Smith chart

{{Short description|Electrical engineers graphical calculator}} {{For|other uses of the term Smith diagram|Smith diagram (disambiguation)}} {{Redirect|Volpert nomogram|other types of graphs attributed to Volpert|Volpert graph (disambiguation){{!}}Volpert graph}} {{Use British English|date=August 2017}} {{Use dmy dates|date=June 2023|cs1-dates=y}} {{Use list-defined references|date=June 2023}} {{Multiple image|total_width = 600  | width = 600 | caption_align = center | image_style = border:none  | image_gap = 8 | image1 = Bare Bones Smith Chart - with annotations.png | link1 = File:Bare Bones Smith Chart - with annotations.png | caption1 = (a)  | image2 = Animated Smith Chart (cropped).gif | link2 = File:Animated Smith Chart (cropped).gif | caption2 = (b) | footer = A smith chart is a graphical overlay that allows plotting a complex reflection coefficient, <math>\Gamma</math>, on top of grid lines of constant normalized impedance, <math>z</math>.{{efn|Both the reflection coefficient, <math>\Gamma</math>, and the normalized impedance, <math>z</math>, are unitless quantities; <math>\Gamma</math> is defined a ratio of voltages, and <math>z</math> is defined as a ratio of impedances}} Since the normalized impedance is also a complex quantity, the Smith Chart shows both lines of constant <math>\Re e[z]</math> and lines of constant <math>\Im m[z]</math>.{{efn|The <math>\Re e[z]</math> corresponds to the electrical resistance and the <math>\Im m[z]</math> correspond to the electrical reactance.}} The Smith chart is limited to values of normalized resistance, <math>z</math>, for which <math>\Re e[z]\ge0</math>, since Smith charts are mainly used for passive circuits.{{efn|Negative resistance, which corresponds to <math>\Re e[z]<0</math>, is associated with active circuitry.}} (a) A sample Smith chart in which the lines of constant <math>\Im m[z]</math> are depicted as blue arcs{{efn|name="z pure real"|For the case of <math>\Im m[z]=0</math>, the arc becomes a straight line (which is a circle of infinite radius).}} and lines of constant <math>\Re e[z]</math> are depicted as red circles. (b) an animated transformation of lines of constant <math>\Re e[z]</math> and lines of constant <math>\Im m[z]</math> from the <math>z-</math>space (where the lines appear straight vertical and horizontal) to the <math>\Gamma-</math>space (where the lines appear as circles). The transformation is a conformal mapping. Pink lines are used to denote <math>\Re e[z]<0</math> and black lines are used to denote <math>\Re e[z]\ge0</math>.}} The '''Smith chart''' (sometimes also called '''Smith diagram''', '''Mizuhashi chart''' ({{lang|ja|水橋チャート}}), '''Mizuhashi–Smith chart''' ({{lang|ja|水橋スミスチャート}}),<ref name="Okamura_1959"/><ref name="Kenichi_1999"/><ref name="Mori_2013"/> '''Volpert–Smith chart''' ({{lang|ru|Диаграмма Вольперта—Смита}})<ref name="Kurochkin_2009"/><ref name="Salov_2022"/> or '''Mizuhashi–Volpert–Smith chart''') is a graphical calculator or nomogram designed for electrical and electronics engineers specializing in radio frequency (RF) engineering to assist in solving problems with transmission lines and matching circuits.<ref name="Ramo-Whinnery-Duzer_1965"/><ref name="Ramo-Whinnery-Duzer_1994"/><ref name="Smith_1969"/><ref name="Smith_1995"/><ref name="MAX_2012"/>

It was independently<ref name="Voltmer_2007"/><ref name="Kurochkin_2009"/><ref name="ETHW_2018"/><ref name="Salov_2022"/> proposed by Tōsaku Mizuhashi ({{lang|ja|水橋東作}}) in 1937,<ref name="Mizuhashi_1937"/> and by {{ill|Amiel Rafailovich Volpert|ru|Вольперт, Амиэль Рафаилович|lt=Amiel R. Volpert}} ({{lang|ru|Амиэ́ль Р. Во́льперт}})<ref name="Volpert_1940"/><ref name="Kurochkin_2009"/> and Phillip H. Smith in 1939.<ref name="Smith_1939"/><ref name="Smith_1944"/> Starting with a rectangular diagram, Smith had developed a special polar coordinate chart by 1936, which, with the input of his colleagues Enoch B. Ferrell and James W. McRae, who were familiar with conformal mappings, was reworked into the final form in early 1937, which was eventually published in January 1939.<ref name="Smith_1939"/><ref name="Smith_1995"/><ref name="Inan_2005"/> While Smith had originally called it a "''transmission line chart''"<ref name="Smith_1939"/><ref name="Smith_1944"/> and other authors first used names like "''reflection chart''", "''circle diagram of impedance''", "''immittance chart''" or "''Z-plane chart''",<ref name="Smith_1995"/> early adopters at MIT's Radiation Laboratory started to refer to it simply as "''Smith chart''" in the 1940s,<ref name="Smith_1995"/><ref name="Inan_2005"/> a name generally accepted in the Western world by 1950.<ref name="Linton_1950"/><ref name="GeneralRadio_1950"/>

The Smith chart can be used to simultaneously display multiple parameters including impedances, admittances, reflection coefficients, <math>S_{nn}\,</math> scattering parameters, noise figure circles, constant gain contours and regions for unconditional stability.<ref name="Pozar_2005"/><ref name="Gonzalez_1997"/>{{rp|pages=93–103}} The Smith chart is most frequently used at or within the unity radius region. However, the remainder is still mathematically relevant, being used, for example, in oscillator design and stability analysis.<ref name="Gonzalez_1997"/>{{rp|pages=98–101}} While the use of paper Smith charts for solving the complex mathematics involved in matching problems has been largely replaced by software based methods, the Smith chart is still a very useful method of showing<ref name="Bevelacqua_2013"/> how RF parameters behave at one or more frequencies, an alternative to using tabular information. Thus most RF circuit analysis software includes a Smith chart option for the display of results and all but the simplest impedance measuring instruments can plot measured results on a Smith chart display.<ref name="Tektronix_2017"/> thumb|290x290px|An impedance Smith chart (with no data plotted)

==Overview== [[Image:NetworkAnalyzer.jpg|400px|thumb|A network analyzer set up to display measured data on a Smith chart.]]

The Smith chart is a mathematical transformation of the two-dimensional Cartesian complex plane. Complex numbers with positive real parts map inside the circle. Those with negative real parts map outside the circle. If we are dealing only with impedances with non-negative resistive components, our interest is focused on the area inside the circle. The transformation, for an impedance Smith chart, is:

<math display="block">\Gamma = \frac{Z - Z_0}{Z + Z_0} = \frac{z - 1}{z + 1},</math>

where {{math|1= ''z'' = {{sfrac|''Z''|''Z''{{sub|0}}}}}}, i.e., the complex impedance, {{mvar|Z}}, normalized by the reference impedance, {{math|''Z''{{sub|0}}}}. The impedance Smith chart is then an Argand plot of impedances thus transformed. Impedances with non-negative resistive components will appear inside a circle with unit radius; the origin will correspond to the reference impedance, {{math|''Z''{{sub|0}}}}.

The Smith chart is plotted on the complex reflection coefficient plane in two dimensions and may be scaled in normalised impedance (the most common), normalised admittance or both, using different colours to distinguish between them. These are often known as the Z, Y and YZ Smith charts respectively.<ref name="Gonzalez_1997"/>{{rp|page=97}} Normalised scaling allows the Smith chart to be used for problems involving any characteristic or system impedance which is represented by the center point of the chart. The most commonly used normalization impedance is 50 ohms. 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). Reflection coefficients can be read directly from the chart as they are unitless parameters.

The Smith chart has a scale around its circumference or periphery which is graduated in wavelengths and degrees. The wavelengths scale is used in distributed component problems and represents the distance measured along the transmission line connected between the generator or source and the load to the point under consideration. The degrees scale represents the angle of the voltage reflection coefficient at that point. The Smith chart may also be used for lumped-element matching and analysis problems.

Use of the Smith chart and the interpretation of the results obtained using it requires a good understanding of AC circuit theory and transmission-line theory, both of which are prerequisites for RF engineers.

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. This is often adequate for narrow band applications (typically up to about 5% to 10% bandwidth) but for wider bandwidths it is usually necessary to apply Smith chart techniques at more than one frequency across the operating frequency band. Provided the frequencies are sufficiently close, the resulting Smith chart points may be joined by straight lines to create a locus.

A locus of points on a Smith chart covering a range of frequencies can be used to visually represent: *how capacitive or how inductive a load is across the frequency range *how difficult matching is likely to be at various frequencies *how well matched a particular component is. The accuracy of the Smith chart is reduced for problems involving a large locus of impedances or admittances, although the scaling can be magnified for individual areas to accommodate these.

