Power amplifier circuit

Abstract

Provided is a power amplification circuit capable of adjusting the phase of a reflection coefficient for a 3rd harmonic. The power amplification circuit (10) includes an amplifier (101) that amplifies an input signal (RFin); a matching circuit (102) that is connected to an output terminal (1012) of the amplifier (101) at an input and is connected to an output terminal (1002) at an output, and matches the impedance between the output terminal (1012) of the amplifier (101) and the output terminal (1002); and a resonance circuit (103) that is provided between a signal path (P1) connecting the output terminal (1012) of the amplifier (101) and the input of the matching circuit (102) and a ground, and resonates at a resonance frequency that is higher than the frequency of a 4th harmonic of an amplified signal (RF1) obtained by amplifying the input signal (RFin).

Description

Technical Field

[0001] This invention relates to power amplifier circuits. Background Technology

[0002] In mobile communications such as portable telephones, power amplifier circuits are used to amplify the power of transmitted signals. For these power amplifier circuits, it is required to efficiently amplify the transmitted signal according to its frequency. To achieve efficient amplification of the transmitted signal, control is performed by adjusting the phase of the reflection coefficient of the harmonics of the transmitted signal, thereby making the amplifier in the power amplifier circuit operate more efficiently. Patent Document 1 shows a power amplifier circuit in which a third-harmonic variable line tuner is connected to a harmonic reflection filter, and the phase of the reflection coefficient of the harmonics is adjusted according to the frequency of the transmitted signal.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-138430

[0006] In power amplifier circuits, the amplifier can operate efficiently by adjusting the impedance observed from the amplifier's output side and adjusting the phase of the reflection coefficient for harmonics. However, in the harmonic filter and the variable line tuner for third harmonics described in Patent Document 1, it is difficult to properly adjust the phase of the reflection coefficient for harmonics (especially third harmonics). Summary of the Invention

[0007] The problem the invention aims to solve

[0008] The present invention was made in view of the following circumstances, and its object is to provide a power amplifier circuit capable of appropriately adjusting the phase of the reflection coefficient for a third harmonic.

[0009] Technical solutions for solving the problem

[0010] One aspect of the present invention relates to a power amplifier circuit comprising: an amplifier that outputs an amplified signal obtained by amplifying an input signal; a matching circuit whose input is connected to the output terminal of the amplifier and whose output is connected to an output terminal, thereby matching the impedance between the output terminal of the amplifier and the output terminal; and a resonant circuit disposed between a signal path connecting the output terminal of the amplifier and the input of the matching circuit and ground, and resonating at a resonant frequency of 4 times or higher than the frequency of the amplified signal.

[0011] Invention Effects

[0012] According to the present invention, a power amplifier circuit capable of adjusting the phase of the reflection coefficient for a third harmonic is provided. Attached Figure Description

[0013] Figure 1 This is a block diagram of the power amplifier circuit involved in this embodiment.

[0014] Figure 2 This is a circuit diagram of the power amplifier circuit involved in this embodiment.

[0015] Figure 3 This is a graph illustrating an example of the losses in the power amplifier circuit according to this embodiment.

[0016] Figure 4 This is a Smith chart showing the impedance characteristics of the power amplifier circuit according to this embodiment.

[0017] Figure 5 This is a graph illustrating an example of the losses in the power amplifier circuit according to this embodiment.

[0018] Figure 6 This is a Smith chart showing the impedance characteristics of the power amplifier circuit according to this embodiment.

[0019] Figure 7 This is a graph illustrating an example of the losses in the power amplifier circuit according to this embodiment.

[0020] Figure 8 This is a Smith chart showing the impedance characteristics of the power amplifier circuit according to this embodiment.

[0021] Figure 9 This is a graph illustrating an example of the losses in the power amplifier circuit according to this embodiment.

[0022] Figure 10 This is a Smith chart showing the impedance characteristics of the power amplifier circuit according to this embodiment.

