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AD9361 I/Q data swap

Thread Summary

The user observed data swapping on the AD9361 2R2T configuration with BIST enabled and I or Q channel masked. The solution is to clear bit 6 (PP RX SWAP IQ) of register 0x10 to eliminate the swap issue in BIST mode. The swap is only relevant for BIST and not for real RF signal processing; Figure 79 is valid for both configurations.
AI Generated Content

Hi,

I am using AD9361 as 2R2T with NO-OS software. I see that when I enable the BIST and mask one of the I or Q channel on the receivers, I see data swapped.

BIST config is - 0x3F4 = 0x3B

                          0x3F5 = 0x00

                          0x3F6 = 0x34

In this case I see that data is present on channel 1 I although it is masked.

When I am using a CW signal input after disabling BIST, I do not see spectrum inversion.

I would like to know what could be the possible reason for this ?

Edit Notes

Added more information
[edited by: Curious at 6:02 AM (GMT 0) on 4 Feb 2019]
  • Yes there is an internal swap in the case of BIST that causes this issue.

    You can clear the bit 6(PP RX SWAP IQ) of 0x10 to eliminate this swapping issue in BIST mode.

  • Hello,
    do I understand that right that by clearing bit 6(PP RX SWAP IQ) I just disable the swap which is set by default? I have proven that by observing LVDS signal and now it matches - Figure 79 from UG-570 with the BIST settings. 
    However real  RF test  (bit6 still clear) with CWlo+10 kHz positive offset provides negative 10kHz offset in baseband signal (spectral inversion).

    Can you confirm that mentioned swap is related only to BIST and not to the RF signal processing?

    Which configuration (BIST or RF signal processing) and 0x010 register settings the "Figure 79. Receive Data Path, LVDS" is valid for?

  • Can you confirm that mentioned swap is related only to BIST and not to the RF signal processing? Yes, clearing bit D6 only needs to be done in case of BIST.

    Do I understand that right that by clearing bit 6(PP RX SWAP IQ) I just disable the swap which is set by default? Yes, correct. The default setting of swap is required for proper reception of the I and Q data in case of real RF testing. Disabling of the swap is required for testing with BIST. Figure 79 is valid in both cases(BIST case- disable the bit real RF testing case-enable the bit )

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