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AD9364 Signal Distortion at Rx in MGC mode

Category: Hardware
Product Number: AD9364

Hi

I am using ADRV9364 board with ADRV1CRR-BoB. I am running the no-os. When I run the no-os in default settings, I see clean Rx data. but when I change the mode to MGC and give a small gain (i.e. 0-30, that does not cause overflow) then the signal at the Rx has some noise in it.
I want to know how can I remove the noise and where is it coming form.

MGC 20:

MGC 5:

The second issue is that the here adc and dac valid is high once every 1 cycle (1 valid in 2 cycles). But with AD9361, I have observed that the adc and dac valid is high once every 3 cycle (1 valid in 4 cycles).

A clean picture with default AGC enabled. Here the signal received at the adc is clean:

  • but when I change the mode to MGC and give a small gain (i.e. 0-30, that does not cause overflow) then the signal at the Rx has some noise in it.

    Can you check the FFT plot in this case? There might be saturation in the RX path. 

    The second issue is that the here adc and dac valid is high once every 1 cycle (1 valid in 2 cycles). But with AD9361, I have observed that the adc and dac valid is high once every 3 cycle (1 valid in 4 cycles).

    Are you referring to Aux ADC valid signal? How are you probing the DAC valid signal?

  • I have not connected any FFT IP and I am using the No-OS implementation so there is no spectrum available. If there was some saturation, then the values on the adc would also be very high but this is not the case here. Since when my MGC is at lower value, how can there be saturation with lower values. My external signal is also -30dBm. 

    I am probing the dac valid signal in the ILA. I am unaware of AUX adc signal.

  • If the gain set for the RX path is too low a compared to the input signal, then the signal amplitude will be very less and get buried in noise. You can try increasing the input signal amplitude with the same gain  and you will see clean spectrum at the output.