[0023] Explanation of reference numerals in the attached figures

[0024] 10: Power amplifier circuit; 101: Amplifier; 102: Matching circuit; 103, 104, 205: Resonant circuit; 1031: Variable capacitor element; 1032: Inductor; 1041: Capacitor element; 1042, 1043, 1044: Inductor; 1045, 1046: Switch. Detailed Implementation

[0025] This implementation method will be described. Figure 1 A block diagram of a power amplifier circuit 10 according to the first embodiment is shown. The power amplifier circuit 10 includes an amplifier 101, a matching circuit 102, and resonant circuits 103 and 104.

[0026] The power amplifier circuit 10 amplifies the input signal RFin input from the input terminal 1001 through the amplifier 101 and outputs the output signal RFout from the output terminal 1002, thereby amplifying the power.

[0027] Amplifier 101 has an input terminal 1011 and an output terminal 1012. Input terminal 1011 is connected to input terminal 1001. Output terminal 1012 is connected to matching circuit 102 and resonant circuits 103 and 104 via signal path P1.

[0028] Amplifier 101 amplifies power, for example, through bipolar transistors such as heterojunction bipolar transistors (HBTs) or field-effect transistors such as MOSFETs (Metal-oxide-semiconductor Field-Effect Transistors).

[0029] Amplifier 101 amplifies the input signal RFin to obtain the amplified signal RF1, which is then output from the output terminal 1012.

[0030] The input of the matching circuit 102 is connected to the output terminal 1012, and the output is connected to the output terminal 1002. The matching circuit 102 is a circuit that matches the impedance between the output terminal 1012 and the output terminal 1002. The matching circuit 102 transforms the impedance so that the low impedance on the output terminal 1012 side matches the high impedance on the output terminal 1002 side.

[0031] A resonant circuit 103 is positioned between the signal path P1 and ground. The resonant circuit 103 adjusts the impedance when viewed from the output terminal 1012 towards the output terminal 1002, thereby preventing harmonics of the amplified signal RF1 from propagating to the output terminal 1002. This adjustment of impedance to prevent harmonic propagation to the output terminal 1002 is also referred to as harmonic termination. The resonant circuit 103 terminates harmonics within a frequency range of 4 to 7 times the fundamental frequency of the amplified signal RF1. Specifically, the resonant circuit 103 resonates at frequencies within a frequency range of 4 to 7 times the fundamental frequency of the amplified signal RF1, thereby making the harmonics at that frequency conduct to ground. Hereinafter, harmonics with frequencies N times the fundamental frequency are referred to as N-fold harmonics.

[0032] Resonant circuit 104 is positioned between signal path P11 and ground. Resonant circuit 104 is positioned after resonant circuit 103. Resonant circuit 104 terminates the double-amplification of signal RF1.

[0033] The power amplifier circuit 10 adjusts the phase of the reflection coefficient of the third harmonic wave when viewed from the output terminal 1002 via a resonant circuit 103 located in the low-impedance signal path P1. Furthermore, the power amplifier circuit 10 adjusts the phase of the reflection coefficient of the second harmonic wave when viewed from the output terminal 1012 via a resonant circuit 104. Thus, the power amplifier circuit 10 can adjust the impedance conditions for the amplifier 101 to operate more efficiently.

[0034] Reference Figure 2 The details of the power amplifier circuit 10 will be explained. Figure 2 The circuit diagram of power amplifier circuit 10 is shown.

[0035] In the following description, the impedance when viewing output terminal 1002 from output terminal 1012 will be defined as impedance Z1, the impedance when viewing output terminal 1002 from connection point 2011 will be defined as impedance Z2, and the impedance when viewing output terminal 1002 from connection point 2021 will be defined as impedance Z3. For example, the impedance “for 2x wave” when viewing output terminal 1002 from output terminal 1012 will be defined as impedance Z1 for 2x wave.

[0036] The resonant circuit 103 (the first resonant circuit) has a variable capacitor element 1031 and an inductor 1032. One end of the variable capacitor element 1031 is connected to the connection point 2011 of the signal path P1, and the other end is connected to one end of the inductor 1032. The other end of the inductor 1032 is connected to ground.

