Research Of The 5G Mm-wave Slot-coupled Directional Coupler Based On ISCGW

In 2020,5G will usher in a new peak period.Millimeter-wave technology will accelerate its maturity and application with the development of 5G.Directional couplers are used in millimeter-wave communication systems to measure reflections,mixed signals,and isolate signal sources in microwave and millimeter-wave systems so that the coupler is essential passive components.Therefore,it is significant to research and design a broadband miniaturized directional coupler.The integrated substrate gap waveguide has the advantages of low loss,planarization,and suitability for millimeter waves,which provides research directions for the design of new directional couplers.In this paper,two types of ISGW directional couplers are proposed using integrated substrate gap waveguide structure combined with aperture(slot)coupling theory:(1)An integrated substrate coupling gap waveguide(ISCGW)based on an integrated substrate gap waveguide(ISGW)is proposed.The structure of ISCGW is the same as that of ISGW.It is also composed of two layers of dielectric substrate,namely a via layer dielectric substrate and a gap layer dielectric substrate.The difference is that ISCGW has coupling slots on the metal ground of the gap layer dielectric substrate for electromagnetic fields of coupling.The ISCGW has the same low loss,planarization and other good transmission characteristics.(2)A single-slot coupler based on an integrated substrate coupling gap waveguide is proposed.The coupler consists of two ISCGWs,and the coupling is realized through a single slot on the common surface of the two ISCGWs.Exploring the analysis of the coupler using the even-odd mode analysis method and the quasi-static analysis method,the design theory of the single-slot coupler is derived.Then,the paper analyzes the influence of the EBG arrangement around the coupling conducting ridge on the coupler,and gives the optimal arrangement position of the EBG that can effectively reduce the return loss of the coupler and improve the isolation of the coupler.Further,the paper analyzes the transition line shapes of the conducting ridge and the coupling conducting ridge and finds that the curve transition can effectively reduce the return loss of the coupler.Through simulation optimization,the paper obtains 3dB,6dB,and 12 dB couplers with different coupling values.The working frequency band of the 3dB coupler is 23.07 to 28.55 GHz,the working frequency band of the 6dB coupler is 24.48 to 30.73 GHz,and the working frequency band of 12 dB coupler is 25.79 to 30.52 GHz.The designed coupler has a coupling fluctuation of ± 1dB in the working frequency band,isolation is higher than 20 dB,and return loss is lower than-20 dB.Finally,the 3dB and 12 dB single-slot couplers proposed in this paper were fabricated.The results show that the measured results of the single-slot coupler designed in this paper are in good agreement with the simulated results.Compared with the coupler published in the literature,the single-slot coupler proposed in this paper has the advantages of low loss,high isolation,and miniaturization.(3)A multi-slot coupler based on an integrated substrate coupling gap waveguide is proposed.The coupler is also composed of two ISCGWs.Unlike the single-slot coupler described above.The coupler realizes coupling through multiple coupling slots on the common surface of the two ISCGWs.The coupling slot is composed of a rectangular slot and a circular slot.The paper proposes to use the multi-slot coupling theory to conduct theoretical research on the coupler.At the same time,the paper analyzes the size of the coupling slot and the size of the coupling conducting ridge,and shows that the coupling degree of the coupler can be adjusted by adjusting the size of the coupling slot and the size of the coupling conducting ridge.The multi-slot coupler achieves different coupling values,through different number of slots and different slot sizes.Through simulation and optimization,couplers with different coupling values of 12 dB,8dB,6dB,and 3dB are obtained.The 12 dB coupler is realized by 5 coupling slots,and the working frequency band is 24.14 GHz to 31.5GHz,and bandwidth is 7.4GHz.The 8dB coupling is realized by 7 coupling slots,the working frequency band is 27.12 GHz to 35.16 GHz,and the bandwidth is 8GHz.The 6dB coupler and 3dB are achieved by 9 slots,of which the 6dB coupler operates at a frequency band of 24.22 GHz to 33.25 GHz to achieve 9GHz bandwidth and the 3dB coupler operates at a frequency band of 28.35 GHz to 35.49 GHz to achieve 7.1GHz bandwidth.The isolation of all couplers higher than 20 dB,return loss lower than-20 dB,and the coupling fluctuates of ± 1dB.Compared with the coupler published in the literature,the paper proposes that the multi-slot coupler has the advantages of high isolation,miniaturization and broadband.