| With the rapid development of 5th generation mobile communication technology,it is of great significance and value to study high frequency band,high performance and multi-function communication front-end devices.Filters and couplers are indispensable components of communication systems,so their development is very important to the performance of communication systems.Gap waveguide is one of the hot spots of millimeter wave microwave research in recent years.It forms the surface of artificial magnetic conductor(AMC)through the periodic arrangement of electrical tape gap(EBG)structural units,and can form a non-contact electromagnetic shielding structure together with the parallel ideal electrical conductor,which can produce a wide electromagnetic gap.In addition,the gap waveguide has the characteristics of low loss and self-encapsulation.The gap waveguide structure can be subdivided into ridge gap waveguide,slot gap waveguide and inverted microstrip line gap waveguide.Compared with slot gap waveguides,ridge gap waveguides are smaller and easier to integrate.Compared to inverted microstrip line gap waveguides,ridge gap waveguides have a lower profile and can use air as a propagation medium,greatly reducing dielectric loss.Therefore,this thesis focuses on the study of millimeter wave devices based on ridge gap waveguides.Taking the gap waveguide as the research object,the electrical tape gap(EBG)structural unit and the gap waveguide characteristics are explored and analyzed in this thesis.HFSS simulation tool and CST simulation tool are used to assist observation and research,and the influence of each parameter on the electromagnetic band gap is obtained.Based on the ridge gap waveguide structure,two filter structures and two coupler structures are studied and designed.The details are as follows:(1)A wideband bandpass filter based on ridge gap waveguide is designed.Based on the odd-even mode theory,a novel three-mode wideband bandpass filter is designed based on the double-ended open-circuit half-wavelength microstrip resonator and step impedance resonator.The measured results are basically consistent with the simulation results,and both have low insertion loss.The 3dB relative bandwidth reaches 30%,and the in band echo loss is low.There is a transmission zero on both sides of the passband,which has good out of band suppression.(2)A double passband filter based on ridge gap waveguide is designed.In this design,a dual passband filter is constructed by combining the double-ended open-circuit half-wavelength microstrip resonator with the lower rectangular cavity resonator composed of electrical tape gap(EBG)structural unit.The center frequency of the filter is 25.5 GHz and 32.6 GHz,the relative bandwidth of 3dB is 8.3% and 4%,the insertion loss is 0.27 dB and 0.43 dB,the in-band return loss is 29 dB and 28 dB,and there are four zeros lower than 40 dB.(3)A 3dB coupler based on ridge gap waveguide is designed.This design uses the ridge gap waveguide transmission line to construct a new type of branch line coupler,break the traditional branch line coupler structure,replace the λ/4 transmission line structure,reduce the volume of the device,change the coupling path between the two main transmission line,construct a new type of 3dB coupler.The measured results are basically consistent with the simulation results,and both can achieve a center frequency of 31 GHz,a relative bandwidth of 13.4%,a coupling degree of 3.9 ± 0.4 dB,and a phase difference of 89.35°± 5.85°.(4)A reconfigurable coupler based on ridge gap waveguide is designed.Based on Design(3),several PIN diodes are loaded in the bottom gap to construct an innovative reconfigurable coupler.The coupler can realize the coupler coupling degree adjustable quickly and simply.The simulation results show that the center frequency of the coupler is 28.9 GHz,the relative bandwidth is 14.5%,the coupling degree is 5 dB to 12 dB adjustable in 26.8-31 GHz,and the phase difference is-270°±5°.The measurement and simulation results are basically consistent. |
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