Ways to analyze the harmonic distortions after mixing

Hi all, when design a transmitter, the harmonic distortions after mixing are unwanted especially the in-band distortions. Clearly widely known the LO signal should be prevented from going into the in band. I wonder are there any good ways to analyze the in-band harmonics because these cannot be moved out using filter. many thanks to your response!

Here you can find few methods how to test the IP3 (and in-band distortions) of a mixer.

https://www.markimicrowave.com/blog/...error-sources/