## 500MHz RF input impedance mismatch

An incorrect impedance matching has been found throught schematic
review.

The RF input jack is connected to a Minicircuit's RF transformer line
balun, the secondary is connected to a 100ohm resistor (R76). The
equivalent circuit after R76 has an impedance greater than 100ohm. The
configuration of the RF tranformer is a "Guanella Transformer" (see
[1]) which has an equivalent impedance on the primary equal to the
impedance of the secondary (1:1). Since R76 has 100ohm of impendace, an
impedance mismatch occurs. Minicircuit contacted [2], they agrees.

[1]
http://electronica.ugr.es/~amroldan/microwaves/modulos/apuntes/material/RF_Trans_Design.pdf

[2] Dear Mattia,Thank you for your query.

We have reviewed the diagram you provided and in order to be correctly
matched the secondary impedance would need to be 50 Ohm differential. As
the following circuits are high impedance we would agree that a 50 Ohm
resistor should provide a better match than 100 Ohms.

Joe Coppinger