Polar modulation transmitter with envelope modulator path switching

A radio frequency (RF) transmitter, comprising:

• a radio frequency power amplifier (RF PA) having a power supply port, an RF input port configured to receive an RF input signal, and an RF output port configured to provide a modulated RF output signal;
• a power control circuit having first and second power supply paths that are selectively configurable between a power supply and the power supply port of the RF PA;
• and
• a path selection circuit operable to select which of the first and second power supply paths is configured between the power supply and the power supply port of the RF PA;
• wherein the path selection circuit is operable to select the first power supply path during times when the output power of the RF PA is required to be within a first output power range, and select the second power supply path during times when the output power of the RF PA is required to be within a second output power range.

A method of controlling power in a polar modulation transmitter, comprising:

• generating a radio frequency (RF) phase modulated signal from a phase signal containing phase information of a communications signal;
• applying the RF phase modulated signal to an RF input of an RF power amplifier (RF PA);
• selecting a power supply path from among a plurality of power supply paths that are each individually and separately configurable between a power supply and a power supply input of the RF PA;
• modifying one or more electrical characteristic of the selected power supply path according to amplitude variations in an envelope signal containing envelope information of said communications signal, to generate an envelope modulated power supply signal;
• and
• applying the envelope modulated power supply signal to the power supply input of the RF PA;
• wherein selecting a power supply path from among a plurality of power supply paths comprises switching from a first selected power supply path to a second power supply path when the power required by the RF PA reduces below a predetermined power threshold.