Research On Miniaturized Filter Technology Based On Substrate Integrated Waveguide Structure

With the development of communicate technology,the popularity of 4G technology and the arrival of the 5G era,the demands of wireless communication systems are increasing.As an important part of the communication system,the filter which has feature of high performance and small size is becoming more and more important.Due to its advantages of planarization,high performance,easy integration,low loss and high isolation,The Substrate Integrated Waveguide(SIW)has become an important choice in microwave circuit design.However the size of SIW structure which is similar to the metal waveguide structure is larger than the microstrip structure limits its application in microwave circuits.Therefore,the research of miniaturization technology of SIW and exploring new miniaturized design method of SIW structure have an important application value and a long-term scientific significance.In this paper,several miniaturization methods of SIW structure are analyzed and cross use to increase the miniaturization of SIW structure.Main research work and innovations of this paper are as follows:1.The electric field distribution of each resonant mode in the half-mold substrate integrated waveguide structure(HMSIW)is analyzed in this paper,and a slot which is in a specific position is used to offset the high-order mode,so that the resonant mode which is disturbed is forced close to the fundamental mode to form a passband.The position of the input and output ports is determined by the electromagnetic distribution of each resonant mode,the interference of other high-order modes of the HMSIW structure is avoided.As the capacitive loading effect of CSRR which is loaded on the HMSIW,the miniaturized result is achieved.Based on this,the second passband of the SIW filter is designed by using the self-resonant frequency of the CSRR structure.The frequency selectivity of the filter is enhanced by the coupling between the input and output.2.Loading the annular ring miniaturized element structure is an effective means to realize the miniaturization of the SIW structure.This structure is essentially a circular or rectangular miniaturized-element(CRME/RRME).The equivalent circuit model and electromagnetic field distribution inside the SIW which is loaded the RRME structure is analyzed.An improvement in miniaturization is achieved by QMSIW,as we can perform the segmentation similar to QMSIW for the SIW loaded with the RRME structure.Secondly,the electromagnetic field distribution of QMSIW loaded with RRME structure which is analyzed shows that the coupling polarity between the two resonators can be changed by adjusting the structure.This method is used to design and implement a single-passband SIW filter,and obtain two transmission zeros through the coupling between input and output,which suppresses the interference of high-order modes and achieves a good out-of-band suppression effect.A single-passband filter which have a center frequency in 3.96GHZ is designed by the resonator of QMSIW loaded by this quarter RRNME structure.The miniaturization rate of this filter is 94%.3.The miniaturization rate of the SIW structure is effectively improved by using a new type of feeding method which can combine the coplanar waveguide structure with the RRME structure to save the area of the resonant cavity.Moreover,this new feed structure generates two zero points,which improve the selectivity of the pass band.And on this basis,a slot which is in the inside of the RRME slotting position is utilizedto further increase the miniaturization of this structure,which is more compact than the RRME structure which is mentioned in above.This structure can also be combined with the QMSIW structure to achieve a higher miniaturization rate.We designed a single-passband filter in this way with a center frequency of 2.47 GHZ and a miniaturization rate of 98.7%.