TC1-1-13MA+ RF Transformer

Could someone please let me know what transformers are actually on the board. If you compare the datasheets from Minicircuit with the LimeSDR schematics it doesn’t make sense:

TCM1-63AX+ Has a winding connecting the primary and secondary. How is that going to work? For sure there is no isolation.

TC1-1-13MA+ Part does not have a center-tap. How is that going to work?

Please explain. I’m doing my own LMS7002-based design and need to get this fixed ASAP.


Well the isolation is done more with the capacitor than transformer …

and when dealing with a 1:1 transformer as long as the input and output are not in series or parallel … it will work, but keeping primary separate from secondary always helps with ESD/loop isolation …

I didn’t look hard at the board placement of the 1.4V board …

Id say place the transformers as you see fit …

1 Like

It is not a transformer. It is a balun!

Wires around a form …

Balanced to unbalanced …

Same device used in different ways … some times doing both , impedance transformation AND balToUnBal …


It’s a transformer with characterized RF performance and a specific turns ratio.

1 Like

You’re going to shoot yourself in the foot if you’re doing an RF design without any requisite RF knowledge. As good of an all-in-one the Lime Transceivers are, they’re still dealing with RF signals.

1 Like

To be more specific:
It is a balun. Acting as a “common mode choke” aka “current balun”.
No impedance transformation.
Below its cutoff frequency the output signal is not symmetrical any more.