why the received Q signal is always distorted?

https://wiki.analog.com/resources/fpga/docs/axi_ad9361#register_map

Did you properly set all the ADC and DAC channel registers? This looks like DAC_DDS_SEL is still set to DDS for the Q channel....

-Michael

int32_t dac_datasel(struct ad9361_rf_phy *phy, int32_t chan, enum dds_data_select sel)

https://github.com/analogdevicesinc/no-OS/blob/master/ad9361/sw/platform_xilinx/dac_core.c#L468

dac_datasel should set all channels when chan is set to -1.

In your case when set to 0 it only set's the first channel which is I.

-Michael

Hello xiao quan,

Are you using No-OS or Linux in your experiments ?

What LO frequency are you using ?

Are you using loopback cables or Antennas ?

What carrier and what evaluation board ?

Regards,

Adrian

Hi AdrianC,

Thanks for your reply! No-OS is adopted in the design, and the LO frequency is 2.4GHz. Loopback cable is used from TX1A to RX_1A, and ZC706+fmcomms3 is adopted.

thanks,

xiao quan

Can you send a snapshot of how you connect the ILA ?

Regards,

Adrian

hello Michael,

Thank you very much! what you said is truly a possible case for this phenomenon. But I want to know that whether DAC_SEL_DDS can be set to Q channel  independently, and I channel is set to DAC_SEL_DMA  in one tx path?  In SDK, I write a statement dac_datasel(ad9361_phy,0,DATA_SEL_DMA); in main.c after AD9361 is initialized.

thanks,

xiao quan

hello Adrian,

ILA and axi_ad9361 connected relation is shown below,

thanks,

xiao quan

Hi Michael,

Thank you very much! you are a master! The question is solved. I believe naively that '-1' represents that it means two tx path TX_1A and TX_2A previously.

thanks,

xiao quan

Hi Michael,

The last question is solved, and there is an new question occurred, which is the received IQ signals are exchanged totally, as followed. Would you like to give me some tips?

thanks,

xiao quan

Hi,

What you are seeing is a so called phase shift. This is a normal thing in RF signals. You'll either have to use a differential QPSK (DQPSK) encoding. Or embedded a preamble in your datastream that allows to recover the original phase.

- Lars