==Mathematical basis== [[File:Smith chart explanation.svg|thumb|500px|right|Most basic use of an impedance Smith chart. A wave travels down a transmission line of characteristic impedance {{math|''Z''{{sub|0}}}}, terminated at a load with impedance {{math|''Z''{{sub|L}}}} and normalised impedance {{math|1=''z'' = ''Z''{{sub|L}}/''Z''{{sub|0}}}}. There is a signal reflection with coefficient {{math|Γ}}. Each point on the Smith chart simultaneously represents both a value of {{mvar|z}} (bottom left), and the corresponding value of {{math|Γ}} (bottom right), related by {{math|1=''z'' = (1 + Γ)/(1 − Γ).}}]]

===Actual and normalised impedance and admittance=== A transmission line with a characteristic impedance of <math>Z_0\,</math> may be universally considered to have a characteristic admittance of <math>Y_0\,</math> where :<math>Y_0 = \frac{1}{Z_0}\,</math> Any impedance, <math>Z_\text{T}\,</math> expressed in ohms, may be normalised by dividing it by the characteristic impedance, so the normalised impedance using the lower case ''z''T is given by :<math>z_\text{T} = \frac{Z_\text{T}}{Z_0}\,</math> Similarly, for normalised admittance :<math>y_\text{T} = \frac{Y_\text{T}}{Y_0}\,</math> The SI unit of impedance is the ohm with the symbol of the upper case Greek letter omega (Ω) and the SI unit for admittance is the siemens with the symbol of an upper case letter S. Normalised impedance and normalised admittance are dimensionless. Actual impedances and admittances must be normalised before using them on a Smith chart. Once the result is obtained it may be de-normalised to obtain the actual result.

===The normalised impedance Smith chart=== thumb|right|300px|Transmission lines terminated by an open circuit (top) and a short circuit (bottom). A pulse reflects perfectly off both these terminations, but the sign of the reflected voltage is opposite in the two cases. Black dots represent electrons, and arrows show the electric field. Using transmission-line theory, if a transmission line is terminated in an impedance (<math>Z_\text{T}\,</math>) which differs from its characteristic impedance (<math>Z_0\,</math>), a standing wave will be formed on the line comprising the resultant of both the incident or '''f'''orward (<math>V_\text{F}\,</math>) and the '''r'''eflected or reversed (<math>V_\text{R}\,</math>) waves. Using complex exponential notation: :<math>V_\text{F} = A \exp(j \omega t)\exp(+\gamma \ell)~\,</math> and :<math>V_\text{R} = B \exp(j \omega t)\exp(-\gamma \ell)\,</math> where

:<math>\exp(j \omega t)\,</math> is the temporal part of the wave :<math>\exp(\pm\gamma \ell)\,</math> is the spatial part of the wave and :<math>\omega = 2 \pi f\,</math> where :<math>\omega\,</math> is the angular frequency in radians per second (rad/s) :<math>f\,</math> is the frequency in hertz (Hz) :<math>t\,</math> is the time in seconds (s) :<math>A\,</math> and <math>B\,</math> are constants :<math>\ell\,</math> is the distance measured along the transmission line from the load toward the generator in metres (m) Also :<math>\gamma = \alpha + j \beta\,</math> is the propagation constant which has SI units radians/meter where :<math>\alpha\,</math> is the attenuation constant in nepers per metre (Np/m) :<math>\beta\,</math> is the phase constant in radians per metre (rad/m) The Smith chart is used with one frequency (<math>\omega</math>) at a time, and only for one moment (<math>t</math>) at a time, so the temporal part of the phase (<math>\exp(j \omega t)\,</math>) is fixed. All terms are actually multiplied by this to obtain the instantaneous phase, but it is conventional and understood to omit it. Therefore, :<math>V_\text{F} = A \exp(+\gamma \ell)\,</math> and :<math>V_\text{R} = B \exp(-\gamma \ell)\,</math>

where <math>A\,</math> and <math>B\,</math> are respectively the forward and reverse voltage amplitudes at the load.

====The variation of complex reflection coefficient with position along the line==== [[File:SmithChartLineLength.svg|thumb|right|500px|Looking towards a load through a length {{mvar|{{ell}}}} of lossless transmission line, the impedance changes as {{mvar|{{ell}}}} increases, following the blue circle; this impedance is characterized by its reflection coefficient {{math|''V''{{sub|reflected}}/''V''{{sub|incident}}}}. The blue circle, centered within the impedance Smith chart, is sometimes called an ''SWR circle'' (short for ''constant standing wave ratio'').]] The complex voltage reflection coefficient <math>\Gamma\,</math> is defined as the ratio of the reflected wave to the incident (or forward) wave. Therefore, :<math>\Gamma = \frac{V_\text{R}}{V_\text{F}} = \frac{B \exp(-\gamma \ell)}{A \exp(+\gamma \ell)} = C \exp(-2 \gamma \ell)\,</math> where {{math|''C''}} is also a constant.

For a uniform transmission line (in which <math>\gamma\,</math> is constant), the complex reflection coefficient of a standing wave varies according to the position on the line. If the line is lossy (<math>\alpha\,</math> is non-zero) this is represented on the Smith chart by a spiral path. In most Smith chart problems however, losses can be assumed negligible (<math>\alpha \approx 0\,</math>) and the task of solving them is greatly simplified. For the loss free case therefore, the expression for complex reflection coefficient becomes :<math>\Gamma = \Gamma_\text{L} \exp(-2 j \beta \ell)\,</math> where <math>\Gamma_\text{L}\,</math> is the reflection coefficient at the load, and <math>\ell\,</math> is the line length from the load to the location where the reflection coefficient is measured. The phase constant <math>\beta\,</math> may also be written as :<math>\beta = \frac{2 \pi}{\lambda}\,</math> where <math>\lambda\,</math> is the wavelength ''within the transmission line'' at the test frequency.

Therefore, :<math>\Gamma = \Gamma_\text{L} \exp\left(\frac{-4 j \pi}{\lambda}\ell\right)\,</math> This equation shows that, for a standing wave, the complex reflection coefficient and impedance repeats every half wavelength along the transmission line. The complex reflection coefficient is generally simply referred to as reflection coefficient. The outer circumferential scale of the Smith chart represents the distance from the generator to the load scaled in wavelengths and is therefore scaled from zero to 0.50.

====The variation of normalised impedance with position along the line==== If <math>\,V\,</math> and <math>\,I\,</math> are the voltage across and the current entering the termination at the end of the transmission line respectively, then :<math>V_\mathsf{F} + V_\mathsf{R} = V \,</math> and :<math> V_\mathsf{F} - V_\mathsf{R} = Z_0\, I \,</math>. By dividing these equations and substituting for both the voltage reflection coefficient :<math> \Gamma = \frac{V_\mathsf{R}}{\, V_\mathsf{F} \,} \,</math> and the normalised impedance of the termination represented by the lower case {{mvar|z}}, subscript T :<math> z_\mathsf{T} = \frac{V}{\, Z_0\, I \,} \,</math> gives the result: :<math> z_\mathsf{T} = \frac{1 + \Gamma}{\, 1 - \Gamma \,} \,.</math> Alternatively, in terms of the reflection coefficient :<math> \Gamma = \frac{z_\mathsf{T} - 1}{\, z_\mathsf{T} + 1 \,} \,</math> These are the equations which are used to construct the {{math|Z}} Smith chart. Mathematically speaking <math>\,\Gamma\,</math> and <math>\,z_\mathsf{T}\,</math> are related via a Möbius transformation.

Both <math>\,\Gamma\,</math> and <math>\,z_\mathsf{T}\,</math> are expressed in complex numbers without any units. They both change with frequency so for any particular measurement, the frequency at which it was performed must be stated together with the characteristic impedance.

<math>\,\Gamma\,</math> may be expressed in magnitude and angle on a polar diagram. Any actual reflection coefficient must have a magnitude of less than or equal to unity so, at the test frequency, this may be expressed by a point inside a circle of unity radius. The Smith chart is actually constructed on such a polar diagram. The Smith chart scaling is designed in such a way that reflection coefficient can be converted to normalised impedance or vice versa. Using the Smith chart, the normalised impedance may be obtained with appreciable accuracy by plotting the point representing the reflection coefficient ''treating the Smith chart as a polar diagram'' and then reading its value directly using the characteristic Smith chart scaling. This technique is a graphical alternative to substituting the values in the equations.

