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Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while typing up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
All trademarks, copyrights, patents, and other rights of ownership to images
and text used on the RF Cafe website are hereby acknowledged.
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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 -
- 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
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)
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
- linSmith - Smith Chart program for Linux
- PowerSmith - DOS compatible, old,
but works, VA3DIW, OK1RR
- QuickSmith, very nice FREE Smith Chart program,
- Electronic Applications of the Smith Chart
- 1st part of Phillip H. Smith book
|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.
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