Qucs

Qucs, also known as Quite Universal Circuit Simulator, is a tool that allows you to design integrated circuits in a very schematic way to verify their performance. It includes an extensive component data base that can be inserted into the circuit. Each one has its respective electronic properties: resistances, voltage sources, diodes, transistors, gates, LEDs, bridges, etc. Qucs also allows you to calculate the electronic properties of different transmission lines and radio frequencies through a module known as QucsTranscalc. It manually introduces the values of the different parameters to obtain a precise result. Another similar tool to Qucs is Kicad, although this one is much more developed. It's your choice.