J. Freed

Before the hoidays as shown in 81658, the Double Mixer had large phase noises at 4096Hz that were thought to be caused by phase offest difference in the Double Mixer. Thanks to Marc Pirello for the suggestion and help to manually adjust the phase difference by extending the wire lengths inside the double mixer. 

DM_PN2.pdf Shows the lower 4096Hz peak in the path adjust(green) as compared to the no path adjust (blue) and both compared to an independant SRS (orange). The harmonics are still large so  DAC output had a ~5kHz low pass applied but with negledgable improvement. Investigation was ongoing when I went on holiday. 

Today I plugged in the double mixer into a network analyzer to see the power spectrum density of the signal 

DM_NA_WIDE.pdf Shows that although the DM has better noise floor, the harmonics of the double mixer are quite a bit worse in the Power spectral desnity than shown in phase noise DM_PN2. The best result (shown) was with NO added length. Unsure why this is. 

DM_NA_NARROW.pdf Besides that the signal has a fairly pure tone, though this is limmited by the resolution.

Investigations ongoing