Research On The Background Noise Cancelling Technology In EMI Testing

With the rapid development of electronic and communication technology,more and more electronic equipments have been popularized to the people's daily life,which cause even more serious electromagnetic interference problems to us.In order to ensure the normal working of electronic equipment,the manufacturer needs to give EMI testing to the equipments that sales on the market.If the reliability of the test cannot be guaranteed,the accurate electromagnetic characteristics of the equipment cannot be obtained,so it is necessary to suppress the noise signal of the test and restore the real signal.In this paper,we study the noise cancellation technique of background noise in EMI test.This paper investigates the technology of EMI testing,analyzes the possible test environments and the different test schemes in its corresponding environment.After considering the possible interference of different EMI test environments,this paper studied some main noise in those environments.Based on the above researchs and the analysis of some interference suppression techniques,this paper design a noise suppression scheme with virtual chamber technique and at the same time using the method of software test and verify the scheme.The work of the paper includes the following parts:The design of noise canceller that based on adaptive theory.This paper considering the change of the test environments and in order to deal with the different kinds of noises,the adaptive method is chosen to suppress non-stationary interference.This paper selects two kinds of adaptive filtering methods based on different ways to minimize cost functions,and makes a detailed theoretical analysis of them.Considering the physical constraints of hardware devices,the algorithm structure is modified so that it can receive noise online and process it in real time.Finally,various methods are simulated and verified.The design of nonlinear noise canceller based on kernel method.Considering the EMI testing often exists nonlinear noise,the conventional adaptive algorithm does work well on it,so based on the previous content this paper introduced kernel adaptive method for nonlinear signal processing.From the mathematical point of view,this paper introduce the concept of RKHS and kernel,is theoretically proved that it has the ability to solve the problem of nonlinear,at the same time in order to ensure that in the actual application,adopted the algorithm practical kernel trick.By introducing the representer theorem,the ability of converting all kinds of nonlinear signals into linear signal combinations is described.In order to deal with different types of signals,this paper also introduces various kernel functions.Then compared the similarities and differences between traditional adaptive method and kernel adaptive method,deduce the calculation steps of the kernel algorithm,and the simulation verification,proved its superiority compared with traditional adaptive algorithm.Finally,the result of software simulation confirms the feasibility of the proposed algorithm,which indicates that it can achieve the expected target.