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Adams' resistive splitter

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

Click here to go to our main page on unequal splitters

Here's a link to a cool calculator that will provide you with Adams' splitter resistor values. Thanks to Brian!

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 that 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!

Note that in the image below, there is a resistor in series with port 2.  It should not be there... Port 2 should directly connect to the junction of RT and Ru. Thanks to Brian for pointing that out!  We'll fix the image one day.  Meanwhile, it has served as a Mountweazel all these years...

We used his equations to solve the for the splitter resistor values based on the insertion loss from the input to the first port. The calculator at the bottom of the page will calculate all the resistor values for a given insertion loss. We have normalized all the resistor values to the reference impedance(Zo) of the network to give a more general result. The network as configured is not realizable for an input greater than 6 dB and the calculator will give an error message as a result.

Every performance and design parameter for the splitter is determined uniquely by the value of the first splitter output, so we have saved you some time and plotted the resulting split at port 2 and the overall efficiency of the circuit below.

Likewise, we have plotted the normalized values of the resistors used in the splitter as a function of the first output port power split.

We have information from Andy on additional degrees of freedom with resistive splitters:

We at TEGAM were designing an amplifier test bench and had occasion to look on your site for some splitter design input. I was intrigued with the approach taken by Adams at but really wanted to be able to control the attenuation to both output ports. After a bit of fiddling, I came up with a two output port splitter design calculator that lets you set the attenuation to each port (within practical limits). The derivation and calculator are attached in the files names, “Two Output Four DOF”. In a further step, our design needed a splitter with two equal outputs and a third monitoring output with some “nice” ratio to the others. That was a relatively simple step and is attached as “Three Output Four DOF”. Go to our download area and grab the Zip file that contains a lot of math manipulation that they reduced into 5 simple design equations. Thanks, Andy!

MTT-S Approval

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