ADRV9025 DPD ACPR Issue

Dears.

It is being developed with ADRV9025, and the DPD is being tested.

Lowering the signal generator's input causes ACPR degradation.
The rated input level yields the expected level of ACPR characteristics.
As the signal generator output goes down, the amp output goes down. Therefore, it does not overdrive the Amp.

Lowering the GAIN of the ADRV9025 does not cause ACPR degradation.
ACPR degradation does not occur when lowering the GAIN between CFR/DPD.
However, by lowering the signal applied to the CFR, ACPR degradation occurs when the PAR increases.

The DpdPeakSearchWindowSize(Default = 491520) value was changed to 1024 and tested.
Please guide me on how to set the DpdPeakSearchWindowSize value.
Please guide us on what we need to check.

The issue is ACPR degradation.

The test set up is as follows.

Test Setup and ADRV9025 Info :
Signal generator -> Mater Unit -(Optic Cable)-> Remote Unit(ADRV9025) -> Spectrum Analyzer

Center Frequency : 889 Mhz
FDD
Band Width : 10 Mhz
ADRV9025 User Case No : UC50_Nonlinksharing
Direc/Indirect : Indirect
DPD Mode0,1,2 : DPD MODE0
DPD GMP MODEL NO : Gen_3 model_67
PA TR Info : RFHIC IE08330D

[getdpdstatus]
# dpdErrorCode : 0x0
# dpdPercentComplete : 0
# dpdIterCount : 584
# dpdUpdateCount : 575
# dpdSyncStatus : 4
# dpdModelTable : 0
# - statistics
# dpdMeanTuPower : 33129378 -15.11
# dpdPeakTuPower : 253584464 -6.27
# dpdMeanTxPower : 32955052 -15.13
# dpdPeakTxPower : 285458752 -5.75
# dpdMeanOrxPower : 38077952 -14.50
# dpdPeakOrxPower : 282798816 -5.79
# dpdDirectEvm : 0.015645
# dpdIndirectEvm : 0.080374
# dpdSelectError : 0.009935
# dpdIndirectError : 0.010250
# - dpdErrorStatus0
# dpdMetricsMask : 128
# dpdActionMask : 1
# - dpdErrorStatus1
# dpdMetricsMask : 0
# dpdActionMask : 0
# - dpdPersistentErrorStatus0
# dpdMetricsMask : 0
# dpdActionMask : 0
# - dpdPersistentErrorStatus1
# dpdMetricsMask : 0
# dpdActionMask : 0

[Before DpdPeakSearchWindowSize  value change]

/cfs-file/__key/communityserver-discussions-components-files/910/A2KHS-ADRV9025-p1.mp4


[After DpdPeakSearchWindowSize = 1024]

It has been slightly improved by changing the DpdPeakSearchWindowSize  value.

/cfs-file/__key/communityserver-discussions-components-files/910/ADRV9025-p2.mp4

Thank you.

  • 0
    •  Analog Employees 
    on Oct 6, 2021 4:10 AM

    When the input power is reduced, are you adjusting the CFR engine Thresholds to maintain the PAPR at expected level?

    If there is any change in the baseband power level, the CFR thresholds have to be adjusted so the PAR is maintained

  • DEAR. RAMARAO

    The threshold value cannot be changed whenever the level of the upper signal is changed.

    I would like to know how to make it work without any problem even if the input level changes during DPD operation.

    After changing the DpdPeakSearchWindowSize value, it seems to be improving.
    Please let us know how we can improve it.

    PA uses GaN.
    How is DPD performance affected by GaN properties?

    In order to improve DPD performance, please guide me on which parts other than DPD Mode, Direct/Indirect, and GMP MODEL should be checked.

    Thank you

  • 0
    •  Analog Employees 
    on Oct 6, 2021 10:29 AM in reply to Henry J

    Can you try increasing the peak search window size, may be 2x65585, 4x65535..etc?

    Can you try reducing the regularization value?

    Also, we recommend to use Mode 2 for GaN PAs as their characterestics would change from low power to high power.

    Can you please share the CFR and DPD statistics in a good (Rated output power) and bad (lower power) ACPR condition?

  • DEAR. RAMARAO

    Measured at a level 2dB lower than the rated input.
    Changed to DPD MODE 2.
    CFR is 8.5dB.
    At peakwindowsize = 1024, it is -55dB, but at other values, it is about -44dB.

    During DPD operation, the output level changes by 0.3~0.4dB, and ACPR fluctuates by 3~5dB.


    What's the problem with using peakwindowsize = 1024?

    Please suggest a value for peakwindowsize.

    Peakwindowsize = 1024

    Peakwindowsize = 2*65538

    Peakwindowsize = 4*65535

    Peaskwindowsize = 491520


    The CCDF for each input level is as follows.

    There is no improvement when applying Peakwindowsize = default and changing the Reguralization value = 5/75.

    Thank you.

  • 0
    •  Analog Employees 
    on Oct 8, 2021 5:59 AM in reply to Henry J

    At peakwindowsize = 1024, it is -55dB, but at other values, it is about -44dB.

    During DPD operation, the output level changes by 0.3~0.4dB, and ACPR fluctuates by 3~5dB.


    What's the problem with using peakwindowsize = 1024?

    There is no problem using lower peak search window size.

    To overcome the ACLR fluctuations, can you run the below step as per the User guide and optimize the M-threshold value.