Power amplifier circuit

Abstract

The present invention provides a power amplifier circuit that efficiently amplifies power when performing envelope tracking control to amplify a radio frequency signal. The power amplifier circuit (10) comprises: a transistor (11), a power supply voltage (Vcc) that varies according to the envelope of the amplitude of the radio frequency signal input to the base is supplied to the collector, and an amplified signal after the radio frequency signal is amplified is output from the collector; a first termination circuit (21) that is arranged at the rear stage of the transistor (11) to attenuate the higher harmonic components of the amplified signal; and a second termination circuit (31) that is arranged at the rear stage of the transistor to attenuate the higher harmonic components of the amplified signal. The first termination circuit (21) and the second termination circuit (31) have the following characteristics, namely, they resonate with respect to a radio frequency signal having a frequency between the frequency of the second harmonic component and the frequency of the third harmonic component.

Description

Technical Field

[0001] The invention relates to a power amplifier circuit. Background Art

[0002] In the communication using radio frequency (RF) signals of mobile devices such as mobile phones, a power amplifier circuit is used to amplify the RF signal. As a control method for efficiently amplifying the RF signal, envelope tracking (ET) control is known. ET control is a control that amplifies the power using a power supply voltage that varies according to the envelope of the amplitude of the RF signal.

[0003] When performing ET control, it is necessary to appropriately process higher harmonic components such as the second harmonic component of the RF signal in the power amplifier circuit. Patent Document 1 discloses a higher harmonic power amplifier that suppresses power leakage of the second harmonic component of the fundamental wave.

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2010-87934

[0007] In a power amplifier circuit that performs ET control, the power supply voltage is controlled so as to use the saturation region of the transistor. When the transistor is operated in the saturation region at a certain power supply voltage, the output power of the transistor at the power supply voltage is large. When the output power is large, in addition to the increase in the fundamental component of the RF signal, the higher harmonic components also increase. As described in Patent Document 1, when a higher harmonic power amplifier is used such as adjusting the impedance only for the second harmonic component, the higher harmonic components above the third harmonic component are not adjusted. The power amplifier circuit in this case is affected by the higher harmonic components above the third harmonic component, so the region with the highest efficiency of the transistor cannot be used for each power supply voltage controlled by ET. Since the region with the highest efficiency cannot be used, the optimization of the power amplifier circuit that performs ET control cannot be achieved. Summary of the invention

[0008] Problems to be solved by the invention

[0009] The present invention has been made in view of such a situation, and an object of the present invention is to provide a power amplifier circuit that efficiently amplifies power when amplifying a radio frequency signal by performing envelope tracking control.

[0010] Means for solving problems

[0011] A power amplifier circuit according to one embodiment of the present invention comprises: a transistor, a power supply voltage that varies according to the envelope of the amplitude of a radio frequency signal input to the base is supplied to the collector, and an amplified signal obtained by amplifying the radio frequency signal is output from the collector; a first termination circuit that is provided at the rear stage of the transistor and attenuates the higher harmonic components of the amplified signal; and a second termination circuit that is provided at the rear stage of the transistor and attenuates the higher harmonic components of the amplified signal, wherein the first termination circuit and the second termination circuit have the following characteristics: they resonate with respect to a radio frequency signal having a frequency between the frequency of a second harmonic component and the frequency of a third harmonic component.

[0012] Effects of the Invention

[0013] According to the present invention, it is possible to provide a power amplifier circuit that efficiently amplifies power when performing envelope tracking control to amplify a radio frequency signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a circuit diagram of the power amplifier circuit according to the first embodiment.

[0015] Figure 2 It is a Smith chart showing the impedance characteristics of the power amplifier circuit according to the first embodiment.

[0016] Figure 3 It is a graph showing the insertion loss in the power amplifier circuit according to the first embodiment.

[0017] Figure 4 It is a graph showing the efficiency in the power amplifier circuit according to the first embodiment.

