Design Of Substrate Integrated Waveguide Filter Based On Defected Ground Structure

With the continuous progress of communication technology and its application,microwave and millimeter-wave communication systems with small volume,light weight,high reliability,multi-purpose and low cost have been greatly developed.The filter is located in the front end of the communication system,which can pre-select the required frequency band and suppress the interference.Band-pass filter is a common type of filter,and there are many methods to design it.Substrate Integrated Waveguide(SIW)band-pass filter is one of them,which has the advantages of small size,low loss and easy integration,and is very suitable for the design of future microwave and millimeter wave circuits.In this thesis,several novel SIW and HMSIW bandpass filters and HMSIW multi-passband filters with excellent performance are studied by using SIW technology and Defected Ground Structure(DGS).The main content of this thesis includes the following parts:In the first part,the filter classification,performance parameters and microwave implementation of the filter are analyzed.Then it focuses on the basic theory of SIW,including the basic structure and transmission characteristics of SIW,and then it studies the three transition structures connecting SIW and microstrip line,and their transmission characteristics are simulated and analyzed.Finally,based on the miniaturization technology of SIW,the basic structure and transmission characteristics of Half Mode Substrate Integrated Waveguide(HMSIW)are studied,which provide a theoretical basis for the design of HMSIW filters in the following sections.In the second part,the transmission characteristics of traditional DGS and a new type of DGS are analyzed.It is found that the new type of DGS has steeper attenuation characteristics and deeper stopband suppression.Then the influence of this new DGS on the transmission characteristics of microstrip line is studied,and this new type of DGS is periodically etched on the grounding plate of the SIW structure to realize a SIW bandpass filter with excellent performance.The influence of each size parameter in this DGS on the performance of the SIW bandpass filter is emphatically studied.In order to reduce the overall circuit size of the filter,this kind of DGS is also periodically etched on the ground floor of HMSIW to realize an HMSIW wideband bandpass filter,which not only has a wider operating bandwidth,but also reduces the circuit size about 50%.In the third part,the basic structure and transmission characteristics of CSRR are first studied.Then,by etching two pairs of square CSRR structures of different sizes on the upper surface of the HMSIW structure,a HMSIW filter capable of three-band filtering in the frequency range of2GHz?12GHz is designed.In order to improve the out-of-band attenuation steepness of the filter,the periodic C-shape DGS is etched on the interface floor of the filter,and finally a miniaturized HMSIW-CSRR three-band filter with flat passband and high channel selectivity is realized.The three-band filter can be used in high-speed Wireless Local Area Network(LAN),Global Interoperability for Microwave Access(Wi MAX),and Industrial,Scientific,and Medical(ISM)RF system front-end circuits to facilitate access to different services using a single multi-mode terminal.