Calculate Distributed Line Length

Distributed element wavelengths occur at fractional wavelengths.

1/4 for Digital Paths
1/12 for RF Paths
1/16 for Analog Paths

Use the Saturn PCB Toolkit v7.05 to calculate lumped / distributed wavelengths.

Note that 1/Time = Freq and 1/Freq = Time, they are reciprocals.

In the Saturn PCB Toolkit select the Wavelength Calculator tab.

Example: 

Select the Period to enter the edge rate transition time. 

Enter 1nS for the Risetime period. (10% to 90%)
Enter the Er Eff (effective Er (Dk) Dielectric Constant.
Set Wavelength Divide to 1/4 Wave Length.

click on image to view

As shown above the distributed 1/4 wavelength = 1.46 inches for a rise time of 1 nS.

Paths shorter than this length are lumped lengths and longer lengths are distributed length paths. Distributed lengths should be impedance controlled paths.

Something for the RF Geeks:  Quarter Wave Tricks

Something for Everyone: Admiral Grace Hopper Explains the Nanosecond

Who is Grace Hopper? - YouTube

That's it !