Once the circle is placed over the origin of the Smith chart, the input impedance to the pi network will be 50V. As shown, the VSWR is almost 3:1, and so the pi network must be tuned to place the “O” directly over the center (origin) of the Smith chart. These parameters are: Z (complex impedance), Y (complex admittance), S (S-parameter, S11, or return loss in decibels and the reflection angle), G (gamma, or reflection coefficient and reflection angle), V (VSWR) and F (frequency). If the “O” is highlighted with the mouse pointer, the “O” and the connecting arc will turn yellow, and several parameters will be listed in the top right corner of the screen. (It can be set to any desired value.) On the chart, the “X” represents the impedance at the load (output of the circuit at the right) and the “O” represents the impedance at the input to the circuit at the left. This VSWR circle is set to a VSWR of 1.5:1. This feature can be turned on or off as desired. The dotted circle around the center of the chart represents the constant VSWR circle. The values of the components are: C1 = 25pF, L1 = 50nH and C2 = 25pF. In Figure 1, the selected component is C1. The value of the selected component is shown in the box just below the schematic. If the program is not in the insert mode, the selected component will be replaced with the desired new component. The selected component is the one in the boxed area. In the insert mode, the new component will be placed just to the left of the selected component. In the insert mode, you can place a component on the schematic by simply clicking on the desired component button on the tool bar. All of the available components are shown as buttons on the tool bar. Navigating in the program First, a few notes about the screen snapshot.
#Smith chart software series
Here, a pi matching network is used to match a load consisting of a series resistor of 120ohm and an inductive reactance of 37ohm (120 + j37) to 50ohm. (Sourcing is given at the end.)įigure 1 below is a screen snapshot of the winSMITH computer program. A few examples will serve to illustrate just how useful this tool can be. The use of the winSMITH computerized Smith chart provides an excellent insight into transmission lines and matching networks. However, understanding transmission lines and impedance matching is valuable to all who work with radio frequency equipment. The Smith chart is not used by land mobile radio technicians in performing their routine duties.