To design high frequency complex electromagnetic structures with TLM is not trivial in spite of the simplicity of the fundamental TLM algorithm. This is because TLM is a time and space discretization method in which the entire computational domain must be filled with nodes. In three-dimensional cases, the computational effort to solve realistic problems would soon become intractable unless special techniques are used. To be attractive to the design engineer, field simulation tools must include these advanced techniques automatically in the models. New TLM features and computational techniques have been developed in this thesis to overcome the above mentioned problems. An experimental multi-purpose electromagnetic field simulation tool has also been created to demonstrate the features and techniques developed in this thesis can be easily integrated into a well designed tool.