High-frequency amplifier

Abstract

The high-frequency amplifier (30) includes a carrier amplifier (11) that amplifies a first signal, a peak amplifier (12) that amplifies a second signal, a first matching circuit (33) connected to the output terminal of the carrier amplifier (11), a second matching circuit (36) connected to the output terminal of the peak amplifier (12), and a first transmission line (40) connected between the first matching circuit (33) and the second matching circuit (36) and having an electrical length of 1 / 4 wavelength less than the center frequency of a specified frequency band. The parallel inductors (35) and (38) that form one end of the first matching circuit (33) and the second matching circuit (36) are grounded, and the phase rotation they bring is opposite to the phase rotation brought by the first transmission line (40).

Description

Technical Field

[0001] The present disclosure relates to high-frequency amplifiers, and particularly to high-frequency amplifiers typified by Doherty amplifiers. Background Art

[0002] As a high-efficiency high-frequency amplifier used for wireless communication or the like, a Doherty amplifier is known which is constituted by combining a carrier amplifier that performs class-AB operation or class-B operation and a peak amplifier that performs class-C operation. In the Doherty amplifier, in an operation region where the output power is low, only the carrier amplifier operates, and in an operation region where the output power is high, both the carrier amplifier and the peak amplifier operate, and the output signals of the carrier amplifier and the peak amplifier are combined.

[0003] For the combination of output signals, in the Doherty amplifier, a first transmission line having an electrical length of 1 / 4 wavelength of the center frequency in the communication band is connected between the output terminal of the carrier amplifier and the output terminal of the peak amplifier. Here, as problems of using the first transmission line having a 1 / 4 wavelength, a reduction in broadband characteristics due to dispersion of the load impedance of the carrier amplifier, a reduction in efficiency due to an increase in high-frequency power loss, and an increase in the size of the circuit due to the lengthening of the transmission line can be cited. In addition, the "load impedance" of a certain circuit element is the impedance observed from the circuit element toward the output side (that is, the load side). Further, "dispersion" means frequency dependence, and "dispersion" means that the frequency dependence becomes large.

[0004] Therefore, conventionally, in order to achieve broadbandization of the Doherty amplifier, various techniques have been proposed (for example, refer to Patent Document 1).

[0005] In the technique of Patent Document 1, a second transmission line having an electrical length of 1 / 2 wavelength of the center frequency in the communication band is connected between the first transmission line and the output terminal of the peak amplifier. Thereby, in the operation region where the output power of the Doherty amplifier is low and the peak amplifier does not operate, the frequency characteristics of the load impedance of the carrier amplifier are compensated, and the broadband characteristics of the Doherty amplifier are improved.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014-197755 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] However, in the technology of Patent Document 1, in the high output power operation region of the Doherty amplifier that operates both the carrier amplifier and the peak amplifier, since the output signal of the carrier amplifier does not flow through the second transmission line, the frequency characteristics of the load impedance of the carrier amplifier are not compensated. Therefore, in such a high output power operation region, there is still a problem in the reduction of the broadband characteristics of the Doherty amplifier. In addition, in the technology of Patent Document 1, there remain problems in the reduction of the efficiency of the Doherty amplifier and the increase in the size of the circuit. In addition, the "efficiency" of the amplifier refers to the power conversion efficiency (that is, the ratio of the output power to the input power).

[0011] Therefore, an object of the present disclosure is to provide a high-frequency amplifier that is more broadband, efficient, and compact than the prior art.

[0012] Means for Solving the Problem

[0013] In order to achieve the above object, a high-frequency amplifier according to an aspect of the present disclosure is a high-frequency amplifier that amplifies a first signal and a second signal in a predetermined frequency band and outputs a signal from an output terminal, and includes: a first amplifier that amplifies the first signal; a second amplifier that amplifies the second signal; a first matching circuit connected to an output terminal of the first amplifier; a second matching circuit connected to an output terminal of the second amplifier; a first transmission line connected between an output terminal of the first matching circuit and an output terminal of the second matching circuit and having an electrical length less than 1 / 4 wavelength of the center frequency of the predetermined frequency band; a second transmission line connected to an input terminal of one of the first amplifier and the second amplifier and having an electrical length less than 1 / 4 wavelength of the center frequency of the predetermined frequency band; and a third transmission line connected between one end of the first transmission line and the output terminal and having an electrical length of 1 / 4 wavelength of the center frequency of the predetermined frequency band, and the phase rotation caused by the first matching circuit or the second matching circuit connected to the output terminal of the other of the first amplifier and the second amplifier is in the opposite direction to the phase rotation caused by the first transmission line.

