Abstract:

The Smith Chart has demonstrated for long to be an excellent graphical tool in assisting to the solution of wave-guides and transmission lines problems, by avoiding the need of long and tedious calculation procedures. The Smith Chart allows to graphically solve impedance matching problems, such as the matching of an arbitrary load impedance to a given transmission line or the matching of two lines with different characteristic impedances. Due to the huge importance of the Smith Chart usage, it has be included as a topic in the most of the courses related to radio frequency (RF) designs.

Traditionally, the Smith chart has been used in the form of hard-copy diagrams. In fact, most of the current findings of internet search engines to the 'Smith Chart' words are still linking to such printed material. With the improvement of the graphical and calculation capabilities of personal computers, different realizations of the Smith chart have appeared. These can be divided into two general groups: web based courses and software tools. The former are mainly developed by institutions reading RF, antenna design and microwave topics. In the second group we can find Smith Chart based software for different platforms: specifically compiled, addends to Matlab or Excel, or interactive remote flash/Java applications.

In this work, we present an evolved Smith chart software code specifically conceived as a computer aid for academic teaching purposes at the graduate or postgraduate level. The software includes, firstly, an independent and basic Smith Chart flexible tool. This way, the students can, on one hand, have a versatile and interactive Smith Chart tool including the managing of the following parameters: impedances/admittances (load, normalized, ...), electrical length, phase, attenuation factor, stationary wave ratio (SWR), ... It also can graphically display stationary waves of voltage and current, at any point of a loaded lossy transmission line.

On the other hand, and as an additional package, we also present a course in impedance matching, based in this tool. After a brief introduction to the Smith Chart characteristics, the software is able to deal with different types of impedance matching schemes with lumped and distributed parameters, stubs, serial and parallel, and avoiding the forbidden regions. It guides the student towards the optimal solution, by highlighting and detailing the more difficult steps.

With this philosophy, the presented package is filling the gap between Smith Chart tools and Smith Chart courses. The software kernel is, finally, flexible enough to be extended in the future with grading tools in order to be also used as an examination tool.