The source block is placed near one end of the grid, positioned to inject a signal into the microstrip. The injected signal has a frequency content in the desired range, from 0Hz up to at least 10Ghz, and injects the signal as a voltage source.
The probes are placed in sets of four - the traditional quartet used for the LC pulse measurements - as shown in figure 3. The S-parameter analysis only uses the voltage and current measurements, but we might want to use the other probes (charge and magnetic flux) when examining line impedance or other parameters. Note that the probes are not specified as ideal; for instance, although we only need a to specify single infinitely thin line of integration to find the voltage, in this analysis a thick pillar is used. The probe is set to find the average voltage in the entire pillar. This is done partly because it gives a a smoother measurement value, and partly because it is convenient to design and place all the probes if they have the same width and depth.