[0037] The variable capacitor element 1031 is a digitally controlled capacitor (DTC) whose capacitance value can be controlled. The DTC switches the capacitance value according to a supplied control signal. In this embodiment, the variable capacitor element 1031 controls the capacitance value according to the frequency of the input signal RFin. For example, when the frequency of the input signal RFin is relatively low, the capacitance value of the variable capacitor element 1031 is controlled to a relatively large value, and when the frequency of the input signal RFin is relatively high, the capacitance value of the variable capacitor element 1031 is controlled to a relatively small value. Alternatively, a varactor diode can be used with respect to the variable capacitor element 1031.

[0038] The resonant circuit 103 is an LC series resonant circuit controlled to resonate at a frequency within the range of 4th to 7th harmonics. When the resonant circuit 103 resonates at a given resonant frequency, harmonics with frequencies close to the resonant frequency are short-circuited. That is, the impedance Z2 for the signal at that resonant frequency becomes close to zero. Furthermore, at this time, the impedance Z2 for the 3rd harmonic also becomes a value corresponding to the capacitance of the variable capacitor element 1031. However, the impedance Z2 for the 3rd harmonic is not close to zero.

[0039] The impedance Z1 of the 3x wave undergoes impedance transformation through the inductance generated by the wiring of the signal path P1 between the output terminal 1012 and the connection point 2011. Additionally, in Figure 2 In this context, the inductance is represented by lumped parameters as the inductance generated by inductor 201. The impedance Z1 for a third harmonic is the value of the impedance Z2 for a third harmonic after impedance transformation through inductor 201. Therefore, the phase of the impedance Z1 for a third harmonic and the reflection coefficient for a third harmonic can be adjusted.

[0040] The resonant circuit 104 (the second resonant circuit) has a capacitor element 1041, inductors 1042, 1043, 1044, and switches 1045, 1046.

[0041] One end of capacitor 1041 is connected to connection point 2021 of signal path P1, and the other end is connected to one end of each of inductors 1042, 1043, and 1044.

[0042] Inductor 1042 is connected to ground. Inductor 1043 is connected to ground via switch 1045. Inductor 1044 is connected to ground via switch 1046.

[0043] The switching on and off of switches 1045 and 1046 is controlled by a control signal corresponding to the frequency band of the input signal RFin. Based on the on / off state of switches 1045 and 1046, the combined inductance value based on the inductance values ​​of inductors 1042, 1043, and 1044 can be controlled. Therefore, inductors 1042, 1043, 1044, and switches 1045 and 1046 can also be considered as a variable inductance element. For example, when the frequency of the input signal RFin is relatively low, the combined inductance value is controlled to be relatively large; when the frequency of the input signal RFin is relatively high, the combined inductance value is controlled to be relatively small.

[0044] The resonant circuit 104 is an LC series resonant circuit, comprising a capacitor element 1041 and inductors 1042, 1043, and 1044 connected in series with the capacitor element 1041, and is controlled to resonate at a frequency of 2 times the harmonic. By resonating the resonant circuit 104 at the frequency of 2 times the harmonic, the 2 times harmonic is short-circuited. That is, the impedance Z3 for the 2 times harmonic becomes close to zero.

[0045] The impedance Z3 for the second harmonic is transformed by inductor 202, which is expressed in the same lumped parameter manner as inductor 201. Through this impedance transformation, the phase of the impedance Z1 for the second harmonic and the reflection coefficient for the second harmonic can be adjusted.

[0046] Matching circuit 102 includes inductor 203 and resonant circuit 205. One end of inductor 203 is connected to connection point 2021, and the other end is connected to output terminal 1002. Resonant circuit 205 is configured to connect the other end of inductor 203 and output terminal 1002 to ground.

[0047] The resonant circuit 205 includes a variable capacitor 2051, a capacitor 2052, and an inductor 2053. One end of the variable capacitor 2051 is connected to the other end of the inductor 2053, and the other end is connected to one end of the inductor 2053. The other end of the inductor 2053 is connected to ground. The capacitor 2052 is connected in parallel with the variable capacitor 2051.

[0048] Variable capacitor element 2051 is the same DTC as variable capacitor element 1031. Variable capacitor element 2051 controls its capacitance value according to the frequency band of the input signal RFin. For example, when the frequency of the input signal RFin is relatively low, the capacitance value of variable capacitor element 2051 is controlled to be relatively large; when the frequency of the input signal RFin is relatively high, the capacitance value of variable capacitor element 2051 is controlled to be relatively small. Alternatively, a varactor diode can be used with variable capacitor element 2051.

