Ports and excitation

Ports add to the design from the Draw Tools menu. There are two types: a normal point Port, and a distributed Area Port.

The normal point port is the right choice in most cases. The area port is for simulating a very wide feed, or for cases where you need to excite a large region uniformly and measure the response.

Key port parameters

• Active. Whether this port is an active excitation source. Currently only one port may be active at a time, which keeps S-parameters meaningful. Hobby supports two ports (one active, one passive). Pro allows an arbitrary number of ports, with the same single-active-at-a-time rule and unlimited passive ports. Multiple ports let you measure transmission coefficients like S₂₁, S₃₁, and so on, in addition to S₁₁. Passive ports also act as matched energy absorbers, which matters for filters: a properly terminated second side behaves differently from an open, a short, or no port at all.
• Port Number. An index used to keep track of what is where.
• Impedance. The reference impedance the response is measured against. Typically 50 ohms, but it does not have to be if your system uses a different characteristic impedance.
• Bottom Layer. The bottom reference layer.
• Top Layer. The top (signal) layer.

Once you accept the configure dialog, place the port with a left click.

Point port vs area port

The point port has a purely cosmetic parameter called Icon Size in the properties panel. It changes how large the point port looks in the editor only. The area port size, on the other hand, is physically meaningful: it controls how the port is quantised into a cell region. A point port always resolves to a single 1 by 1 column of cells over the layer height, so its radius is purely visual.

The mesh preview makes the difference clear. A point port shows up as a single-cell column:

An area port spans the rectangular footprint you drew:

When a port is not over copper

Pressing Run on a project with a port not over copper opens the Simulation Blocked dialog. It lists the offending port and layer pairs and tells you what to fix: either move the port, or extend the copper for the reference layer.

Once a simulation has run, the S-Parameters tab shows the response produced at each port.