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CC3351: CC33XX INI PowerLimitArray minimum value

DAVID NEPERUD
Prodigy 20 points
Part Number: CC3351


Tool/software:

The INI PowerLimitArray value cannot be set low enough to meet the Korean Channel 48 conducted limit of 4dBm/MHz for RU26 allocations.

Calibrator Tool was used to determine the power setting for compliance where the TX_POWER can be set in the range of -10 to 21 dBm in 1 dB steps.

The minimum INI PowerLimitArray setting I have found that works is 0x01 which corresponds to a TX_POWER setting of 0.5dBm.  Note - if the PowerLimitArray setting is 0x00, the device will transmit at max power.

Why is there a disconnect between the Calibration Tool and the INI file for available power settings?  How do we call for a lower INI power setting in order to be compliant on this channel in Korea? 

  • 0
    TI__Expert 3840 points

    Hi David,

    Calibrator tool is used for testing, that's why more possible power options were added for negative power testing. 

    The lowest possible power limit available in the INI PowerLimit Array is 0.5dBm, there is no option for negative values as limits. 

    Is there any reason why you need negative power limit? At what power level in calibrator tool did you pass certification? 

    Regards,

    Jonathan

  • 0 in reply to Jonathan Cohen
    Expert 1511 points

    Hi Jonathon,

    The array is in dBm, and negative values are still positive power. They are just low power values.

    Low power values are needed for some narrow bandwidth (26RU) OFDMA configurations to meet power spectral density requirements.

    Also note that a value of 0 should not result in max power - it should be 1mW (0dBm)

    Dean

  • 0
    Prodigy 20 points

    Hi Jonathan,

    The power needs to be set to -1dBm in order to pass the PSD limit on channel 48.  

    Dave

  • 0 in reply to DAVID NEPERUD
    TI__Expert 3840 points

    Hi David,

    Can you explain how you got to -1dBm setting in order to pass this PSD setting? 

    According to my calculations if you need to have a conducted PSD limit of 4dBm/MHz for RU26 allocations, the limit should be 5.5dBm, no need for negative power limits.

    If you tested this with calibrator tool, please share the commands you used when testing tx power and screenshots of the spectrum analyzer.

    Regards,

    Jonathan

  • 0
    Prodigy 20 points

    Hi Jonathan,

    Here are the calibrator tool commands used:

    calibrator wlan0 plt power_mode on

    calibrator wlan0 cc33xx_plt tune_channel 48 1 0

    calibrator wlan0 cc33xx_plt set_manual_calib -tx 1

    calibrator wlan0 cc33xx_plt set_tx -default 0

    calibrator wlan0 cc33xx_plt set_tx -length const packet 30 -delay 1100

    calibrator wlan0 cc33xx_plt set_tx -preamble_type 8

    calibrator wlan0 cc33xx_plt set_tx -phy_rate 13 

    calibrator wlan0 cc33xx_plt set_tx -tx_power 9

    calibrator wlan0 cc33xx_plt set_tb_tx -tb_auto 1 -he_ltf_num 2 -ul_bw 0

    calibrator wlan0 cc33xx_plt set_tb_tx -ru_alloc 0

    calibrator wlan0 cc33xx_plt start_tx

    Here is a screen capture with the transmit power set to +5 dBm as you suggested.  The green display line is the 4dBm/MHz limit.

    These screen captures are with the transmit power set to -1 dBm (-tx_power 9)

     

    Thank you,

    Dave