Design Of Bandpass Filters Based On Substrate Integrated Waveguide And CSRR

With the rapid development of modern wireless communication,more new technologies and standards have been proposed,the requirement of microwave circuits of communication system is becoming higher and higher.The filter plays a very significant role in the communication system,which can screen out the required signal and filter the clutter signal,so its performance also determines the performance of the whole system.With the increasing scarcity of spectrum resources,the requirements of multi-band,miniaturization and high performance of filter devices are becoming higher and higher.These requirements pose great challenges to the design of modern microwave filters.In this paper,the multi-mode properties of substrate integrated waveguide resonator,complementary split resonator ring structure and defected ground structure are studied and analyzed.At the same time,several miniaturized,multifrequency and wide stopband filters are designed.The research contents of the dissertation are summarized as follows:1.Design of dual-mode Bandpass Filter based on square SIW resonator:Firstly,according to the multi-mode property of the resonator,the electric field distribution of the first four resonant modes of the square SIW resonator is analyzed.Using the characteristic that a pair of degenerate modes have the same resonant frequency,the electric field of one of the modes is perturbed by inserting a metallized via into the resonator,so as to separate its frequency and form a passband.At the same time,according to the design principle of Chebyshev filter,the higher the order of the filter,the stronger the out-of-band suppression,the two same square resonators are cascaded to improve the out-of-band selectivity of the filter.In addition,by connecting the input and output with a microstrip line to generate electrical coupling,a transmission zero can be introduced in the lower stopband to further accelerate the stopband attenuation speed of the filter.2.Design of dual-band Filter based on double-layer SIW resonator:By vertically stacking the double-layer SIW resonators and opening a circular window in the middle layer metal,the modes of the upper and lower layers of resonators are coupled,thus forming a passband.By setting the input and output positions,some interference modes can be suppressed,thus forming a dual-mode dual-passband filter and realizing the miniaturization of the multi-frequency filter.At the same time,some metal vias are inserted in a specific position of the resonator to change the frequency of a specific mode,so that the center frequency ratio of the two passbands can be adjusted.3.Design of Wide Stopband Filter based on CSRR and improved DGS Technology:By using the characteristics of negative permittivity and negative permeability of CSRR structure,the resonant frequency of the resonator can be reduced to achieve miniaturization.At the same time,by using the low-pass characteristics of DGS structure,it can be cascaded with the SIW resonator to suppress all interference modes except the dominant mode.Theoretically,the stopband can be extended to infinity,thus achieving the accuracy of the filter.Because of the existence of magnetic wall,halfmode SIW has the same transmission characteristics as SI W,so the size of the filter can be further reduced by utilizing HMSIW.The simulation and measured results are in good agreement.