[0018] Figure 5 It is a graph showing the gain in the power amplifier circuit according to the first embodiment.

[0019] Figure 6 It is a circuit diagram of a power amplifier circuit according to the second embodiment.

[0020] Figure 7 It is a Smith chart showing the impedance characteristics of the power amplifier circuit according to the second embodiment.

[0021] Figure 8 It is a graph showing the insertion loss in the power amplifier circuit according to the second embodiment.

[0022] Fig. 9 It is a circuit diagram of a power amplifier circuit according to a third embodiment.

[0023] Fig.10 is a circuit diagram of a power amplifier circuit according to a comparative example.

[0024] Fig.11 is a Smith chart showing the impedance characteristics of the power amplifier circuit according to the comparative example.

[0025] Fig.12 It is a graph showing the insertion loss in the power amplifier circuit according to the comparative example.

[0026] Fig.13 It is a graph showing the efficiency in the power amplifier circuit according to the comparative example.

[0027] Fig.14 is a graph showing the gain in the power amplifier circuit according to the comparative example.

[0028] Description of Reference Numerals

[0029] 10, 10A, 10Z...power amplifier circuit, 11...transistor, 21, 21Z...first termination circuit, 31, 31Z...second termination circuit, 41...third termination circuit, 51, 611, 612, 613...attenuation inductance element, 61...variable inductor section, L, L1...loop. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same reference numerals are given to the same elements, and repeated descriptions are omitted as much as possible.

[0031] A power amplifier circuit 10 according to the first embodiment will be described. Figure 1 2 shows a circuit diagram of the power amplifier circuit 10. The power amplifier circuit 10 includes a transistor 11, capacitors 12 and 13, pads 14 and 15, a first termination circuit 21, a second termination circuit 31, and a third termination circuit 41.

[0032] The base of transistor 11 is connected to capacitor 12. The collector of transistor 11 is connected to pad 14. The emitter of transistor 11 is grounded. Transistor 11 is supplied with power supply voltage Vcc controlled by a control circuit (not shown) according to the amplitude of input signal RFin through pad 14.

[0033] An input signal RFin is supplied from one end of the capacitor 12. One end of the capacitor 13 is connected to the pad 15, and the other end is connected to the third termination circuit 41. The capacitors 12 and 13 are provided to extract an AC component from an RF signal.

[0034] The pads 14 and 15 are provided to connect the power amplifier circuit 10 to the outside.

[0035] The first termination circuit 21 is provided at a subsequent stage of the transistor 11. The second termination circuit 31 is provided at a subsequent stage of the transistor 11. The third termination circuit 41 is provided at a subsequent stage of the transistor 11.

[0036] The first termination circuit 21 includes an inductor 211, a capacitor 212, and an inductor 213. One end of the inductor 211 is connected to the collector of the transistor 11. One end of the capacitor 212 is connected to the other end of the inductor 211. One end of the inductor 213 is connected to the other end of the capacitor 212. The other end of the inductor 213 is connected to the ground. In addition, the connection relationship between the capacitor and the inductor may be reversed.

[0037] As an example, the first termination circuit 21 performs impedance mismatching for the second harmonic component among the harmonic components included in the RF signal output from the collector of the transistor 11. By performing impedance mismatching, the second harmonic component is not output from RFout.

[0038] In addition, the frequency of the RF signal amplified by the power amplifier circuit 10, that is, twice the frequency between the lowest frequency and the highest frequency of the transmission frequency, is defined as the "second harmonic component". The frequency of the RF signal amplified by the power amplifier circuit 10, that is, three times the frequency between the lowest frequency and the highest frequency of the transmission frequency, is defined as the "third harmonic component". The higher harmonic components after the fourth harmonic component are defined in the same way.

