Design Of Microstrip Line Filter Based On The New Resonator

In recent years,wireless communication technology obtained a rapid development,along with the emergence and application of the wireless communication,filter technology become better developed and more diverse.At the same time,the transmission performance of wireless system directly affects the demand of people.The filter,as one of core devices of the wireless,plays a key role in the whole system.Filter is primarily used in the communication system of,for example,aerospace,satellite,electronic countermeasures.It performs a selective blockage and passage to the signals,which allows most needed signals to pass,and impedes most unwanted signals.Compared to other kinds of filters,microstrip filter has many exclusive advantages,for example the simplicity of its structure,the low cost and easiness of its integration,processing and mass production.Therefore its application gained comprehensive endorsement in the communication system,the study of filters becomes more important.The main contents are summarized as follows:This paper begins with a review and summarization of related research achievements in China and abroad,followed with an introduction of the classification and technical parameters of the filter,the design idea and the basic theory of the resonator.Based on ring resonator and the introducing of perturbation structure,a dual-mode single band filter was designed.Perturbation structure can make its degenerate mode split and form a dual-mode filter.Its advantage is a dual-mode resonator can produce the same frequency response which is produced by two coupled ordinary resonators.Conventionally the number of cavity decreases by half,it has great application value in the miniaturization design of filter.Secondly,it introduces the dual-mode resonator with stub loaded to design single frequency band filter.This paper covers the basic principle of open circuit and short circuit stub loaded dual-mode resonator,and the design of two microstrip filter based on dual-mode resonator with center frequency of 3.5GHz,bandwidth of 200 MHz,filters play good performance.The structure of the transmission zeros are inherent transmission zeros and additional transmission zeros,by introducing the source and load the inductive coupling and capacitive coupling to generate an additional transmission zeros,by changing the direct coupling between the source and load,and the coupling between input / output feeder and resonator two modes to adjust the location of the transmission zeros to improve the performance of the filter.Finally,a high selective dual band bandpass filter is designed.The filter is used in WiMAX /WLAN,input and output structure used the common feeder.The stepped impedance resonator(SIR)loaded short stubs to generate the first band,the center frequency and bandwidth of the filter can be adjusted.It produced a total of 4 transmission zeros,while providing high inhibition the stop band and high band suppression.