Design And Implementation Of SIW Bandpass Filter

With the development of communication technology,Radio Frequency(RF)front-end systems are developing towards miniaturization,'lightweight,high reliability,versatility and low cost.As an important part of RF front-end system,the performance of microwave passive filter has important influence on the whole RF front-end system.The large volume of the traditional filter at high frequency is not conducive to the miniaturization of the system,while the filter designed based on Substrate Integrated Waveguide(SIW)not only retains the characteristics of high quality factor,low insertion loss and high performance 'of the traditional filter,but also has the advantages of light mass,small volume and easy integration.Based on SIW theory,this paper designs and implements four SIW filters that can be applied to Wireless Local Area Network(WLAN),two of which can be applied' to 5GHz band of WLAN,and the remaining two can be applied to 2.4GHz band of WLAN.The main work of this paper is as follows:(1)Three kinds of microstrip transform structures are analyzed according to the used SIW resonator,among which the microstrip transform structure using coplanar waveguide can achieve the minimum return loss and insertion loss compared with the other two.Then under the SIW filter surface etching the defects in Structure of dumbbell Defected Ground Structure(DGS)to change its transmission characteristics,designed a center frequency of 5.6 GHz,insertion loss is less than 1 dB,return loss is more than 10 dB,3 dB bandwidth reaches 1 GHz SIW bandpass filter.Then,based on the Half Mode Substrate Integrated Waveguide(HMSIW)theory,a HMSIW filter with center frequency of 5.6GHz,3dB bandwidth of 1.5GHz,insertion loss less than 1dB and return loss greater than 15dB is designed.The two filters can be applied to the 5GHz band of WLAN.(2)Based on the theory of hexagonal SIW,carrying on the hexagonal SIW filter surface four Complementary Split Ring Resonator(CSRR)reduce its resonant frequency,designed a center frequency of 2.4 GHz,3 dB bandwidth of 100 MHz hexagonal SIW filter.And then on the basis of hexagonal SIW filter design,continue to design the half structure of hexagonal SIW filter,under the same design index,the half structure of hexagonal SIW filter compared with hexagonal SIW filter with smaller size,more miniaturization.The two filters can be applied to the 2.4GHz band of WLAN.