[0039] More specifically, the first termination circuit 21 functions to reflect the second harmonic component. The second harmonic component reflected by the first termination circuit 21 is synthesized with the second harmonic component output from the transistor 11 to generate a standing wave. As a result, the second harmonic component is not output from the pad 15. By preventing the second harmonic component from being output from the pad 15, the second harmonic component of the output signal RFout can be attenuated.

[0040] The second termination circuit 31 includes a capacitor 312 and an inductor 313. One end of the capacitor 312 is connected to the other end of the inductor 211. One end of the inductor 313 is connected to the other end of the capacitor 312. The other end of the inductor 313 is connected to the ground. In addition, the connection relationship between the capacitor and the inductor may be reversed.

[0041] The second termination circuit 31 functions to reflect the third harmonic component among the harmonic components included in the RF signal, as in the first termination circuit 21, so that the third harmonic component is not output from the pad 15. Therefore, the third harmonic component of the output signal RFout can be attenuated.

[0042] The third termination circuit 41 includes an inductance element 411, a capacitance element 412, and an inductance element 413. One end of the inductance element 411 is connected to the other end of the inductance element 211. The other end of the inductance element 411 is connected to one end of the capacitance element 13. One end of the capacitance element 412 is connected to the other end of the inductance element 411. One end of the inductance element 413 is connected to the other end of the capacitance element 412. The other end of the inductance element 413 is connected to the ground. In addition, the connection relationship between the capacitance element and the inductance element may be reversed.

[0043] The third termination circuit 41 functions to reflect the fourth harmonic component among the harmonic components included in the RF signal, as in the case of the first termination circuit 21, so that the fourth harmonic component is not output from the pad 15. Therefore, the fourth harmonic component of the output signal RFout can be attenuated.

[0044] The input signal RFin input to the power amplifier circuit 10 is amplified by the transistor 11. The second harmonic component of the fundamental wave in the amplified signal is attenuated by the first termination circuit 21. The third harmonic component of the fundamental wave is attenuated by the second termination circuit 31. The fourth harmonic component of the fundamental wave is attenuated by the third termination circuit 41.

[0045] Figure 2 1 is a Smith chart showing the impedance viewed from the collector of the transistor 11 in the power amplifier circuit 10. The Smith chart is standardized with respect to a specific impedance. The Smith chart is drawn based on the parameters described below.

[0046] As an example, the inductance of the inductance element 211 is set to 0.4 nH, the capacitance of the capacitance element 212 is set to 8 pF, and the inductance of the inductance element 213 is set to 1.5 nH. The capacitance of the capacitance element 312 is set to 8 pF, and the inductance of the inductance element 313 is set to 0.9 nH.

[0047] As an example, the inductance of the inductance element 411 is set to 4.3 nH, the capacitance of the capacitance element 412 is set to 8.6 pF, and the inductance of the inductance element 413 is set to 0.4 nH. The capacitance of the capacitance element 13 is set to 27 pF.

[0048] Regarding the power amplifier circuit 10, the frequency is changed from 100 MHz to 5 GHz, thereby describing Figure 2 The Smith chart shown. Figure 2 As an example, a fundamental frequency band f0 from 663 MHz to 748 MHz, a second harmonic frequency band 2f0 from 1.326 GHz to 1.496 GHz, and a third harmonic frequency band 3f0 from 1.989 GHz to 2.244 GHz are shown by bold lines.

[0049] exist Figure 2 It can be seen that in the fundamental frequency band f0, the impedance is located near the center of the Smith chart and is matched with the standardized impedance.

[0050] In addition, it can be seen that the second harmonic band 2f0 and the third harmonic band 3f0 are located away from the center of the Smith chart, and the standardized impedance is not matched in each band. The closer to the outer side of the Smith chart, the greater the reflection coefficient at that frequency. The reflection coefficient here is Figure 1 Shown is the reflection coefficient S11 observed from the collector of the transistor 11.