By substituting the expression for how reflection coefficient changes along an unmatched loss-free transmission line :<math> \Gamma = \frac{B \exp(-\gamma \ell)}{A \exp(\gamma \ell)} = \frac{B \exp(-j \beta \ell)}{A \exp(j \beta \ell)} \,</math> for the loss free case, into the equation for normalised impedance in terms of reflection coefficient :<math> z_\mathsf{T} = \frac{1 + \Gamma}{\, 1 - \Gamma \,} \,.</math> and using Euler's formula :<math> \exp(j\theta) = \text{cis}\, \theta = \cos \theta + j\, \sin \theta \,</math> yields the impedance-version transmission-line equation for the loss free case:<ref name="Hayt_1981"/> :<math>Z_\mathsf{in} = Z_0 \frac{\, Z_\mathsf{L} + j\, Z_0 \tan (\beta \ell) \,}{\, Z_0 + j\, Z_\mathsf{L} \tan (\beta \ell) \,} \,</math> where <math>\,Z_\mathsf{in}\,</math> is the impedance 'seen' at the input of a loss free transmission line of length <math>\,\ell\, ,</math> terminated with an impedance <math>\,Z_\mathsf{L}\,</math>

Versions of the transmission-line equation may be similarly derived for the admittance loss free case and for the impedance and admittance lossy cases.

The Smith chart graphical equivalent of using the transmission-line equation is to normalise <math>\, Z_\mathsf{L} \, ,</math> to plot the resulting point on a {{math|Z}} Smith chart and to draw a circle through that point centred at the Smith chart centre. The path along the arc of the circle represents how the impedance changes whilst moving along the transmission line. 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.

====Regions of the {{math|Z}} Smith chart==== If a polar diagram is mapped on to a cartesian coordinate system it is conventional to measure angles relative to the positive {{mvar|x}}-axis using a counterclockwise direction for positive angles. The magnitude of a complex number is the length of a straight line drawn from the origin to the point representing it. The Smith chart uses the same convention, noting that, in the normalised impedance plane, the positive {{mvar|x}}-axis extends from the center of the Smith chart at <math>\, z_\mathsf{T} = 1 \pm j 0 \,</math> to the point <math>\, z_\mathsf{T} = \infty \pm j \infty \,.</math> The region above the x-axis represents inductive impedances (positive imaginary parts) and the region below the {{mvar|x}}-axis represents capacitive impedances (negative imaginary parts).

If the termination is perfectly matched, the reflection coefficient will be zero, represented effectively by a circle of zero radius or in fact a point at the centre of the Smith chart. 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.

====Circles of constant normalised resistance and constant normalised reactance==== The Smith chart is composed of two families of circles: circles of constant normalised resistance (constant lines of <math>\Re e[z]</math>) and circles of constant normalised reactance (constant lines of <math>\Im m[z]</math>). In the complex reflection coefficient plane the Smith chart occupies a circle of unity radius centred at the origin. In cartesian coordinates therefore the circle would pass through the points (+1,0) and (−1,0) on the {{mvar|x}}-axis and the points (0,+1) and (0,−1) on the {{mvar|y}}-axis.

Substituting <math>z= \Re e[z] + j\Im m[z]</math> (where <math>j</math> is the imaginary number<math>=\sqrt{-1}</math>) into the equation <math>\Gamma = \frac{z - 1}{\, z + 1 \,} </math> yields the following result (after eliminating the imaginary number <math>j</math> from the denominator by multiplying both the numerator and denominator by the complex conjugate of the denominator): :<math>\Gamma = \left[\frac{\Re e[z]^2 + \Im m[z]^2 - 1}{\,(\Re e[z] + 1)^2 + \Im m[z]^2\,}\right] + j \left[\frac{2\,\Im m[z]}{\,(\Re e[z] + 1)^2 + \Im m[z]^2\,}\right] .</math> This equation produces circles when plotting lines of constant <math>\Re e[z]</math> or constant <math>\Im m[z]</math>. For passive pasive components, the lines of the Smith charted are only plotted for values of <math>\Re e[z]>0</math>.<ref name="Davidson_1989"/>

===Practical examples=== thumbnail|Example points plotted on the normalized impedance Smith chart A point with a reflection coefficient magnitude 0.63 and angle 60° represented in polar form as <math>0.63\angle60^\circ\,</math>, is shown as point P1 on the Smith chart. To plot this, one may use the circumferential (reflection coefficient) angle scale to find the <math>\angle60^\circ\,</math> graduation and a ruler to draw a line passing through this and the centre of the Smith chart. The length of the line would then be scaled to P1 assuming the Smith chart radius to be unity. For example, if the actual radius measured from the paper was 100 mm, the length OP1 would be 63 mm.

The following table gives some similar examples of points which are plotted on the ''Z'' Smith chart. For each, the reflection coefficient is given in polar form together with the corresponding normalised impedance in rectangular form. The conversion may be read directly from the Smith chart or by substitution into the equation.

{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;" |+Some examples of points plotted on the normalised impedance Smith chart !width="200"|Point identity !width="250"|Reflection coefficient (polar form) !width="300"|Normalised impedance (rectangular form) |- |P1 (Inductive) |<math>0.63\angle60^\circ\,</math> |<math>0.80 + j1.40\,</math> |- |P2 (Inductive) |<math>0.73\angle125^\circ\,</math> |<math>0.20 + j0.50\,</math> |- |P3 (Capacitive) |<math>0.44\angle-116^\circ\,</math> |<math>0.50 - j0.50\,</math> |}

===Working with both the ''Z'' Smith chart and the ''Y'' Smith charts=== In RF circuit and matching problems sometimes it is more convenient to work with admittances (representing conductances and susceptances) and sometimes it is more convenient to work with impedances (representing resistances and reactances). Solving a typical matching problem will often require several changes between both types of Smith chart, using normalised impedance for series elements and normalised admittances for parallel elements. For these a dual (normalised) impedance and admittance Smith chart may be used. Alternatively, one type may be used and the scaling converted to the other when required. In order 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 180 degrees at the same radius. For example, the point P1 in the example representing a reflection coefficient of <math>0.63\angle60^\circ\,</math> has a normalised impedance of <math> z_P = 0.80 + j1.40\,</math>. 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. This is equivalent to moving the point through a circular path of exactly 180 degrees. Reading the value from the Smith chart for Q1, remembering that the scaling is now in normalised admittance, gives <math>y_P = 0.30 - j0.54\,</math>. Performing the calculation :<math>y_\text{T} = \frac{1}{ z_\text{T} }\,</math> manually will confirm this.

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.

The table below shows examples of normalised impedances and their equivalent normalised admittances obtained by rotation of the point through 180°. Again, these may be obtained either by calculation or using a Smith chart as shown, converting between the normalised impedance and normalised admittances planes.

{| border="1" cellpadding="2" |+ Values of reflection coefficient as normalised impedances and their {{nobr|equivalent normalised admittances}} !width="200"| Normalised impedance !width="200"| Normalised admittance |- | P1 (<math>z = 0.80 + j1.40\,</math>) | Q1 (<math>y = 0.30 - j0.54\,</math>) |- | P10 (<math>z = 0.10 + j0.22\,</math>) | Q10 (<math>y = 1.80 - j3.90\,</math>) |} thumbnail|Values of complex reflection coefficient plotted on the normalized impedance Smith chart and their equivalents on the normalized admittance Smith chart

===Choice of Smith chart type and component type=== 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. Impedances in series and admittances in parallel add while impedances in parallel and admittances in series are related by a reciprocal equation. If <math>Z_\text{TS} </math> is the equivalent impedance of series impedances and <math>Z_\text{TP} </math> is the equivalent impedance of parallel impedances, then :<math>Z_\text{TS} = Z_1 + Z_2 + Z_3 + ... \,</math> :<math>\frac{1}{Z_\text{TP}} = \frac{1}{Z_1} + \frac{1}{Z_2} + \frac{1}{Z_3} + ... \,</math> For admittances the reverse is true, that is :<math>Y_\text{TP} = Y_1 + Y_2 + Y_3 + ... \,</math> :<math>\frac{1}{Y_\text{TS}} = \frac{1}{Y_1} + \frac{1}{Y_2} + \frac{1}{Y_3} + ... \,</math> Dealing with the reciprocals, especially in complex numbers, is more time-consuming and error-prone than using linear addition. In general therefore, most RF engineers work in the plane where the circuit topography supports linear addition. The following table gives the complex expressions for impedance (real and normalised) and admittance (real and normalised) for each of the three basic passive circuit elements: resistance, inductance and capacitance. Using just the characteristic impedance (or characteristic admittance) and test frequency an equivalent circuit can be found and vice versa.

