Doherty power amplifier network
View Patent ↗The present invention is directed to a network that includes an output matching network coupled to an amplifier. The output matching network is configured to transform the at least one amplifier transistor output impedance to an output matching network impedance. A combiner network is coupled to the output matching network. The combiner network includes a first quarter wavelength transmission line coupled between the in-phase signal path and a combiner node. The combiner network further includes a bandwidth enhancement element coupled to the quadrature signal path at the combiner node and an impedance transformation element coupled between the combiner node and a load. The impedance transformation element is configured to substantially transform a combined output matching network impedance at the combiner node to the load impedance.
1. A network comprising:
an output matching network coupled to a Doherty amplifier including_an amplifier transistor characterized by at least one amplifier transistor output impedance, the output matching network including an in-phase signal path disposed in parallel with a quadrature signal path, the Doherty amplifier including a carrier amplifier disposed in the quadrature signal path, and a peak amplifier disposed in the in-phase signal path, the output matching network being configured to transform the at least one amplifier transistor output impedance to an output matching network impedance, the output matching network impedance being intermediate the at least one amplifier transistor output impedance and a load impedance; and
a combiner network coupled to the output matching network, the combiner network including a first quarter wavelength transmission line coupled between the in-phase signal path and a combiner node, the first quarter wavelength transmission line being configured to substantially eliminate a phase delay between an in-phase signal and a quadrature signal, the combiner network further including a bandwidth enhancement element coupled to the quadrature signal path at the combiner node, and an impedance transformation element coupled between the combiner node and a load, the impedance transformation element being configured to substantially transform a combined output matching network impedance at the combiner node to the load impedance.
2. The network of claim 1 , wherein the bandwidth enhancement element is shunted to ground.
3. The network of claim 2 , wherein the bandwidth enhancement element is a quarter wavelength transmission line coupled between the combiner node and ground.
4. The network of claim 3 , wherein the bandwidth enhancement element is configured to improve linearity by substantially preventing propagation of even order harmonic products.
5. The network of claim 3 , wherein the bandwidth enhancement element is configured to improve efficiency by substantially preventing even order harmonic signals from being supported in the combiner network.
6. The network of claim 2 , wherein the bandwidth enhancement element is configured to assist in transforming the combined output matching network impedance to the load impedance at off-center frequencies to at least double the bandwidth relative to a Doherty network not including the bandwidth enhancement_element.
7. The network of claim 6 , wherein the bandwidth enhancement element is configured to provide at least a seven-fold increase in the bandwidth relative to an inverted Doherty network not including the bandwidth enhancement element.
8. The network of claim 6 , wherein the impedance transformation element is configured to substantially transform the combined output matching network impedance to the load impedance at a center frequency.
9. The network of claim 1 , wherein the load impedance is substantially equal to about 50 Ohms.
10. The network of claim 9 , wherein the combined output matching network impedance is substantially equal to about 25 Ohms.
11. The network of claim 10 , wherein the combination of the bandwidth enhancement element and the impedance transformation element is configured to substantially transform the combined output matching network impedance to the load impedance.
12. The network of claim 11 , wherein the bandwidth enhancement element and the impedance transformation element are quarter wavelength transmission lines.
13. The network of claim 1 , wherein the bandwidth enhancement element is disposed between the combiner node and the impedance transformation element.
14. The network of claim 1 , wherein the first quarter wavelength transmission line transforms in-phase signal path circuits to an open circuit at combiner node when the peak amplifier is OFF.
15. The network of claim 1 , wherein the combiner network is disposed in a single integrated circuit package.
16. The network of claim 1 , wherein the combiner network is configured as a multi-layered integrated circuit.
17. The network of claim 16 , wherein the first quarter wavelength transmission line is configured as a stripline circuit element.
18. The network of claim 17 , wherein the stripline circuit element may be implemented as an asymmetric stripline circuit element, a symmetric stripline circuit element or as a microstripline circuit element.
19. The network of claim 16 , wherein the bandwidth enhancement element is configured as a stripline circuit element.
20. The network of claim 19 , wherein the bandwidth enhancement element is a quarter wavelength transmission line.
21. The network of claim 19 , wherein the stripline circuit element may be implemented as an asymmetric stripline circuit element, a symmetric stripline circuit element or as a microstripline circuit element.
22. The network of claim 16 , wherein the impedance transformation element is configured as a symmetrical stripline circuit element.
23. The network of claim 22 , wherein the impedance transformation element is a quarter wavelength transmission line.
24. The network of claim 22 , wherein the stripline circuit element may be implemented as an asymmetric stripline circuit element, a symmetric stripline circuit element or as a microstripline circuit element.
25. A combiner network for a Doherty amplifier, the network comprising:
a quarter wavelength transmission line coupled between an in-phase signal path and a combiner node, the quarter wavelength transmission line being configured to substantially eliminate a phase delay between an in-phase signal and a quadrature signal, the Doherty amplifier including a carrier amplifier disposed in the quadrature signal path, and a peak amplifier disposed in the in-phase signal path;
a bandwidth enhancement element coupled to a quadrature signal path at the combiner node; and
an impedance transformation element coupled between the combiner node and a load, the impedance transformation element being configured to substantially transform a combined output matching network impedance at the combiner node to the load impedance.
26. The network of claim 25 , wherein the bandwidth enhancement element is shunted to ground.
27. The network of claim 26 , wherein the bandwidth enhancement element is a quarter wavelength transmission line coupled between the combiner node and ground.
28. The network of claim 27 , wherein the bandwidth enhancement element is configured to improve linearity by substantially preventing propagation of even order harmonic products.
29. The network of claim 27 , wherein the bandwidth enhancement element is configured to improve efficiency by substantially preventing even order harmonic signals from being supported in the combiner network.
30. The network of claim 26 , wherein the bandwidth enhancement element is configured to assist in transforming the combined output matching network impedance to the load impedance at off-center frequencies to at least double the bandwidth relative to an inverted Doherty network not including the bandwidth enhancement element.
31. The network of claim 30 , wherein the bandwidth enhancement element is configured to provide at least a seven-fold increase in the bandwidth relative to an inverted Doherty network not including the bandwidth enhancement element.
32. The network of claim 30 , wherein the impedance transformation element is substantially configured to substantially transform the combined output matching network impedance to the load impedance at a center frequency.
33. The network of claim 25 , wherein the load impedance is substantially equal to about 50 Ohms.
34. The network of claim 33 , wherein the output matching network impedance is substantially equal to about 25 Ohms.