[0051] exist Figure 2 In the Smith chart, the impedance changes toward the center of the Smith chart from the second harmonic band 2f0 to the third harmonic band 3f0, and the loop L is drawn once to reach the third harmonic band 3f0.

[0052] The impedance moves from the second harmonic frequency band 2f0 to the third harmonic frequency band 3f0 to match, and changes so as not to match again when exceeding a certain frequency, thereby drawing a loop L. In the present embodiment, such a change in impedance is called "resonance." That is, the first termination circuit 21 and the second termination circuit 31 have a characteristic of resonating with respect to a radio frequency signal having a frequency between the frequency of the second harmonic component and the frequency of the third harmonic component.

[0053] By generating resonance, the relative positions of the second harmonic band 2f0 and the third harmonic band 3f0 on the Smith chart can be adjusted. Adjusting the impedance so that the relative positions of the impedances on the Smith chart are close means reducing the phase difference between the impedance in the second harmonic band 2f0 and the impedance in the third harmonic band 3f0.

[0054] exist Figure 2 In the Smith chart, the phase Φ2 of the frequency with respect to the center value of the second harmonic frequency band 2f0 is about 140 degrees, and the phase Φ3 of the frequency with respect to the center value of the third harmonic frequency band 3f0 is about 90 degrees.

[0055] Regarding the frequency characteristics of the power amplifier circuit 10, Fig.10 A power amplifier circuit 10Z shown as a comparative example is used for comparison.

[0056] The power amplifier circuit 10Z includes a transistor 11 , capacitors 12 and 13 , pads 14 and 15 , a first termination circuit 21Z, and a second termination circuit 31Z.

[0057] The first termination circuit 21Z includes an inductance element 211Z, a capacitance element 212Z, an inductance element 213Z, a capacitance element 214Z, and an inductance element 215Z. The first termination circuit 21Z attenuates the second harmonic component among the harmonic components included in the RF signal, similarly to the first termination circuit 21 .

[0058] The second termination circuit 31Z includes an inductance element 311Z, a capacitance element 312Z, and an inductance element 313Z. The second termination circuit 31Z attenuates the third harmonic component among the harmonic components included in the RF signal, similarly to the second termination circuit 31 .

[0059] Fig.11 1 is a Smith chart showing the impedance viewed from the collector of the transistor 11 in the power amplifier circuit 10Z. The Smith chart is standardized with a specific impedance. The Smith chart is drawn based on the parameters described below.

[0060] As an example, the inductance of the inductance element 211Z is set to 0.4 nH, the capacitance of the capacitance element 212Z is ​​set to 8 pF, the inductance of the inductance element 213Z is set to 1.7 nH, the capacitance of the capacitance element 214Z is set to 1.7 nH, and the inductance of the inductance element 215Z is set to 1.7 nH.

[0061] As an example, the inductance of the inductance element 311Z is set to 4.3 nH, the capacitance of the capacitance element 312Z is ​​set to 8.6 pF, and the inductance of the inductance element 313Z is set to 0.62 nH. The capacitance of the capacitance element 13 is set to 27 pF.

[0062] In the power amplifier circuit 10Z, the frequency is changed from 100 MHz to 5 GHz, thereby describing Fig.11 The Smith chart shown. Fig.11 In the Smith chart, the fundamental frequency band f0, the second harmonic frequency band 2f0, and the third harmonic frequency band 3f0 are also shown by thick lines.

[0063] exist Fig.11 In the Smith chart, the line showing the frequency characteristics of the impedance does not draw a loop from the second harmonic band 2f0 to the third harmonic band 3f0. Therefore, it can be seen that no resonance occurs.

[0064] Reference Figure 3 For Figure 2 The attenuation of the higher harmonic components in the power amplifier circuit 10 having the impedance characteristics shown in FIG. Figure 3 , the relationship between insertion loss and frequency in the power amplifier circuit 10 is shown. The fundamental frequency band f0, the second harmonic frequency band 2f0, the third harmonic frequency band 3f0, and the fourth harmonic frequency band 4f0 from 2.652 GHz to 2.992 GHz are shown by bold lines.