{| border="1" cellpadding="1" |+ <big>'''Expressions for impedance and admittance'''</big> normalised by impedance {{mvar|Z}}{{sub|0}} or admittance {{mvar|Y}}{{sub|0}} !rowspan="2" width="100" style="text-align:center;"| '''Element type''' |colspan="2" width="180" style="text-align:center;"| '''Impedance''' ({{mvar|Z}} or {{mvar|z}}) or '''Reactance''' ({{mvar|X}} or {{mvar|x}}) |colspan="2" width="180" style="text-align:center;"| '''Admittance''' ({{mvar|Y}} or {{mvar|y}}) or '''Susceptance''' ({{mvar|B}} or {{mvar|b}}) |- |style="text-align:center;"| '''Actual''' (Ω) |style="text-align:center;"| '''Normalised''' (no units) |style="text-align:center;"| '''Actual''' (S) |style="text-align:center;"| '''Normalised''' (no units) |- |style="text-align:center;"| '''Resistance''' ({{mvar|R}}) | <math>\; Z = R \;</math> | <math>\; z = \frac{R}{Z_0} = R Y_0 \;</math> | <math>\; Y = G = \frac{1}{R} \;</math> | <math>\; y = g = \frac{1}{R Y_0} = \frac{Z_0}{R} \;</math> |- |style="text-align:center;"| '''Inductance''' ({{mvar|L}}) | <math>\; Z = j X_\text{L} = j \omega L \;</math> | <math>\; z = j x_\text{L} = j \frac{\omega L}{Z_0} = j \omega L Y_0 \;</math> | <math>\; Y = -jB_\text{L} = \frac{-j}{\omega L} \;</math> | <math>\; y = -jb_\text{L} = \frac{-j}{\omega L Y_0} = \frac{-j Z_0}{\omega L} \;</math> |- |style="text-align:center;"| '''Capacitance''' ({{mvar|C}}) | <math>\; Z = -j X_\text{C} = \frac{-j}{\omega C} \;</math> | <math>\; z = -j x_\text{C} = \frac{-j}{\omega C Z_0} = \frac{-j Y_0}{\omega C} \;</math> | <math>\; Y = j B_\text{C} = j \omega C \;</math> | <math>\; y = j b_\text{C} = j\frac{\omega C}{Y_0} = j \omega C Z_0 \;</math> |}

==Using the Smith chart to solve conjugate matching problems with distributed components== Distributed matching becomes feasible and is sometimes required when the physical size of the matching components is more than about 5% of a wavelength at the operating frequency. Here the electrical behaviour of many lumped components becomes rather unpredictable. This occurs in microwave circuits and when high power requires large components in shortwave, FM and TV broadcasting.

For distributed components the effects on reflection coefficient and impedance of moving along the transmission line must be allowed for using the outer circumferential scale of the Smith chart which is calibrated in wavelengths.

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.

thumbnail|Smith chart construction for some distributed transmission-line matching Supposing a loss-free air-spaced transmission line of characteristic impedance <math>Z_0 = 50 \ \Omega</math>, operating at a frequency of 800 MHz, is terminated with a circuit comprising a 17.5 <math>\Omega</math> resistor in series with a 6.5 nanohenry (6.5 nH) inductor. How may the line be matched?

From the table above, the reactance of the inductor forming part of the termination at 800 MHz is :<math>Z_L = j \omega L = j 2 \pi f L = j32.7 \ \Omega\,</math> so the impedance of the combination (<math>Z_T</math>) is given by :<math>Z_T = 17.5 + j32.7 \ \Omega\,</math> and the normalised impedance (<math>z_T</math>) is :<math>z_T = \frac{Z_T}{Z_0} = 0.35 + j0.65\,</math> This is plotted on the Z Smith chart at point P20. The line OP20 is extended through to the wavelength scale where it intersects at the point <math>L_1 = 0.098 \lambda\,</math>. As the transmission line is loss free, a circle centred at the centre of the Smith chart is drawn through the point P20 to represent the path of the constant magnitude reflection coefficient due to the termination. At point P21 the circle intersects with the unity circle of constant normalised resistance at :<math>z_{P21} = 1.00 + j1.52\,</math>. The extension of the line OP21 intersects the wavelength scale at <math>L_2 = 0.177 \lambda\,</math>, therefore the distance from the termination to this point on the line is given by :<math>L_2 - L_1 = 0.177\lambda - 0.098\lambda = 0.079\lambda\,</math> Since the transmission line is air-spaced, the wavelength at 800 MHz in the line is the same as that in free space and is given by :<math>\lambda = \frac{c}{f}\,</math> where <math>c\,</math> is the velocity of electromagnetic radiation in free space and <math>f\,</math> is the frequency in hertz. The result gives <math>\lambda = 375 \ \mathrm{mm}\,</math>, making the position of the matching component 29.6 mm from the load.

The conjugate match for the impedance at P21 (<math>z_{match}\,</math>) is :<math>z_{match} = - j (1.52),\!</math> As the Smith chart is still in the normalised impedance plane, from the table above a series capacitor <math>C_m\,</math> is required where :<math>z_{match} = - j 1.52 = \frac{-j}{\omega C_m Z_0} = \frac{-j}{2 \pi f C_m Z_0}\,</math> Rearranging, we obtain :<math>C_m=\frac{1}{(1.52) \omega Z_0} = \frac{1}{(1.52)(2 \pi f) Z_0}</math>. Substitution of known values gives :<math>C_m = 2.6 \ \mathrm{pF}\,</math> To match the termination at 800 MHz, a series capacitor of 2.6 pF must be placed in series with the transmission line at a distance of 29.6 mm from the termination.

An alternative shunt match could be calculated after performing a Smith chart transformation from normalised impedance to normalised admittance. Point Q20 is the equivalent of P20 but expressed as a normalised admittance. Reading from the Smith chart scaling, remembering that this is now a normalised admittance gives :<math>y_{Q20} = 0.65 - j1.20\,</math> (In fact this value is not actually used). However, the extension of the line OQ20 through to the wavelength scale gives <math>L_3 = 0.152 \lambda\,</math>. The earliest point at which a shunt conjugate match could be introduced, moving towards the generator, would be at Q21, the same position as the previous P21, but this time representing a normalised admittance given by :<math>y_{Q21} = 1.00 + j1.52\,</math>. The distance along the transmission line is in this case :<math>L_2 + L_3 = 0.177\lambda + 0.152\lambda = 0.329\lambda\,</math> which converts to 123 mm.

The conjugate matching component is required to have a normalised admittance (<math>y_{match}</math>) of :<math>y_{match} = - j1.52\,</math>. From the table it can be seen that a negative admittance would require an inductor, connected in parallel with the transmission line. If its value is <math>L_m\,</math>, then :<math>-j1.52 = \frac{-j}{\omega L_m Y_0}= \frac{-jZ_0}{2\pi f L_m}\,</math> This gives the result :<math>L_m = 6.5 \ \mathrm{nH}\,</math> A suitable inductive shunt matching would therefore be a 6.5 nH inductor in parallel with the line positioned at 123 mm from the load.

==Using the Smith chart to analyze lumped-element circuits== thumbnail|A lumped-element circuit which may be analyzed using a Smith chart|alt=|325x325px thumbnail|Smith chart with graphical construction for analysis of a lumped circuit|alt=|325x325px The analysis of lumped-element components assumes that the wavelength at the frequency of operation is much greater than the dimensions of the components themselves. 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. In this case the wavelength scaling on the Smith chart circumference is not used. The following circuit will be analyzed using a Smith chart at an operating frequency of 100 MHz. At this frequency the free space wavelength is 3 m. The component dimensions themselves will be in the order of millimetres so the assumption of lumped components will be valid. Despite there being no transmission line as such, a system impedance must still be defined to enable normalization and de-normalization calculations and <math>Z_0 = 50 \ \Omega\,</math> is a good choice here as <math>R_1 = 50 \ \Omega\,</math>. If there were very different values of resistance present a value closer to these might be a better choice.

The analysis starts with a Z Smith chart looking into R1 only with no other components present. As <math>R_1 = 50 \ \Omega\,</math> is the same as the system impedance, this is represented by a point at the centre of the Smith chart. The first transformation is OP1 along the line of constant normalized resistance in this case the addition of a normalized reactance of -''j''0.80, corresponding to a series capacitor of 40 pF. Points with suffix P are in the ''Z'' plane and points with suffix Q are in the ''Y'' plane. Therefore, transformations ''P''1 to ''Q''1 and ''P''3 to ''Q''3 are from the Z Smith chart to the Y Smith chart and transformation ''Q''2 to ''P''2 is from the Y Smith chart to the Z Smith chart. The following table shows the steps taken to work through the remaining components and transformations, returning eventually back to the centre of the Smith chart and a perfect 50 ohm match. {| border="1" cellpadding="2" |+Smith chart steps for analysing a lumped-element circuit !width="100"|Transformation !width="100"|Plane !width="100"|''x'' or ''b'' Normalized value !width="100"|Capacitance/Inductance !width="150"|Formula to Solve !width="100"|Result |- |<math> O \rightarrow P_1\,</math> |<math>Z\,</math> |<math>-j0.80\,</math> |Capacitance (Series) |<math>-j0.80 = \frac{-j}{\omega C_1 Z_0}\,</math> |<math>C_1 = 40 \ \mathrm{pF}\,</math> |- |<math> Q_1 \rightarrow Q_2\,</math> |<math>Y\,</math> |<math> -j1.49\,</math> |Inductance (Shunt) |<math>-j1.49 = \frac{-j}{\omega L_1 Y_0}\,</math> |<math>L_1 = 53 \ \mathrm{nH}\,</math> |- |<math> P_2 \rightarrow P_3\,</math> |Z |<math>-j0.23\,</math> |Capacitance (Series) |<math>-j0.23 = \frac{-j}{\omega C_2 Z_0}\,</math> |<math>C_2 = 138 \ \mathrm{pF}\,</math> |- |<math> Q_3 \rightarrow O\,</math> |Y |<math>+j1.14\,</math> |Capacitance (Shunt) |<math>+j1.14 = \frac{j \omega C_3}{Y_0}\,</math> |<math>C_3 = 36 \ \mathrm{pF}\,</math> |}

