With the development of modern communication technology, the requirements on systems with high integration, small volume and low cost are becoming more and more stringent. As we know, the cost of RF front end usually occupy the most of the total cost of a whole system, it is thus very meaningful to investigate some techniques to develop RF front end with the features of compactness, transportable possibility and low cost. This project will be directed to the theoretical and engineering investigation of RF front end system for communication application, which is based on SoS technology. The highlight of this project may lie in that, the non-planar waveguide structures can be implemented into substrate and dissimilar waveguides can be integrated together with other planar circuits. We may make good use of the advantages of probably all the transmission lines, including planar and non-planar ones. This may create many possible new components and circuits. In addition, the electromagnetic bandgap concept, even the metamaterials can be also incorporated for further development of novel microwave circuits. Some physical insights and engineering design techniques should be investigated for discontinuity design with lower radiation and reflection losses; this should be very useful in large-scale beam feeding network for antenna array and some other applications. In this project, one of the main works is to develop powerful EM computational methods suitable for the analysis of complex structures, for example, combination of planar and non-planar structures, metal posts, vertical connections and some others. Based on the solid grounding of EM computational work in this group, several computational methods should be combined and lead to a powerful method for analysis and design guidance of the microwave circuits or subsystems based on SoS technology. In order to demonstrate the theoretical strategies, one RF front end for potential application in communication technology will be developed.