A diagram designed by Phillip Hagar Smith in 1937 and published in 1939 in the January issue of Electronics magazine. This circular chart often used by electrical engineers shows graphically the complex impedance anywhere along a transmission line. The chart is simply the unit circle of the complex plane representing the generalized reflection coefficient. Constant real and imaginary line impedances are represented by overlayed contours. The chart can be used to directly determine the normalized line impedance at any position of the transmission line as well as the reflection coefficient. The chart can also be used as a units converter. No math is needed to use the chart because all quantities are simply determined graphically.

A collection of Smith chart resources can be found at http://sss-mag.com/smith.html

The professor showed us the Smith chart in class. I looked at the incomprehensible chart composed of umpteen million circles and polar scales. I thought to myself, "How could this chart make anybody's life simpler?" Knowing that this chart had all kinds of graphical goodness, but couldn't match my HP48's algebraic wizardry, I discarded all knowledge of how to use the chart.

Later on, it came to be known that the final exam would have Smitch chart problems on it. Bastard. I went to the professor and asked him if he could help me with the chart. He asked what I needed help with, as though it was so simple a child could use it. Bastard. I told him that I couldn't remember any of it, and the book had deleted it, noting that computers made it obsolete. He refused to help me because I hadn't been paying attention in class. Bastard. I needed answers and I needed them fast.

I remembered a really really old guy on the sixth floor who was named Smith. It must be him! I raced to his office, shoved the damn chart in his face and demanded to know why he had done this to me. He claimed innocence, noting that the chart was invented in the late 30's. Just be sure, I gave him a good beating.

Unfortunately, the neat faces and pictures I made out of the Smith chart on the final did not help me.

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