ENHANCED DOHERTY AMPLIFIER

• US 20120235734A1
• Filed: 03/16/2011
• Published: 09/20/2012
• Est. Priority Date: 03/16/2011
• Status: Active Grant

• Current Assignee: MACOM Technology Solutions Holdings, Inc.
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Pengelly, Raymond Sydney
• Granted Patent: US 8,749,306 B2
• Time in Patent Office: Days
• US Class Current: 330/124.D
• CPC Class Codes: H03F 1/0288 using a main and one or several auxiliary peaking amplifiers whereby the load is connected to the main amplifier using an impedance inverter, e.g. Doherty amplifiers
• CPC Class Codes: H03F 1/42 Modifications of amplifiers to extend the bandwidth
• CPC Class Codes: H03F 2200/111 the amplifier being a dual or triple band amplifier, e.g. 900 and 1800 MHz, e.g. switched or not switched, simultaneously or not
• CPC Class Codes: H03F 2200/36 the amplifier comprising means for increasing the bandwidth
• CPC Class Codes: H03F 2200/39 Different band amplifiers are coupled in parallel to broadband the whole amplifying circuit
• CPC Class Codes: H03F 2200/429 Two or more amplifiers or one amplifier with filters for different frequency bands are coupled in parallel at the input or output
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2203/20 Indexing scheme relating to power amplifiers, e.g. Class B amplifiers, Class C amplifiers
• CPC Class Codes: H03F 3/189 High-frequency amplifiers, e.g. radio frequency amplifiers
• CPC Class Codes: H03F 3/20 Power amplifiers, e.g. Class B amplifiers, Class C amplifiers H03F3/26 - H03F3/30 take precedence
• CPC Class Codes: H03F 3/211 using a combination of several amplifiers H03F3/60 takes precedence
• CPC Class Codes: H03F 3/68 Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics power amplifiers using a combination of several semiconductor amplifiers H03F3/211; combinations of amplifiers using coupling networks with distributed constants H03F3/602

Abstract

The disclosure relates to an enhanced Doherty amplifier that provides significant performance improvements over conventional Doherty amplifiers. The enhanced Doherty amplifier includes a power splitter, combining node, a carrier path, and a peaking path. The power splitter is configured to receive an input signal and split the input signal into a carrier signal provided at a carrier splitter output and a peaking signal provided at a peaking splitter output. The carrier path includes carrier power amplifier circuitry, a carrier input network coupled between the carrier splitter output and the carrier power amplifier circuitry, and a carrier output network coupled between the carrier power amplifier circuitry and the Doherty combining node. The peaking path includes peaking power amplifier circuitry, a peaking input network coupled between the peaking splitter output and the peaking power amplifier circuitry, and a carrier output network coupled between the power amplifier circuitry and the Doherty combining node.

Claims

1. An enhanced Doherty amplifier comprising:

a power splitter configured to receive an input signal and split the input signal into a carrier signal provided at a carrier splitter output and a peaking signal provided at a peaking splitter output;

a Doherty combining node;

a carrier path comprising a carrier power amplifier circuitry and a carrier input network coupled between the carrier splitter output and the carrier power amplifier circuitry; and

a peaking path comprising peaking power amplifier circuitry and a peaking input network coupled between the peaking splitter output and the peaking power amplifier circuitry,

wherein the carrier and peaking input networks are configured to impose phase shifts causing the peaking signal to lag the carrier signal by approximately 90 degrees when the carrier and peaking signals are respectively presented to the carrier and peaking power amplifier circuitries.

2. The enhanced Doherty amplifier of claim 1 wherein:

the carrier path further comprises a carrier output network coupled between the carrier power amplifier circuitry and the Doherty combining node,

the peaking path further comprises a peaking output network coupled between the peaking power amplifier circuitry and the Doherty combining node, and

the carrier and peaking output networks are configured to respectively impose compensated carrier and peaking phase offsets causing the peaking and carrier signals to arrive at the Doherty combining node for reactive combining to generate an output signal.

3. The enhanced Doherty amplifier of claim 2 wherein the carrier input and output networks and the peaking input and output networks are at least second order networks.

4. The enhanced Doherty amplifier of claim 3 wherein the carrier input and output networks and the peaking input and output networks are lumped element networks comprising lumped elements.

5. The enhanced Doherty amplifier of claim 2 wherein the carrier input and output networks and the peaking input and output networks are lumped element networks comprising lumped elements.