[0049] The resonant circuit 205 is an LC series resonant circuit controlled to terminate 2nd, 3rd, and 4th harmonic waves. Additionally, capacitor element 2052 is provided to ensure its capacitance value. By resonating at a given frequency between the 2nd and 4th harmonic waves using the resonant circuit 205, these harmonic waves are short-circuited. Since the 2nd to 4th harmonic waves are signals with higher power than higher-order harmonics, they can be adequately terminated using both resonant circuits 104 and 205.

[0050] In the matching circuit 102, the low impedance on the output terminal 1012 side is transformed into a high impedance on the output terminal 1002 side through the inductor 203 and the resonant circuit 205, thereby achieving impedance matching.

[0051] Regarding the advantages of the power amplifier circuit 10, for example, let's describe the case where amplifier 101 operates close to F-class operation. In this case, the impedance of the 2x wave is preferably closer to the short-circuit side on the Smith chart, and the impedance of the 3x wave is preferably closer to the open-circuit side on the Smith chart. In this case, the phase of the reflection coefficient of the 2x wave is close to 180 degrees, and the phase of the reflection coefficient of the 3x wave is close to 0 degrees, respectively. Furthermore, when making amplifier 101 operate close to F-class operation, the impedance of the 2x wave is preferably closer to the short-circuit side on the Smith chart, but it does not need to be a complete short circuit. Similarly, the impedance of the 3x wave is preferably closer to the open-circuit side on the Smith chart, but it does not need to be a complete open circuit.

[0052] In the power amplifier circuit 10, the phase of the impedance Z1 for the second harmonic and the phase of the reflection coefficient for the second harmonic are adjusted by the resonant circuit 104, and the phase of the impedance Z1 for the third harmonic and the phase of the reflection coefficient for the third harmonic are adjusted by the resonant circuit 103. The resonant circuit 103 is not a circuit that terminates the third harmonic, therefore the impedance Z2 for the third harmonic is not zero.

[0053] Therefore, in the power amplifier circuit 10, the impedance Z2 for the third harmonic, which is located slightly off the open-circuit side on the Smith chart, can be impedance transformed by the inductor 201. The impedance Z1 for the third harmonic at the output terminal 1012 becomes closer to the open-circuit side on the Smith chart. In other words, the phase of the reflection coefficient of the third harmonic at the output terminal 1012 becomes closer to 0 degrees. As a result, the operation of the amplifier 101 can be made closer to F-class operation.

[0054] In this way, the power amplifier circuit 10 can change the phase of the reflection coefficient of the third harmonic at the output terminal 1012 according to the resonant frequency of the resonant circuit 104, thereby adjusting the phase of the reflection coefficient of the third harmonic to a phase corresponding to the operation of the amplifier 101.

[0055] Furthermore, the power amplifier circuit 10 can adjust the phase of the reflection coefficient of the third harmonic wave to a phase corresponding to the operation of the amplifier 101 with a small structure. Assuming the resonant circuit 103 is located after the matching circuit 102, in this case, the high impedance value after the impedance transformation based on the matching circuit 102 needs to be adjusted, thereby adjusting the impedance Z1. In this case, the component values ​​also increase, so the size of the components located in the resonant circuit 103 becomes larger. On the other hand, in the power amplifier circuit 10, by providing the resonant circuit 103 before the matching circuit 102, it is possible to adjust the phase of the reflection coefficient of the third harmonic wave using smaller components.

[0056] Reference Figures 3 to 6 The phase adjustment of the reflection coefficient of the 3rd harmonic wave using the power amplifier circuit 10 is explained. Figure 3 This is a graph showing the power loss in the output signal RFout when an input signal RFin of a given frequency with a 600MHz band (VLB: Very Low Band) passes through the power amplifier circuit 10.

