Quite Universal Circuit Simulator (Qucs) is a circuit simulator with graphical user interface. The program aims to support all kinds of circuit simulation types, e.g. DC, AC, S-parameter, Transient, Noise and Harmonic Balance analysis. Pure digital simulations are also supported.
After that simulation has finished you can view the simulation results on a presentation page or window.
Qucsator, the simulation backend, is a command line circuit simulator. It takes a network list in a certain format as input and outputs a Qucs dataset. It has been programmed for usage in the Qucs project but may also be used by other applications.

The license of this software is Free, you can free download and free use this cad software.