Group delay calibration method for power amplifier envelope tracking

A method for calibrating a group delay for an open loop envelope tracking system comprising:

• generating a radio frequency power amplifier output signal having a first output power at an output of a radio frequency power amplifier based on a modulated signal as a function of a control signal delayed in time by a first delay relative to the modulated signal;
• generating the radio frequency power amplifier output signal having a second output power at the output of the radio frequency power amplifier as the function of the control signal delayed in time by a second delay relative to the modulated signal;
• determining a calibrated offset delay as a function of the second delay and the first delay;
• calculating a power difference between the first output power and the second output power;
• and
• determining that the first output power substantially equals the second output power based on the power difference.

A method for calibrating a group delay for the open loop envelope tracking system comprising:

• obtaining an initial value for a negative fine tuning delay and an initial value for a positive fine tuning delay;
• receiving a substantially symmetric modulated signal with a radio frequency power amplifier;
• until a determination that a negative fine tuning delay output power is substantially equal to a positive fine tuning delay output power, iteratively performing sub-steps of:
• generating a modulated power amplifier supply control signal related to the substantially symmetric modulated signal based on the positive fine tuning delay;
• generating a modulated power amplifier supply voltage related to the substantially symmetric modulated signal based on the modulated power amplifier supply control signal advanced in time by the negative fine tuning delay;
• measuring the negative fine tuning delay output power of the radio frequency power amplifier;
• generating the modulated power amplifier supply control signal related to the substantially symmetric modulated signal based on the positive fine tuning delay;
• generating the modulated power amplifier supply voltage related to the substantially symmetric modulated signal based on the modulated power amplifier supply control signal delayed in time by the positive fine tuning delay;
• measuring the positive fine tuning delay output power of the radio frequency power amplifier;
• determining whether the negative fine tuning delay output power is substantially equal to the positive fine tuning delay output power;
• and
• in response to a determination that the negative fine tuning delay output power is not substantially equal to the positive fine tuning delay output power, adjusting the negative fine tuning delay and the positive fine tuning delay based on the negative fine tuning delay output power and the positive fine tuning delay output power;
• and
• after the determination that the negative fine tuning delay output power is substantially equal to the positive fine tuning delay output power, determining a calibrated fine tuning delay based on the negative fine tuning delay and the positive fine tuning delay.

A method for calibrating a group delay for an open loop envelope tracking system comprising:

• at a first time, generating a radio frequency power amplifier output signal having a first output power at an output of a radio frequency power amplifier based on a modulated signal as a function of a control signal delayed in time by a first delay relative to the modulated signal;
• at a different time, generating the radio frequency power amplifier output signal, such that the radio frequency power amplifier output signal has a second output power at the output of the radio frequency power amplifier as a function of the control signal delayed in time by a second delay relative to the modulated signal;
• and
• determining a calibrated offset delay as a function of the second delay and the first delay.