6. The enhanced Doherty amplifier of claim 2 wherein each of the carrier input and output networks and the peaking input and output networks does not comprise a transmission line configured to provide a desired phase shift.

7. The enhanced Doherty amplifier of claim 2 wherein the carrier input and output networks and the peaking input and output networks are synthesized as a group to provide a desired performance characteristic.

8. The enhanced Doherty amplifier of claim 2 wherein the respective compensated carrier and peaking phase offsets effectively reverse the approximately 90 degree phase shift provided by the carrier and peaking input networks as well as remove carrier and peaking phase offsets, the carrier phase offset substantially corresponding to a reactive component of an impedance presented to an output of the carrier power amplifier circuitry at an intended operating frequency range or ranges and the peaking phase offset substantially corresponding to a reactive component of an impedance presented to an output of the peaking power amplifier circuitry at the intended operating frequency range or ranges.

9. The enhanced Doherty amplifier of claim 8 wherein the impedance presented to the output of the carrier power amplifier circuitry is effectively a composite impedance provided by the carrier output network, the peaking path, and a transformer coupled to the Doherty combining node at the intended operating frequency range or ranges and the impedance presented to the output of the peaking amplifier circuitry is effectively a composite impedance provided by the peaking output network, the carrier path, and the transformer coupled to the Doherty combining node at the intended operating frequency range or ranges.

10. The enhanced Doherty amplifier of claim 8 wherein the carrier input network advances a phase of the carrier signal by approximately 45 degrees and the peaking input network delays a phase of the peaking signal by approximately 45 degrees such that the phase of the peaking signal lags the phase of the carrier signal by approximately 90 degrees when the carrier and peaking signals are respectively presented to the carrier and peaking power amplifier circuitries.

11. The enhanced Doherty amplifier of claim 2 wherein the carrier input network advances a phase of the carrier signal by approximately 45 degrees and the peaking input network delays a phase of the peaking signal by approximately 45 degrees such that the phase of the peaking signal lags the phase of the carrier signal by approximately 90 degrees when the carrier and peaking signals are respectively presented to the carrier and peaking power amplifier circuitries.

12. The enhanced Doherty amplifier of claim 11 wherein the compensated carrier and peaking phase offsets effectively reverse the approximately 90 degree phase shift provided by the carrier and peaking input networks as well as remove the respective compensated carrier and peaking phase offsets, the carrier phase offset substantially corresponding to a reactive component of an impedance presented to an output of the carrier power amplifier circuitry at an intended operating frequency range or ranges and the peaking phase offset substantially corresponding to a reactive component of an impedance presented to an output of the peaking power amplifier circuitry at the intended operating frequency range or ranges.

13. The enhanced Doherty amplifier of claim 2 wherein the power splitter is configured to receive the input signal and evenly split the input signal into the carrier signal and the peaking signal such that the carrier and peaking signals are associated with approximately the same power.

14. The enhanced Doherty amplifier of claim 2 wherein the power splitter is configured to receive the input signal and unevenly split the input signal into the carrier signal and the peaking signal such that the carrier and peaking signals are not associated with approximately the same power.

15. The enhanced Doherty amplifier of claim 14 wherein the carrier signal is associated with a split of approximately −

1.7 dB and the peaking signal is associated with a split of approximately −

4.7 dB.

16. The enhanced Doherty amplifier of claim 2 wherein the carrier power amplifier circuitry is one of a class A/B and class B amplifier and the peaking power amplifier circuitry is a class C amplifier.

17. The enhanced Doherty amplifier of claim 2 wherein the carrier input network provides impedance matching between the carrier splitter output and the carrier power amplifier circuitry;

the carrier output network provides impedance matching between the carrier power amplifier circuitry and the Doherty combining node;

the peaking input network provides impedance matching between the peaking splitter output and the peaking power amplifier circuitry; and

the peaking output network provides impedance matching between the peaking power amplifier circuitry and the Doherty combining node.

18. The enhanced Doherty amplifier of claim 2 wherein the carrier input and output networks and the peaking input and output networks are configured as a group to provide impedance phase tracking between the carrier and peaking paths.

19. The enhanced Doherty amplifier of claim 2 wherein the carrier input and output networks and the peaking input and output networks are configured such that a frequency response of the of the enhanced Doherty amplifier provides a first pass-band for a first communication band in a first frequency range and a second pass-band for a second communication band in a second frequency range, which is separate from the first pass-band.

20. The enhanced Doherty amplifier of claim 19 wherein the frequency response provides a dip between the first and second pass-bands.

