Theoretical And Experimental Research On Slow-wave Structure Of Terahertz Staggered Double Grating

Terahertz(THz)technology has broad application prospects of communication,imaging,radar,and other fields.THz traveling wave tube has the advantages of wide frequency bandwidth,moderate power level,and lightweight.The staggered double grating(SDG)slow-wave structure(SWS)is a kind of interaction circuit suitable for sheet beam traveling wave tubes.It has the advantages of simple structure,easy processing,and the ability to work in a wide frequency band.The characteristics of the SDG SWS are in-depth studied from three aspects:theoretical research,simulation analysis,and experimental verification.The main work include the following parts:1.The theoretical model of the SGD SWS is established by using the eigenfunction and field matching method,and the expressions of dispersion,coupling impedance,and loss are obtained.It is worth noting that the dispersion equation is a universal theoretical model.By reasonably setting the height of the metal grating and the staggered distance,it can successfully degenerate into the traditional double grating slow-wave structure aligned up and down and the rectangular waveguide grating slow-wave structure.It is numerically solved by adopting a suitable series truncation,and the calculation result is proved to be accurate.2.The working mode of the SDG SWS and the reasons for its broadband advantages have been clarified through the study of the staggered distance.The dispersion curves of the lowest two modes of SDG SWS converge when the staggered distance is exactly half a period,which broadens the frequency band.3.The approximate distribution of the loss of the SDG SWS is analyzed through the theoretical model of high-frequency loss.It is found that the top of the metal grating is the main loss occurrence area.The beam-wave interaction process under small-signal conditions is studied,and the"hot"dispersion equation is then derived.A kind of SDG SWS and a corresponding input and output coupler working in the G-band are designed,and the overall PIC simulation is performed.The actual circuit of the SDG SWS is processed,and the transmission loss value was obtained by the measurement using a vector network analyzer,and the conductivity of 2.6×10~7S/m is found to be in accord with it.The results of the actual measurement match well with the simulation results.