[0057] exist Figure 3 The diagram shows the fundamental frequency f31 and the harmonic frequencies f32 to f37. The loss near f32 is based on the termination of the second harmonic by resonant circuit 104 and the termination of the second harmonic by resonant circuit 205. The loss near f34 is based on the termination of the fourth harmonic by resonant circuit 205.

[0058] exist Figure 3 In the section highlighted by the dashed circle, specifically at frequencies between f36 and f37, the loss increases. This loss is based on the resonance loss of the resonant circuit 103.

[0059] exist Figure 4 In the diagram, curve S4 is shown on the Smith chart, illustrating the frequency response of impedance Z1 in this case. Positions S41, S42, and S43 correspond to the impedance Z1 at the fundamental, second harmonic, and third harmonic frequencies, respectively.

[0060] Suppose we now want to make the situation... Figure 4 The impedance Z1 of position S43 is closer to the open circuit side, and the phase of the reflection coefficient of the 3rd harmonic wave is closer to 0 degrees, thereby realizing the control of the operation of amplifier 101.

[0061] At this time, in the power amplifier circuit 10, the following control is performed: the capacitance value of the variable capacitor element 1031 in the resonant circuit 103 is increased. Thus, as... Figure 5 As emphasized by the dashed circle, the resonant frequency of the resonant circuit 103 decreases. Furthermore, in Figure 5 In the middle, the loss of termination based on the 2-fold wave does not change much.

[0062] exist Figure 6 In the middle, curve S6 is shown on the Smith chart, curve S6 shows Figure 5 The frequency characteristics of impedance Z1 under the loss condition are shown. Positions S61, S62, and S63 correspond to impedance Z1 at the fundamental, second harmonic, and third harmonic frequencies, respectively.

[0063] right Figure 4 as well as Figure 6 Comparing positions S41 and S42 with positions S61 and S62, there is no difference, but positions S43 and S63 are significantly different. That is, the position S61 of the impedance Z1 at the fundamental frequency and the position S62 of the impedance Z1 at the second harmonic frequency remain unchanged, while the position S63 of the impedance Z1 at the third harmonic frequency becomes closer to the open-circuit side. Therefore, in the power amplifier circuit 10, it is possible to adjust the phase of the reflection coefficient of the third harmonic to close to 0 degrees without changing the impedance at the fundamental and second harmonic frequencies. Thus, while suppressing the influence of the impedance on the gain and output characteristics of the amplifier 101, which affects the fundamental frequency, the reflection coefficient of the third harmonic can be adjusted to optimize the output power and current in the saturation region of the amplifier 101.

[0064] Reference Figures 7 to 10 Other examples of phase adjustment of the reflection coefficient of a 3x wave using power amplifier circuit 10 will be explained. Figure 7 This is a graph showing the power loss in the output signal RFout when an input signal RFin at a given frequency in the 800MHz band (LB: Low Band) passes through the power amplifier circuit 10. The power amplifier circuit 10 can amplify any signal from VLB and LB. In the power amplifier circuit 10, the capacitance value of the variable capacitor element 1031, the on / off state of switches 1045 and 1046, and the capacitance value of the variable capacitor element 2051 can be controlled according to the frequency of the input signal RFin.

[0065] exist Figure 7 The diagram shows the fundamental frequency f71 and the harmonic frequencies f72 to f76. The losses near f72 are based on the termination of the second harmonic by resonant circuit 104 and resonant circuit 205. The losses between f73 and f74 are based on the termination of the third and fourth harmonics by resonant circuit 205.

[0066] exist Figure 7In the section highlighted by the dashed circle, specifically at frequencies near f76, the loss increases. This loss is based on the resonance loss of the resonant circuit 103.

[0067] exist Figure 8 In the diagram, curve S8 is shown on the Smith chart, illustrating the frequency response of impedance Z1 in this case. Positions S81, S82, and S83 correspond to the impedance Z1 at the fundamental, second harmonic, and third harmonic frequencies, respectively.

[0068] Assuming the same logic applies as with VLB, in LB, we also want to ensure that the value in the VLB is... Figure 8 The impedance Z1 of position S83 is closer to the open circuit side, and the phase of the reflection coefficient of the 3rd harmonic wave is closer to 0 degrees, thereby realizing the control of the operation of amplifier 101.

