raschu created the topic: Coplanar Waveguide Marchand Balun

I was playing around in Sonnet Lite to learn more about RF and I simulated an simple cpw marchand balun with one or more coupled on the balanced and unbalanced port. I found US patent 6819199 on google patents has a good image or two of the balun, except the patent adds capacitors on both ends of the unbalanced port. I just used the standard cpw line and space widths and it worked fine. Two balanced lines and one unbalanced gives 100/50 ohms, one and one does not. No ground is needed, and if there are multiple unbalanced lines need to be connected at the middle to keep the currents symmetric.

I have a question because something seems weird about my simulation results. I read that a marchand balun has an unequal group delay to create a phase shift on the balanced port. My results do not show that. They end up very close to equal, and can even cross. The phase is still 180 degrees. Is this a correct way to look at the results, or is this a simulation error?