Smith chart properties Inverse Smith Chart (Complex Admittance) The Smith chart format is useful for looking for mismatch introduced by parasitic elements connected in series with the DUT. Use the Smith chart to assess circuit mismatch and determine whether the load is resistive, inductive, capacitive, or complex. The u nit circle diagram corresponds to an unmatched circuit with total reflection | | = 1. The center of the diagram corresponds to a matched circuit with no reflect signal ( = 0). Thus, any circle with the center coinciding with the center of the diagram contains equal values of the modulus of the reflection coefficient. Reflection coefficient value ( ) at any point of the diagram is determined by the distance from it to the center of the diagram.The upper and lower halves of the diagram correspond to the positive (inductive) and negative (capacitive) reactive components of impedance.Location of the unit circle at a scale greater than 1 The measured points inside the unit circle correspond to the passive load, the points outside to the active load. The outer circle of the diagram at scale = 1 (or unit circle) corresponds to a zero resistance value ( reactance only ).At the leftmost point of the horizontal axis, the impedance value is zero (Short circuited load).At the rightmost point of the horizontal axis, the impedance has an infinitely large value (Open circuited load).The center of the diagram corresponds to the system reference impedance (Z/Z0 = 1).Grid lines of the diagram consist of circles of constant resistance and arcs of constant reactance.The horizontal axis is resistance reactance on this axis is equal to zero.Where - real part of the impedance (resistance), - imaginary part of the impedance (reactance). Each point on the diagram is equivalent to the complex impedance of the DUT :.The angle is calculated counterclockwise.īasic properties of the Smith chart (See figure below ): The length of this vector is equal to the response amplitude, and the angle between the vector and the positive part of the real coordinate axis is equal to the phase of the response. Parameters of the vector directed to the point from the center of the diagram.Coordinates of the point (Re, Im) on the real and imaginary coordinate axes.On circular diagrams (Polar and Smith chart), any point of the trace can be defined in the following two ways (See figure below):
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