Miniaturization Design Of Bandpass Filter Based On Substrate Integrated Waveguide Structure

With the rapid development of the 5th generation mobile communication technology(5G),the performance of equipment in the front-end system of radio frequency(RF)will be highly demanded.As a key device of RF front-end,the excellent performance of filter will play a key role in the normal work of communication system.Substrate Integrated Waveguide(SIW)has the advantages of low loss,high quality(Q)factor,and high power capacity.It also has the advantages of miniaturization,low cost,and easy integration.It is very suitable for today's mobile communication RF front-end system.Based on SIW,a band-pass filter working in 24.25GHz~27.5GHz and a band-pass filter working in 4GHz~5.6GHz at low frequency band are designed and fabricated for high frequency band of 5G communication,and miniaturization is realized.Specific work is as follows:A millimeter-wave MEMS bandpass filter with a center frequency of about26 GHz is designed and fabricated by combining the SIW structure with the micro-electro-mechanical system(MEMS)technology.Firstly,according to the three-dimensional processing characteristics of the MEMS process,the metal through-hole form of the traditional SIW structure is converted to the metal long column form.Then,according to the requirements of design indicators,the design is carried out according to the steps of network synthesis method.A model is built in the HFSS.The parameters of the filter are scanned and simulated.Finally,the specific process steps in the MEMS process are explained.The MEMS process is used to fabricate the physical object and the performance of the filter chip is tested,which proves the correctness of the design method.Since the Half-mode Substrate Integrated Waveguide(HMSIW)structure not only has the advantages of SIW,but also has an effective circuit area of only half of the SIW,it can better realize the miniaturization design of filters.In this paper,the design of SIW and HMSIW miniaturization filters based on Defected Ground Structure(DGS)isproposed.Firstly,the conversion structure between SIW and microstrip line is introduced.On this basis,the conversion structure between HMSIW and microstrip line is designed and analyzed.Then,the influence of the size parameters of rectangular DGS units on its transmission characteristics is discussed.Finally,DGS is loaded onto the transmission lines of SIW and HMSIW.A SIW filter with a center frequency of4.8GHz and a relative bandwidth of 33.3% and a HMSIW filter are designed.