Multi-band Doherty amplifier device and method therefor

1. A Doherty amplifier device, the device comprising:

a plurality of amplifiers;

a combiner circuit comprising a plurality of impedance inverters and a plurality of switches coupled between the plurality of impedance inverters and outputs of the plurality of amplifiers; and

a controller circuit coupled to the plurality of amplifiers and to the combiner circuit, the controller circuit configured to:

output a carrier bias signal to a first amplifier of the plurality of amplifiers and a peaking bias signal to a second amplifier of the plurality of amplifier as part of a first operating configuration of a plurality of operating configurations that are configurable on the device, the first operating configuration associated with a first frequency band, and

output the peaking bias signal to the second amplifier and the carrier bias signal to a third amplifier of the plurality of amplifiers as part of a second operating configuration, the second operating configuration associated with a second frequency band, wherein

the carrier bias signal is configured to place a receiving amplifier of the plurality of amplifiers in a carrier mode and the peaking bias signal is configured to place a receiving amplifier of the plurality of amplifiers in a peaking mode.

2. The device of claim 1 , further comprising:

an adjustable power splitter circuit coupled to inputs of the plurality of amplifiers, the adjustable power splitter circuit configured to:

drive a main signal to one of the plurality of amplifiers that is configured to operate in the carrier mode, and

drive a shifted signal to another one of the plurality of amplifiers that is configured to operate in the peaking mode.

3. The device of claim 2 , wherein the main signal and the shifted signal are phase shifted from one another by approximately 90 degrees.

4. The device of claim 1 , wherein

the controller circuit is further configured to:

select a first impedance inverter coupled between outputs of the first amplifier and the second amplifier as part of the first operating configuration, wherein

the first impedance inverter is tuned to a first center frequency of the first frequency band, and

an output signal from the second amplifier is combined in phase with an output signal from the first impedance inverter; and

select a second impedance inverter coupled between outputs of the second amplifier and the third amplifier as part of the second operating configuration, wherein

the second impedance inverter is tuned to a second center frequency of the second frequency band, and

an output signal from the second amplifier is combined in phase with an output signal from the second impedance inverter.

5. The device of claim 1 , wherein

the controller circuit is further configured to:

output the peaking bias signal to the first amplifier and the carrier bias signal to the third amplifier as part of a third operating configuration, the third operating configuration associated with a third frequency band.

6. The device of claim 5 , wherein

the controller circuit is further configured to:

select a compound impedance inverter comprising a first impedance inverter and a second impedance inverter coupled in series as part of the third operating configuration, wherein

the compound impedance inverter is coupled between outputs of the first amplifier and the third amplifier, and

an output signal from the first amplifier is combined in phase with an output signal from the compound impedance inverter.

7. The device of claim 6 , wherein

the first impedance inverter is tuned to a first center frequency having a first wavelength,

the second impedance inverter is tuned to a second center frequency having a second wavelength,

the compound impedance inverter is approximately tuned to a third center frequency having a third wavelength, and

a quarter of the third wavelength is approximately equal to a sum of a quarter of the first wavelength plus a quarter of the second wavelength.

8. The device of claim 1 , wherein

the controller circuit is further configured to:

receive an input signal,

determine that the input signal falls within a particular frequency band, and

implement one of the plurality of operating configurations that is associated with the particular frequency band.

9. The device of claim 1 , further comprising:

a plurality of input matching networks, each coupled to an input of a respective one of the plurality of amplifiers; and

a plurality of output matching networks, each coupled to an output of a respective one of the plurality of amplifiers, wherein

each respective one of the plurality of amplifiers is configurable to operate over two or more different frequency bands, and

each input and output matching network coupled to the respective one of the plurality of amplifiers is configurable to operate over the two or more different frequency bands.

10. A Doherty amplifier device, the device comprising:

a plurality of amplifiers;

a combiner circuit comprising a plurality of impedance inverters and a plurality of switches coupled between the plurality of impedance inverters and outputs of the plurality of amplifiers; and

a controller circuit coupled to the plurality of amplifiers and to the combiner circuit, the controller circuit configured to:

select an impedance inverter configuration of a plurality of impedance inverter configurations configurable in the combiner circuit, wherein

each impedance inverter configuration is associated with a respective frequency band,

at least one impedance inverter configuration comprises a compound impedance inverter comprising two or more impedance inverters coupled in series, the compound impedance inverter coupled between

an output of a carrier conduction path that includes a first amplifier of the plurality of amplifiers, and

an output of a peaking conduction path that includes a second amplifier of the plurality of amplifiers,

at least one node between the two or more impedance inverters is coupled to an output of a third amplifier of the plurality of amplifiers, and

the combiner circuit is further configured to combine signals from the carrier and peaking conduction paths in phase according to the impedance inverter configuration to produce an output signal.

