Abaque de Smith – Download as PDF File .pdf), Text File .txt) or read online. EXERCICE ABAQUE DE – Download as PDF File .pdf), Text File .txt) or read online. fr. abaque de Smith, m diagramme de Smith, m diagramme polaire d’impédance, m. représentation graphique en coordonnées polaires du facteur de réflexion.
|Published (Last):||6 November 2013|
|PDF File Size:||4.87 Mb|
|ePub File Size:||4.47 Mb|
|Price:||Free* [*Free Regsitration Required]|
The Smith chart is plotted on the complex reflection coefficient plane in two dimensions and is scaled in normalised impedance the most commonnormalised admittance or both, using different colours to distinguish between them. The region above the x -axis represents capacitive admittances and the region below the x -axis represents inductive admittances.
File:Smith chart bmd.gif
This is equivalent to moving the point through a circular path of exactly degrees. This technique is a graphical alternative to substituting the values in the equations. Reflection coefficients can be read directly from the chart as they are unitless parameters.
This is the equation which describes how the complex reflection coefficient changes with the normalised impedance and may be used to construct both families of circles.
The Smith chart is actually constructed on such a polar diagram. The length of the line would then be scaled to P 1 assuming the Smith chart radius to be unity. Once a transformation from impedance to admittance has been performed, the scaling changes to normalised admittance until a later transformation back to normalised impedance is performed.
In avaque to change from normalised impedance to normalised admittance or vice versa, the point representing the value of reflection coefficient under consideration is moved through exactly degrees at the same radius.
File:Smith chart – Wikimedia Commons
The following table gives some similar examples of points which are plotted on the Z Smith chart. If there were very different values of resistance present a value closer to these might be a better choice. These are the equations which are used to construct the Z Smith chart.
An alternative shunt match could be calculated after performing a Aabaque chart transformation from normalised impedance to normalised xmith. Views Read Edit View anaque. The choice of whether to use the Z Smith chart or the Y Smith chart for any particular calculation depends on which is more convenient.
The following example shows how a transmission line, terminated with an arbitrary load, may be matched at one frequency either with a series or parallel reactive component in each case connected at precise positions. The outer circumferential scale of the Smith chart represents the distance from the generator to the load scaled in wavelengths and ed therefore scaled from zero to 0. In this case the circumferential wavelength scaling must be used, remembering that this is the wavelength within the transmission line and may differ from the free space wavelength.
In general therefore, most RF engineers work in the plane where the circuit topography supports linear addition.
Actual impedances and abaqhe must be normalised before using emith on a Smith chart. The degrees scale represents the angle of the voltage reflection coefficient at that point. Dealing wmith the reciprocalsespecially in complex numbers, is more time consuming and error-prone than using linear addition.
Provided the frequencies are sufficiently close, the resulting Smith chart points may be joined by straight lines to create a locus. If the termination was a perfect open or short circuit the magnitude of the voltage reflection coefficient would be unity, all power would be reflected and the point would lie at some point on the unity circumference circle of the Smith chart.
The earliest point at which a absque conjugate match could be introduced, moving towards the generator, would be at Q 21the same position as the previous P 21but this time representing a normalised admittance given by.
The Smith chart may be used to analyze such circuits in which case the movements around the chart are generated by the normalized impedances and admittances of the components at the frequency of operation.
Using complex exponential notation:. By substituting the expression for how reflection coefficient changes aabque an unmatched loss free transmission line. The conversion may be read directly from the Smith chart or by substitution into the equation.
Smith chart – Wikipedia
From Wikipedia, the free encyclopedia. They both change with frequency so for any particular measurement, the frequency at which it was performed must be stated together with the characteristic smjth. In this case the wavelength scaling on the Smith chart circumference is not used. To graphically change this to the equivalent normalised admittance point, say Q1, a line is drawn with a ruler from P1 through the Smith chart centre to Q1, an equal radius in the opposite direction.
The analysis starts with a Z Smith chart looking into R 1 only with no other components present.
As impedances and admittances change with frequency, problems using the Smith chart can only be solved manually using one frequency at a time, the result being represented by a point. The north pole is the perfect matching point, while the south pole s,ith the perfect mismatch point.
If the termination was a perfect open circuit or short circuit the magnitude of the reflection coefficient would be unity, all power would be reflected and the point would lie at some point on the unity circumference circle. Once an answer is obtained through the graphical constructions described below, it is straightforward to convert between normalised impedance or normalised admittance and the corresponding unnormalized value by multiplying by the characteristic impedance admittance.
For each, the reflection coefficient is given in polar form together with the corresponding normalised impedance in rectangular form.
Normalised impedance and normalised admittance are dimensionless. Considering the point at infinity, the space of the new chart includes all possible loads.