[0069] In this case, such as Figure 9 As shown, the capacitance value of the variable capacitor element 1031 can be controlled so that the resonant frequency of the resonant circuit 103 is near the frequency f95.

[0070] exist Figure 10 In the figure, curve S10 is shown on the Smith chart. Curve S10 shows... Figure 9 The frequency characteristics of impedance Z1 under the loss condition are shown. Positions S101, S102, and S103 correspond to the impedance Z1 at the fundamental, second harmonic, and third harmonic frequencies, respectively.

[0071] right Figure 8 as well as Figure 10 Comparing positions S81 and S82 with positions S101 and S102, positions S83 and S103 are quite different. Position S103 is closer to the open-circuit side. Therefore, even in the case of LB, the power amplifier circuit 10 can perform adjustments to bring the phase of the reflection coefficient of the 3rd harmonic wave close to 0 degrees.

[0072] In the power amplifier circuit 10, as illustrated in the cases of VLB and LB, the phase of the reflection coefficient of the input signal RFI with multiple frequencies can be adjusted to be close to 0 degrees.

[0073] The exemplary embodiments of the present invention have been described above. The power amplifier circuit 10 includes: an amplifier 101 for amplifying an input signal RFin; a matching circuit 102, whose input is connected to the output terminal 1012 of the amplifier 101 and whose output is connected to an output terminal 1002, thereby matching the impedance between the output terminal 1012 and the output terminal 1002 of the amplifier 101; and a resonant circuit 103 disposed between a signal path P1 connecting the output terminal 1012 of the amplifier 101 and the input of the matching circuit 102 and ground, resonating at a resonant frequency at or above a harmonic of four times the frequency of the amplified signal RF1 obtained by amplifying the input signal RFin.

[0074] The resonant circuit 103 resonates at a resonant frequency higher than the fourth harmonic, therefore the third harmonic is not terminated by the resonant circuit 103. Consequently, the impedance Z2 for the third harmonic will not be near zero. When the impedance Z2 for the third harmonic is near zero, the phase of the reflection coefficient of the third harmonic becomes near 180 degrees. When the third harmonic is terminated, the value near 180 degrees regarding the phase of the reflection coefficient becomes the initial adjustment value. In the power amplifier circuit 10, the impedance Z2 for the third harmonic can be set to a value other than near zero by the resonant circuit 103, therefore the initial adjustment value of the phase of the reflection coefficient of the third harmonic can be adjusted based on the resonant frequency of the resonant circuit 103. Thus, the power amplifier circuit 10 can appropriately adjust the phase of the reflection coefficient of the third harmonic of the amplified signal RF1.

[0075] Unlike power amplifier circuit 10, when a phase adjustment circuit is provided on the output terminal side to adjust the phase of the harmonic reflection coefficient, the phase adjustment circuit adjusts the phase of the harmonic reflection coefficient flowing through a high-impedance signal path. The phase of the harmonic reflection coefficient when viewed from the amplifier output side becomes the phase of the reflection coefficient adjusted by the phase adjustment circuit, further changed by the impedance transformation of the matching circuit. Therefore, when a phase adjustment circuit is provided after the matching circuit, the phase adjustment circuit needs to adjust the phase while taking into account the effect of the matching circuit on the phase. Due to the effect of the impedance transformation of the matching circuit on the phase, it is sometimes impossible to properly adjust the impedance when viewed from the amplifier output side. In contrast, power amplifier circuit 10 can properly adjust the phase of the reflection coefficient of the third harmonic of the amplified signal RF1.

[0076] Furthermore, in the power amplifier circuit 10, by providing a resonant circuit 103 before the matching circuit 102, the phase of the reflection coefficient of the third harmonic can be adjusted using smaller components. Therefore, the power amplifier circuit 10 is a smaller power amplifier circuit compared to a power amplifier circuit that provides a resonant circuit after the matching circuit 102.

