US-12627264-B2 - Doherty power amplifiers with controllable capacitor for tuning harmonic termination and inverter

Abstract

Doherty power amplifiers with a controllable capacitor are disclosed. In certain embodiments, a Doherty power amplifier includes a carrier amplifier that amplifies a first radio frequency (RF) input signal, a peaking amplifier that amplifies a second RF input signal, and a combiner having a first input coupled to an output of the carrier amplifier, a second input coupled to an output of the peaking amplifier, and an output that provides a combined RF output signal. The combiner includes an inverter for providing impedance inversion between the first input and the output of the combiner, and a first controllable capacitor and a first inductor in series and operable to provide harmonic termination to the output of the carrier amplifier. A capacitance of the first controllable capacitor is controllable to tune both the inverter and the harmonic termination of the carrier amplifier.

Inventors

• Philip John Lehtola

Assignees

• SKYWORKS SOLUTIONS, INC.

Dates

Publication Date

20260512

Application Date

20231024

Claims (20)

1. 1 . A power amplifier system comprising: a carrier amplifier configured to amplify a first radio frequency input signal; a peaking amplifier configured to amplify a second radio frequency input signal; and a combiner having a first input electrically connected to an output of the carrier amplifier, a second input electrically connected to an output of the peaking amplifier, and an output that provides a radio frequency output signal, the combiner including an inverter configured to provide an impedance inversion between the first input and the output of the combiner, and a first inductor and a first controllable in series and operable to provide harmonic termination to the output of the carrier amplifier, the first controllable capacitor having a capacitance that is controllable to tune both the inverter and the harmonic termination of the carrier amplifier, the first controllable capacitor including a plurality of circuit branches electrically connected in parallel, the plurality of circuit branches including a first circuit branch with a fixed capacitor and a second circuit branch with a series combination of a first field-effect transistor switch and a first switchable capacitor.
2. 2 . The power amplifier system of claim 1 wherein the combiner further includes a second inductor and a second controllable capacitor in series and operable to provide harmonic termination to the output of the peaking amplifier.
3. 3 . The power amplifier system of claim 2 wherein the first inductor and the first controllable capacitor are electrically connected in series between the output of the carrier amplifier and a ground voltage, and the second inductor and the second controllable capacitor are electrically connected in series between the output of the carrier amplifier and the ground voltage.
4. 4 . The power amplifier system of claim 3 wherein the inverter is connected between the output of the carrier amplifier and the output of the peaking amplifier.
5. 5 . The power amplifier system of claim 1 wherein the inverter includes a quarter wave transformer.
6. 6 . The power amplifier system of claim 1 further comprising an input splitter configured to receive a radio frequency transmit signal and to output the first radio frequency input signal and the second radio frequency input signal.
7. 7 . The power amplifier system of claim 6 further comprising an input signal selection circuit configured to select the radio frequency transmit signal from amongst two or more radio frequency transmit signals each associated with a different frequency band.
8. 8 . The power amplifier system of claim 7 wherein the radio frequency transmit signal is selected based on a band signal, the band signal further operable to control the capacitance of the first controllable capacitor.
9. 9 . The power amplifier system of claim 1 further comprising a series matching inductor connected between the output of the combiner and a radio frequency output terminal, and a shunt matching capacitor in shunt to the radio frequency output terminal.
10. 10 . The power amplifier system of claim 1 wherein the carrier amplifier includes a class AB bias circuit, and the peaking amplifier includes a class C bias circuit.
11. 11 . The power amplifier system of claim 1 wherein the first controllable capacitor and the first inductor provide harmonic termination at a second harmonic frequency of the first radio frequency input signal.
12. 12 . The power amplifier system of claim 11 wherein the plurality of circuit branches further include a third circuit branch with a second field-effect transistor switch and a second switchable capacitor.
13. 13 . A method of radio frequency amplification, the method comprising: amplifying a first radio frequency input signal using a carrier amplifier that has an output connected to a first input of a combiner; amplifying a second radio frequency input signal using a peaking amplifier that has an output connected to a second input of the combiner; providing an impedance inversion between the first input of the combiner and an output of the combiner using an inverter of the combiner; providing harmonic termination to the output of the carrier amplifier using a first inductor and a first controllable capacitor of the combiner, the first inductor and the first controllable capacitor in series; and controlling a capacitance of the first controllable capacitor to tune both the inverter and the harmonic termination of the carrier amplifier, the first controllable capacitor including a plurality of circuit branches electrically connected in parallel, the plurality of circuit branches including a first circuit branch with a fixed capacitor and a second circuit branch with a series combination of a first field-effect transistor switch and a first switchable capacitor.
14. 14 . A mobile device comprising: an antenna configured to transmit a radio frequency output signal; and a front end-system including a power amplifier system including a carrier amplifier configured to amplify a first radio frequency input signal, a peaking amplifier configured to amplify a second radio frequency input signal, and a combiner having a first input electrically connected to an output of the carrier amplifier, a second input electrically connected to an output of the peaking amplifier, and an output that provides the radio frequency output signal, the combiner including an inverter configured to provide an impedance inversion between the first input and the output of the combiner, and a first inductor and a first controllable in series and operable to provide harmonic termination to the output of the carrier amplifier, the first controllable capacitor having a capacitance that is controllable to tune both the inverter and the harmonic termination of the carrier amplifier, the first controllable capacitor including a plurality of circuit branches electrically connected in parallel, the plurality of circuit branches including a first circuit branch with a fixed capacitor and a second circuit branch with a series combination of a first field-effect transistor switch and a first switchable capacitor.
