R&D (FilterCavity)
MarcEisenmann - 16:03, Friday 08 January 2021 (2331)
Test of DDS2 amplifier & ground issue

Participants : Marc, Yuhang

 

To test the effect of the amplifier we checked the spectrum of CH0 when disconnecting the amplifier :

    FIg1 shows the CH0 spectrum when the voltage supply of the amplifier is disconnected but amplifier is still connected to CH2.

     Fig2 shows the same with the ground also disconnected.

     Fig3 shows the CH0 without the amplifier at all.

In all these configurations the peak around 20kHz is present : The 20kHz peak does not arise from the amplifier

 

We used the spectrum analyzer of the elec shop to check if the 20kHz peak is present in the voltage supply of this board.

     Fig4 shows in yellow CH0 and blue the 1.8V supply : same peak in both at 17.4 kHz

     Fig5 shows in yellow CH0 and blue before the regulator of the 1.8V supply : same as previous

     Fig6 shows in yellow CH0 and blue the 24V supply : same as previous

Finally, we found out that the ground may be connected to all voltage supply of this board as well as DDS output channels (see connection.mp4)

Images attached to this report
2331_20210108080723_nosupply.jpg 2331_20210108080728_noground.jpg 2331_20210108080732_noampli.jpg 2331_20210108080737_img20210108142919.jpg 2331_20210108080742_img20210108143248.jpg 2331_20210108080747_img20210108143435.jpg
Non-image files attached to this report
Comments related to this report
YuhangZhao - 13:41, Tuesday 12 January 2021 (2332)

Marc and Yuhang

We checked again the connection from ground to power supply or signal output today. And we realize that we were not checking in a good way last week.

This time, we measured the resistor between ground and many other parts. We found the resistor is as high as from 0.3kOhm to 0.9kOhm. In this case, it means the ground is well isolated with those channels. So there should not be ground issue.

MarcEisenmann - 18:48, Wednesday 13 January 2021 (2338)

For reference and future similar investigations :

     The power supply was tested using a DC block (here up to 50V).

     The ground was tested with the power supply disconnected.