Envelope tracking power amplifier with low impedance supply feed

1. A supply feed network for an envelope tracking power amplifier arrangement comprising a power amplifier and a voltage modulator for providing a supply voltage to the power amplifier, the supply feed network comprising:

a power distribution plane arranged to connect the supply voltage from the voltage modulator to the power amplifier, in which the power amplifier is a radio frequency (RF) power amplifier for amplifying an RF carrier signal, the supply feed network further comprising an RF de-coupling capacitor with a first and second terminal, wherein the first terminal is connected to the power distribution plane and the second terminal is directly connected to electrical ground.

2. The supply feed network of claim 1 further comprising an inductor, wherein the power distribution plane is connected to one side of the inductor and a power transistor is connected to another side of the inductor such that the supply voltage is provided to the power amplifier via the power distribution plane and the inductor, wherein the capacitance of the power transistor forms a resonant circuit with the inductor.

3. The supply feed network of claim 1 further comprising a transmission line, wherein the power distribution plane is connected to one side of the transmission line and a power transistor is connected to another side of the transmission line such that the supply voltage is provided to the power amplifier via the power distribution plane and the transmission line.

4. The supply feed network of claim 3 in which the power distribution plane is arranged to provide the transmission line.

5. The supply feed network of claim 1 further adapted to connect the supply voltage from the voltage modulator to a plurality of power amplifiers.

6. The supply feed network of claim 5 further comprising a plurality of inductors, wherein the power distribution plane is connected to one side of each of the inductors and each power transistor is connected to another side of each of the inductors such that the supply voltage is provided to the plurality of power amplifiers via the power distribution plane and the inductors, wherein the capacitance of each power transistor forms a resonant circuit with each inductor.

7. The supply feed network of claim 5 further comprising:

a plurality of transmission lines, wherein the power distribution plane is connected to one side of each transmission line and a respective power transistor is connected to another side of each respective transmission line such that the supply voltage is provided to the power amplifiers via the power distribution plane and the respective transmission lines.

8. The supply feed network of claim 7 in which the power distribution plane is arranged to provide each of the transmission lines.

9. A supply feed network for an envelope tracking power amplifier arrangement comprising a power amplifier and a voltage modulator for providing a supply voltage to the power amplifier, the supply feed network comprising:

a power distribution plane arranged to connect the supply voltage from the voltage modulator to the power amplifier, in which the power amplifiers comprise multiple radio frequency (RF) power amplifiers for amplifying an RF carrier signal, the supply feed network further comprising a plurality of RF de-coupling capacitors each associated with a respective power amplifier, wherein each of the plurality of RF de-coupling capacitors has a first and second terminal, wherein each of the first terminals is connected to the power distribution plane and each of the second terminals is directly connected to electrical ground.

10. The supply feed network of claim 1 wherein the frequency at which a minimum impedance resonance occurs in the impedance presented to the voltage modulator by the power amplifier is increased, thereby allowing an increase in the stable bandwidth of the voltage modulator.