[0065] The insertion loss in the fundamental frequency band f0 is small. This is because Figure 2 As shown, matching is performed with impedance in the fundamental frequency band f0.

[0066] The insertion loss is large in the second harmonic band 2f0 and the third harmonic band 3f0. That is, the signals in the second harmonic band 2f0 and the third harmonic band 3f0 are attenuated. This is because Figure 2 As shown, the impedances are mismatched in the second harmonic band 2f0 and the third harmonic band 3f0. Therefore, the second harmonic component and the third harmonic component are reflected by the first termination circuit 21 and the second termination circuit 31, thereby causing attenuation.

[0067] The insertion loss is also large in the fourth harmonic band 4f0. That is, the signal in the fourth harmonic band 4f0 is attenuated. This is the attenuation caused by the third termination circuit 41 reflecting the fourth harmonic component.

[0068] exist Fig.12 , the relationship between insertion loss and frequency in the power amplifier circuit 10Z is shown. In the fundamental frequency band f0, the second harmonic frequency band 2f0, and the third harmonic frequency band 3f0, the same as the power amplifier circuit 10. In the fourth harmonic frequency band 4f0, since the power amplifier circuit 10Z does not have the third termination circuit 41, no Figure 3 That kind of decay.

[0069] Next, refer to Figure 4 as well as Figure 5 The efficiency of the power amplifier circuit 10 will be described. Figure 4 , the relationship between the output power of the collector of the power amplifier circuit 10 and the efficiency of the power amplifier circuit 10 is shown. Figure 4 The curves E1, E2, E3, and E4 are curves showing the efficiency of the transistor 11 at different power supply voltages. The power amplifier circuit 10 performs ET control, and thus can utilize the peak value of the efficiency at each power supply voltage supplied to the transistor 11. Figure 4 Curve ETe shows the efficiency of the power amplifier circuit 10.

[0070] In the power amplifier circuit 10, when the output power is 20 dBm, the efficiency is 48%, when the output power is 34 dBm, the efficiency is 60%, and the saturation efficiency is 62%.

[0071] The power amplifier circuit 10 and the power amplifier circuit 10Z are compared in terms of efficiency. Fig.13 In the figure, it is shown that Figure 4 The relationship between the efficiency and the output power in the power amplifier circuit 10Z when ET control is performed under the same conditions.

[0072] In the power amplifier circuit 10Z, when the output power is 20 dBm, the efficiency is 44%. When the output power is 34 dBm, the efficiency is 58%. The saturation efficiency is 60%. It can be seen that the efficiency of the power amplifier circuit 10 to which the present invention is applied is higher when the output power is 20 dBm and 34 dBm.

[0073] Reference Figure 5 as well as Fig.14 The reason why the efficiency of the power amplifier circuit 10 is high will be described. Figure 5 is a graph showing the relationship between the output power and the gain of the power amplifier circuit 10. Figure 5 In, with Figure 4 The gains of the transistor 11 at the power supply voltages corresponding to the curves E1, E2, E3, and E4 in FIG. 1 are respectively shown by the curves G1, G2, G3, and G4.

[0074] exist Figure 5 In FIG. 1 , the gain when ET control is performed is shown as ETg. By ET control, the gain of the power amplifier circuit 10 is set to a predetermined value for various output powers.

[0075] exist Figure 5 In FIG. 1 , among the relationships between the gain and the output power of the transistor 11 at various power supply voltages, the combination of the output power and the gain with the highest efficiency is plotted as points. In addition, an approximate curve ME of these points is shown.

[0076] exist Fig.14 The relationship between the output power and gain of the power amplifier circuit 10Z is shown in FIG. Fig.14 The point with the highest efficiency and the approximate curve ME deviate upward from the curve ETg in the region where the output power is higher than 30 dBm. In this case, the power amplifier circuit 10Z cannot operate at the point with the highest efficiency.

