Adams' resistive splitter

Updated April 17, 2008

Click here to go to our main page on resistive splitters

Click here to check out the Owen resistive splitter, it can also provides unequal splits

This page describes an unequal-split resistive splitter conceived by Greg Adams. We first came across it on the web site that no longer exists. They didn't give closed form equations for any of the elements, just a few example resistor values for three different splits.

The splitter was later fully described in an article by Greg Adams in the March 2007 issue of High Frequency Electronics. (thanks to David for correcting the link!) In the article there are equations for solving for the resistors. Greg describes a clever simplification that we overlooked!

We asked Greg what is the significance of the nomenclature Rs, Rt and Ru. Rs was named because it is a series resistor, Rt and Ru are merely the next letters in the alphabet!

For "fun" we tried to solve the Adams splitter resistor values in terms of split values. Which was a lot harder than it looks. Here is what we came up with for the resistor values:

First choose Rs. Then Rt can be solved as a function of Z0 and Rs, but it's an ugly quadratic equation. Ru is easily solved from Rs and Rt. Greg's article explains some clever observations that make this splitter much easier to model than the brute force method we employed!

(one of these days we'll post some more info on this!!!)

For the example splitter, there is only one unique solution for the three resistor values, RS, RT and RU (we'll use the same notation that was used by RF Cascade). Below they are plotted against the coupling ratio.

More to come!