How to config DPD on AD9375?

Hi,

I use default DPDconfig to configure DPD on my custom board:

static mykonosDpdConfig_t dpdConfig =
{
    10,              /* 1/2^(damping + 8) fraction of power `forgotten' per sample (default: `1/8192' = 5, valid 0 to 15), 0 = infinite damping*/
    1,              /* number of weights to use for int8_cpx weights weights member of this structure (default = 1)*/
    2,              /* DPD model version: one of four different generalized polynomial models: 0 = same as R0 silicon, 1-3 are new and the best one depends on the PA (default: 2)*/
    1,              /* 1 = Update saved model whenever peak Tx digital RMS is within 1dB of historical peak Tx RMS*/
    20,             /* Determines how much weight the loaded prior model has on DPD modeling (Valid 0 - 32, default 20)*/
    0,              /* Default off = 0, 1=enables automatic outlier removal during DPD modeling */
    512,            /* Number of samples to capture (default: 512, valid 64-32768)*/
    4096,           /* threshold for sample in AM-AM plot outside of 1:1 line to be thrown out. (default: 50% = 8192/2, valid 8192 to 1)*/
    0,              /* 16th of an ORx sample (16=1sample), (default 0, valid -64 to 64)*/
    255,            /* Default 255 (-30dBFs=(20Log10(value/8192)), (valid range  1 to 8191)*/
    {{64,0},{0,0},{0,0}}/* DPD model error weighting (real/imag valid from -128 to 127)*/
};

My system have multi mode BPSK, QPSK, QUAM16,QUAM64 with bandwidth 5MHz, 10MHz, 20Mhz. 

I have feedback Tx2 signal into ORX2 with power -24dbm and configure dpd follow ug992. But i don't see any different between have setup DPD and no have DPD.

Here is status that I read using MYKONOS_getDpdStatus:

 dpdStatus.dpdErrorStatus = 0,

dpdStatus.dpdExtPathDelay = 0x73B ,

dpdStatus.dpdIterCount = 0,

dpdStatus.dpdMaxAdaptation = 0,

dpdStatus.dpdModelErrorPercent = 1000,

dpdStatus.dpdTrackCount = 0

Can you suggest for me how to solve? Thanks. This is my output from tx:



dpdStatus.dpdErrorStatus = 0, dpdStatus.dpdExtPathDelay = 0x73B , dpdStatus.dpdIterCount = 0, dpdStatus.dpdMaxAdaptation = 0, dpdStatus.dpdModelErrorPercent = 1000, dpdStatus.dpdTrackCount = 0
[edited by: sonminh at 2:00 AM (GMT 0) on 24 Apr 2020]

Top Replies

    •  Analog Employees 
    Jun 17, 2020 in reply to sonminh +1 verified
    BUT I don't understand why system no have dpd run better than system have DPD.

    What do you mean by run better here ? 

Parents Reply Children
  • 0
    •  Analog Employees 
    on Apr 29, 2020 11:20 AM in reply to sonminh

    What is the raw ACLR (without DPD) of PA for same power at frequencies 4,5 G, 4.6G  and  4.8G ?

  • Hi

    ACLR without DPD:

    4.6G: -30dbc for right adj channel, -35dbc for left adj channel

    4.5G: -29dbc for right adj channel, -33dbc for left adj channel

    4.8: -36dbc for right adj channel, -37dbc for left adj channel

    Here are image of 3 above frequency. Thanks

  • 0
    •  Analog Employees 
    on May 4, 2020 4:29 AM in reply to sonminh

    What is your target output power,?

    Above measurements are done at different power and hence the variation in ACLR is more.For comparison you need to make measurements at same output power. You can keep Tx1 as primary (center) so that you can read ACLR directly.

    4.5 -28.54 dBm
    4.6 - -26.84 dBm
    4.8 - 25.4 dBm

    Bandwidth is 22MHz , IS the waveform custom?

    The ACLR is not symmetric, The right and left adjacent are having upto 5 dB variation.You may need to correct that for better DPD performnce.

  • Hi

    My system run custom waveform with bandwidth 21.4Mhz. And now different frequency, output power may be not the same. My target output power is 30dbm. Above system has output power with attenuation 30dbm. 

    You say: "The ACLR is not symmetric, The right and left adjacent are having upto 5 dB variation.You may need to correct that for better DPD performence". So what is the maximum different  variation between right and left adjacent that AD9375 can still DPD? 

  • 0
    •  Analog Employees 
    on May 4, 2020 8:11 AM in reply to sonminh

    I don't have a exact value for symmetry , Its recommended to be within +/- 1 dB.

    For different power levels the linearity of PA will be different and different ACLR and DPD correction is as well dependent on that. So I guess what you see is expected.

    Mykonos DPD is good for LDMOS PA's where the memory effects are less. For GAN PA's electron trapping adds to short term memory effects and it becomes difficult for DPD to correct.