A full-wave analysis model, which uses the current-source port concept for combined electromagnetic and circuit simulation of linear and nonlinear uniplanar circuits is proposed. The passive distributed parts of the circuit are analyzed by the mixed-potential integral-equation formulation, and the connections between distributed parts and lumped elements are treated by the current-source ports. Based on this model, all electromagnetic effects associated with the distributed circuit parts, as well as the interactions between lumped elements (active or passive) and distributed elements (passive) can easily be characterized. In this study, the proposed model is tested by applying it to the problems with a chip capacitor, spiral inductor, and active slot antenna. The model is then employed to design and analyze two novel uniplanar mixers. The simulation results are also validated by the measurements.