Research And Design Of SIW Filter Based On The SRR Structure

Microwave filter is an important component of RF front-end.With the development of modern mobile technology,high performance and miniaturization of filters are required.The substrate integrated waveguide(SIW)has the advantages of high quality factor,low transmission loss,large power capacity,easy integration and low cost.It can be used to design high-performance,miniaturized filters.The split ring resonator(SRR)and its derived complementary split ring resonator(CSRR)have evanescent mode resonance effect,which can form a passband below the cut-off frequency of waveguide and further reduce the size of SIW filter.Therefore,SIW and SRR are concerned by scholars.In this thesis,a series of SIW band-pass filters based on SRR structure are studied and designed below the cut-off frequency of waveguide.First of all,in order to realize the miniaturization of the band-pass filter,a step impedance complementary split ring resonator(SICSRR)and a dual-iris coupling structure are proposed,then a miniaturized HMSIW band-pass filter is designed.The structure of designed HMSIW band-pass filter is compact,and its effective size is0.128?_g×0.307?_g.Compared with the same size CSRR,the proposed SICSRR structure works at a lower frequency,and the proposed dual-iris coupling method is smaller than the direct coupling method and the single-iris coupling method.For further miniaturization,a SW-HMSIW band-pass filter is designed based on the study of slow-wave substrate integrated waveguide(SW-SIW).Compared with traditional SIW,SW-SIW structure achieves slow wave effect by physically separating the electric field and the magnetic field.The structure of designed SW-HMSIW band-pass filter is compact,and its effective size is 0.077?_g×0.182?_g.The simulation results show that the center frequency is 3.48 GHz and the 3 d B bandwidth is 0.24 GHz.Then,in order to achieve high filter performance and miniaturization of band-pass filter,a structure of Z-shaped slot is presented and a SIW band-pass filter loaded with Z-shaped slot and SICSR structure is designed.The introduction of Z-shaped slot can increase transmission zeros,widen the bandwidth,and enhance in-band flatness.After loading Z-shaped slot,the two transmission zeros of the upper and lower sidebands make the passband have a steeper transition band,improve the frequency selectivity of the filter,and obtain the filtering performance equivalent to that of the multi-order filter.In addition,the center frequency of the passband shifts to the left,which means that it can make the size of filter smaller.The structure of designed filter is compact,and its effective size is0.218?_g×0.102?_g.The measurement results show that center frequency is 3.48 GHz and 3d B bandwidth is 0.41 GHz.Finally,in order to realize the dual-band band-pass filter,a new CSRR structure is proposed,and a dual-band band-pass filter with Z-shaped slot is designed.The new CSRR structure has two passbands,and the working frequency is lower than the traditional CSRR with the same size.The introduction of Z-shaped slot increases the transmission zero,widens the passband,improves the flatness of the passband,and realizes the shift of the center frequency of the passband to the left.The structure of designed filter is compact,and its effective size is 0.179?_g×0.097?_g.The measurement results show that the center frequency of the first-band is 1.94 GHz,the 3 d B bandwidth is 0.28 GHz,and the center frequency of the second-band is 4.85 GHz,the 3 d B bandwidth is 0.13 GHz.