Research And Design Of EMC Bandstop Filter

At present,the electromagnetic environment in which electronic equipment is located is becoming more and more severe.Electromagnetic compatibility design has become a key issue in the design process of electronic equipment.There are certain electromagnetic leakages in microwave components,which also leads to serious challenges in the design of electromagnetic compatibility of electronic equipment.The filter plays an important role in the design of modern microwave systems.Filter technology plays an important role in ensuring that electronic equipment is free from electromagnetic interference and the separation of available signals.Compared with bandpass filter,bandpass filter has the advantages of high power and low insertion loss.This advantage makes it not only can be used to attenuate narrow band signals,but also play a role in electromagnetic compatibility system testing.The problem of parasitic response is widely used in the design of microwave filter.This phenomenon is due to the periodic effect of the distributed parameter components used in the microwave filter design,which will leads to a number of parasitic bands in the response of the bandstop filter,and the existence of parasitic hindrance restricts the upper pass band of the bandstop filter Bandwidth,If a filter with a parasitic response is used to suppress the strong interference signal,the work signal may not be transmitted normally;if it is applied to the EMC test,all the test signals will not be proposed.At the same time,in modern microwave / RF systems,in order to ensure the less loss of the whole system and the compact structure of the equipment,the size of the filter is also required.Therefore,the miniaturization of the filter is also an important problem to be considered in the process of the filter design.To sum up,when designing EMC microwave filter,it is important to suppress the parasitic response and make it miniaturized.The main work of this paper is to study how to suppress the spurious response of the band stop filter and the miniaturization of the microwave band stop filter.The main contents are as follows:(1)The basic characteristics of the step impedance(SIR)are studied.A SIR bandstop filter with coupling structure is proposed.The structure is realized by a planar strip line.By analyzing and adjusting the structural parameters such as the impedance ratio and coupling coefficient,the parasitic band can be stabilized beyond the 6 times the center frequency.The design of the band stop filter is far from the parasitic stop band and the stopband rejection is low.The structure is suitable for a band stop filter design with relatively long requirements for parasitic stop band and low stop band rejection.(2)On the basis of the study of the original hairpin microstrip line SIR bandstop filter,an improved SIR new microstrip hairpin band stop filter structure is proposed.By adding the grounding hole and the open branch of a certain shape,it can push the parasitic band of the original hairpin band stop filter at the 2 times center frequency to 3.3 times center frequency.The structure is suitable for high requirements for miniaturization,although the requirements for the pass band on the band stop filter are not too high.(3)A wideband band-stop filter with a rectangular coaxial resonator is designed and implemented.The bandstop filter can push the parasitic resistance band far to 5.5 times center frequency.The filter made with the coaxial cavity structure has a high Q value and a larger power,so the structure is suitable for power requirements and is suitable for the structure that there is a high requirement for the suppression of parasitic response.