way, thus it is necessary to detect what dominant component produce the failure of radiated EMI test in addition to the general measurement of total EMI radiation noise. As seen in Fig.1 of radiation model, in the near-field the electromagnetic field performance of electric dipole radiation or CM radiation is [5] (1) On the other hand the electromagnetic field performance of magnetic dipole radiation or CM radiation is 0 cos ) ( 1 ) ( 1 2 sin ) ( 1 ) ( 1 ) ( 1 4 3 2 0 3 3 2 0 3 =       + - =       + + - = - - φ θ θ πωε θ πωε E e kr j kr Idlk E e kr j kr kr j Idlk E jkr r jkr ( ) 0 sin ) ( 1 1 4 2 2 = =       + - ⋅ = - θ φ θ π H H e kr kr j Idlk H r jkr 978-1-4244-1880-0/08/$25.00 ©2008 IEEE. ICMMT2008 Proceedings