21. The enhanced Doherty amplifier of claim 19 wherein the first communication band is one of a PCS band, a UMTS band, and GSM band and the second communication band is one of an LTE band and a WiMax band.

22. The enhanced Doherty amplifier of claim 19 wherein the first communication band is one for a given communication standard and the second communication band is another for the given communication standard.

23. The enhanced Doherty amplifier of claim 22 wherein the given communication standard is one of GSM, PCS, UMTS, LTE, and WiMax standards.

24. The enhanced Doherty amplifier of claim 19 wherein an instantaneous bandwidth of at least 15 percent and an efficiency of greater than 45 percent between 6 dB backed-off power and peak maximum output power is provided by the enhanced Doherty amplifier when amplifying radio frequency signals in both the first and second communication bands.

25. The enhanced Doherty amplifier of claim 24 wherein the first and second communication bands are separated by at least 300 MHz.

26. The enhanced Doherty amplifier of claim 2 wherein an instantaneous bandwidth of at least 15 percent and an efficiency of greater than 40 percent between 6 dB backed-off power and peak maximum output power are provided by the enhanced Doherty amplifier when amplifying radio frequency signals.

27. The enhanced Doherty amplifier of claim 2 wherein an instantaneous bandwidth of at least 20 percent and an efficiency of greater than 35 percent between 6 dB backed-off power and peak maximum output power are provided by the enhanced Doherty amplifier when amplifying radio frequency signals.

28. The enhanced Doherty amplifier of claim 2 wherein an instantaneous bandwidth of at least 20 percent and an efficiency of greater than 40 percent between 6 dB backed-off power and peak maximum output power are provided by the enhanced Doherty amplifier when amplifying radio frequency signals.

29. The enhanced Doherty amplifier of claim 2 wherein an instantaneous bandwidth of at least 10 percent and an efficiency of greater than 45 percent between 6 dB backed-off power and peak maximum output power are provided by the enhanced Doherty amplifier when amplifying radio frequency signals.

30. The enhanced Doherty amplifier of claim 2 wherein an instantaneous bandwidth of at least 250 MHz and an efficiency of greater than 40 percent between 6 dB backed-off power and peak maximum output power are provided by the enhanced Doherty amplifier when amplifying radio frequency signals.

31. An enhanced Doherty amplifier comprising:

a plurality of enhanced Doherty modules wherein each of the enhanced Doherty modules is configured to receive the input signal and provide an output signal;

an input power splitter configured to receive a radio frequency signal and split the radio frequency signal into the input signal supplied to each of the plurality of enhanced Doherty modules;

a combiner configured to combine each output signal received from the plurality of enhanced Doherty modules;

wherein each of the enhanced Doherty modules comprises;

a power splitter configured to receive an input signal and split the input signal into a carrier signal provided at a carrier splitter output and a peaking signal provided at a peaking splitter output;

a Doherty combining node;

a carrier path comprising a carrier power amplifier circuitry, a carrier input network coupled between the carrier splitter output and the carrier power amplifier circuitry, and a carrier output network coupled between the carrier power amplifier circuitry and the Doherty combining node; and

a peaking path comprising peaking power amplifier circuitry, a peaking input network coupled between the peaking splitter output and the peaking power amplifier circuitry, and a peaking output network coupled between the peaking power amplifier circuitry and the Doherty combining node,

wherein;

the carrier and peaking input networks are configured to impose phase shifts causing the peaking signal to lag the carrier signal by approximately 90 degrees when the carrier and peaking signals are respectively presented to the carrier and peaking power amplifier circuitries; and

the carrier and peaking output networks are configured to respectively impose compensated carrier and peaking phase offsets causing the peaking and carrier signals to arrive at the Doherty combining node for reactive combining to generate the output signal.

32. An enhanced Doherty amplifier comprising:

a carrier path comprising carrier power amplifier circuitry, a carrier input network coupled between a carrier splitter output and the carrier power amplifier circuitry, and a carrier output network coupled between the carrier power amplifier circuitry and a Doherty combining node; and

a peaking path comprising peaking power amplifier circuitry, a peaking input network coupled between a peaking splitter output and the peaking power amplifier circuitry, and a peaking output network coupled between the peaking power amplifier circuitry and the Doherty combining node, wherein an instantaneous bandwidth of at least 15 percent and an efficiency of greater than 40 percent between 6 dB backed-off power and peak maximum output power are provided by the enhanced Doherty amplifier when amplifying radio frequency signals.