[0077] In the power amplifier circuit 10 , by making the impedance of the second harmonic band 2f0 and the impedance of the third harmonic band 3f0 close to each other, the point of maximum efficiency is located near the curve ETg in a region where the output power is high.

[0078] By locating the point with the highest efficiency near the curve ETg, the power amplifier circuit 10 can be operated at the point with the highest efficiency even in the case of high output power such as 34 dBm. Therefore, the power amplifier circuit 10 can efficiently amplify the power when performing ET control to amplify the RF signal.

[0079] In the first embodiment, the first termination circuit 21, the second termination circuit 31, and the third termination circuit 41 are connected in order from the transistor 11, but the order of the first termination circuit 21, the second termination circuit 31, and the third termination circuit 41 may be reversed. For example, the second termination circuit 31, the first termination circuit 21, and the third termination circuit 41 may be connected in order from the transistor 11.

[0080] A power amplifier circuit 10A according to a second embodiment will be described. In the second embodiment and thereafter, descriptions of matters common to the first embodiment will be omitted, and only differences will be described. In particular, similar effects based on similar structures will not be mentioned one by one in each embodiment.

[0081] like Figure 6 As shown in FIG. 1 , the power amplifier circuit 10A according to the second embodiment is obtained by further providing a decrement inductance element 51 in the power amplifier circuit 10 according to the first embodiment.

[0082] One end of the attenuation inductance element 51 is connected to the first termination circuit 21 and the second termination circuit 31, and the other end is connected to the ground. More specifically, one end of the attenuation inductance element 51 is connected to the other end of the inductance element 213 and the other end of the inductance element 313. The other end of the attenuation inductance element 51 is connected to the ground. The attenuation inductance element 51 is provided to attenuate the second harmonic component. The attenuation inductance element 51 is formed of, for example, a microstrip line.

[0083] Figure 7 1 is a Smith chart showing the impedance observed from the collector of the transistor 11 in the power amplifier circuit 10A. The Smith chart is normalized with a specific impedance. The Smith chart plots the same components as those of the power amplifier circuit 10 according to the first embodiment using the same parameters. As an example, the inductance of the damping inductance element 51 is set to 0.2 nH.

[0084] In the power amplifier circuit 10A, a loop L1 is also generated on the line showing the frequency characteristic of impedance from the second harmonic band 2f0 to the third harmonic band 3f0. That is, resonance is also generated in the power amplifier circuit 10A.

[0085] Figure 8 Shown with Figure 7 The impedance characteristics of the power amplifier circuit 10A shown in FIG. 1 show the relationship between insertion loss and frequency in the power amplifier circuit 10. The fundamental frequency band f0, the second harmonic frequency band 2f0, the third harmonic frequency band 3f0, and the fourth harmonic frequency band 4f0 from 2.652 GHz to 2.992 GHz are shown in bold lines.

[0086] exist Figure 8It can be seen that through the attenuation inductor element 51, the signal of the second harmonic band 2f0 is Figure 3 In this way, the second harmonic component can be reduced while forming a loop L1 on the line showing the frequency characteristic of the impedance. In the power amplifier circuit 10A, a loop L1 can also be formed on the line showing the frequency characteristic of the impedance, so that the efficiency when performing ET control can be improved.

[0087] A power amplifier circuit 10B according to the third embodiment will be described. In the power amplifier circuit 10B, Fig. 9 As shown in FIG. 1 , a variable inductor unit 61 is provided between the first termination circuit 21 and the second termination circuit 31 and the ground.

[0088] The variable inductor unit 61 includes damping inductance elements 611 , 612 , and 613 and a switching element 614 .

[0089] One end of each of the attenuation inductance elements 611, 612, and 613 is connected to the ground. The other end of each of the attenuation inductance elements 611, 612, and 613 is connected to the switch element 614. The inductances of the attenuation inductance elements 612, 613, and 614 are different from each other.

