Networks

A netlist project contains a netlist which consists of one or more networks with elements connected together. The netlist provides a map in which the ports of individual elements in the netlist are connected to the ports of other elements by the use of nodes. Nodes represent a connection between netlist elements. In other words, you use ports in your circuits to define connections, but you use nodes in a netlist. In order to connect a circuit in a netlist, you must assign its ports to nodes in the netlist. This is done when you define the circuit as an element in a netlist.

The picture above shows the network represented by the netlist shown in the project editor below it. The nodes are represented by the numbered black dots. The geometry project, steps.son, is connected between nodes 1 and 2 with node 1 corresponding to Port 1 in the geometry project and node 2 corresponding to Port 2. A resistor is connected between nodes 2 and 3. A capacitor is connected between node 3 and ground. The project steps.son is also connected between nodes 3 and 4, with Port 1 corresponding to node 4 and Port 2 corresponding to node 3. Port 1 of the network example_net corresponds to node 1 and port 2 of the network corresponds to node 4.

A netlist project is simply a list of these elements, as you can see in the netlist pictured above. Notice that the first number after the name of the element is the network node which corresponds to port 1 of the element, the second number is the network node which corresponds to port 2 of the element, and so on, for all the ports in an element.

The sequence of steps for a netlist project analysis may be summarized as follows:

1.   You input the netlist using the project editor in netlist mode. The project editor allows you to create and edit networks, network elements, project elements, modeled elements, and data elements in your netlist. You also input the analysis controls which may include defining parameters in the netlist.
2.   Em reads the netlist project which contains circuit and analysis control information. This includes S-, Y- and Z-parameter data files, modeled elements, geometry subprojects (project elements) and network elements.
3.   Em uses the analysis controls input as part of the netlist project to run each electromagnetic analysis invoked by the network file. It is possible to configure the analysis controls in such a way that geometry subprojects are analyzed using their own analysis controls. Netlist subprojects always inherit their analysis controls from the present netlist.
4.   Once the analysis of geometry subprojects is complete, em performs the circuit analysis specified in the netlist.
5.   Em combines the electromagnetic results with the circuit results to obtain the desired output results.

Note that the above sequence of steps is generalized for analyses which include both electromagnetic and circuit analysis. In cases where the overall analysis is restricted to either electromagnetic analysis or circuit analysis, some of the steps are omitted.

Example of Node Assignments in a Complex Circuit