microwave software®
MStrip+® User Manual
Transmission Line Analysis and Synthesis Utility
STRIPLINE MODULE
A stripline transmission line is formed as a sandwich
of two circuit boards. One board, the bottom board,
has a circuit pattern etched onto it, and the facing side, i.e., the top
board, is blank. Both top and bottom boards either have full backside
metallization, or are compressed between backing
plates, or some such.
Introduction
Like microstrip, a single line on a board is described in terms of its characteristic impedance, Z0. However, unlike microstrip, propagation of a signal down this line is in a pure, and non-dispersive TEM mode. Line lengths are calculated using the dielectric constant, ER, of the board material, instead of using an effective relative dielectric constant, ER', as in microstrip.
The characteristic impedance, Z0, of a stripline, is a function of the following physical and electrical parameters.
- Line width
- Ground plane spacing
- Dielectric constant
- Metallization thickness
A sketch of a typical stripline is shown below. The terms used to describe it are standard in the industry.
The Stripline Menu
| Stripline Menu
|
| (1) Synthesize
|
| (2) Analyze
|
| (3) Tabular Data
|
| (4) Main Menu
|
| Choose (1-4) ? _
|
Line Synthesis Mode
When use choose "(1) Synthesize" from the Stripline
Menu, in the same manner as before, the screen display will
look as follows:
Synthesis Mode
Enter Z0,T,B,Er [<Enter>=Quit] ? _
Enter each of the four values requested. The units are ohms and inches.
Let's create a 50 ohm stripline using 0.060 in. thick Rogers RT/duroid (Er=2.2), with 1 oz. copper metallization. Note: 1 oz. = 0.0014 in. = 1.4 mils. Note: "B" is the overall dielectric thickness.
Enter the data as follows and then press <Enter>:
50,.0014,.12,2.2
Note: At this point, you'll be asked "Print Logfile (Y/N) [<Enter>=No] ? _" Please press <Enter>.
If you choose the option to 'Print Logfile,' the data will be directed to 'Logfile.txt' within the \mwdata3 sub-directory, and to the screen. Right-click on 'Logfile.txt' to print it, and then DELETE the file; it will re-create when next needed.
MStrip+ will display the input data on-screen, IF you pressed <Enter>, as follows:
| MStrip+ SL Synthesis
|
| Input Data
|
| Z0
= 50 ohms
|
| T
= .0014 in.
|
| B
= .12 in.
|
| ER = 2.2 |
| Output Data |
| W/B = 0.7948 |
| - Press any Key - |
Line Analysis Mode
When use choose "(2) Analyze" from the Stripline
Menu, the screen display will look as follows:
Analysis Mode
Enter W,T,B,Er [<Enter>=Quit] ? _
This option works the same as those shown earlier. Try working backwards using the results of the line synthesis just completed.
Tabular Data Mode
When use choose "(3) Tabular Data" from the Stripline
Menu, the screen display will look as follows:
| Tabular Data
|
| (1) Z0 vs W/B
|
| (2) W/B vs Z0 |
| (3) SL Menu |
| Choose (1-3) ? _ |
Z0 is in ohms, and W/b is a ratio.
Let's tabulate Z0 vs W/B over the range of 0.1 to 1 in steps of 0.1, using Rogers RT/duroid (Er=2.2), with 1/2 oz. copper and 0.060 in. thick dielectric material.
Choose "(1) Z0 vs W/B" from the Tabular Data menu.
Z0 vs W/B Mode
Enter W/B Start, Stop, Step [<Enter>=Quit] ? _
Type the following and press <Enter>.
.1,1,.1
Next, enter the line data as requested by the prompt and press <Enter> once again.
.0007,.12,2.2
You'll see the following on-screen:
| MStrip+ SL Z0
vs W/B Analysis
|
| Input Data
|
| T
= .0007 in.
|
| B
= .12 in.
|
| ER = 2.2
|
| W/B
Z0
|
| 0.10 126.3880 |
| 0.20 100.6354 |
| 0.30
85.3967
|
| 0.40
74.6939
|
| 0.50
66.5638
|
| 0.60
60.1025
|
| 0.70
54.8133
|
| 0.80
50.3908
|
| 0.90
46.6330
|
| 1.00
43.3983
|
| - Press any Key - |
Follow the on-screen instruction to " - Press any Key - " to return to the Tabular Data menu.