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Original question:

ADC12DJ5200RF: ddc

ADC12DJ5200RF: ddc IQmisalignment

xiaxin
Prodigy 70 points
Part Number: ADC12DJ5200RF


Tool/software:

Hello,
I'm facing a problem about the ddc of adc12dj5200: after decoding the ADC's IQ data, I plotted the constellation diagram of I+jQ and noticed that it is sometimes not a perfect circle. Could this indicate that my I and Q data are misaligned? How can I solve this issue?
Additionally, I tried reading the buffer_adjust value of JESD204B, and it is 0. Is this normal?My register configuration as below:

24'h0000B0, //soft_reset,self clearing for 750ns last
24'h002B15, //all time default
24'h02A230, //all time set
24'h02C200, //all alarm will not be masked
24'h020000, //JESD_EN = 0
24'h006100, //CAL_EN = 0
24'h0220CA, //FREQA0
24'h022139,
24'h0222D9,
24'h022349,
24'h020110, //JMODE = 16
24'h02020F, //K=16
24'h020500, //test_mode,0:normal
24'h006001, //all time default
24'h021500, //select which of 4 nco used to as active nco.[3:2] CSELB & [1:0] CSELA. range:0-3 00:use nco0 for chA and chB
24'h020400, //8b/10b offset_binary use_syncse_pin:all time default
24'h002920, //set sysref_recv_en =1
24'h002960, //set sysref_proc_en = 1 & sysref_recv_en = 1
24'h002970, //set sysref_proc_en = 1 & sysref_recv_en = 1 & zoom in sysref window status,smaller delay
24'h002969, //set sysref_delay according to sysref_pos
24'h006101, //CAL_EN = 1
24'h020001, //JESD_EN = 1
24'h006C00, //CAL_SOFT_TRIG = 0
24'h02C100, //alarm flag,if =1.alarm active
24'h006C01, //CAL_SOFT_TRIG = 1 ;form 0 to 1 means a cal_trig generated,start calibration.

delay 100usec


24'h021902,
24'h021903

  • 0
    Prodigy 70 points

    By the way,I have a question: if the buffer_adjust values of the 4 lanes corresponding to the I-channel signal are not equal to those of the 4 lanes corresponding to the Q-channel signal, will this cause the problem? Because I noticed that the constellation diagram is a perfect circle only when the buffer_adjust values of my I-channel and Q-channel are completely equal, but I don’t understand what the relationship is between these two.

  • 0
    TI__Prodigy 670 points

    Hi xiaxin, I sent you a private message with a request before we can proceed.