[0014] In addition, in order to achieve the above object, a high-frequency amplifier according to another aspect of the present disclosure is a high-frequency amplifier that amplifies a first signal and a second signal in a specified frequency band and outputs a signal from an output terminal, and includes: a substrate; one or two semiconductor chips mounted on the substrate; a first amplifier formed on the semiconductor chip for amplifying the first signal; a second amplifier formed on the semiconductor chip for amplifying the second signal; an eighth transmission line formed on the semiconductor chip, one end of which is connected to an output terminal of the first amplifier; a ninth transmission line formed on the semiconductor chip, one end of which is connected to an output terminal of the second amplifier; a first capacitor formed on the semiconductor chip; a second capacitor formed on the semiconductor chip; a fourth transmission line formed on the substrate, one end of which is connected to the other end of the eighth transmission line; a fifth transmission line formed on the substrate, one end of which is connected to the other end of the ninth transmission line; a first transmission line formed on the substrate, connected between one end of the fourth transmission line and one end of the fifth transmission line and having an electrical length less than 1 / 4 wavelength of the center frequency of the specified frequency band; a second transmission line connected to an input terminal of one of the first amplifier or the second amplifier and having an electrical length less than 1 / 4 wavelength of the center frequency of the specified frequency band; and a third transmission line connected between one end of the first transmission line and the output terminal and having an electrical length of 1 / 4 wavelength of the center frequency of the specified frequency band, the other end of the fourth transmission line being connected to the first capacitor, and the other end of the fifth transmission line being connected to the second capacitor.

[0015] Advantages of the Invention

[0016] According to the present disclosure, a high-frequency amplifier with a wider bandwidth, higher efficiency, and smaller size is provided compared to the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a circuit diagram of a high-frequency amplifier according to a comparative example.

[0018] Figure 2 is a Smith chart showing impedance transformation in the high-frequency amplifier according to the comparative example.

[0019] Figure 3 is a graph showing the phase angle of a matching circuit included in the high-frequency amplifier according to the comparative example.

[0020] Figure 4A is a Smith chart showing Zc11 when the PA is turned on in the high-frequency amplifier according to the comparative example.

[0021] Figure 4BIt is a diagram showing the frequency characteristics of the efficiency when the PA is turned on in the high-frequency amplifier related to the comparative example.

[0022] Figure 5A It is a Smith chart of Zc11 when the PA is turned off in the high-frequency amplifier related to the comparative example.

[0023] Figure 5B It is a diagram showing the frequency characteristics of the efficiency when the PA is turned off in the high-frequency amplifier related to the comparative example.

[0024] Figure 6 It is a circuit diagram of the high-frequency amplifier related to Embodiment 1.

[0025] Figure 7 It is a Smith chart showing the impedance transformation in the high-frequency amplifier related to Embodiment 1.

[0026] Figure 8 It is a diagram showing the phase angle of the matching circuit included in the high-frequency amplifier related to Embodiment 1.

[0027] Figure 9A It is a Smith chart of Zc21 when the PA is turned on in the high-frequency amplifier related to Embodiment 1.

[0028] Figure 9B It is a diagram showing the frequency characteristics of the efficiency when the PA is turned on in the high-frequency amplifier related to Embodiment 1.

[0029] Figure 10A It is a Smith chart of Zc21 when the PA is turned off in the high-frequency amplifier related to Embodiment 1.

[0030] Figure 10B It is a diagram showing the frequency characteristics of the efficiency when the PA is turned off in the high-frequency amplifier related to Embodiment 1.

[0031] Figure 11 It is a circuit diagram of the high-frequency amplifier related to Embodiment 2.

[0032] Figure 12 It is a circuit diagram of the high-frequency amplifier related to Embodiment 3.

[0033] Figure 13 It is a circuit diagram of the high-frequency amplifier related to Embodiment 4.

[0034] Figure 14 It is a circuit diagram of the high-frequency amplifier related to Embodiment 5.

[0035] Figure 15 It is a Smith chart showing the region of the load impedance in the high-frequency amplifiers related to Embodiments 1 to 5.

[0036] Figure 16 It is a layout diagram of the high-frequency amplifier according to Embodiment 6.

