Going back to basic electricity classes, you will remember that impedance is a sum of resistance and reactance and as such, is more often than not, a complex number, as a result of this, the reflection coefficient is also a complex number, since it is completely determined by the impedance ZL and the "reference" impedance Z0.īased on this, the reflection coefficient can be obtained by the equation
#ADMITTANCE SMITH CHART SERIES#
In Impedance matching activities, it helps identify how a parallel or series component affects the impedance with less effort.Īs mentioned in the introduction, the Smith Chart displays the complex reflection coefficient, in polar form, for a particular load impedance. It is as useful as combining the ability of both the admittance and impedance smith charts can be. The picture below shows a typical Immittance Smith Chart. Its a literally effective solution to the problem as it is formed by superimposing both the Impedance and Admittance smith charts on one another. To solve this, the immittance smith chart is used. While the “common” impedance Smith Chart is super useful when working with series components and the admittance Smith Chart is great for parallel components, a unique difficulty is introduced when both series and parallel components are involved in the setup. The complexity of the smith chart increases down the list. The image below shows the admittance Smith Chart. True to their relationship described by the relationship above, the admittance smith chart possesses an inverse orientation to the Impedance smith chart. Where YL is the admittance of the load, ZL is the impedance, C is the real part of the admittance known as Conductance, and S is the imaginary part known as Susceptance.
An equation to establish the relationship between admittance and impedance is shown below. From basic electricity classes, you will remember that admittance is the inverse of impedance as such, an admittance chart makes sense for the complex parallel situation as all you will need to do is to examine the admittance of the antenna rather than the impedance and just add them up. To allow the same simplicity, the admittance chart was developed. The Impedance chart is great when dealing with load in series as all you need to do is simply add the impedance up, but the math becomes really tricky when working with parallel components( parallel inductors, capacitors or shunt transmission lines). The focus of today’s article will be on them so more details will be provided as the article proceeds. The image below shows an impedance smith chart. They are the most popular, with all references to smith charts usually pointing to them and others being regarded as derivatives. The Impedance smith charts are usually referred to as the normal smith charts since they relate with impedance and works really well with loads made up of series components, which are usually the main elements in impedance matching and other related RF engineering tasks. While the impedance smith charts are the most popular and the others rarely get a mention, they all have their “superpowers” and can be extremely useful when used interchangeably. Based on this scaling, smith charts can be categorized into three different types Smith chart is plotted on the complex reflection coefficient plane in two dimensions and is scaled in normalised impedance (the most common), normalised admittance or both, using different colours to distinguish between them and serving as a means to categorize them into different types.
#ADMITTANCE SMITH CHART SOFTWARE#
As a result of this, most RF Analysis Software and simple impedance measuring instruments include smith charts in the display options which makes it an important topic for RF Engineers. Smith chart can be used to display several parameters including impedances, admittances, reflection coefficients, scattering parameters, noise figure circles, constant gain contours and regions for unconditional stability, and mechanical vibrations analysis, all at the same time. However, the Smith charts method of displaying data have managed to retain its preference over the years and it remains the method of choice for displaying how RF parameters behave at one or more frequencies with the alternative being tabulating the information. It was originally developed to be used for solving complex maths problem around transmission lines and matching circuits which has now been replaced by computer software.