Tying method for RWG basis functions

Since the triangular patches can efficiently discretize arbitrary surfaces, the RWG basis function is the most popular basis function for the method of moments (MOM). However, for the modeling details of some parts, like thin wires, to use RWG the mesh has to be so fine that the number of unknowns increases dramatically. To overcome this, several kinds of basis functions are needed to work together. It is well known that to model a monopole antenna, three kinds of basis functions are needed, such as wire basis function, surface basis function and junction basis function. Though the number of unknown is reduced effectively without the loss of accuracy, the complexity causes the difficulty in code maintenance. The simplicity and generality of the triangular mesh are attractive. For the structure details, the number of patches will increase dramatically, However, a problem may not need that many unknowns. Hence, it is expedient to tie some unknowns together to reduce their number or the degree of freedom in solving the problem.