[0037] Figure 17 It is a layout diagram of the high-frequency amplifier according to Embodiment 7.

[0038] Figure 18 It is a layout diagram of semiconductor chips for a carrier amplifier and a peak amplifier included in the high-frequency amplifier according to Embodiment 8.

[0039] Figure 19 It is a layout diagram of the high-frequency amplifier according to Embodiment 8. Detailed Embodiment

[0040] Figure 1 It is a circuit diagram of the high-frequency amplifier 10 according to the comparative example. The arrows in the figure and the reference numerals Zci, Zpi (i is a number) recorded near them indicate the impedance (that is, the load impedance) when viewed from the direction of the arrow from that point. The high-frequency amplifier 10 is a Doherty amplifier that amplifies a first signal and a second signal in a specified frequency band and outputs a signal from the output terminal 22, and includes a carrier amplifier (CA) 11, a peak amplifier (PA) 12, a first matching circuit 13, a second matching circuit 16, a first transmission line 20, a second transmission line 19, a third transmission line 21, an output terminal 22, a first input terminal 23, and a second input terminal 24. The first matching circuit 13 is composed of a series inductor 14 and a shunt capacitor 15 with one end grounded. The second matching circuit 16 is composed of a series inductor 17 and a shunt capacitor 18 with one end grounded. In addition, a "series inductor" is an inductor inserted into the transmission path from the input terminal to the output terminal. Further, a "shunt capacitor" is a capacitor connected between the transmission path from the input terminal to the output terminal and the reference potential (that is, the ground potential). In addition, "grounding" includes not only DC grounding (that is, directly connected to the reference potential) but also high-frequency grounding (that is, connected to the reference potential via a capacitor or the like that becomes a very low impedance in a specified frequency band).

[0041] The carrier amplifier 11 is an amplifier that performs class AB or class B operation and amplifies the first signal, and operates in all regions of the output power of the high-frequency amplifier 10. The peak amplifier 12 is an amplifier that performs class C operation and amplifies the second signal, and operates in the operation region where the output power of the high-frequency amplifier 10 is high.

[0042] The first transmission line 20 is connected between the output terminal of the carrier amplifier 11 and the output terminal of the peak amplifier 12, and has an electrical length of 1 / 4 wavelength of the center frequency of the specified frequency band. The characteristic impedance Zo1 of the first transmission line 20 is 50 Ω. In the high-frequency amplifier 10, since the length of the first transmission line 20 is 1 / 4 wavelength, the dispersion of the load of the carrier amplifier is large and the reduction of the broadband characteristics becomes a problem. In addition, the high-frequency power loss is large and the reduction of the amplifier efficiency becomes a problem. In addition, the increase in the circuit area becomes a problem.

[0043] The second transmission line 19 is connected to the input side of the peak amplifier 12, and is set to have the same electrical length as the first transmission line 20 in order to compensate for the phase rotation caused by the first transmission line 20. In this case, since the length of the second transmission line 19 is 1 / 4 wavelength, the high-frequency power loss is large and the reduction of the amplifier gain becomes a problem. In addition, the increase in the circuit area becomes a problem. In addition, the "phase rotation" based on a certain circuit element is the difference between the phase angle of the signal input to the circuit element and the phase angle of the signal output from the circuit element (that is, (phase angle of the output signal) - (phase angle of the input signal)).

[0044] Now, the connection point of the first transmission line 20 and the second matching circuit 16 is set as the terminal X. The third transmission line 21 is connected between the terminal X and the output terminal 22, and has an electrical length of 1 / 4 wavelength of the center frequency of the specified frequency band. The characteristic impedance Zo3 of the third transmission line 21 is a value (for example, 35.36 Ω) that transforms the impedance of the terminal X (for example, 25 Ω) into the impedance of the output terminal 22 (for example, 50 Ω).

[0045] When the peak amplifier 12 operates (when PA is on), Zc14 is designed to be 50 Ω + j0 Ω. When the peak amplifier 12 does not operate (when PA is off), Zc14 is designed to be 25 Ω + j0 Ω.

