![]() In this plot, the distance along the horizontal axis is used to denote the real part of the impedance. The image below shows an example Smith chart used to plot the impedance Z = 1.2 - i0.7 Ohms. Suppose our unmatched load impedance is Z = 60 - i35 Ohms if the system impedance is 50 Ohms, then we divide the load and system impedances, giving a normalized impedance of Z = 1.2 - i0.7 Ohms. The system impedance might be a 50 Ohm transmission line. To start working with a Smith chart for impedance matching, we need to normalize our load component that requires impedance matching to the desired system impedance. However, some commercial applications and simulation tools will display impedance data in a Smith chart. As a graphical method for performing impedance matching, it was very useful before the time of graphical computers and simulation tools for plotting impedance. This unique type of chart was developed by Philip Smith at Bell Telephone's Radio Research Lab in the 1930s. What Is a Smith Chart?Ī Smith chart is a type of graph used to plot the normalized impedance of a circuit, a circuit element, or an interconnect. Smith charts are a standard tool used by many RF engineers, so it pays to know how to use a Smith chart for impedance matching. Using a Smith chart might seem complicated to new designers, and one might question why it is any more or less useful than a graph in Cartesian coordinates. In some cases, such as with transmission line stub matching in RF circuits or input impedance matching to a feedline’s characteristic impedance, a graphical representation of impedance can aid impedance matching.Ī Smith chart provides just such a graphical representation of impedance, and it is a useful tool for understanding how impedance varies in different systems. In many cases, you need to measure and carefully simulate the appropriate impedance required to ensure impedance matching and prevent power reflection. High speed and high frequency systems need impedance matching to ensure efficient power transfer and prevent reflections. Impedance matching in this PCB can be determined using a Smith chart Once impedance matching requirements are determined, the results can be simulated in a SPICE-based simulation application. One popular method for plotting impedance and determining impedance matching is to use a Smith chart. Maxwell published his famous equations governing all electrical and electronic phenomenon (with some quantum mechanics in some cases) in 1873.There are many methods for impedance matching in your circuits. It is too cubersome to derive the solution of a particular problem.įirst, the math of solving the Maxwell equation consists of vector analysis and partial differential equation. It seems that there is a dilemma to get a full picture of a simple dipole antenna. SMITH CHART IMPEDANCE AND ADMITTANCE FULL Solving Maxwell equations provides the accurate solution, but loses the physical intuition and not practical due to the computation complexity. 6: Different abstraction in electrical discipline Lumped circuit model provides a simple approximation of a dipole antenna, it is useful but only valid within limited frequency range. Luckily, there is a another tool originally derived from transmission line, namely Smith Chart, provides useful physical insight and enough accuracy for understanding the dipole antenna. ![]() A brief introduction of Smith Chart is on the other article. Lumped circuit is a subset included in Smith Chart. ![]() Smith Chart (transmission line) is based on a specific EM wave called TEM (transverse EM) wave where the dynamic electrical and magnetic fields are perpendicular to the wave propagation direction. The majority of EM wave and waveguide either belong to the TEM domain or can be approximated by TEM wave. That is, Smith Chart is a very useful tool to solve most electrical problems. ![]() SMITH CHART IMPEDANCE AND ADMITTANCE FULL.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |