![]() Once impedance matching requirements are determined, the results can be simulated in a SPICE-based simulation application.įor more information on Smith Chart, click here. Smith charts are a standard tool used by many RF engineers, so it pays to know how to use a Smith chart for impedance matching. Using a Smith chart might seem complicated to new designers, and one might question why it is any more or less useful than a graph in Cartesian coordinates. Find real and imaginary parts of the source/load impedance We will use Spectre simulation tool in this reference to find the impedance values. In some cases, such as with transmission line stub matching in RF circuits or input impedance matching to a feedline’s characteristic impedance, a graphical representation of impedance can aid impedance matching.Ī Smith chart provides just such a graphical representation of impedance, and it is a useful tool for understanding how impedance varies in different systems. General Approach The general approach is fairly simple, and can be done by taking the following steps: 1. To find the reflection coefficient from impedance, we use the formula that we previously derived, where ZL Z L is the load impedance, and zL ZL Z0 z L Z L Z 0 is the normalized load impedance. In many cases, you need to measure and carefully simulate the appropriate impedance required to ensure impedance matching and prevent power reflection. The reflection coefficient can be found from impedance or admittance. High speed and high frequency systems need impedance matching to ensure efficient power transfer and prevent reflections. ![]()
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