Peak around 800kHz in FRA

Support & Troubleshooting Moku:Go
1

HI,
When I testing Moku:go’s FRA, I found that the signal strength increased more than 20dB and the phase was reversed around 800 kHz(a peak) in FRA without any signal inputs.
I just curious about why I can found the peak on the frequency.
Could you please explain to me?

  • I’m sorry I can’t upload the captured image with my office computer.
  • Device : Moku:Go
  • App : FRA
  • Measurement : In ÷ Out
  • Input / Output : No connection

Best Regards.

2

Hi @minodori ,

I am sorry for the inconvenience you are experiencing.

I tried to reproduce your issue. I can see a similar peak around 850 kHz. However, that was due to the crosstalk between the DAC and ADC. I have attached a screenshot to this response. Would you please help us confirm if this is what you were seeing on your end?

Thank you very much for your understanding and patience!

Best regards,
Hank

image
image1212×931 94.9 KB

3

Hi, Hanklog

Thank you for your explanlation for my question.
Yes, that’s right. The results you repoduced are same to what I have seen before.
You can also find another peak at 425kHz if you look at the frequency x-axis from 100kHz.
Is it natual freqency response of moku:go?
When I test FRA with my device, can the natural frequency resposne affects on the result?

Best Regares.

Minho.

4

Hi Minho,

I am sorry that I can only find a peak around 500 kHz, but not the 425 kHz frequency. The 500 kHz peak is caused by the power supply switches. It is not noticeable on the Moku:Go units without a power supply.

Unfortunately, yes, this frequency response is the crosstalk floor on Moku:Go. In other words, a signal which has a lower magnitude response than this crosstalk floor couldn’t be measured because the signal will be covered by the crosstalk floor.

Thank you very much for your patience and understanding!

Best regards,
Hank