[0090] The switch element 614 is provided between the first termination circuit 21 and the second termination circuit 31 and the attenuation inductance elements 611, 612, and 613. The switch element 614 connects the first termination circuit 21 and the second termination circuit 31 to the other end of the attenuation inductance element 611, 612, or 613 based on the frequency of the input signal RFin. The switch element 611 switches the connection destination by, for example, inputting a control signal based on the frequency of the input signal RFin from the outside.

[0091] The impedance observed from the collector of the transistor 11 is changed by connecting the first termination circuit 21 and the second termination circuit 31 to the attenuation inductance element 611, 612 or 613 having different inductances by using the switch element 614. Based on the frequency of the input signal RFin, the impedance observed from the collector of the transistor 11 is changed to a value suitable for attenuation of the second harmonic component at each frequency, whereby the second harmonic component is appropriately attenuated.

[0092] The variable inductor unit 61 changes the impedance so that the second harmonic component of each frequency of the input signal RFin is reduced and a line showing the frequency characteristic of the impedance viewed from the collector of the transistor 11 forms a loop. This can improve the efficiency when performing ET control. Fig. 9 In the structure of , the variable inductor section is composed of three attenuation inductance elements. The number of attenuation inductance elements constituting the variable inductor section is not limited to three, and may be two, four, or n.

[0093] The above is a description of an exemplary embodiment of the present invention. The power amplifier circuit 10 involved in this embodiment includes: a transistor 11, a power supply voltage Vcc that varies according to the envelope of the amplitude of the radio frequency signal input to the base is supplied to the collector, and an amplified signal after the radio frequency signal is amplified is output from the collector; a first termination circuit 21 that is provided at the rear stage of the transistor 11 to attenuate the second harmonic component of the amplified signal; and a second termination circuit 31 that is provided at the rear stage of the transistor 11 to attenuate the third harmonic component of the amplified signal. The first termination circuit 21 and the second termination circuit 31 have the following characteristics, that is, they resonate with respect to a radio frequency signal having a frequency between the frequency of the second harmonic component and the frequency of the third harmonic component.

[0094] Since the first termination circuit 21 and the second termination circuit 31 have characteristics of resonating with respect to a radio frequency signal having a frequency between the second harmonic component and the third harmonic component, the impedance with respect to the second harmonic component and the third harmonic component can be adjusted.

[0095] By adjusting the impedance for the second harmonic component and the third harmonic component, the transistor 11 can be operated at the most efficient operating point for each power supply voltage Vcc. Therefore, the power amplifier circuit 10 can efficiently amplify power when performing envelope tracking control to amplify the radio frequency signal.

[0096] The power amplifier circuit 10A further includes a damping inductance element 51 having one end connected to the first termination circuit 21 and the second termination circuit 31 and the other end connected to the ground.

[0097] This makes it possible to adjust the impedance for the second harmonic component and the third harmonic component while ensuring attenuation of the second harmonic component. The power amplifier circuit 10A can also efficiently amplify power in ET control.

[0098] The power amplifier circuit 10B further includes a variable inductor section 61 disposed between the first termination circuit 21 and the second termination circuit 31 and the ground. The variable inductor section 61 includes: attenuation inductance elements 611, 612, and 613, one end of which is connected to the ground; and a switch element 614, which connects the first termination circuit 21 and the second termination circuit 31 to the other end of any one of the attenuation inductance elements 611, 612, and 613 based on the frequency of the radio frequency signal.

[0099] Thus, even for radio frequency signals of different frequencies, the impedance for the second harmonic component and the third harmonic component can be adjusted at each frequency while ensuring the attenuation of the second harmonic component. The power amplifier circuit 10B can also efficiently amplify power in ET control.

