==Plotting the S-Parameter on Smith Chart==
The Smith chart is a very useful graphical tool for RF engineers. [[RF.Spice A/D]] allows you to plot the S-[[parameters]] of your circuit on the Smith Chart. For this purpose, open the Network Analysis Test Panel of the Toolbox once again, and this time choose the '''S''' radio button in the "Parameter Set" section of the Output tab. For the "Graph Type", check the "Smith" checkbox. In order to better view the data points on the Smith chart, change the step size to 500MHz in the Sweep tab of the test panel. Run a network analysis of your RF circuit with the following [[parameters]]:
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Let's analyze the S11-parameter data plotted on the Smith chart in a little bit more detail. The S11-parameter data points over the frequency range 1-5GHz form a perfect circle around the center of the circular chart. The distance from the center is the magnitude of the reflection coefficient S11 (also known as the return loss). Since your T-Line segment is lossless (alpha = 0), its delivers the input signal to the load without attenuation. However, it causes a phase shift in the signal, which can also be interpreted as a time delay.
You can read the values of the data points on the Smith chart using the "Tracking Crosshairs" feature. For this purpose, click the '''Track Selected Plot''' [[File:b2TrackCH_Tool.png]] button of the '''[[Graph toolbar|Graph Toolbar]]''' and then move the mouse onto the surface of the Smith Chart. A tracking bar appears on the graph that connects the current cursor position to the data points. On the Status Bar, you can view the frequency associated with each data point as well as the real and imaginary parts of the reflection coefficient at that point. The 2GHz point is located at the center of the Smith chart.
== Exploring the Effect of Varying the Line Segment Length ==