How to set the frequency when measuring mixer IMD?

[John_li]

mixer imd

Hi all,
we use heterodyne system, I want to measure mixer IMD.RF frequency=5.8GHz,LO=3.9GHz(IF=1.9GHz),now i want to measure mixer IMD,i know the equation:2F1-Frf-Flo as attached:
My question how to set the frequency F1?and anybody kindly share my the measurement about the mixer,LNA and oscillator?Thanks in advance

 

[flatulent]

You have to put two signals that are inside the RF passband and separated by about 10% of the RF bandwidth. You will then see extra frequencies in the IF that are separated from the original two frequencies by the same amount as the first two frequencies are separated.

 

[John_li]

Is it the same as other amplifier measrement e.g. LNA?

 

[flatulent]

Yes, this is the standard method. If you are using a simulator no extra precautions are required. If you are making physical measurements you have to use circulators on the outputs of the two signal generators and a high isolation combiner.

In real world signal generators there is a leveling loop that rectifies the output and sends it back to a leveling circuit. If some other signal is put into the output of the generator a hetrodyne is created which AM modulates the output.