Hi Gabriel,
As an experiment, you could try to make a more symmetrical balun by placing the core vertically over the pcb and making sure the wires have equal length. Another request, could you publish the schematics in pdf? I'd like to study them and give some feedback. I don't use gEDA, I stick with KiCAD, Pulsonix, Ultiboard and Altium.
Happy 2020!, Reinier
Op 6-1-2020 om 08:40 schreef Gabriel Tenma White:
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I just tried the TC1-1-13M on two units. With a balanced (symmetrical) bridge circuit (like the one in v2_0) the directivity is not good, around 8 to 10dB up to 3GHz, but just out of curiosity I tried it on a new unit (v2_2) that has the 0.3pF tuning, and the directivity graph turned out nearly identical as before with the old balun (TOKO 617DB-1023=P3), with 17dB worst directivity. Looking at the pictures it seems to have the same physical asymmetry as the 617DB-1023=P3 (see attached), but the good news is this tuning seems to be applicable to more than one manufacturer's baluns, so I can have a second source just in case.
I'm not sure why the simulation doesn't match measurements, but it might be that the asymmetry isn't accounted for because the balun was never intended for this use case ;) The model probably accurately predicts CMRR, but doesn't predict "Common Mode to Differential Mode transfer".