[0046] Here, the specific circuit constants in the case where GaN with a total gate width of 3 mm is used for the carrier amplifier 11 and the peak amplifier 12 in the high-frequency amplifier 10 are described. At the center frequency of 4.5 GHz of the specified frequency band, when PA is on, Zc11 = 10 Ω + j43 Ω and Zp11 = 10 Ω + j43 Ω are set, and when PA is off, Zc11 = 6 Ω + j39 Ω is set to obtain the best characteristics. In addition, for the obtained characteristics, use Figure 4A 、 Figure 4B 、 Figure 5A 、 Figure 5BThis will be described later. Therefore, the series inductor 14 is set to 2.2 nH, the parallel capacitor 15 is set to 1.4 pF, the series inductor 17 is set to 2.2 nH, and the parallel capacitor 18 is set to 1.4 pF.

[0047] Figure 2 is a Smith chart showing the impedance transformation in the high-frequency amplifier 10 according to the comparative example. More specifically, it shows the impedance transformation based on the first matching circuit 13 and the first transmission line 20. When Figure 2 the PA shown in (a) is turned on, it is transformed from Zc14 = 50 Ω + j0 Ω to Zc11 = 10 Ω + j43 Ω. Here, regarding the transformation from Zc14 to Zc13, since the characteristic impedance of the first transmission line 20 is 50 Ω, it remains 50 Ω without being transformed. When Figure 2 the PA shown in (b) is turned off, it is transformed from Zc14 = 25 Ω + j0 Ω to Zc11 = 6 Ω + j39 Ω. Through the first transmission line 20, it is transformed from Zc14 = 25 Ω + j0 Ω to Zc13 = 100 Ω + j0 Ω.

[0048] Figure 3 is a diagram showing the phase angles of the matching circuits included in the high-frequency amplifier 10 according to the comparative example. When the PA is turned on, the phase angle of Zc14 is 0°, the phase angle of Zc11 is 189°, and the phase difference between Zc14 and Zc11 is 189° ( Figure 3 solid line in). Similarly, when the PA is turned off, the phase difference between Zc14 and Zc11 is 201° ( Figure 3 dashed line in). Both have a large phase difference exceeding 180°. In such a high-frequency amplifier 10, the phase difference from the terminal X to the carrier amplifier 11 becomes large, so the dispersion of Zc11 becomes a problem (for the dispersion of Zc11, it will be described later). Figure 4A This will be described later.

[0049] Figure 4A is a Smith chart showing the dispersion of Zc11 when the PA in the high-frequency amplifier 10 according to the comparative example is turned on. It shows the dispersion of Zc11 at frequencies 4.3 GHz, 4.5 GHz, and 4.7 GHz. When the dispersion of Zc11 is large, for example, when optimally designed at the center frequency of 4.5 GHz, the characteristics of the high-frequency amplifier 10 deviate from the optimal design at the two end frequencies of 4.3 GHz and 4.7 GHz and deteriorate. If the change amount (ΔZc11) of Zc11 from the frequency of 4.3 GHz to 4.7 GHz is observed, then ΔZc11 = -1.4 Ω + j6.7 Ω.

[0050] Figure 4BRepresents the frequency characteristics of the efficiency when the PA in the high-frequency amplifier 10 related to the comparative example is turned on. An efficiency of 70% is obtained at the center frequency of 4.5 GHz, but at the frequencies of 4.3 GHz and 4.7 GHz at both ends, the efficiency decreases to 60%. The reduction of this characteristic is due to Figure 4A as shown, ΔZc11 is large.

[0051] Figure 5A is a Smith chart showing the dispersion of Zc11 when the PA in the high-frequency amplifier 10 related to the comparative example is turned off. If ΔZc11 from the frequency of 4.3 GHz to 4.7 GHz is observed, ΔZc11 = -1.6 Ω + j8.6 Ω. From Figure 5B , an efficiency of 50% is obtained at the center frequency of 4.5 GHz, but at the frequencies of 4.3 GHz and 4.7 GHz at both ends, the efficiency decreases to 42%. The reduction of this characteristic is due to the large ΔZc11.

