US-12620950-B2 - Power amplifier circuit

Abstract

A power amplifier circuit includes: a power splitter; a first amplifier; a second amplifier; a first balun that splits a first amplified signal into a third amplified signal and a fourth amplified signal having a different phase from the third amplified signal; a third amplifier and a fourth amplifier that respectively amplify the third amplified signal and the fourth amplified signal; a second balun that splits a second amplified signal into a fifth amplified signal and a sixth amplified signal having a different phase from the fifth amplified signal; a fifth amplifier that amplifies the fifth amplified signal if a power level of the fifth amplified signal is equal to or higher than a predetermined power level; and a sixth amplifier that amplifies the sixth amplified signal if a power level of the sixth amplified signal is equal to or higher than a predetermined power level.

Inventors

• Shohei Imai
• Satoshi Tanaka

Assignees

• MURATA MANUFACTURING CO., LTD.

Dates

Publication Date

20260505

Application Date

20230426

Priority Date

20201027

Claims (9)

1. 1 . A power amplifier circuit comprising: a power splitter configured to split an input signal into a first signal and a second signal having a different phase from the first signal; a first amplifier configured to amplify the first signal and to output a first amplified signal; a second amplifier configured to amplify the second signal and to output a second amplified signal; a first balun configured to split the first amplified signal into a third amplified signal and a fourth amplified signal having a different phase from the third amplified signal; a third amplifier configured to amplify the third amplified signal; a fourth amplifier configured to amplify the fourth amplified signal; a second balun configured to split the second amplified signal into a fifth amplified signal and a sixth amplified signal having a different phase from the fifth amplified signal; a fifth amplifier configured to amplify the fifth amplified signal when a power level of the fifth amplified signal is equal to or greater than a first predetermined power level; and a sixth amplifier configured to amplify the sixth amplified signal when a power level of the sixth amplified signal is equal to or greater than a second predetermined power level.
2. 2 . The power amplifier circuit according to claim 1 , wherein the power amplifier circuit is on a single semiconductor substrate, and wherein the first balun or the second balun comprises a terminal configured to externally connect the semiconductor substrate.
3. 3 . The power amplifier circuit according to claim 1 , wherein the power splitter does not comprise a terminal grounded through a resistor.
4. 4 . The power amplifier circuit according to claim 1 , wherein the power splitter comprises a terminal grounded through a resistor.
5. 5 . The power amplifier circuit according to claim 4 , wherein the power splitter comprises: a first inductor having a first end to which the input signal is supplied and a second end that supplies the first signal; a second inductor electromagnetically coupled to the first inductor and having a first end that is the terminal, and a second end that supplies the second signal; a first capacitor having a first end connected to the first end of the first inductor, and a second end connected to the first end of the second inductor; and a second capacitor having a first end connected to the second end of the first inductor, and a second end connected to the second end of the second inductor.
6. 6 . The power amplifier circuit according to claim 1 , wherein the first balun is on a semiconductor substrate and comprises a third capacitor, and wherein the first balun is connected to an output terminal of the first amplifier and comprises a terminal configured to externally connect the semiconductor substrate through the third capacitor.
7. 7 . The power amplifier circuit according to claim 1 , wherein the second balun is on a semiconductor substrate and comprises a fourth capacitor, and wherein the second balun is connected to an output terminal of the second amplifier and comprises a terminal configured to externally connect the semiconductor substrate through the fourth capacitor.
8. 8 . The power amplifier circuit according to claim 1 , further comprising: a power combiner configured to combine amplified signals respectively output from the third amplifier, the fourth amplifier, the fifth amplifier, and the sixth amplifier, wherein a first part of the power combiner comprises a semiconductor substrate, and second part of the power combiner comprises a module substrate.
9. 9 . The power amplifier circuit according to claim 8 , wherein a part of the power combiner comprises a lumped constant circuit element, and wherein at least a part of the lumped constant circuit element is a surface mount device mounted on the module substrate.

Description

CROSS REFERENCE TO RELATED APPLICATION This is a continuation of International Application No. PCT/JP2021/039036 filed on Oct. 22, 2021 which claims priority from Japanese Patent Application No. 2020-179858 filed on Oct. 27, 2020. The contents of these applications are incorporated herein by reference in their entireties. BACKGROUND ART Technical Field The present disclosure relates to a power amplifier circuit. The Doherty amplifier is a highly efficient power amplifier. In the Doherty amplifier, in general, a carrier amplifier that operates regardless of the power level of an input signal and a peak amplifier that is turned off if the power level of the input signal is low and is turned on if the power level of the input signal is high are connected in parallel. If the power level of the input signal is high, the carrier amplifier operates while maintaining saturation at the saturation output power level. That is, in a back-off state in which only the carrier amplifier performs an amplification operation, since only the carrier amplifier operates, the peak amplifier does not consume an unnecessary current and the efficiency is increased. In a differential Doherty amplifier in which Doherty amplifiers are combined, if signals (for example, noise or the like) having the same amplitude and the same phase are simultaneously input to the respective two amplification elements, the signals having the same amplitude and the same phase can be cancelled. Accordingly, it is possible to suppress generation of noise and harmonic waves of an input signal in the power amplifier circuit (for example, see Patent Document 1). Patent Document 1: Japanese Unexamined Patent Application Publication No. 2009-153193 BRIEF SUMMARY A power combining power amplifier circuit described in Patent Document 1 has a configuration in which a first push-pull amplifier and a second push-pull amplifier having the same configuration are connected in parallel. A power splitter splits an input signal input from an input terminal to a path provided with the first push-pull amplifier and a path provided with a phase shifter and the second push-pull amplifier. The first push-pull amplifier amplifies the input signal by a class-B operation. On the other hand, the second push-pull amplifier amplifies the input signal by a class-C operation. A combiner receives the output power of the first push-pull amplifier and the output power of the second push-pull amplifier through a first isolator and a second isolator, respectively, and combines these output powers. The first push-pull amplifier is provided with a first balun that splits the input signal supplied from the power splitter to a path provided with a first class-B operation transistor and a path provided with a second class-B operation transistor. The second push-pull amplifier is also provided with a balun substantially the same as the first balun. In many cases, the balun implements conversion from a balanced signal to an unbalanced signal or vice versa by, for example, arranging two lines close to each other and electromagnetically coupling the lines. In order to implement a balun having good characteristics, it is common to make the two lines closer to each other. However, if a line-to-line distance is about the minimum processing accuracy of a manufacturing apparatus, variations in characteristics such as the input impedance of the balun are likely to be significant due to manufacturing errors in the line-to-line distance. For example, if the input impedance of the balun varies significantly during mass production, the possibility that a reflected wave of the input signal is generated in the balun increases. Isolation characteristics for suppressing the passage of the reflected wave in an output terminal of the power splitter to another terminal and reflection to the input terminal are not ideal in the power splitter. As a result, if the balun is directly connected to the output of the power splitter as in the power combining power amplifier circuit, a reflected wave generated in the balun in one push-pull amplifier propagates to a circuit in a preceding stage of the power splitter through the power splitter or propagates to the other push-pull amplifier. Accordingly, a power split ratio and split phase of the power splitter, and hence distortion characteristics of the circuit in the preceding stage, may be adversely affected, which is not suitable for mass production. The present disclosure provides a power amplifier circuit suitable for mass production in a configuration in which signals split by a balun are differentially amplified. A power amplifier circuit according to an aspect of the present disclosure includes: a power splitter that splits an input signal into a first signal and a second signal having a different phase from the first signal; a first amplifier that amplifies the first signal and outputs a first amplified signal; a second amplifier that amplifies the second signal and