Apparatus and methods for envelope shaping in mobile devices

A power amplifier system comprising:

• a modulator configured to generate a radio frequency signal;
• a power amplifier configured to provide amplification to the radio frequency signal, the power amplifier powered by a power amplifier supply voltage;
• an envelope shaping circuit configured to generate a shaped envelope signal by shaping an envelope of the radio frequency signal, the envelope shaping circuit including a shaping table configured to maintain a substantially constant distortion in a transmit band of the power amplifier system across a range of the envelope of the radio frequency signal;
• and
• an envelope tracker configured to control a voltage level of the power amplifier supply voltage based on the shaped envelope signal.

A method of envelope shaping in a mobile device, the method comprising:

• generating a radio frequency signal using a modulator;
• amplifying the radio frequency signal using a power amplifier;
• powering the power amplifier using a power amplifier supply voltage;
• controlling a voltage level of the power amplifier supply voltage based on a shaped envelope signal using an envelope tracker;
• and
• generating the shaped envelope signal by shaping an envelope of the radio frequency signal using an envelope shaping circuit, including using a shaping table to maintain a substantially constant distortion in a transmit band of the mobile device across a range of the envelope of the radio frequency signal.