In this paper we use the moment method to analyze the characteristics of an isolated centered inclined slot on the broad face of a rectangular waveguide. Then we derive the scattering

matrix and the. equivalent impedance formulas. There are several triple integrals in the elements of admittance matrix. During numerical integration the triple integral is time consuming and divergent when the number of higher waveguide medes increases. Thus

we use an appropriate methed to reduce the triple integrals to double integrals

which are convergent

time saving and have better accuracy during numerical integration.The characteristic paramters obtained in this paper may be used to design a centered inclined slot array.