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Smith Chart Use in RF Design and EMC Testing

This paper presents the basic concepts behind the Smith Chart and illustrates its use in several RF applications and ElectroMagnetic Compatibility (EMC) testing. The Smith Chart, is a graphical tool for analyzing and designing transmission line circuits as well as designing RF impedance matching circuits without the need for detailed and tedious numerical calculations. It is also extensively used in EMC testing and performance verification. In this paper the fundamentals of the Smith Chart are explained and followed by the input impedance calculations. Subsequently, several practical examples of the RF matching networks design are illustrated. Examples include L and Pi networks used for matching the source to the load antenna. EMC examples include vector network analyzer (VNA) calibration and measurements, line impedance stabilization network (LISN) impedance measurements, passive component impedance curves, and EMC filter characteristics.