[0052] Therefore, the high-frequency amplifier according to one aspect of the present disclosure is a high-frequency amplifier that amplifies a first signal and a second signal in a specified frequency band and outputs a signal from an output terminal, and includes: a first amplifier that amplifies the first signal; a second amplifier that amplifies the second signal; a first matching circuit connected to the output terminal of the first amplifier; a second matching circuit connected to the output terminal of the second amplifier; a first transmission line connected between the output terminal of the first matching circuit and the output terminal of the second matching circuit and having an electrical length less than 1 / 4 wavelength of the center frequency of the specified frequency band; a second transmission line connected to an input terminal of one of the first amplifier and the second amplifier and having an electrical length less than 1 / 4 wavelength of the center frequency of the specified frequency band; and a third transmission line connected between one end of the first transmission line and the output terminal and having an electrical length of 1 / 4 wavelength of the center frequency of the specified frequency band, and the phase rotation based on the first matching circuit or the second matching circuit connected to the output terminal of the other of the first amplifier and the second amplifier is in the opposite direction to the phase rotation based on the first transmission line.

[0053] Thus, since the phase rotation based on the first matching circuit is in the opposite direction to the phase rotation based on the first transmission line, the dispersion of the load impedance of the carrier amplifier is reduced, and it is possible to achieve a wider bandwidth, higher efficiency, and smaller size compared to the prior art.

[0054] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In addition, the embodiments described below all represent a specific example of the present disclosure. The frequencies, impedances, characteristic impedances, constants of circuit elements, materials, etc. shown in the following embodiments are examples and do not limit the gist of the present disclosure. In addition, the drawings are not necessarily drawn precisely. In each drawing, the same reference numerals are given to substantially the same structures, and redundant explanations may be omitted or simplified. The specified frequency band is a frequency band used for communication, for example, a frequency band of 3 THz or less used for wireless communication.

[0055] (Embodiment 1)

[0056] Figure 6 It is a circuit diagram of a high-frequency amplifier 30 according to Embodiment 1. The high-frequency amplifier 30 is a Doherty amplifier that amplifies a first signal and a second signal in a specified frequency band (for example, a frequency band with a center frequency of 4.5 GHz) and outputs a signal from an output terminal 22. It includes: a carrier amplifier 11, which is an example of a first amplifier; a peak amplifier 12, which is an example of a second amplifier; a first matching circuit 33; a second matching circuit 36; a first transmission line 40; a second transmission line 39; a third transmission line 21; an output terminal 22; a first input terminal 23, and a second input terminal 24. The first matching circuit 33 is composed of a series inductor 34 and a shunt inductor 35 grounded at one end. The second matching circuit 36 is composed of a series inductor 37 and a shunt inductor 38 grounded at one end.

[0057] Specifically, the carrier amplifier 11 and the peak amplifier 12 used in the high-frequency amplifier 30 are constituted by a high-frequency amplification device such as a field-effect transistor (FET) or a bipolar junction transistor (BJT) made of GaN, GaAs, SiGe, or Si. In addition, the transmission lines (the first transmission line 40, the second transmission line 39, and the third transmission line 21) are, for example, microstrip lines or striplines, and are constituted by a substrate material for general high-frequency circuits such as semiconductor, ceramic, or resin materials, and a transmission line for transmitting high-frequency signals made of a material such as Cu with excellent electrical characteristics. In an actual circuit, the shunt inductors 35 and 38 are grounded via capacitors for grounding, but the capacitors for grounding are omitted in this figure. In addition, the lines for supplying power from the power source are omitted.

[0058] Hereinafter, regarding the high-frequency amplifier 30 according to the present embodiment, the differences from the high-frequency amplifier 10 according to the comparative example will be mainly described. In the high-frequency amplifier 10 according to the comparative example, the first matching circuit 13 is composed of a series inductor 14 and a shunt capacitor 15 with one end grounded. In contrast, in the high-frequency amplifier 30 according to the present embodiment, the first matching circuit 33 is composed of a series inductor 34 and a shunt inductor 35 with one end grounded. Further, in the high-frequency amplifier 10 according to the comparative example, the second matching circuit 16 is composed of a series inductor 17 and a shunt capacitor 18 with one end grounded. In contrast, in the high-frequency amplifier 30 according to the present embodiment, the second matching circuit 36 is composed of a series inductor 37 and a shunt inductor 38 with one end grounded. Additionally, the "shunt inductor" is an inductor connected between the transmission path from the input terminal to the output terminal and the reference potential (i.e., the ground potential).

[0059] Here, regarding the high-frequency amplifier 30 according to the present embodiment, the specific circuit constants in the case where GaN with a total gate width of 3 mm is used for the carrier amplifier 11 and the peak amplifier 12, respectively (i.e., the same GaN as the high-frequency amplifier 10 according to the comparative example) will be described.

