Smith Chart™ Resources - Forbidden Regions

This list of Smith Chart software is a mixture of professional packages for purchase, shareware, and freeware, plus links to websites featuring Smith Chart topics.

• Electronic Applications of the Smith Chart - Phillip H.Smith
• Smith Chart Video Tutorials - Dr. Cynthia Furse, U. of Utah
• Smith Chart Flash Presentation - by Brent Locher. An interactive Smith Chart tutorial with 5 different flash programs that contain a lot of embedded audio.
• Smith Chart  - Animated tutorial by Keith Schaub of Savvy Paper
• Smith Chart Artwork - A researched collection by RF Cafe
• Smith Chart Tutorial - Extremely well-done PowerPoint presentation
• Mysteries of the Smith Chart - Stephen D. Stearns, K6OIK
• Impedance Matching - Smith Chart  from the National Taiwan University (in English)
• Smith Chart for Excel by RF Cafe - two unique spreadsheets that allow entering either
        S-parameters or complex numbers - FREE
• Smith Chart for Visio by RF Cafe - built on the MS Visio grid in vector format so that resizing
        retains all the detail. Use it for reports and presentations.
• Agilent's handy Smith Chart display applet
• PDF file version from the University of San Diego
• History of Phil and Smith Chart by Randy Rhea (Spread Spectrum)
• DaVinci, Smith Chart and parameter conversion (S, Z, Y, G, H, ABCD)
• Smith charts with MathCAD from The Circuit Sage
• Smith Chart items by Spread Spectrum magazine
• How to use a Smith Chart from Test and Measurement World magazine
• Smith Chart for Palm OS by John Forste
• Smith 2.00 - advanced Smith Chart software
• linSmith - Smith Chart program for Linux
• PowerSmith - DOS compatible, old, but works, VA3DIW, OK1RR
• QuickSmith, very nice FREE Smith Chart program, Nathan Iyer
• Electronic Applications of the Smith Chart - 1st part of Phillip H. Smith book

Forbidden Regions of Impedance Matching

Because of the way in which the addition of series and parallel capacitances and inductances move along lines of admittance and reactance, there are certain areas on the Smith Chart, known as forbidden regions, within which the combinations of inductance and capacitance cannot be used to translate the impedance to the center of the chart (perform an impedance match). The reason can be made clear by an example.

Series-added reactive components (inductors and capacitors) move the impedance point along constant resistance lines as shown in red and purple to the right. Shunt-added reactive components move the impedance point along the constant conductance lines as shown in blue and green to the right. Recall that adding a shunt capacitor increases overall capacitance, and adding a series capacitor decreases the overall capacitance. The opposite is true for inductance. Suppose the impedance of a source lies in the Forbidden Region in the Smith Chart in the upper right (above). Adding series inductor increases the overall inductance and therefore moves the point along the red line (constant resistance), which keeps the impedance within the Forbidden Region. The addition of a shunt capacitor increases the overall capacitance and moves the point along the green line (constant conductance), but can never move the point to the center where 50 Ω lies.