<FONT face=Verdana>The UTD method applied to arbitrary surfaces is studied in this paper where the NURBS technique is introduced to construct electrically large targets and on the basis of the ray-tracing work done before

the calculation of ray fields including reflected ray field and creeping ray field are given. Combining the definition of NURBS with basic principles of differential geometry

parameters used in formulas are solved by numerical means while the line integral is expended by definition. Aiming at analyzing electrically large targets with arbitrary shapes

method presented

which doesn’t need much calculation resources and possesses higher precision

can be applied not only to typical analytical objects but also to arbitrary surfaces and examples of application are given.