# Determining LO drive voltage for 13dBm mini-circuits mixer

I am interested in using the following mixer by mini-circuits: RMS25-MH+. In the datasheet it is specified that the required LO drive power is 13dBm.

As i understand it double balanced mixers use diodes and so are non-linear devices. I only have available a signal generator that I can set the peak voltage to. My question is how can I determine the required LO input voltage. Do I assume that the input impedance looking into the LO port is 50 ohms and calculate from there?

• You're quite right that those diodes present a non-linear load to the LO driver... anything BUT 50 ohms. You substitute a 50 ohm load to the driver instead of the mixer, and deliver 20mW to that 50-ohm load. When you then substitute the mixer for that 50-ohm resistor, no doubt the peak voltage will be different (and most likely non-sinusoidal too). Aug 1, 2022 at 18:08

$$\ P = \frac{V_{\mathrm{rms}}^2}{Z_0} \Leftrightarrow V_{\mathrm{peak}} = \sqrt{2} \sqrt{P \cdot Z_0} = \sqrt{2 \cdot 20~\mathrm{mW} \cdot 50~\Omega} = 1.41~\mathrm{V} \$$