==Variations and extensions== ===The {{math|Y}} Smith chart=== [[File:Bare Bones Smith Chart - Admittance with annotations.png|thumb|The Smith chart for admittance instead of impedance. Everything is the same, but all the grid lines are rotated 180° about the point <math>\Gamma=0+j0</math> (which occurs when <math>z=y=1+j0</math>).]] The {{math|Y}} Smith chart is constructed in a similar way to the {{math|Z}} Smith chart case but by expressing values of voltage reflection coefficient in terms of normalised admittance instead of normalised impedance. The normalised admittance {{mvar|y}} is the reciprocal of the normalised impedance {{mvar|z}}, so :<math> y \equiv \frac{1}{z} ~.</math> Therefore: :<math> y = \frac{1-\Gamma}{\, 1 + \Gamma \,} \,,</math> and :<math> \Gamma = \frac{ 1 - y }{\, 1 + y \,} ~.</math> The {{math|Y}} Smith chart appears like the normalised impedance, type but with the graphic nested circles rotated through 180°, but the numeric scale remaining in its same position (not rotated) as the {{math|Z}} chart.

Similar to the expansion performed for normalized impedance, :<math> \Gamma = \left[\frac{1 - \Re e[y]^2 - \Im m[y]^2}{\, (\Re e[y] + 1)^2 + \Im m[y]^2 \,}\right] + j \left[\frac{ -2\,\Im m[y] }{\,(\Re e[y] + 1)^2 + \Im m[y]^2 \,}\right] ~.</math>

The region above the {{mvar|x}}-axis represents capacitive admittances and the region below the {{mvar|x}}-axis represents inductive admittances. Capacitive admittances have positive imaginary parts and inductive admittances have negative imaginary parts.

Again, if the termination is perfectly matched the reflection coefficient will be zero, represented by a 'circle' of zero radius or in fact a point at the centre of the Smith chart. 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.

=== Extension for negative resistance (Real part of {{math|z}} < 0) === [[File:Bare Bones Smith Chart - extended for negative resistance.png|thumb|A Smith chart in which the lines of constant <math>\Re e[z]<0</math> are depicted as purple circles{{efn|For the case of <math>\Re e[z]=-1</math>, the circle becomes a straight line (which is a circle of infinite radius)}} and the lines of constant <math>\Im m[z]</math> (the blue circles{{efn|name="z pure real"}}) extended beyond the largest red circle which corresponds to the line <math>\Re e[z]=0</math>]] The Smith chart can be extended for negative resistance <math>(\Re e[z]<0)</math>, but such an extended chart is rarely used in practice. In such cases, the amplitude of the reflection coeffient, <math>\Gamma</math>, is greater than 1, which means more energy is reflected than was incident. This is not necessarily a violation of the concept of the conservation of energy, as it is the usual case of electronic amplification in which the additional power is taken from an external DC bias.

=== Mapping of the Smith chart onto a unit sphere === {{Multiple image|total_width = 600  | width = 600 | header = The Smith chart projected onto a unit hemisphere{{efn|For clarity, only the top hemisphere is plotted. For the bottom hemisphere, the blue arcs of constant <math>\Im m[z]</math> are mirror imaged to form complete circles, and the red circles of constant <math>\Re e[z]</math> are mirror imaged by the rule that a circle of <math>\Re e[z]=x</math> is mirror imaged with the circle of <math>\Re e[z]=-x</math>. The mirroring is about the plane containing the circle <math>\Re e[z]=0</math>}} | caption_align = center | image_style = border:none | image_gap = 8 | image1 = Bare Bones Smith Chart projected on a sphere - Lines of constant positive resistance.png | link1 = File:Bare Bones Smith Chart projected on a sphere - Lines of constant positive resistance.png | caption1 = Lines of constant resistance <math>\left(\Re e[z]\right)</math> only  | image2 = Bare Bones Smith Chart projected on a sphere - Lines of constant reactance (cropped for positive resistance).png | link2 = File:Bare Bones Smith Chart projected on a sphere - Lines of constant reactance (cropped for positive resistance).png | caption2 = Lines of constant reactance <math>\left(\Im m[z]\right)</math> only  | image3 = Bare Bones Smith Chart projected on a sphere - positive resistance only (top half of sphere).png | link3 = File:Bare Bones Smith Chart projected on a sphere - positive resistance only (top half of sphere).png | caption3 = Combined lines of constant resistance and constant reactance (both <math>\Re e[z]</math> and <math>\Im m[z]</math>) | footer = }}

In 2011, Muller, ''et al'' proposed a mapping of the Smith chart from the two-dimension complex plane for the reflection coefficient, <math>\Gamma</math>, into a Riemann sphere. The mapping from the plane to the sphere is accomplished using a stereographic projection.{{efn|The transformation used by Muller, ''et al'', is slightly different than the one presented in the Wikipedia article on stereographic projection. Muller, ''et al'', used the transformation <math>\Gamma_{sphere} = \left(\frac{2\cdot\Re e[\Gamma]}{1+\Re e[\Gamma]^2+\Im m[\Gamma]^2},\frac{2\cdot\Im m[\Gamma]}{1+\Re e[\Gamma]^2+\Im m[\Gamma]^2},\frac{1-(\Re e[\Gamma]^2+\Im m[\Gamma]^2)}{1+\Re e[\Gamma]^2+\Im m[\Gamma]^2}\right)</math>.}} The resulting Riemann sphere is a unit sphere with the following characteristics:<ref name="Muller-Soto-Dascalu-Neculoiu-Boria_2011"/> * The top point <math>(x=0, y=0, z=1)</math> represents the point <math>\Gamma=0</math> (which occurs when <math>z=1+j0</math>){{efn|name="double meaning for z"|Please note that the same symbol <math>z</math> is used to denote two different parameters: a coordinate axis in 3D Cartesian coordinate system (when presented as a real number alongside values for <math>x</math> and <math>y</math>, and a noramlized impedance (when presented as a complex number).}} * The top half of the sphere corresponds to the region interior to the circle <math>\left|\Gamma\right|=1</math> (which occurs for the <math>z</math>-space half-plane <math>\Re e[z]>0</math>) * The circle separating the top half of the sphere from the bottom half of the sphere corresponds to the circle <math>\left|\Gamma\right|=1</math> (which occurs for the <math>z</math>-space line <math>\Re e[z]=0</math>) * The bottom half of the sphere corresponds to the region exterior to the circle <math>\left|\Gamma\right|=1</math> (which occurs for the <math>z</math>-space half-plane <math>\Re e[z]<0</math>) * The bottom point <math>(x=0, y=0, z=-1)</math> represents the case of <math>\left|\Gamma\right|\to\infty</math> (which occurs when <math>z=-1 +j0</math>){{efn|name="double meaning for z"}}

The last two characteristics mean that the infinite plane of the exterior of the circle <math>\Gamma=1</math> maps on to a finite hemisphere.

The point on the sphere <math>\left(x=1, y=0, z=0\right)</math>, which corresponds to the value (<math>\Gamma=1+j0</math>) is a mathematical singularity as it is the only point on the sphere in which multiple values of <math>\Gamma</math> <math>\left(\Re e[z]=\pm\infty\right.</math>, <math>\Im m[z]=\pm\infty</math>, or <math>\left.z=-1+j0\right)</math> map on to.{{efn|name="double meaning for z"}} This is why all the circles contain that point.

