Lumped element Wilkinson power divider example 1

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New for January 2022. This design is at "low frequency" and therefore uses lumped elements as quarter-wave lines would be ridiculously long. It was designed by Sebastian, a long-time contributor to Microwaves 101.

Below is a video where Sebastian explains a mathematical technique for designing a 28 MHz, narrow-band Wilkinson power divider using lumped elements. He goes through the design, explaining basic algebra for rearranging equations.  As he suggests, you'd better be able to do that correctly if you plan on a career in engineering.  First, he calculates the series inductors, which need to provide 70.7 ohms reactance to transform the individual 50-ohm loads to 100 ohms (~400 nH). Then, he calculates the shunt capacitance needed to resonate out the reactance of the inductors (80 pF). After breadboarding the circuit, he shows how to evaluate it on a Tektronix MDO4000 mixed domain oscilloscope using fixed CW signals as well as a broad-band noise source. The measured center frequency is perhaps 25% lower than the design frequency, and Sebastian has some comments on how this occurred. Note that at microwave frequencies, the design will be much more complex in order to absorb the parasitic effects of lumped elements, and we recommend you use a linear EDA design tool to try for first-pass success.

Bonus material: Sebastian winds his own toroidal inductors, to produce the required 400 nH value. Bravo! We most definitely need a page explaining the formula for this component.  Coming soon!

Designing a Wilkinson Splitter / Combiner by Sebastion KF5OBS

Here is a link to a paper that Sebastian wrote on the same design that is featured in the video.

Note that you can calculate Sebastian's inductor value using our on-line reactance calculator and calculate his resonant capacitor value using our on-line resonant frequency calculator.

Thanks again, Sebastian!





Author : Unknown Editor