testing a mixer for saturation

[john23]

Hello , I am using a DBM shown bellow TXF-18075,unlike amplifier Its mixer is more complicated.
How can I see in the lab the saturation on my DBM?
How can I see that LIVE the saturation and see if I have a good LO or RF signal?
Thanks.

[bairdbankovic]

Feed in a waveform and use an o-scope to check for clipping? Am I missing something here?

[john23]

I have two power levels the IF and LO
How do I test for clipping when there are two possible problematic power sources, maybe the LO power is two low ?
How can I see that my LO is too low ?
Thanks .

[john23]

What si the LO is too low.
I dont have a datsheet.
Thanks.

[EggertEnjoyer123]

Generally +10dBm is good enough for double balanced mixers. If you have two signal sources, set the RF to -30dBm and plot the conversion loss vs LO power. You can see when the conversion loss levels out, and that is your minimum LO power.

Here is some random picture I found on the internet. You can see that somewhere around +7dBm LO power is ideal for this mixer.

You can also determine the input IP3 of your setup. Attach an isolator on the output and feed a slightly offset signal from a signal generator back in (like maybe input frequency + 1kHz). Make sure that your signal generator can take reverse power (some power will leak through the isolator). You can then determine linearity by measuring the 3kHz harmonic on the IF of the mixer.

[john23]

Hello eggerEnjoyer,I have three ports,RF LO IF.
I use this mixer in downconverting.
So I need to block and cancel the IF so nothing will return.
Where do i need to feed the signal?
Ip3 is spposed to be the input at which the output is compressed.
our output is blocked.
WHat is the logic in this method?
Thanks.

You can also determine the input IP3 of your setup. Attach an isolator on the output and feed a slightly offset signal from a signal generator back in (like maybe input frequency + 1kHz). Make sure that your signal generator can take reverse power (some power will leak through the isolator). You can then determine linearity by measuring the 3kHz harmonic on the IF of the mixer.