Research On Miniaturized High Performance Filter Based On Substrate Integrated Waveguide

With the rapid development and application of broadband and high-speed wireless systems,RF microwave devices with small size,high performance,and easy integration have become the mainstream direction of development in the modern information industry.Filters,as important components of communication systems,have received increasing attention.In order to meet the requirements of wireless communication technology for miniaturization and high-performance filters,various novel microwave filters with clever structures have been designed successively.Substrate integrated waveguide（SIW）,as a new waveguide structure,not only inherits the advantages of traditional metal waveguides and microstrip lines,but also has the characteristics of large power capacity,small size,and easy processing,so it has been widely used in the miniaturization design of modern microwave filters.The folded substrate integrated waveguide（FSIW）structure and the half-mode substrate integrated waveguide（HMSIW）structure developed based on the SIW structure have opened up new possibilities for miniaturization design of filters.Therefore,SIW,FSIW and HMSIW technologies have been widely applied in the design of miniaturized and high-performance filters.The main work of this thesis is as follows:（1）Three different bandpass filters are designed based on the HMSIW structure.Firstly,a miniaturized bandpass filter based on slot-line perturbation is proposed.The filter reduced the resonant frequency by cutting slot-lines on the metal layer of the HMSIW structure in the strong magnetic field area,achieving miniaturization of the filter.Compared to the structure without slot-lines,the size of the filter is reduced by10%under the same bandwidth conditions.Simulation and testing results show that the filter is centered at 10.4GHz with a relative bandwidth of 30.7%,with an insertion loss within the passband of less than 0.5d B and a return loss better than 15d B.Secondly,a wide stopband bandpass filter with high-order mode suppression is proposed.By adding metal columns near the metal via of the HMSIW structure,the high-order modes outside the filter band are effectively suppressed,achieving high selectivity of the filter.From the simulation and testing results,the filter is centered at 4.5GHz with a relative bandwidth of 46.7%,with an insertion loss within the passband of less than 0.7d B and a return loss better than 15d B.Moreover,the stopband of 6.5-17GHz had a|S₂₁|<-25d B,indicating that the filter had an ultra-wide stopband.Finally,a bandpass filter with ultra-wide bandwidth and stopband is designed by utilizing the high-pass characteristic of the HMSIW structure and the passband characteristic formed by coupling between the quarter-wavelength resonator composed of resonators.The center working frequency of the filter is 6.8GHz,and the relative bandwidth reach 52.18%.The frequency range outside the passband is 8.6-18 GHz,and|S₂₁|<-25d B.（2）To further achieve miniaturization and high-performance filter design,a double-folded waveguide technique combined with Low Temperature Co-fired Ceramics（LTCC）technology is utilized to design a miniaturized C-band bandpass filter and a high-performance Ka-band bandpass filter with dual transmission zeros.The center frequency of the miniaturized C-band filter is 4.95GHz,and its planar size is reduced by three-quarters compared to a planar waveguide filter.The minimum insertion loss in the passband is 1.17d B,and the relative bandwidth is 11%.Subsequently,by analyzing the hybrid electromagnetic theory of SIW cavity,a bandpass filter with dual transmission zeros on both sides of the passband was designed using a vertically stacked cavity coupling structure.Simulation and testing results show that the filter has a minimum insertion loss of 1.57d B in the passband of 25.65-29.1GHz,with a return loss better than 20d B.Additionally,there are two transmission zeros at25.26GHz and 30.79GHz,greatly improving the out-of-band selectivity.