Power amplifier
View Patent ↗The invention relates to improving the performance of load modulation power amplifiers through the use of coupled transmission line-based power combiners. Exemplary embodiments disclosed include a power amplifier comprising an input connected to first and second amplifier stages and an output stage configured to combine phase shifted amplified outputs from the first and second amplifier stages and to provide an amplified signal at an output of the power amplifier, wherein the output stage comprises coupled first and second transmission lines connected between the output of the first amplifier stage and an output load connection.
1. A power amplifier comprising:
an input connected to first and second amplifier stages; and
an output stage configured to combine phase shifted amplified outputs from the first and second amplifier stages and provide an amplified signal at an output of the power amplifier, wherein the output stage includes magnetically coupled first and second transmission lines connected between the output of the first amplifier stage and an output load connection and the first transmission line is connected between the output of the first amplifier stage and the output of the second amplifier stage, wherein the first and second transmission lines share a common electrical and magnetic field.
2. The power amplifier of claim 1 , wherein the power amplifier is configured as a Doherty amplifier.
3. The power amplifier of claim 2 , wherein the first transmission line is connected between the output of the first amplifier stage and the output load connection, and the second transmission line is connected to the output of the second amplifier stage.
4. The power amplifier of claim 3 , wherein the first and second transmission lines have a length of a quarter of a wavelength of an operating frequency of the power amplifier.
5. The power amplifier of claim 4 , wherein the second transmission line is connected to the output load connection via a third transmission line having a length of at least the quarter of the wavelength of the operating frequency of the power amplifier.
6. The power amplifier of claim 4 , wherein the operating frequency is within a range of 1 to 3 GHz.
7. The power amplifier of claim 5 , wherein the third transmission line is connected to the output load connection and ground.
8. The power amplifier of claim 2 , further comprising:
a third amplifier stage having an output connected to the output load connection; and
magnetically coupled third and fourth transmission lines connected betweeen the output of the second amplifier stage and the output load connection.
9. The power amplifier of claim 8 , further comprising:
magnetically coupled fifth and sixth transmission lines connected betweeen the output of the third amplifier stage and the output load connection.
10. The power amplifier of claim 1 , wherein the power amplifier is configured as a Chireix outphasing amplifier, the power amplifier further comprising:
magnetically coupled third and fourth transmission lines connected betweeen the output of the second amplifier stage and the output load connection.
11. The power amplifier of claim 10 , wherein the first to fourth transmission lines each have a length of a quarter of a wavelength of an operating frequency of the power amplifier.
12. The power amplifier of claim 11 , wherein the second transmission line is connected to the output load connection via a fifth transmission line and the fourth transmission line is connected to the output load connection via a sixth transmission line, the fifth and sixth transmission lines each having a length of at least the quarter of the wavelength of the operating frequency of the power amplifier.
13. A method of operating a power amplifier, the method comprising:
receiving a signal at an input of the power amplifier;
dividing the received signal between first and second amplifier stages;
amplifying the divided signal by the first and second amplifier stages;
combining the resulting amplified signals from outputs of the first and second amplifier stages in an output stage, wherein a first transmission line is connected between the output of the first amplifier stage and the output of the second amplifier stage, a second transmission line is connected between the output of the first amplifier stage and an output load connection, and the first and second transmission lines share a common electrical and magnetic field;
providing an amplified output signal at an output of the power amplifier.
14. The power amplifier of claim 1 , wherein the coupled first and second transmission lines are strip lines.
15. The power amplifier of claim 14 , wherein the strip lines are symmetric strip lines.
16. The power amplifier of claim 14 , wherein the strip lines are asymmetric strip lines.
17. A power amplifier comprising:
an input connected to a first amplifier stage, a second amplifier stage, and a third amplifier stage;
a first pair of magnetically coupled transmission lines connected to an output of the first transmission stage; and
a second pair of magnetically coupled transmission lines connected to an output of the second amplifier stage, wherein the first and second pairs of magnetically coupled transmission lines share a common electrical and magnetic field.
18. The power amplifier of claim 17 , wherein the first pair of magnetically coupled transmission lines is connected to the output of the second transmission stage and the second pair of magnetically coupled transmission lines is connected to an output load connection.
19. The power amplifier of claim 17 , further comprising:
a third pair of magnetically coupled transmission lines connected between the first pair of magnetically coupled transmission lines and the second pair of magnetically coupled transmission lines.
20. The power amplifier of claim 19 , wherein both the first pair of magnetically coupled transmission lines and the third pair of magnetically coupled transmission lines are connected to an output load connection.