15. 15 . The mobile device of claim 14 wherein the combiner further includes a second inductor and a second controllable capacitor in series and operable to provide harmonic termination to the output of the peaking amplifier.
16. 16 . The mobile device of claim 15 wherein the first inductor and the first controllable capacitor are electrically connected in series between the output of the carrier amplifier and a ground voltage, and the second inductor and the second controllable capacitor are electrically connected in series between the output of the carrier amplifier and the ground voltage.
17. 17 . The mobile device of claim 14 wherein the power amplifier system further includes an input splitter configured to receive a radio frequency transmit signal and to output the first radio frequency input signal and the second radio frequency input signal.
18. 18 . The mobile device of claim 17 wherein the power amplifier system further includes an input signal selection circuit configured to select the radio frequency transmit signal from amongst two or more radio frequency transmit signals each associated with a different frequency band.
19. 19 . The mobile device of claim 18 wherein the radio frequency transmit signal is selected based on a band signal, the band signal further operable to control the capacitance of the first controllable capacitor.
20. 20 . The mobile device of claim 14 wherein the plurality of circuit branches further include a third circuit branch with a second field-effect transistor switch and a second switchable capacitor.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Patent Application No. 63/381,256, filed Oct. 27, 2022 and titled “DOHERTY POWER AMPLIFIERS WITH CONTROLLABLE CAPACITOR FOR TUNING HARMONIC TERMINATION AND INVERTER,” which is herein incorporated by reference in its entirety. BACKGROUND Field Embodiments of the invention relate to electronic systems, and in particular, to radio frequency (RF) electronics. Description of the Related Technology Power amplifiers are used in RF communication systems to amplify RF signals for transmission via antennas. Examples of RF communication systems with one or more power amplifiers include, but are not limited to, mobile phones, tablets, base stations, network access points, customer-premises equipment (CPE), laptops, and wearable electronics. For example, in wireless devices that communicate using a cellular standard, a wireless local area network (WLAN) standard, and/or any other suitable communication standard, a power amplifier can be used for RF signal amplification. An RF signal can have a frequency in the range of about 30 kHz to 300 GHz, such as in the range of about 400 MHz to about 7.125 GHz for Frequency Range 1 (FR1) of the Fifth Generation (5G) communication standard or in the range of about 24.250 GHz to about 71.000 GHz for Frequency Range 2 (FR2) of the 5G communication standard. SUMMARY In certain embodiments, the present disclosure relates to a power amplifier system. The power amplifier system includes a carrier amplifier configured to amplify a first radio frequency input signal, a peaking amplifier configured to amplify a second radio frequency input signal, and a combiner having a first input electrically connected to an output of the carrier amplifier, a second input electrically connected to an output of the peaking amplifier, and an output that provides a radio frequency output signal. The combiner includes an inverter configured to provide an impedance inversion between the first input and the output of the combiner, and a first inductor and a first controllable in series and operable to provide harmonic termination to the output of the carrier amplifier. The first controllable capacitor having a capacitance that is controllable to tune both the inverter and the harmonic termination of the carrier amplifier. In some embodiments, the combiner further includes a second inductor and a second controllable capacitor in series and operable to provide harmonic termination to the output of the peaking amplifier. According to a number of embodiments, the first inductor and the first controllable capacitor are electrically connected in series between the output of the carrier amplifier and a ground voltage, and the second inductor and the second controllable capacitor are electrically connected in series between the output of the carrier amplifier and the ground voltage. In accordance with several embodiments, the inverter is connected between the output of the carrier amplifier and the output of the peaking amplifier. In various embodiments, the inverter includes a quarter wave transformer. In several embodiments, the power amplifier system further includes an input splitter configured to receive a radio frequency transmit signal and to output the first radio frequency input signal and the second radio frequency input signal. According to a number of embodiments, the power amplifier system further includes an input signal selection circuit configured to select the radio frequency transmit signal from amongst two or more radio frequency transmit signals each associated with a different frequency band. In accordance with various embodiments, the radio frequency transmit signal is selected based on a band signal, the band signal further operable to control the capacitance of the first controllable capacitor. In some embodiments, the power amplifier system further includes a series matching inductor connected between the output of the combiner and a radio frequency output terminal, and a shunt matching capacitor in shunt to the radio frequency output terminal. In several embodiments, the carrier amplifier includes a class AB bias circuit, and the peaking amplifier includes a class C bias circuit. In some embodiments, the first controllable capacitor and the first inductor provide harmonic termination at a second harmonic frequency of the first radio frequency input signal. In various embodiments, the first controllable capacitor includes a plurality of circuit branches electrically connected in parallel, the plurality of circuit branches including a first circuit branch with a fixed capacitor and a second circuit branch with a series combination of a first field-effect transistor switch and a first switchable capacitor. According to a number of embodiments, the plurality of circuit branches further include a third circuit branch with a second field-effect transistor switch and a se