The Design Of SSPP Bandpass Filter Based On Substrate Integrated Waveguide

Substrate Integrated Waveguide(SIW)is similar to rectangular waveguide,but unlike rectangular waveguide,substrate integrated waveguide is a planar transmission line structure.After more than ten years of development,it is widely used in different fields.Various types of devices are manufactured.This paper mainly studies the application of substrate integrated waveguide structure on filter devices.Due to the rapid development of communication technology,the spectrum resources of low frequency bands are becoming increasingly tight,and the spectrum division and application of high frequency bands are on the agenda.Among them,9-15 GHz,as the carrier frequency band of future wireless communication,is also receiving more and more attention.This paper combines surface plasmon and substrate integrated waveguides to study the filter design in the 9-15 GHz band.Suface Plasmon Polaritons(SPP)are a special type of surface electromagnetic wave propagating along the surface of a conductor in the field of optical frequencies.Due to the advantages of limiting light in the sub-wavelength region,SPP has potential applications in the design of high density integrated optical components and circuits.SSPP(Spoof SPP)is a concept derived from the field of optics.It refers to the transmission of SPP surface waves in the microwave band through a special structural design.This paper studies the SSPP structure that has emerged in the last two years,analyzes its main characteristics,optimizes innovation,and proposes a new square-panel SSPP structure.Two kinds of SSPP bandpass filter based on SIW are designed.The main research contents are as follows:1.9-15 GHz bandpass filter based on high-pass and low-pass cascading is proposed.A high-pass filter is designed by using the similar filtering characteristics of the SIW transmission line and the rectangle.The cut-off frequency(9 GHz)of the high-pass filter is cascaded to form the lower cutoff frequency of the band-pass filter.By adding a waveguide transition structure on the SIW transmission line,the problem of excessive in-band loss of the SIW high-pass characteristic near the cut-off frequency is solved,and the in-band loss is reduced to below 17 dB.The low-pass part uses a grooved SSPP structure to design a broadband low-pass filter with a cutoff frequency of 15 GHz.The grooved SSPP structure consists of grooved microstrips arranged vertically on the microstrip line,and the transition band is realized.The transition from waveguide to SSPP structure is continued and HFSS electromagnetic simulation software is used to optimize the parameters to achieve the optimal structure.2.A new type of square-panel SSPP structure is proposed.The isolated metal square plate is formed by etching the closed gap on the upper metal surface and grounded through the metal through hole to form the main body of the SSPP structure.This new type of square disk type SSPP The cut-off frequency of the structure is mainly determined by the length L of the square disk.Other parameters such as the gap width,the square disk width and the distance between the periodic square plates may affect the in-band ripple.The 9-15 GHz band-pass filter is designed by using the proposed square-panel SSPP structure,which reduces the length of the device compared with the conventional loaded SSPP structure,such as a metal blind hole type and an etched cross structure.The structure is more compact.In summary,the proposed two band-pass filters have the advantages of flexible adjustment of the upper and lower cut-off frequencies,and the groove-type band-pass filter is simple in design and convenient in processing.The square-type bandpass filter is compact in size.Can be applied to other frequency bands.