[0060] The conditions for obtaining the best characteristics at a frequency of 4.5 GHz are the same as those of the high-frequency amplifier 10 according to the comparative example. When the PA is on, Zc21 = 10Ω + j43Ω, Zp21 = 10Ω + j43Ω, and when the PA is off, Zc21 = 6Ω + j39Ω. Therefore, the series inductor 34 can be set to 0.82 nH, the shunt inductor 35 can be set to 0.89 nH, the series inductor 37 can be set to 0.82 nH, and the shunt inductor 38 can be set to 0.89 nH. The electrical length of the first transmission line 40 can be set to less than 1 / 4 wavelength instead of 1 / 4 wavelength. Here, it is set to 1 / 10 wavelength. In addition, the second transmission line 39 is set to the same electrical length as the first transmission line 40 in order to compensate for the phase rotation based on the first transmission line 40, that is, the electrical length is set to 1 / 10 wavelength. The characteristic impedances of the first transmission line 40 and the second transmission line 39 are both 50Ω. Since the electrical length of the first transmission line 40 is shorter than 1 / 10 wavelength compared to the comparative example, the dispersion of Zc21 becomes smaller and the broadband characteristics are improved. In addition, the loss of high-frequency power becomes smaller and the efficiency of the amplifier is improved. Furthermore, miniaturization of the circuit becomes possible.

[0061] Figure 7 It is a Smith chart showing the impedance transformation in the high-frequency amplifier 30 according to Embodiment 1. More specifically, it shows the impedance transformation brought about by the first matching circuit 33 and the first transmission line 40. As Figure 7As shown in (a), when PA is turned on, it is transformed from Zc24 = 50Ω + j0Ω to Zc21 = 10Ω + j43Ω. Looking in detail, the transformation from Zc24 to Zc23 is brought about by the first transmission line 40 with a characteristic impedance of 50Ω, so both Zc24 and Zc23 are 50Ω. The transformation from Zc23 to Zc22 is based on the shunt inductor 35 with one end grounded, and it becomes a counterclockwise rotation. Compared with the transformation from Zc13 to Zc12 in (a) of Figure 2 which is clockwise, the direction of rotation of the transformation from Zc23 to Zc22 becomes opposite. In addition, the transformation from Zc22 to Zc21 is brought about by the series inductor 34. Compared with the transformation from Zc12 to Zc11 in (a) of Figure 2 , the inductance of the series inductor 34 becomes smaller from 2.2nH to 0.82H, so the transformation amount of the transformation from Zc22 to Zc21 becomes smaller.

[0062] As Figure 7 shown in (b), when PA is turned off, it is transformed from Zc24 = 25Ω + j0Ω to Zc21 = 6Ω + j39Ω. Looking in detail, the transformation from Zc24 to Zc23 brought about by the first transmission line 40 has a transformation amount that becomes smaller from 1 / 4 wavelength to 1 / 10 wavelength compared with the transformation from Zc14 to Zc13 based on the first transmission line 20 in (b) of Figure 2 . The transformation from Zc23 to Zc22 is brought about by the shunt inductor 35 with one end grounded, and it becomes a counterclockwise rotation. Compared with the transformation from Zc13 to Zc12 shown in (b) of Figure 2 , the transformation from Zc23 to Zc22 becomes a rotation in the opposite direction. In addition, the transformation from Z22 to Z21 is brought about by the series inductor 34, and the transformation amount becomes smaller compared with the transformation from Zc12 to Zc11 in (b) of Figure 2 .

[0063] Figure 8 is a diagram showing the phase angle of the matching circuit included in the high-frequency amplifier 30 according to Embodiment 1. When PA is turned on, the phase difference between Zc24 and Zc21 is only 7° ( Figure 8 solid line). Compared with the phase difference of 189° of the high-frequency amplifier 10 according to the comparative example shown in Figure 3 , it is greatly reduced. In the high-frequency amplifier 10 according to the comparative example, the phase difference brought about by the first transmission line 20 is 90°, and adding the phase difference brought about by the first matching circuit 13, the sum of the phase differences necessarily becomes 90° or more. In contrast, in the high-frequency amplifier 30 according to the present embodiment, the sum of the phase difference based on the first matching circuit 33 and the phase difference based on the first transmission line 40 is less than 90°, which is an obvious difference. The main reason for this will be analyzed below.