In 2020, Muller, ''et al'' offered a new use for the Smith chart on a sphere in which they plotted parameters such as group delays and Q factors outside the sphere (rather than on the sphere). The visual frequency orientation (clockwise vs. counter-clockwise) enables one to differentiate between a negative / capacitance and positive / inductive whose reflection coefficients are the same when plotted on a 2D Smith chart, but whose orientations diverge as frequency increases.<ref name="Muller-Asavei-Moldoveanu-Sanabria-Codesal-Khadar-Popescu-Dascalu-Ionescu_2020"/>

==Footnotes== {{notelist}}

==References== {{reflist|25em |refs= <ref name="Mizuhashi_1937">{{cite journal |script-title=ja:四端子回路のインピーダンス変成と整合回路の理論 |title=Sì duānzǐ huílù no inpīdansu hensei to seigō kairo no riron |language=ja |trans-title=Theory of Four-Terminals Impedance Transformation Circuit and Matching Circuit |author-last=Mizuhashi [水橋] |author-first=Tōsaku [東作] |journal=The Journal of the Institute of Electrical Communication Engineers of Japan [電気通信学会雑誌] |issn=0914-5273 |publisher=Institute of Electrical Communication Engineers of Japan [電気通信学会] |volume=1937 |number=12 |date=December 1937 |orig-date=1937-11-19 |pages=1053–1058 (29–34) |url=http://www.linkclub.or.jp/~morikuni/mizuhashi-smithchart/Mizuhashi,J.IECEJ(1937).pdf |url-status=dead |archive-url=https://web.archive.org/web/20171116005011/http://www.linkclub.or.jp:80/~morikuni/mizuhashi-smithchart/Mizuhashi,J.IECEJ(1937).pdf |archive-date=2017-11-16}} (6 pages)</ref> <ref name="Okamura_1959">{{cite journal |script-title=ja:スミスチャートは日本人の独創ではないか |title=Sumisuchāto wa nihonjin no dokusōde wanai ka |language=ja |trans-title="Smith Chart" May Have Origin in Japan |author-last=Okamura [岡村] |author-first=Fumiyoshi [史良] / Shirō [獅郎] |journal=The Journal of the Institute of Electrical Communication Engineers of Japan [電気通信学会雑誌] |issn=0914-5273 |publisher=Institute of Electrical Communication Engineers of Japan [電気通信学会] |location=Tokyo, Japan |volume=1959 |number=8 |date=August 1959 |orig-date=1959-04-04 |pages=768–769 (44–45) |url=http://www.linkclub.or.jp/~morikuni/mizuhashi-smithchart/Okamura,J.IECEJ(1959).pdf |url-status=dead |archive-url=https://web.archive.org/web/20171116005338/http://www.linkclub.or.jp/~morikuni/mizuhashi-smithchart/Okamura,J.IECEJ(1959).pdf |archive-date=2017-11-16}} (2 pages) (NB. The article lists the author's given name as {{lang|ja|史良}} in Japanese, which would translate as "Fumiyoshi", whereas the English footnote in the same article transscribed it as "Shirō", which would be associated with {{lang|ja|獅郎}} in Japanese.)</ref> <ref name="Kenichi_1999">{{cite book |script-title=ja:インピーダンスのはなし |title=Inpīdansu no hanashi |language=ja |trans-title=The story of impedance |author-last=Kenichi [伊藤健] |author-first=Ito [一著] |edition=1 |series=Science and Technology |publisher=Nikkan Kogyo Shimbun [日刊工業新聞社] |date=1999-11-01 |isbn=4-526-04463-6 |id={{EAN|978-4-526-04463-2}}. 1923054018007 |page=26}} (4+xi+1+207+3+4 pages)</ref> <ref name="Mori_2013">{{cite web |title=The Mizuhashi-Smith Chart |author-last=Mori [森] |author-first=Kunihiko [邦彦] |date=2013 |work=morikuni_net |url=http://www.linkclub.or.jp/~morikuni/mizuhashi-smithchart/ |access-date=2023-06-24 |url-status=dead |archive-url=https://web.archive.org/web/20130303005317/http://www.linkclub.or.jp/~morikuni/mizuhashi-smithchart/ |archive-date=2013-03-03}}</ref> <ref name="Smith_1939">{{cite magazine |title=Transmission Line Calculator - A "cut-out" calculator for determining impedance and attenuation, in terms of the length of open-wire transmission lines |author-last=Smith |author-first=Phillip Hagar |author-link=Phillip Hagar Smith |magazine=electronics - radio, communication, industrial applications of electron tubes ... engineering and manufacture |issn=0013-5070 |publisher=McGraw-Hill Publishing Company, Inc. |publication-place=New York, USA |volume=12 |issue=1 |pages=29–31 |date=January 1939 |url=https://worldradiohistory.com/Archive-Electronics/30s/Electronics-1939-01.pdf |access-date=2023-07-09 |url-status=live |archive-url=https://web.archive.org/web/20230708221149/https://worldradiohistory.com/Archive-Electronics/30s/Electronics-1939-01.pdf |archive-date=2023-07-08}} (3 pages)</ref> <ref name="Smith_1944">{{cite magazine |title=An Improved Transmission Line Calculator - An extension of the "calculator" originally published in ELECTRONICS in January 1939. New parameters have been added and accuracy has been improved. |author-last=Smith |author-first=Phillip Hagar |author-link=Phillip Hagar Smith |magazine=electronics |issn=0013-5070 |publisher=McGraw-Hill Publishing Company, Inc. |publication-place=New York, USA |volume=17 |issue=1 |pages=130–133, 318, 320, 322, 324–325 |date=January 1944 |url=https://worldradiohistory.com/Archive-Electronics/40s/Electronics-1944-01.pdf |access-date=2023-07-09 |url-status=live |archive-url=https://web.archive.org/web/20230131151634/https://worldradiohistory.com/Archive-Electronics/40s/Electronics-1944-01.pdf |archive-date=2023-01-31}} (4+5 pages)</ref> <ref name="Smith_1969">{{cite book |title=Electronic Applications of the Smith Chart: In Waveguide, Circuit and Component Analysis |author-first=Phillip Hagar |author-last=Smith |author-link=Phillip Hagar Smith |date=June 1969 |edition=1 |publisher=McGraw-Hill Book Company / Kay Electric Company |publication-place=New York, USA |location=Pine Brook, New Jersey, USA |lccn=69-12411 |isbn=0-07058930-5 |id={{ISBN|978-0-07058930-8}}}} (xxvii+1+222 pages + envelope with 4 translucent plastic overlays + Kay Electric Company postcard) (NB. There is a 1983 reprint of the first edition by Robert E. Krieger Publishing Company with {{ISBN|978-0-89874-552-8|0-89874-552-7}}, and a {{citeref|Smith|2000|second edition|style=plain}} by Noble Publishing Corporation.)</ref> <ref name="Smith_1995">{{cite book |title=Electronic Applications of the Smith Chart: In Waveguide, Circuit and Component Analysis |author-first=Phillip Hagar |author-last=Smith |author-link=Phillip Hagar Smith |date=October 2000 |orig-date=1995 |edition=2 |publisher=Noble Publishing Corporation |publication-place=Atlanta, Georgia, USA |lccn=00-045239 |isbn=1-884932-39-8 |id={{ISBN|978-1-884932-39-7}} |quote-page=xiv |quote=[…] From Fleming's equation,{{citeref|Fleming|1912|A}} and in an effort to simplify the solution of the transmission line problem, he developed his first graphical solution in the form of a rectangular plot. […] the diagram gradually evolved through a series of steps. The first rectangular chart was limited by the range of data it could accommodate. He was aware of the limitations and kept working on the problem until some time in 1936, when he developed a new diagram that eliminated most of the difficulties. The new chart was a special polar coordinate form in which all values of impedance components could be accommodated. The data for this diagram was scaled from the earlier rectangular diagram. The impedance coordinates in this case were not orthogonal and were not true circles, but, in the form chosen, the standing wave ratio was linear. The chart closely resembled what ultimately became the final result. Phil, however, suspected that a grid made up of a system of orthogonal circles might be more practical. He felt it would have distinct advantages, particularly as regards reproducibility. With this in mind, he spoke to two of his co-workers, E.B. Ferrell and J.W. McRae. Because they were familiar with the principles of conformal mapping, they were able to develop the transformation whereby all data from zero to infinity could be accommodated. Fortunately, curves of constant standing wave ratio, constant attenuation and constant reflection coefficient were all circles coaxial with the center of the diagram. The scales for these values, while not linear, were entirely satisfactory. A diagram designed along these lines was constructed in early 1937. It was essentially the form still being used today. Smith approached a number of technical magazines with regard to publication of the Chart, but acceptance was slow. There were not many technical magazines at the time, and none in the microwave area. However, in January of 1939, after a delay of two years, the {{citeref|Smith|1939|article was printed|style=plain}} in Electronics magazine. […]}} (xxvi+237+1 pages + envelope with 4 translucent plastic overlays) (NB. There is a 2006 reprint of the second edition by SciTech Publishing, Inc. under the same ISBN and LCCN.)</ref> <ref name="ETHW_2018">{{cite web |title=Smith Chart |website=ETHW.org |date=2018-02-26 |url=https://ethw.org/Smith_Chart |access-date=2021-03-30 |url-status=live |archive-url=https://web.archive.org/web/20230708231337/https://ethw.org/Smith_Chart |archive-date=2023-07-08}}</ref> <ref name="Ramo-Whinnery-Duzer_1965">{{cite book |title=Fields and Waves in Communications Electronics |author-last1=Ramo |author-first1=Simon "Si" |author-link1=Simon Ramo |author-last2=Whinnery |author-first2=John Roy |author-link2=John Roy Whinnery |author-last3=Van Duzer |author-first3=Theodore |date=1965 |edition=1 |publisher=John Wiley & Sons |pages=35–39}}</ref> <ref name="Ramo-Whinnery-Duzer_1994">{{cite book |title=Fields and Waves in Communications Electronics |chapter=5.9. The Smith Transmission-Line Chart / 5.10. Some Uses of the Smith Chart |author-last1=Ramo |author-first1=Simon "Si" |author-link1=Simon Ramo |author-last2=Whinnery |author-first2=John Roy |author-link2=John Roy Whinnery |author-last3=Van Duzer |author-first3=Theodore |date=1994 |edition=3 |publisher=John Wiley & Sons, Inc. |isbn=978-0-471-58551-0 |pages=236–245}}</ref> <ref name="Pozar_2005">{{cite book |title=Microwave Engineering |author-last=Pozar |author-first=David Michael |author-link=David Michael Pozar |date=2005 |edition=3 |publisher=John Wiley & Sons, Inc. |pages=64–71 |isbn=0-471-44878-8}}</ref> <ref name="Gonzalez_1997">{{cite book |title=Microwave Transistor Amplifiers Analysis and Design |author-last=Gonzalez |author-first=Guillermo |author-link= |date=1997 |edition=2 |publisher=Prentice Hall |place=New Jersey, USA |isbn=0-13-254335-4 |pages=93–103}}</ref> <ref name="Bevelacqua_2013">{{cite web |title=The Smith Chart |author-first=Peter Joseph |author-last=Bevelacqua |date=2013-01-11 |orig-date=2010 |website=www.antenna-theory.com |url=https://www.antenna-theory.com/tutorial/smith/chart.php |access-date=2023-07-09 |url-status=live |archive-url=https://web.archive.org/web/20230708231713/https://www.antenna-theory.com/tutorial/smith/chart.php |archive-date=2023-07-08}}</ref> <ref name="Tektronix_2017">{{cite web |title=Antenna Matching with a Vector Network Analyzer |date=2017-10-06 |work=Tek |publisher=Tektronix, Inc. |url=https://www.tek.com/blog/antenna-matching-vector-network-analyzer |access-date=2023-07-09 |url-status=live |archive-url=https://web.archive.org/web/20230708231720/https://www.tek.com/en/blog/antenna-matching-vector-network-analyzer |archive-date=2023-07-08}}</ref> <ref name="Hayt_1981">{{cite book |title=Engineering Electromagnetics |author-last=Hayt, Jr. |author-first=William Hart |author-link=:d:Q59626592 |date=1981 |edition=4 |publisher=McGraw-Hill, Inc. |pages=428–433 |isbn=0-07-027395-2}} (527 pages)</ref> <ref name="Davidson_1989">{{cite book |title=Transmission Lines for Communications with CAD Programs |author-last=Davidson |author-first=Colin William |edition=2 |publisher=Macmillan Education Ltd |publication-place=Basingstoke, Hampshire, UK |isbn=0-333-47398-1 |date=1989 |id=ark:/13960/s2dzmfrhg24 |pages=80–85 |url=https://archive.org/details/transmissionline0000davi/page/n7/mode/1up= |access-date=2023-07-09}} (viii+244 pages)</ref> <ref name="Muller-Soto-Dascalu-Neculoiu-Boria_2011">{{cite journal |title=A 3D Smith chart based on the Riemann sphere for active and passive microwave circuits |author-first1=Andrei A. |author-last1=Muller |author-first2=Pablo |author-last2=Soto Pacheco |author-first3=Dan |author-last3=Dascălu |author-link3=:ro:Dan Dascălu |author-first4=Dan |author-last4=Neculoiu |author-first5=Vicente E. |author-last5=Boria |date=2011 |journal=IEEE Microwave and Wireless Components Letters |issn=1531-1309 |publisher=IEEE Microwave Theory and Techniques Society |volume=21 |issue=6 |pages=286–288 |doi=10.1109/LMWC.2011.2132697 |hdl=10251/55107 |s2cid=38953650 |hdl-access=free}}</ref> <ref name="Muller-Asavei-Moldoveanu-Sanabria-Codesal-Khadar-Popescu-Dascalu-Ionescu_2020">{{cite journal |title=The 3D Smith Chart: From Theory to Experimental Reality |author-last1=Muller |author-first1=Andrei A. |author-last2=Asavei |author-first2=Victor |author-last3=Moldoveanu |author-first3=Alin |author-last4=Sanabria-Codesal |author-first4=Esther |author-last5=Khadar |author-first5=Riyaz A. |author-last6=Popescu |author-first6=Cornel |author-last7=Dascălu |author-first7=Dan |author-link7=:ro:Dan Dascălu |author-last8=Ionescu |author-first8=Adrian M. |date=November 2020 |journal=IEEE Microwave Magazine |issn=1527-3342 |publisher=IEEE Microwave Theory and Techniques Society |volume=21 |issue=11 |pages=22–35 |doi=10.1109/MMM.2020.3014984 |s2cid=222296721 |url=https://infoscience.epfl.ch/record/280816}}</ref> <ref name="Volpert_1940">{{cite news |script-title=ru:Номограмма для расчета длинных линий |title=Nomogramma dlya rascheta dlinnykh liniy |language=ru |trans-title=Nomogram for calculating long lines |author-first=Amiel Rafailovich [Амиэ́ль Рафаи́лович] |author-last=Volpert [Во́льперт] |author-link=:ru:Вольперт, Амиэль Рафаилович |newspaper=Производственно-технический бюллетень (Proizvodstvenno-tekhnicheskiy byulleten') [Industrial and technical bulletin] |location=Leningrad, СССР |date=February 1940 |volume=1940 |number=2 |publisher={{ill|People's Commissariat of the Electrical Industry of the USSR|ru|Народный комиссариат электропромышленности СССР|lt=НКЭП}} |pages=14–18}} (5 pages)</ref> <ref name="Kurochkin_2009">{{cite web |script-title=ru:Диаграмма Вольперта – Смита. Расчет и анализ характеристик усилителей радиосигналов |title=Diagramma Vol'perta – Smita. Raschet i analiz kharakteristik usiliteley radiosignalov |language=ru |trans-title=The Volpert–Smith diagram. Calculation and analysis of the characteristics of amplifiers of radio signals |author-first=Alexander Evdokimovich [Александр Евдокимович] |volume=2009 |number=87 |author-last=Kurochkin [Курочкин] |date=2009  |publisher=Department of Radio Engineering Devices, Belarusian State University of Informatics and Radio Electronics, Ministry of Education of the Republic of Belarus educational institution |location=Minsk, Belarus |isbn=978-9-85-488-422-6  |url=https://libeldoc.bsuir.by/bitstream/123456789/310/2/Kurochkin_Diagr.pdf |access-date=2023-07-09 |url-status=live |archive-url=https://web.archive.org/web/20230709120141/https://libeldoc.bsuir.by/bitstream/123456789/310/2/Kurochkin_Diagr.pdf |archive-date=2023-07-09 |quote-page=4 |script-quote=ru:Диаграмма Смита остается одним из наиболее полезных графических инструментов для разработки высокочастотных усилительных каскадов. В нашей стране аналогичная диаграмма известна как круговая номограмма А. Р. Вольперта, который в 1939 г. независимо от Смита разработал и применил ее для пересчёта проводимостей и сопротивлений в отрезках линий передачи. |quote=Diagramma Smita ostayetsya odnim iz naiboleye poleznykh graficheskikh instrumentov dlya razrabotki vysokochastotnykh usilitel'nykh kaskadov. V nashey strane analogichnaya diagramma izvestna kak krugovaya nomogramma A. R. Vol'perta, kotoryy v 1939 g. nezavisimo ot Smita razrabotal i primenil yeye dlya pereschota provodimostey i soprotivleniy v otrezkakh liniy peredachi. |trans-quote=In our country, a similar diagram is known as a circular nomogram of A. R. Volpert, who in 1939, independently of Smith developed and applied it to recalculate conductances and resistances in segments of transmission lines.}} [https://web.archive.org/web/20230625131917/https://vk.com/wall-185886861_452?lang=en][https://vk.com/doc558553917_527458558?hash=ojEAr3vwhjjd3f2Fh1zr4iCnLRO1oIseQx1QPzHLxgP][https://web.archive.org/web/20230709120115/https://libeldoc.bsuir.by/handle/123456789/310] (40+1 pages)</ref> <ref name="Voltmer_2007">{{cite book |title=Fundamentals Of Electromagnetics 2. Quasistatics And Waves |chapter=8.2. The Smith Chart |author-first=David |author-last=Voltmer |series=Synthesis Lectures On Computational Electromagnetics |volume=2 |date=2007-08-17 |edition=1 |number=Lecture 15 |editor-first=Constantine A. |editor-last=Balanis |editor-link=Constantine A. Balanis |issn=1932-1716 |publisher=Morgan & Claypool |doi=10.2200/S00078ED1V01Y200612CEM015 |isbn=978-1-59829172-8 |id={{ISBN|1-59829172-6}}. LoC 1932-1252. MOBK081-FM |pages=135–141 [135] |s2cid=9045052 |url=https://vdoc.pub/documents/fundamentals-of-electromagnetics-2-quasistatics-and-waves-3qq83vm9q64g |access-date=2023-06-25 |quote-page=135 |quote=Though Volpert of the Soviet Union and Mizuhashi of Japan proposed essentially the same chart during the same year, Smith received the recognition.}}</ref> <ref name="Salov_2022">{{cite book |title=Antenna Impedance Measurement and Matching |chapter=4. Volpert–Smith Chart |author-first=Mikhail |author-last=Salov |type=Application note |date=March 2022 |publisher=Texas Instruments |id=SWRA726 |page=11 |url=https://www.ti.com/lit/an/swra726/swra726.pdf?ts=1687781229182&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FCC1352R |access-date=2023-06-26 |url-status=live |archive-url=https://web.archive.org/web/20230626154445/https://www.ti.com/lit/an/swra726/swra726.pdf?ts=1687781229182&ref_url=https%25253A%25252F%25252Fwww.ti.com%25252Fproduct%25252FCC1352R |archive-date=2023-06-26}} (51 pages)</ref> <ref name="MAX_2012">{{cite web |title=Impedance Matching and Smith Chart Impedance |author= |date=2012 |orig-date=2002-07-22 |id=Tutorial 742 |type=Application note |publisher=Maxim Integrated Products, Inc. |url=https://www.analog.com/en/technical-articles/impedance-matching-and-smith-chart-impedance-maxim-integrated.html |access-date=2023-07-09 |url-status=live |archive-url=https://web.archive.org/web/20230709113110/https://www.analog.com/en/technical-articles/impedance-matching-and-smith-chart-impedance-maxim-integrated.html |archive-date=2023-07-09}}[https://web.archive.org/web/20230709113219/https://www.analog.com/media/en/technical-documentation/tech-articles/impedance-matching-and-smith-chart-impedance-maxim-integrated.pdf] (18 pages) (NB. A previous version of this article appeared in the July 2000 issue of ''RF Design''.)</ref> <ref name="Linton_1950">{{cite magazine |author-last=Linton, Jr. |author-first=R. L. |location=Antenna Laboratory, University of California, Berkeley, California, USA |title=Graph for Smith Chart |magazine=electronics |issn=0013-5070 |publisher=McGraw-Hill Publishing Company, Inc. |publication-place=New York, USA |volume=23 |issue=1 |date=January 1950 |pages=123, 158 |url=https://worldradiohistory.com/Archive-Electronics/50s/Electronics-1950-01.pdf |access-date=2023-07-22 |url-status=live |archive-url=https://web.archive.org/web/20230131151823/https://worldradiohistory.com/Archive-Electronics/50s/Electronics-1950-01.pdf |archive-date=2023-01-31}}</ref> <ref name="GeneralRadio_1950">{{cite magazine |title=Impedance Measurement-Smith Chart with Example Plotted |magazine=General Radio Experimenter |publisher=General Radio Company |publication-place=Cambridge, Massachusetts, USA |volume=XXV |issue=6 |date=November 1950 |pages=5–7 |url=https://worldradiohistory.com/Archive-Company-Publications/Archive-General-Radio/GR%20Exp%201950_11.pdf |access-date=2023-07-22 |url-status=live |archive-url=https://web.archive.org/web/20230722174932/https://worldradiohistory.com/Archive-Company-Publications/Archive-General-Radio/GR%20Exp%201950_11.pdf |archive-date=2023-07-22}}</ref> <ref name="Inan_2005">{{cite conference |title=Remembering Phillip H. Smith on his 100th Birthday |author-first=Aziz S. |author-last=Inan |date=2005-07-03 |conference=2005 IEEE Antennas and Propagation Society International Symposium Digest |publisher=IEEE Antennas and Propagation Society |publication-place=Washington, D.C., USA |location=School of Engineering, University of Portland, Portland, Oregon, USA |volume=3B |isbn=0-7803-8883-6 |issn=1522-3965 |eissn=1947-1491 |doi=10.1109/APS.2005.1552450 |pages=129–132 |url=https://faculty.up.edu/ainan/aps2005inanMarch05.pdf |access-date=2023-07-02 |url-status=live |archive-url=https://web.archive.org/web/20230702163157/https://faculty.up.edu/ainan/aps2005inanMarch05.pdf |archive-date=2023-07-02}} (NB. This is a corrected version of the originally published paper.)</ref> }}

