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Clicj here to learn about Henrik Forstén's on-line 2D EM field solver tool
Click here to see PolyStrata coax analyzed with an Henrik Forstén's on-line EM tool
Click here to learn about the PolyStrata process
Click here to see a GaAs microstrip10dB coupler analysed with Henrik Forstén's tool
New for March 2026. We used Henrik Forstén's on-line 2D EM tool to develop a 10dB coupler in PolyStrata coax
Below is a snapshot of the geometry. In summary, it is an air-dielectric 10dB coupler, the outer jacket is 400um tall by 850um wide. The strips are 200um tall by 120um wide. The gap is 90um. How did we come up with these dimensions? We started with a fixed height for the inner and outer conductors, then came up with the widths and gap by trial and error to get the target even and odd-more impedances. Click the link below to see the stored parameters for this coupler.
Link to geometry
Here are the even and odd mode impedances. For a 10dB coupler in 50 ohm system, Zeven should be 69.7 ohms and Zodd should be 35.2 ohms. The formulas for these parameters can be found on this page. We gave up when we got within a few tenths ohm.
Here are the S-parameters. You don't get to assign the port numbers, the tool picks them. It is almost exactly 10 dB coupling, and reflection coefficient (S11) and isolation (S21) are better than 50 dB. Further tweaking would be a fools errand, you cannot control dimensions well enough to get more than 50 dB.
Now let's look at it compared to a microstrip coupler, EM analyzed on this page,
We downloaded the file, reassigned the port numbers and plotted it in Excel, which is a PITA when you are dealing with four-port parameters. If anyone is interested in the file we used to manipulate ethe data, contact us. Check it out the PolyStrata couplre has mush better isolation and return loss, because it is a TEM structure and microstrip is only quasi-TEM.