What is the significance of LO power for a mixer? What happens if the LO input is below the LO power required for the mixer?

 

poor noise figure and low outut from mixer. fortunatly the power is not very critical.

 

What is the significance of LO power for a mixer? What happens if the LO input is below the LO power required for the mixer?

Several things. The dynamic range is dependent on the LO power, among other things. Also, curiously enough, you can get more oddball intermod products by "underdriving" the mixer. There is an optimum power level for a given number of output products.

Some really high dynamic range mixers use up to 30dBm of LO power. Check out MINICIRCUITS labs for a whole lot of great info on mixer design