tinySA | Main / Measuring a Mixer

Using the LO output as input to an external Mixer, of which the LO input is driven by a generator, you get a tracking generator that can track the tinySA scanning at an offset. This makes it possible to measure frequency translation devices such as a mixer.

The total setup look like this

At the bottom left there is a green module containing the mixer to be tested. The LO output of the right tinySA is used as input to a copper foil cladded mixer through a 20dB attenuator to create the tracking generator. The top tinySA is the LO for the TG mixer. The bottom tinySA is the LO for the mixer being tested

First you set the tracking generator at zero Hz offset like this

and make a direct connection between the TG output and the SA input

and you normalize

Then the mixer to be tested is inserted as in the first picture and the TG is set to an offset to 734MHz resulting in a 300MHz offset

The LO of the mixer to be tested is enabled and set to 300MHz and +7dBm output and you get the conversion loss of the mixer on the SA

The loss is about 8dB, well within spec.

But a second mixer is showing some problems

and it turned out there was an incorrect impedance matching in the output of the mixer being tested.