Overview of the CASTLE circuit simulator

CASTLE (Circuit Analysis and Simulation with Transmission-Line Emphasis) is a PC based code for simulating nonlinear analog circuits, designed primarily for Pulsed Power. CASTLE is an MNA (Modified Nodal Analysis) code that does transient analysis in a way that is very similar to SPICE and its derivatives. One key difference is that CASTLE has a fixed time step while SPICE has a variable time step. There are two main reasons for the fixed time step. One is exact reproduction of the output of our transmission line code, Bertha. This is very important of benchmarking with and transfer of specialized physics based models of Pulsed Power diodes. The second reason is to avoid the too-small-time-step failures that SPICE often has with Pulsed Power circuits. The CASTLE simulator has the ability to speed simulation using a unique matrix reduction technique. CASTLE uses the self-isolating property of transmission lines, in a similar way as transmission-line codes, to turn one large matrix into several smaller ones. This can lead to dramatic speed advantages for very large circuits, compared to SPICE. CASTLE has recently added an MPI (Message-Passing Interface) mode to further speed simulation. Also, there is now a dll version (for both Windows and Linux) of CASTLE that allows it to be run from the command line or other programs such as Python or C++. CASTLE includes a schematic entry GUI with sufficient quality for presentation or publication. This generates a SPICE compatible netlist that is used by the simulator.