What is Smith Chart in transmission lines?

The Smith chart is a chart of normalized impedances (or admittances) in the reflection coefficient plane. As such, it allows calculations of all parameters related to transmission lines as well as impedances in open space, circuits, and the like.

What is a Smith chart and why is it useful in making transmission line calculation?

The Smith Chart is a fantastic tool for visualizing the impedance of a transmission line and antenna system as a function of frequency. Smith Charts were originally developed around 1940 by Phillip Smith as a useful tool for making the equations involved in transmission lines easier to manipulate.

How do you read a Smith S11 chart?

When R is greater than 50 Ohms, S11 is a number from 0 to 1. When R is less than 50 Ohms, S11 is a negative number from 0 to -1. And, S11 is constant with frequency. There will only be one value for all frequencies.

What does a Smith Chart tell you?

The Smith Chart is used to display an actual (physical) antenna’s impedance when measured on a Vector Network Analyzer (VNA). Smith Charts were originally developed around 1940 by Phillip Smith as a useful tool for making the equations involved in transmission lines easier to manipulate.

How do you plot input impedance on a Smith Chart?

By plotting the normalized load impedance on a Smith Chart, the input impedance as a function of line length can be found. To find Z along the line for a particular ZL, find ZL/Z0 on the chart and draw a circle, centered at 1+j0 through that point.

How to calculate the impedance of a transmission line?

For example, the normalized impedance for a load Z. L = 73 + j42  on a 50 transmission line is Z. LN = 1.46 + j0.84. By plotting the normalized load impedance on a Smith Chart, the input impedance as a function of line length can be found.

How is the admittance of a Smith chart calculated?

The Smith Chart. The Smith Chart allows easy calculation of the transformation of a complex load impedance through an arbitrary length of transmission line. It also allows the calculation of the admittance Y = 1/Z of an impedance. The impedance is represented by a normalized impedance z.

How is the impedance of a shorted transmission line cancelled?

As shown previously, the input impedance (admittance) of a shorted transmission line (a “stub”) is purely reactive. By placing a stub in parallel with another transmission line, the reactive component can be cancelled, leaving a pure-real input impedance. This can be used to achieve a perfect match.