[0077] Furthermore, in the power amplifier circuit 10, the resonant circuit 103 includes a variable capacitor element 1031 and an inductor 1032 connected in series. By adjusting the capacitance value of the variable capacitor element 1031, the resonant frequency of the resonant circuit 103 can be adjusted according to the frequency of the input signal RFin. Therefore, even for an input signal RFin with frequencies that can utilize multiple frequency bands, the power amplifier circuit 10 can appropriately adjust the phase of the reflection coefficient of the third harmonic of the amplified signal RF1. Additionally, in the resonant circuit 103, the inductor 1032 can be replaced by a variable inductor whose inductance value can be adjusted. In this case, similarly to the case using the variable capacitor element 1031, even for an input signal RFin with frequencies that can utilize multiple frequency bands, the phase of the reflection coefficient of the third harmonic of the amplified signal RF1 can be appropriately adjusted.

[0078] Furthermore, the power amplifier circuit 10 also includes a resonant circuit 104 disposed between the signal path P1 and ground, resonating at the frequency of the second harmonic of the amplified signal RF1. The resonant circuit 104 allows adjustment of the impedance Z1 at the output terminal 1012 relative to the second harmonic. Therefore, the power amplifier circuit 10 can also appropriately adjust the phase of the reflection coefficient relative to the second harmonic of the amplified signal RF1. The power amplifier circuit 10 can adjust the phase of the reflection coefficient relative to the third harmonic while simultaneously adjusting the phase of the reflection coefficient relative to the second harmonic, enabling the amplifier 101 to operate more efficiently.

[0079] Furthermore, in the power amplifier circuit 10, the resonant circuit 104 includes a capacitor element 1041 connected in series and a variable inductor (second inductor element) comprising inductors 1042, 1043, and 1044 with variable inductance values. Thus, even for an input signal RFin with frequencies capable of multiple frequency bands, the power amplifier circuit 10 can adjust the phase of the reflection coefficient for the third harmonic as well as the phase of the reflection coefficient for the second harmonic. In the resonant circuit 104, the capacitor element 1041 can also be replaced by a variable capacitor element (second capacitor element) whose capacitance value can be adjusted.

[0080] Furthermore, the embodiments described above are intended to facilitate understanding of the present invention and are not intended to limit the scope of the invention. The present invention can be modified / improved without departing from its spirit, and the present invention also includes its equivalents. That is, embodiments to which those skilled in the art have appropriately applied design changes are also included within the scope of the present invention, provided they possess the features of the present invention. For example, the elements, their configurations, materials, conditions, dimensions, etc., of each embodiment are not limited to the illustrated elements, their configurations, materials, conditions, dimensions, etc., and can be appropriately modified. Moreover, each embodiment is exemplified; it is self-evident that partial substitutions or combinations of the structures shown in different embodiments are possible, and such substitutions or combinations are also included within the scope of the present invention, provided they contain the features of the present invention.

Claims

1. A power amplifier circuit, comprising: An amplifier amplifies the input signal; A matching circuit, with its input connected to the output terminal of the amplifier and its output connected to the output terminal, provides impedance matching between the output terminal and the output terminal of the amplifier; and The first resonant circuit is positioned between the signal path connecting the output terminal of the amplifier and the input of the matching circuit and ground, and resonates at a resonant frequency higher than four times the frequency of the amplified signal obtained by amplifying the input signal. The matching circuit includes an inductor and a third resonant circuit. One end of the inductor is connected to the input of the matching circuit, and the other end is connected to the output terminal. The third resonant circuit is configured to connect the other end of the inductor to ground between the output terminal and the ground. The third resonant circuit is an LC series resonant circuit controlled to terminate the 2x, 3x, and 4x waves of the amplified signal.

2. The power amplifier circuit according to claim 1, wherein, The first resonant circuit has a first capacitor element and a first inductor element connected in series. At least one of the capacitance value of the first capacitor element and the inductance value of the first inductor element is variable.

3. The power amplifier circuit according to claim 1 or 2, wherein, The power amplifier circuit also includes: The second resonant circuit is disposed between the signal path and the ground, and resonates at the frequency of twice the frequency of the amplified signal.

4. The power amplifier circuit according to claim 3, wherein, The second resonant circuit has a second capacitor element and a second inductor element connected in series. At least one of the capacitance value of the second capacitor element and the inductance value of the second inductor element can be variable.

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