11. The device of claim 10 , wherein

the compound impedance inverter is approximately tuned to a first center frequency having a first wavelength,

each of the two or more impedance inverters is approximately tuned to a respective one of two or more center frequencies, each of the two or more respective center frequencies having a respective wavelength, and

a quarter wavelength of the first center frequency is approximately equal to the sum of each quarter wavelength of the two or more respective center frequencies.

12. The device of claim 10 , wherein

the controller circuit is further configured to:

receive an input signal, and

determine that the input signal falls within a particular frequency band, wherein

the particular frequency band is associated with a particular impedance inverter configuration.

13. The device of claim 12 , wherein

the particular impedance inverter configuration comprises either a selected single impedance inverter or a selected compound impedance inverter,

the first and second amplifiers are selected from the plurality of amplifiers due to outputs of the first and second amplifiers being respectively coupled to end terminals of the selected single impedance inverter or the selected compound impedance inverter, and

the controller circuit is further configured to:

output a carrier bias signal that configures the first amplifier to operate in the carrier mode,

output a peaking bias signal that configures the second amplifier to operate in the peaking mode.

14. The device of claim 10 , further comprising:

an adjustable power splitter circuit coupled to inputs of the plurality of amplifiers, wherein the adjustable power splitter circuit is configured to:

drive a main signal to one of the plurality of amplifiers that is configured to operate in the carrier mode, and

drive a shifted signal to another one of the plurality of amplifiers that is configured to operate in the peaking mode.

15. The device of claim 10 , further comprising:

a plurality of input matching networks, each coupled to an input of a respective one of the plurality of amplifiers; and

a plurality of output matching networks, each coupled between an output of a respective one of the plurality of amplifiers and the combiner circuit, wherein

each respective one of the plurality of amplifiers is configurable to operate over two or more different frequency bands, and

each input and output matching network coupled to the respective one of the plurality of amplifiers is configurable to operate over the two or more different frequency bands.

16. A method for operating a Doherty amplifier device that includes a plurality of amplifiers, the method comprising:

selecting an impedance inverter configuration of a plurality of impedance inverter configurations configurable in a combiner circuit of the device, wherein

the combiner circuit comprises a plurality of impedance inverters and a plurality of switches coupled between the plurality of impedance inverters and outputs of the plurality of amplifiers,

each impedance inverter configuration is associated with a respective frequency band,

at least one impedance inverter configuration comprises a compound impedance inverter comprising two or more impedance inverters coupled in series, the compound impedance inverter coupled between

an output of a carrier conduction path that includes a first amplifier of the device, and

an output of a peaking conduction path that includes a second amplifier of the device,

at least one node between the two or more impedance inverters is coupled to an output of a third amplifier of the plurality of amplifiers, and

the combiner circuit is further configured to combine signals of the carrier and peaking conduction paths in phase according to the impedance inverter configuration to produce an output signal.

17. The method of claim 16 , wherein

the compound impedance inverter is approximately tuned to a first center frequency having a first wavelength,

each of the two or more impedance inverters is approximately tuned to a respective one of two or more center frequencies, each of the two or more respective center frequencies having a respective wavelength, and

a quarter wavelength of the first center frequency is approximately equal to the sum of each quarter wavelength of the two or more respective center frequencies.

18. The method of claim 16 , further comprising:

receiving an input signal, and

determining that the input signal falls within a particular frequency band, wherein

the particular frequency band is associated with a particular impedance inverter configuration, and

the particular impedance inverter configuration comprises either a selected single impedance inverter or a selected compound impedance inverter.

19. The device of claim 18 , further comprising:

selecting the first amplifier from the plurality of amplifiers for activation, wherein an output of the first amplifier is coupled to a first end terminal of the selected single impedance inverter or the selected compound impedance inverter;

selecting the second amplifier from the plurality of amplifiers for activation, wherein an output of the second amplifier is coupled to a second end terminal of the selected single impedance inverter or the selected compound impedance inverter; and

deactivating remaining ones of the plurality of amplifiers.

20. The device of claim 16 , further comprising:

outputting a carrier bias signal to configure the first amplifier to operate in a carrier mode and outputting a control signal to configure an adjustable power splitter to drive a main signal to the first amplifier;

outputting a peaking bias signal to configure the second amplifier to operate in a peaking mode and outputting a control signal to configure the adjustable power splitter to drive a shifted signal to the second amplifier.