How would you calibrate an FDD system. Surely retuning of the Rx is necessary to calibrate Tx (and vice versa).
Asked by Simon P
For an FDD MIMO system the best approach is to use two separate PLLs, one for Rx and one for Tx. When doing the phase calibration set both PLLs to the same frequency to resolve the divider ambiguity. After that calibration is complete you are free to tune the Rx and Tx PLLs to whatever frequency is needed, without losing the phase calibration results.
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