Working with Transmission Lines
For some types of design work, designing from the layout can save considerable time. This is especially true in designs with complex transmission lines. In layout, transmission lines can be created either by placing transmission line elements manually or by inserting traces and converting them to transmission lines later. Regardless of how you create them, there are a number of ways you can edit them.
Splitting a Transmission Line
You can replace one transmission line element with two identical elements.
- Choose Edit > Transmission Line > Split Transmission Line.
- On the transmission line, and click on a reference point.
Replacing a Transmission Line Element
You can replace one transmission line element with two identical elements and a tee.
- Select Edit > Transmission Line > Tap Transmission Line. A Tap Length dialog box appears where you specify the length of the tee element.
- Type a number for the tap length, and click OK.
Either an MTEE or STEE is inserted, depending on whether an MLIN or SLIN was tapped.
- On the transmission line, click on a reference point where you want the tee element inserted.
The third pin of the tee will be placed on the transmission line edge closest to the cursor.
Stretching a Transmission Line
- Choose Edit > Transmission Line > Stretch Transmission Line.
- Click on a node of the transmission line, and move the pointer away from the element. A flexible dashed line appears and moves with the pointer.
- Click on a second reference point (where you want the element to stretch to). The element is now changed to the new length.
Squeezing a Transmission Line While Maintaining its Length
You can modify an existing transmission line to squeeze it into a smaller space, specifying several characteristics in the process, such as corner type, lead length and minimum spacing.
You can adjust any or all of the following characteristics as needed:
- Corner Type - Select from Mitered, Square, Curve
- Ending Direction - The direction (clockwise or counterclockwise) in which the last two segments connected to the ending lead are drawn
- Minimum Spacing - The minimum spacing between the parallel trace segments
- Mitered Corner Cutoff Ratio (%) - The desired cutoff ratio for the corner type Mitered
- Curve Radius - The desired curve radius for the corner type Curve
- Lead Length - The length of the starting and ending segments
To squeeze a transmission line into a smaller space while maintaining its length:
- Choose Edit > Transmission Line > Squeeze Transmission Line Keeping Length. In the dialog box that appears, set the options as desired and click Apply.
- You are prompted to enter the reference location. Click the pin at one end of the transmission line and you are prompted to enter the offset location.
- Move the pointer toward the other end of the transmission line. When the ghost image of the transmission line represents what you want, click to draw the modified transmission line.