The MPSTD algorithm is applied to model radiating longitudinal slot in the broad face of rectangular waveguide.Firstly

a method of dividing the total field and the scattering field is proposed based on the characteristic variables of Maxwell’s equations.Also the updating functions of the field in the interface between the subdomains of scattering field and total field has been derived.Secondly

the setting of excitation source is proposed by the idea of fields domain partition

which make the subdomains of incident field、 scattering field and total field contacted availably.So it is convenient to place incident field and pick up scattering field.The resonant length and impedance characteristics of longitudinal slot are analyzed by MPSTD.The numerical results show that the MPSTD algorithm is accurate and efficient to analyze the radiating longitudinal slot in the broad face of rectangular waveguide.