Research Of Multi-band Miniaturized Substrate Integration Waveguide Filters

With the birth of 5G technology,filters have played an important role in the application of communication terminal equipment.Compared with the traditional microstrip and metal waveguide filters,substrate integrated Waveguide(SIW)has the advantages of high quality factor,compact size,easy integration and high power capacity.SIW is widely used in the design of millimeter wave filter.In addition,with the miniaturization and high integration design of mobile terminal equipment,the miniaturization filters with high performance will become the top priority of communication system.Based on SIW miniaturized filters,especially multi-band filters,the main contents are as follows:(1)The miniaturization methods of microstrip are introduced into SIW,the E-shaped open loop resonator(ESOLR)is etched in the half-mode square substrate integrated waveguide(HMSSIW).The third-order single frequency response is realized in a single HMSSIW cavity,which reduces the size by 67.5%.(2)Based on HMSSIW,1/4 mode and 1/8 mode SIW are proposed.The second-order single-band differential response is obtained by using the particularity of the electric field structures of the two kinds of cavities.The common mode rejection of the filter is maximized by introducing slot-line and defective ground structure(DGS).Finally,the size of the filter is reduced by 87.5% and the overall performance is excellent.(3)Using the symmetry of two pairs of degenerate mode electric fields in SSIW cavity,cross groove(CG)is introduced to control the length of the groove so that the frequency of the proposed dual frequency filter can be adjusted independently.In order to realize further miniaturization,E-shaped coplanar waveguide(ESCPW)is etched in the HMSSIW cavity,the second-order dual-band responses are realized in a single HMSSIW cavity,which reduces the size by 67.5%.(4)For the first time,quarter circular SIW(QCSIW)is used for designing multi-band filter and its modes and frequency characteristics are derived.QCSIW not only has partial field pattern structure of circular SIW,but also is easier to suppress higher harmonic modes.Based on QCSIW,a dual-layer three frequency filter is designed,which has compact size and excellent performance.In order to further miniaturize,the half-mode QCSIW(HMQCSIW)cavity is proposed based on QCSIW.W-shaped slot-line is introduced for the first time,so that the three frequency responses not only move to the low frequency band,but also increases the couplingstrength of multi-mode between multi-cavity.Compared with the dual-layer structure,the filter has smaller size,lower cost.