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AD9371 Initial Calibrations

We have an application that operates in the 5470-5725MHz band, with channel centre frequencies spaced 10MHz apart. Our total bandwidth for all channels in 260MHz. Currently, we perform the AD9371 initial calibrations at boot as recommended in the user guide at a spot frequency in the middle of the band, and use this for all channels. This slightly breaks the 100MHz change in frequency that it is recommended to do a re-calibration in the PLL setting section of the user guide, but we have found performance to be acceptable at a maximum 130MHz change from the calibration frequency, so have not bothered with the re-calibration.

We now want to extend operation down to the 5180-5240MHz and 5260-5320MHz bands, taking the total system bandwidth to 580MHz (though individual channels are 20MHz). Our RF front end can support this, but we're conscious that the QEC and LOL calibrations may not perform very well with frequency changes of up to 290MHz from the calibration frequency. To combat this, we would like to repeat the AD9371 calibration for the lower sub-bands so we have two calibration points. We don't want to have to re-calibrate each time we move between sub-bands as this takes ~10s which is unacceptable in our system. The user guide does not give much away on the parameters of the calibration but it must be something like IQ gain and phase calibration, presumably writing values to registers. I note that ADI do not give access to the register map, but would it be possible to perform the calibration twice on boot, store the register settings for each calibration and apply them on the fly by sending the register values to the ARM without actually re-performing the calibration?

  • AD9371 doesnot support this feature in which you can store the calibration values at the start and then use it later(this feature of fast locking is available in AD9361 but not in AD9371. We donot provide register map for this chip.

    The calibration time of 10sec is very high, may be you are running all the cals while changing frequency. Instead you can run only the QEC and LOL cals while changing frequency. This will reduce the init cals time.