[0100] In the power amplifier circuit 10, the first termination circuit 21 includes: an inductor element 211, one end of which is connected to the collector of the transistor 11; a capacitor element 212, one end of which is connected to the other end of the inductor element 211; and an inductor element 213, one end of which is connected to the other end of the capacitor element 212 and is arranged between the capacitor element 212 and the ground. The second termination circuit 31 includes: a capacitor element 312, one end of which is connected to the other end of the inductor element 211; and an inductor element 313, one end of which is connected to the other end of the capacitor element 312 and is arranged between the capacitor element 312 and the ground.

[0101] The impedance to the second harmonic component and the third harmonic component can be adjusted by adjusting the inductance of the inductance element 213 and the inductance element 313. That is, by appropriately changing the inductance of the inductance element 213 and the inductance element 313, the power can be amplified efficiently.

[0102] The power amplifier circuit 10 further includes a third termination circuit 41 that is provided at a subsequent stage of the transistor 11 and that attenuates the fourth harmonic component of the amplified signal. This can suppress the fourth harmonic component from being included in the output signal RFout.

[0103] In addition, each embodiment described above is used to make the present invention easy to understand, and is not used to limit and explain the present invention. The present invention can be changed / improved without departing from its main purpose, and its equivalent is also included in the present invention. That is, the embodiment to which the technical personnel in this field appropriately applies design changes to each embodiment, as long as it has the features of the present invention, is also included in the scope of the present invention. For example, each element and its configuration, material, condition, shape, size, etc. possessed by each embodiment are not limited to the illustrated content, and can be appropriately changed. In addition, each embodiment is illustrative, and it is self-evident that partial replacement or combination of the structure shown in different embodiments can be performed, and these are also included in the scope of the present invention as long as they include the features of the present invention.

Claims

1. A power amplifier circuit, comprising: a transistor having a collector supplied with a power supply voltage that varies according to an envelope of the amplitude of a radio frequency signal input to a base, and outputting an amplified signal obtained by amplifying the radio frequency signal from the collector; a first termination circuit, provided at a subsequent stage of the transistor, for attenuating a second harmonic component among higher harmonic components of the amplified signal; and The second termination circuit is provided at the subsequent stage of the transistor to attenuate the third harmonic component among the higher harmonic components of the amplified signal. The first termination circuit and the second termination circuit have a characteristic of resonating with respect to a radio frequency signal having a frequency between a frequency of a second harmonic component and a frequency of a third harmonic component.

2. The power amplifier circuit according to claim 1, wherein: The device further includes a damping inductance element having one end connected to the first termination circuit and the second termination circuit and the other end connected to the ground.

3. The power amplifier circuit according to claim 1, wherein: The invention further comprises: a variable inductor unit provided between the first termination circuit and the second termination circuit and ground; The variable inductor unit includes: A plurality of attenuation inductance elements, one end of which is connected to the ground; and The switch element connects the first termination circuit and the second termination circuit to the other end of any one of the plurality of attenuation inductance elements based on the frequency of the radio frequency signal.

4. The power amplifier circuit according to any one of claims 1 to 3, wherein: The first termination circuit comprises: a first inductor element, one end of which is connected to the collector of the transistor; a first capacitive element having one end connected to the other end of the first inductive element; and a second inductor element having one end connected to the other end of the first capacitive element and arranged between the first capacitive element and the ground; The second termination circuit has: a second capacitor element, one end of which is connected to the other end of the first inductor element; and The third inductance element has one end connected to the other end of the second capacitance element and is disposed between the second capacitance element and the ground.

5. The power amplifier circuit according to any one of claims 1 to 3, wherein: The present invention further comprises: a third termination circuit provided at a subsequent stage of the transistor, and attenuating a fourth harmonic component of the amplified signal.

6. The power amplifier circuit according to claim 4, wherein: The present invention further comprises: a third termination circuit provided at a subsequent stage of the transistor, and attenuating a fourth harmonic component of the amplified signal.

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