Design Of X-band Narrow-band Filter Based On SIW

With the development of communication technology,the fifth generation of communications technology and Internet of Things technology require more communications band,however,the spectrum is a limited resource,and spectrum is divided into narrower band to use,which will course the increasing of demand for narrow-band filter.Narrow-band filter means high selectivity,requires higher quality factor,and characteristics of modern communication systems tend to be miniaturization and integration,the traditional microstrip circuit is easy to integrate,but the loss is relatively high,the quality factor is low,do not apply to design the high selectivity of narrow-band filter,SIW structure is a blend of microstrip and traditional waveguide,the advantages of both ease of integration,but also has the characteristics of high Q,is widely used in various types of filter design.In this thesis,the transmission performance,matching problem of SIW in x-band are studied,and the relation between S parameters and structure size.Filters usually fall into three types:Butterworth filter,generalized Chebyshev filter and elliptic filter,which generalized Chebyshev filter can be artificially introducing suitable transmission zeros,and easy to implement,is often used to design high performance of narrow-band filter.In this thesis,using the method of recursive,generalized Chebyshev function was deduced,and design a generalized Chebyshev filter with 28 MHz bandwidth and center frequency of 11.673 GHz,within the passband S₂₁>1.5 dB,S₁₁<-27 dB.At the same time,the effect of coupling matrix on the zero shift of transmission response curve is studied.By resonance frequency extraction,coupling coefficient extraction,frequency modification and debugging diagnosis technology,a 6 orders generalized Chebyshev filter based on SIW structure with 4 transmissions zeros was designed,the indicators are:bandwidth for 28 MHz,center frequency is 11.673 GHz,within passband S₂₁>1.5 dB,S₁₁<-20 dB,the stop-band rejection is better than 40 dB.The overall size of filter is4.62mm×13.44mm×1.06mm.In order to testing filter precisely,this thesis studies a kind of conversion structure between SIW and microstrip,the relationship between the width and length of the structure is quadratic function,compare to the structure of the linear transformation,the structure size is smaller.In addition,the thesis proposal several kind of load which can be applied to test calibration of SIW devices.Because the performance of SIW filter is sensitive to structural parameters,sensitivity analysis and tolerance analysis are carried out for several main coupling hole sizes of the filter.The analysis shows that S11 in the passband is more sensitive than S21,and the filter is more dependent on tolerance.