News and Information from Besser Associates • February 2009
In this issue:
- Next Webcast: Radar Systems
- Smith Chart ABC's Part II
- Last Chance for Courses in San Diego this February
- Courses Coming to San Jose this March
Next Webcast: Radar Systems
The 2008 Webinar series from Microwave Journal and Besser Associates continues with Radar Systems by instructor Al Scott. This webcast provides background on the following subjects which govern radar operation:
- Frequency Bands
- Principles of Operation
- Major Technology Advancements
- Velocity Measurement
- Range Measurement
- Pulse Radar Block Diagram
- Pulse Doppler
- Antennas
- Angular Resolution
- Modern Components/Applications
The webcast will run February 17th at 8AM Pacific Time. Visit the Microwave Journal Resources page to view the recorded sessions of previous webcasts in the series.
Smith Chart ABC's - Part II
In this series of brief articles, instructor Rex Frobenius gives a very basic introduction to the Smith Chart.
In our previous short examination of the Smith Chart, we learned that it is easy to remember the orientation of short and open circuits on the chart by focusing on the horizontal axis of the chart: impedances increase from left to right. In this segment we explore the formula that defines the relationship between the reflection coefficient and impedance:
Since both the reflection coefficient and the impedance values are complex numbers, you can separate the real and imaginary terms algebraically. The result of this algebra will be the formulas for the circles that make up the Smith Chart [1]. A common problem encountered when learning to use the Smith Chart is remembering this formula. Although it is relatively easy to remember the general appearance of the formula, the actual order of the Zo and ZL terms as well as the addition or subtraction operators are easily confused (especially if you use the Smith Chart infrequently).
Fortunately, by simply remembering the lesson from part 1 regarding the placement of short, matched, and open circuits on the Smith Chart, the terms of this equation can be sorted out, usually in your head in a short period of time. Recall that a short circuit, (ZL = 0) appears on the left side of the chart. The reflection coefficient, Gamma, has a magnitude of one and an angle of 180 degrees. This complex number can also be thought of as another representation of the value –1. An open circuit (ZL = infinity) appears on the right side of the chart, where Gamma = +1).
From these relationships, we know that the result of the equation must equal –1 when ZL = 0, and +1 when ZL = infinity. From these constraints we are limited to two possible arrangements for the terms in the equation:
or .
To determine which of these options is correct, we use the constraint that Gamma must equal zero when ZL = Z0, which limits us to the final, correct form.
Although this may seem to be a tedious process, you can actually perform the checks rather quickly – usually faster than looking up a reference, especially if you are away from your high-speed internet connection.
Be sure to see:
- our free Smith Chart java applet on the BesserNet website.
- instructor Keith Schaub has prepared a video tutorial on impedance matching, demonstrating how to use the applet for this purpose.
- January's issue of High Frequency Electronics magazine features an article on broadband impedance matching using the Smith Chart.
External Reference:
[1] Smith Chart derivation at Queen's University website
Last Chance for San Diego Courses this February
Space is still available in the following courses, to be held in the San Diego area this month.
| Applied RF Techniques I | |
| Feb 23-Feb 27, 2009 | Course 001-4092 |
| Presented by Les Besser | $2195  |
| Signal Processing for Wireless Communications - FREE BOOK! Click here for more information on Joe Boccuzzi's text. |
|
| Feb 23-Feb 26, 2009 | Course 029-4094 |
| Presented by Joe Boccuzzi | $1795 |
| RF Transceiver Architecture, Design and Evaluation | |
| Feb 23-Feb 27, 2009 | Course 031-4087 |
| Presented by Ed Niehenke | $2195 |
Courses Coming to San Jose this March
The following courses will be offered in our San Jose location this March. This location is situated conveniently at First and Tasman streets, with a light rail station just outside the doors. Use public transit and save money on gas and/or rental car fees!
| Wireless Circuits, Systems and Test Fundamentals | |
| Mar 23-Mar 27, 2009 | Course 112-4097 |
| Presented by Rick Fornes | Register by 2/16/2009 and pay $1995, otherwise pay $2195 |
| RF Measurements:Principles & Demonstration - FREE BOOK included! | |
| Mar 23-Mar 27, 2009 | Course 135-4098 |
| Presented by Al Scott and Rex Frobenius | Register by 2/16/2009 and pay $2195, otherwise pay $2395 |
| Semiconductor Device Physics for RF Design | |
| Mar 23-Mar 25, 2009 | Course 183-4100 |
| Presented by Bob Froelich | Register by 2/16/2009 and pay $1395, otherwise pay $1495 |
| EMI/EMC Fundamentals with Emphasis on Successful Shielding Strategies | |
| Mar 26-Mar 27, 2009 | Course 182-4101 |
| Presented by Orin E. Laney | Register by 2/16/2009 and pay $895, otherwise pay $995 |
