A mode analysis is presented for the double-grating rectangular waveguide slow-wave structure(SWS) with arbitrary longitudinal displacements between the two gratings.By matching boundary conditions along the sides of the gratings,the distribution of electromagnetic field and high frequency characteristics of the SWS are studied.The simulation results show that the dispersion curve deduced from field equations is in good agreement with that simulated by software while the interaction impedance is higher than...