Design And Research Of X-Band SIW Generalized Chebyshev Super Structure Filter

With the development of communication technology,the rational use of spectrum resources has become an inevitable trend,and the rational use of spectrum resources needs to divide the spectrum into more narrow-band bands,so the demand for narrow-band filters for frequency selection is also increasing,and its parameters are more and more strict.The narrowband of the filter requires more cavities and less loss of the resonator,which will result in the increase of the filter volume and the increase of Q value of the resonator.The substrate integrated waveguide(SIW)integrates the two advantages of microstrip line integration and high Q value of rectangular waveguide.It is exactly the transmission line needed to make narrow-band filter,so it is widely used in the production of narrow-band filter.In recent years,the electromagnetic superstructures represented by structures with negative permittivity and negative permeability have attracted more and more attention.Its electromagnetic characteristics of passband lower than the cut-off frequency and stopband higher than the cut-off frequency are also widely used in the design of filters,contributing to the miniaturization and narrowband of filters.Although the electromagnetic super structure is used in the filter,it is mainly placed on the surface of the cavity,which is a semi open structure.As a separate resonator,it can add the resonance peak or the transmission pole in band,and it is not combined with the traditional filter.In this paper,we combine the super structure with the Generalized Chebyshev filter,and take the super structure as the coupling structure between the cavities,so as to improve the frequency selectivity of the Generalized Chebyshev in the case of realizing its own resonance,because it is a totally closed structure,which reduces the in band loss.Based on the traditional split resonance ring(SRR)structure,the orthogonal split ring resonator and parallel split ring resonator are designed,and the negative permittivity of SRR is proved.According to its electromagnetic characteristics,the orthogonal resonator coupling structure is designed.Resonance is formed at 12.1ghz,and all the energy is coupled to the coupling port,as well as the parallel resonator coupling structure.Resonance is formed at 11.8ghz,and the energy is directly connected to the through port.By combining the coupling structure of the resonator with the six cavity Generalized Chebyshev filter,an X-band SIW Generalized Chebyshev super structure filter is realized with SIW structure by calculating the coupling coefficient and extracting the coupling coefficient between cavities.The main technical indexes are:center frequency is 10.519 ghz,loss is-0.62 db,relative bandwidth is 0.25%,return loss S11 is less than-20 dB,and out of band suppression is better than-30 dB.In addition,according to the principle of optical interference,the microwave frequency interference cavity is designed,and the four cavity interference filter and six cavity interference filter are designed.In addition,the interference diplexer is designed and compared with the traditional SIW diplexer.