Efficiency improvement of doherty power amplifier using supply switching and digitally controlled gate bias modulation of peaking amplifier

1. An apparatus for amplifying a signal, the apparatus comprising:

a carrier transistor;

a peaking transistor;

a controller; and

a power supply switching unit,

wherein the controller controls the power supply switching unit to switch between two or more power supplies and wherein the power supply switching unit provides power from one of the two or more power supplies to the peaking transistor, and

wherein the power supply switching unit comprises a first transistor, a second transistor, and a diode, the first transistor provided for controlling a supply of power from a high voltage power supply, the second transistor and the diode provided for controlling a supply of power from a low voltage power supply, and the second transistor configured to short the diode when the second transistor is switched on.

2. The apparatus of claim 1 , wherein the power supply switching unit comprises a transistor and a diode, the transistor provided for controlling a supply of power from a first power supply and the diode provided for controlling a supply of power from a second power supply, the first power supply having a voltage higher than that of the second power supply.

3. The apparatus of claim 2 , wherein the controller controls the power supply switching unit by controlling the transistor to switch on and off.

4. The apparatus of claim 2 , wherein the transistor comprises a Metal Oxide Silicon Field Effect Transistor (MOSFET) and the diode comprises a Schottky diode.

5. The apparatus of claim 1 , wherein the controller comprises:

an envelope extractor; and

a supply control unit;

wherein the envelope extractor determines a value of an extracted envelope of a transmission signal, and further wherein the supply control unit outputs a signal to control the power supply switching unit based on the value determined by the envelope extractor.

6. The apparatus of claim 5 , further comprising a gate modulation unit for outputting a gate bias signal to modulate a gate of the peaking transistor based on the value determined by the envelope extractor.

7. The apparatus of claim 6 , wherein the signal output by the supply switching unit is determined by comparing the value determined by the envelope extractor with one or more constants, and wherein the gate modulation unit comprises a Look Up Table (LUT).

8. The apparatus of claim 1 , further comprising:

an RF splitter;

a first quarterwave transformer;

a second quarterwave transformer;

a combiner/matching network; and

an antenna.

9. The apparatus of claim 1 , wherein the controller controls the power supply switching unit by controlling the first transistor to switch on and off at a first voltage and by controlling the second transistor to switch on and off at a second voltage, wherein the second voltage is lower than the first voltage.

10. The apparatus of claim 1 , wherein the first transistor comprises a Metal Oxide Silicon Field Effect Transistor (MOSFET), the second transistor comprises a MOSFET, and the diode comprises a Schottky diode.

11. The apparatus of claim 1 , wherein the power supply switching unit comprises one or more linear regulators for controlling a supply of power from one or more of a low voltage supply and a high voltage supply, respectively.

12. The apparatus of claim 1 , wherein the power supply switching unit provides power from one of the two or more power supplies to the carrier transistor.

13. The apparatus of claim 1 , wherein the power supply switching unit comprises one or more capacitors respectively corresponding to the one or more power supplies.