==Further reading== * {{cite journal |title=Cisoidal oscillations |author-link=George Ashley Campbell |author-first=George Ashley |author-last=Campbell |journal=Proceedings of the American Institute of Electrical Engineers |publisher=American Institute of Electrical Engineers |volume=XXX |issue=1–6 |date=April 1911 |doi=10.1109/PAIEE.1911.6659711 |s2cid=51647814 |pages=789–824 [Fig. 13 on p. 810] |url=https://ia800708.us.archive.org/view_archive.php?archive=/28/items/crossref-pre-1923-scholarly-works/10.1109%252Fpaiee.1910.6660428.zip&file=10.1109%252Fpaiee.1911.6659711.pdf |access-date=2023-06-24}} (37 pages) (NB. Includes an early graphical depiction of something similar to a Smith chart decades before Mizuhashi, Volpert and Smith published their works.) * {{cite book |title=The Propagation of Electric Currents in Telephone and Telegraph Conductors: A Course of Post-graduate Lectures Delivered Before the University of London |author-first=John Ambrose |author-last=Fleming |author-link=John Ambrose Fleming |publisher=Constable & Company Ltd |location=University College, London, UK |date=January 1912 |orig-date=May 1911 |edition=revised 2nd |id=ark:/13960/t3bz6211d |url=https://archive.org/details/propagationofele030887mbp/page/n11/mode/1up |access-date=2023-07-23}} (xiv+316 pages) * {{cite magazine |title=Transmission Line Charts |author-first=Herbert L. |author-last=Krauss |magazine=Electrical Engineering |issn=0095-9197 |eissn=2376-7804 |publisher= |volume=68 |issue=9 |date=September 1949 |doi=10.1109/EE.1949.6444963 |pages=766–774 [767]}} * {{cite web |title=Smith Chart Tuning, Part I |author-first=Donald |author-last=Lee |publisher=SOC Business Unit, Advantest Test Cell Innovations, Advantest |date=2013-01-30 |url=https://www3.advantest.com/documents/11348/e453dfca-1fc8-4b53-a7be-3419f431b3f0 |access-date=2023-07-09 |url-status=live |archive-url=https://web.archive.org/web/20230709184336/https://www3.advantest.com/documents/11348/e453dfca-1fc8-4b53-a7be-3419f431b3f0 |archive-date=2023-07-09}} (29 pages) * {{cite web |title=Mathematical Construction and Properties of the Smith Chart |author-first=Trevor |author-last=Gamblin |date=2015-07-23 |website=allaboutcircuits.com |url=http://www.allaboutcircuits.com/technical-articles/mathematical-construction-and-properties-of-the-smith-chart |access-date=2023-07-09 |url-status=live |archive-url=https://web.archive.org/web/20230709184018/https://www.allaboutcircuits.com/technical-articles/mathematical-construction-and-properties-of-the-smith-chart |archive-date=2023-07-09}} * {{cite web |title=Impedance Matching and Smith Charts |author-first=John |author-last=Staples |date=2015 |publisher=U.S. Particle Accelerator School (USPAS) |url=https://uspas.fnal.gov/materials/08UCSC/mml13_matching+smith_chart.pdf |access-date=2023-07-09 |url-status=live |archive-url=https://web.archive.org/web/20230709114329/https://uspas.fnal.gov/materials/08UCSC/mml13_matching+smith_chart.pdf |archive-date=2023-07-09}} (27 pages)

==External links== {{commons category|Smith charts}} * {{cite web |url=http://www.excelhero.com/blog/2010/08/excel-high-precision-engineering-chart-1.html |title=Excel Smith chart |website=excelhero.com |date=August 2010}} Non-commercial, interactive Smith Chart that looks best in Excel 2007+. * {{cite web |url=https://www.ae6ty.com/Smith_Charts.html |title=SimSmith |website=ae6ty.com}} Non-commercial, available for Windows, Mac, and Linux. Many Smith chart tutorial videos. No circuit size restrictions. Not limited to ladder circuits. * {{cite web |url=http://fritz.dellsperger.net/smith.html |archive-url=https://web.archive.org/web/20150304202453/http://fritz.dellsperger.net/smith.html |url-status=dead |archive-date=2015-03-04 |title=Smith v3 |website=fritz.dellsperger.net}} Commercial and free Smith chart for Windows * {{cite web |url=https://github.com/niyeradori/QuickSmith-Web |title=QuickSmith |website=github.com/niyeradori |date=2021-11-02}} Free web based Smith Chart Educational tool available on GitHub. * {{cite web |url=https://www.3dsmithchart.com/ |title=3D Smith chart tool |website=3dsmithchart.com}} 2D and 3D Smith chart generalized tool for active and passive circuits (free for academia/education). {{Authority control}}

Category:Charts Category:Electrical engineering Category:Eponymous diagrams