Qucs is an integrated circuit simulator which means you will be
able to setup a circuit with a graphical user interface (GUI) and
simulate the large-signal, small-signal and noise behaviour of the
circuit. After that simulation has finished you will be able to
present the simulation results on a presentation page or window.
The software aims to support all kinds of circuit simulation types,
e.g. DC, AC, S-parameter, harmonic balance analysis, noise analysis,
QucsFilter is the filter synthesis tool used by Qucs. By use of
an input dialog the user can create a filter which is then copied into
the system-wide clipboard. In Qucs the user opens an empty
schematic and presses CTRL-V (paste from clipboard). The filter
schematic is now inserted and can be simulated.
Available filter types are: Butterworth, Bessel, Chebyshev, Cauer.