Quadrature combined Doherty amplifiers
Apparatus and methods for quadrature combined Doherty amplifiers are provided herein. In certain embodiments, a separator is used to separate a radio frequency (RF) input signal into a plurality of input signal components that are amplified by a pair of Doherty amplifiers operating in quadrature. Additionally, a combiner is used to combine a plurality of output signal components generated by the pair of Doherty amplifiers, thereby generating an RF output signal exhibiting quadrature balancing.
1. A radio frequency system comprising:
first and second power combiner/splitters each configurable as a combiner or a splitter and each having at least four ports;
a separator configured to separate a radio frequency input signal into a first pair of input signal components and a second pair of input signal components having a quadrature phase relationship with respect to the first pair of input signal components, the separator including the first power combiner/splitter configured as a splitter;
a first Doherty amplifier configured to generate a first pair of amplified signal components based on amplifying the first pair of input signal components;
a second Doherty amplifier configured to generate a second pair of amplified signal components based on amplifying the second pair of input signal components; and
a combiner configured to generate a radio frequency output signal based on combining the first pair of amplified signal components and the second pair of amplified signal components, the combiner including the second power combiner/splitter configured as a combiner.
2. The radio frequency system of claim 1 wherein the first Doherty amplifier includes a first pair of cascode amplification stages, and the second Doherty amplifier includes a second pair of cascode amplification stages.
3. The radio frequency system of claim 1 wherein the first pair of input signal components have a phase difference of about ninety degrees, and the second pair of input signal components have a phase difference of about ninety degrees.
4. The radio frequency system of claim 1 wherein the first and second power combiner/splitters are hybrid couplers.
5. The radio frequency system of claim 1 wherein the separator further includes third and fourth power combiner/splitters configured as splitters, the first power combiner/splitter configured to receive the radio frequency input signal, the third power combiner/splitter connected to a first output of the first power combiner/splitter, and the fourth power combiner/splitter connected to a second output of the first power combiner/splitter.
6. The radio frequency system of claim 1 wherein the first and second power combiner/splitters include first and second conductive coils.
7. The radio frequency system of claim 6 wherein the first and second conductive coils are arranged to provide inductive coupling.
8. The radio frequency system of claim 1 wherein the combiner includes a first inductor between an output of a peaking amplifier of the first Doherty amplifier and an output of a carrier amplifier of the first Doherty amplifier, and a second inductor between an output of a peaking amplifier of the second Doherty amplifier and an output of a carrier amplifier of the first Doherty amplifier.
9. The radio frequency system of claim 1 wherein the separator includes a power splitter and a balun configured to operate in combination with one another.
10. A method of radio frequency signal amplification, the method comprising:
using separator to separate a radio frequency input signal into first and second separated signal components, separate the first separated signal component into a first pair of input signal components, and separate the second separated signal component into a second pair of input signals components, the separator including a first power combiner/splitter including at least four ports connected such that the first power combiner/splitter operates as a splitter;
amplifying the first pair of input signal components to generate a first pair of amplified signal components using a first Doherty amplifier;
amplifying the second pair of input signal components to generate a second pair of amplified signal components using a second Doherty amplifier; and
generating a radio frequency output signal based on the first pair of amplified signal components and the second pair of amplified signal components, the generating performed using a combiner including a second power combiner/splitter including at least four ports connected such that the second power combiner/splitter operates as a combiner.
11. The method of claim 10 wherein amplifying the first pair of input signal components includes amplifying a first input signal component using a cascode peaking amplification stage of the first Doherty amplifier and amplifying a second signal component using a cascode carrier amplification stage of the first Doherty amplifier.
12. The method of claim 10 wherein the first Doherty amplifier includes a first pair of cascode amplification stages, and the second Doherty amplifier includes a second pair of cascode amplification stages.
13. The method of claim 10 wherein the first pair of input signal components have a phase difference of about ninety degrees, and the second pair of input signal components have a phase difference of about ninety degrees.
14. The method of claim 10 wherein the first and second power combiner/splitters are hybrid couplers.
15. The method of claim 10 wherein the separating includes using the first power combiner/splitter and a balun configured to operate in combination with one another.
16. The method of claim 10 wherein the second power combiner/splitter includes first and second conductive coils arranged to provide inductive coupling.
17. A mobile device comprising:
a transceiver configured to generate a radio frequency input signal; and
a power amplifier system configured to amplify the radio frequency input signal to generate a radio frequency output signal, the power amplifier system including a separator configured to separate a radio frequency input signal into a first pair of input signal components and a second pair of input signal components having a quadrature phase relationship with respect to the first pair of input signal components, the separator including a first power combiner/splitter having at least four ports connected to place the first power combiner/splitter in a splitter configuration, the power amplifier system further including a first Doherty amplifier configured to generate a first pair of amplified signal components based on amplifying the first pair of input signal components, and a second Doherty amplifier configured to generate a second pair of amplified signal components based on amplifying the second pair of input signal components, and the power amplifier system further including a combiner including a second power combiner/splitter having at least four ports connected to place the second power combiner/splitter in a combiner configuration, the combiner configured to generate the radio frequency output signal based on the first pair of amplified signal components and the second pair of amplified signal components.
18. The mobile device of claim 17 wherein the first Doherty amplifier includes a first pair of cascode amplification stages, and the second Doherty amplifier includes a second pair of cascode amplification stages.
19. The mobile device of claim 17 wherein the first pair of input signal components have a phase difference of about ninety degrees, and the second pair of input signal components have a phase difference of about ninety degrees.
20. The mobile of claim 17 wherein the first and second power combiner/splitters include first and second conductive coils.
21. The mobile device of claim 20 wherein the first and second conductive coils are arranged to provide inductive coupling.