An open loop envelope tracking system comprising: a digital baseband circuit configured to: generate a modulated signal based on a calibration test signal; generate a control signal based on the calibration test signal and a fine tuning delay setting of a fine tuning delay circuit; an envelope tracker power converter configured to generate a modulated power amplifier supply voltage based on the control signal; a radio frequency power amplifier configured to generate a radio frequency power amplifier output signal based on the modulated signal and the modulated power amplifier supply voltage; and a detector configured to generate an output power measurement for the radio frequency power amplifier output signal; controller circuitry (28, 32) configured to: set the fine tuning delay setting to a first fine tuning delay setting; obtain a first measured output power from the radio frequency power amplifier output signal based on the output power measurement generated by the detector while the fine tuning delay setting is set to the first fine tuning delay setting; set the fine tuning delay setting to a second fine tuning delay setting; obtain a second measured output power from the radio frequency power amplifier output signal based on the output power measurement generated by the detector while the fine tuning delay setting is set to the second fine tuning delay setting; and determine a calibrated fine tuning offset delay setting based on the first fine tuning delay setting and the second fine tuning delay setting. a digital baseband circuit configured to: generate a modulated signal based on a calibration test signal; generate a control signal based on the calibration test signal and a fine tuning delay setting of a fine tuning delay circuit; generate a modulated signal based on a calibration test signal; generate a control signal based on the calibration test signal and a fine tuning delay setting of a fine tuning delay circuit; an envelope tracker power converter configured to generate a modulated power amplifier supply voltage based on the control signal; a radio frequency power amplifier configured to generate a radio frequency power amplifier output signal based on the modulated signal and the modulated power amplifier supply voltage; and a detector configured to generate an output power measurement for the radio frequency power amplifier output signal; controller circuitry (28, 32) configured to: set the fine tuning delay setting to a first fine tuning delay setting; obtain a first measured output power from the radio frequency power amplifier output signal based on the output power measurement generated by the detector while the fine tuning delay setting is set to the first fine tuning delay setting; set the fine tuning delay setting to a second fine tuning delay setting; obtain a second measured output power from the radio frequency power amplifier output signal based on the output power measurement generated by the detector while the fine tuning delay setting is set to the second fine tuning delay setting; and determine a calibrated fine tuning offset delay setting based on the first fine tuning delay setting and the second fine tuning delay setting. set the fine tuning delay setting to a first fine tuning delay setting; obtain a first measured output power from the radio frequency power amplifier output signal based on the output power measurement generated by the detector while the fine tuning delay setting is set to the first fine tuning delay setting; set the fine tuning delay setting to a second fine tuning delay setting; obtain a second measured output power from the radio frequency power amplifier output signal based on the output power measurement generated by the detector while the fine tuning delay setting is set to the second fine tuning delay setting; and determine a calibrated fine tuning offset delay setting based on the first fine tuning delay setting and the second fine tuning delay setting.