[0064] That is, in the high-frequency amplifier 30 according to the present embodiment, the phase difference between Zc24 and Zc23 is 36°, which is significantly reduced compared to the phase difference of 90° between Zc14 and Zc13 in the case of the high-frequency amplifier 10 according to the comparative example. This is the effect of the length of the first transmission line 40 being shortened to 1 / 10 wavelength. The transformation brought about by the first matching circuit 33 is a phase rotation from Zc23 to Zc21, resulting in a phase difference = 20° - 36° = -16°. The phase rotation brought about by the first matching circuit 33 is in the opposite direction to the phase rotation brought about by the first transmission line 40, and has the effect of compensating for the phase difference of the first transmission line 40. Further, if we look in detail, the reason why the phase difference brought about by the first matching circuit 33 becomes negative is that the phase difference brought about by the shunt inductor 35 grounded at one end becomes negative. If we observe the transformation from Zc23 to Zc22, the phase difference is 0° - 36° = -36°. Thus, having a structural element with a phase rotation in the opposite direction to the first transmission line 40 is effective in compensating for the phase difference brought about by the first transmission line 40. The small phase difference between Zc22 and Zc21 reflects the small inductance of the series inductor 37.

[0065] In the same figure, even when the PA is off, in the high-frequency amplifier 30 according to the present embodiment, the phase difference between Zc24 and Zc21 is significantly reduced compared to Figure 2 the phase difference of the high-frequency amplifier 10 according to the comparative example shown ( Figure 8 dashed line). As the reason, similarly to when the PA is on, it can be cited that the first transmission line 40 is shortened, the first matching circuit 33 compensates for the phase difference of the first transmission line 40, the shunt inductor 35 as a structural element of the first matching circuit 33 has a phase rotation in the opposite direction to the phase rotation brought about by the first transmission line 40, and the inductance of the series inductor 37 is small.

[0066] Figure 9A This is a Smith chart showing the dispersion of Zc21 when the PA is on in the high-frequency amplifier 30 according to Embodiment 1. It shows the dispersion of Zc21 at frequencies 4.3 GHz, 4.5 GHz, and 4.7 GHz. Zc21 at each frequency is 9.3 Ω + j41.5 Ω, 10.0 Ω + j43.1 Ω, and 10.7 Ω + j44.6 Ω respectively. If we observe ΔZc21 from frequency 4.3 GHz to 4.7 GHz, then ΔZc21 = 1.4 Ω + j3.1 Ω, and the dispersion is reduced compared to Figure 4A the high-frequency amplifier 10 according to the comparative example shown. The reason is that as Figure 8 shown, the first matching circuit 33 compensates for the phase rotation brought about by the first transmission line 40. That is, the first matching circuit 33 is used to reduce the dispersion of Zc21 brought about by the first transmission line 40.

[0067] Figure 9B It represents the frequency characteristics of the efficiency when the PA in the high-frequency amplifier 30 according to Embodiment 1 is turned on. An efficiency of 72% is obtained at the center frequency of 4.5 GHz. Compared with Figure 4B the comparison example, the efficiency is improved by 2% compared with the high-frequency amplifier 10 according to the comparison example. The reason is that the high-frequency loss is reduced by shortening the first transmission line 40. At the frequencies of 4.3 GHz and 4.7 GHz at both ends, the efficiency of 67% is maintained. As Figure 9A shown, it is the effect of reducing ΔZc21.

[0068] Figure 10A It is a Smith chart showing the dispersion of Zc21 when the PA in the high-frequency amplifier 30 according to Embodiment 1 is turned off. If ΔZc21 from the frequency of 4.3 GHz to 4.7 GHz is observed, then ΔZc21 = 0.5 Ω + j3.3 Ω, and the dispersion is reduced compared with Figure 5A the high-frequency amplifier 10 according to the comparison example shown. Similarly to when the PA is turned on, the first matching circuit 33 is used to reduce the dispersion of Zc21 caused by the first transmission line 40.

[0069] Figure 10B It represents the frequency characteristics of the efficiency when the PA in the high-frequency amplifier 30 according to Embodiment 1 is turned off. An efficiency of 52% is obtained at the center frequency of 4.5 GHz. Compared with Figure 4B the comparison example, the efficiency is improved by 2% compared with the high-frequency amplifier 10 according to the comparison example. The reason is that the high-frequency loss is reduced by shortening the first transmission line 40. At the frequencies of 4.3 GHz and 4.7 GHz at both ends, the efficiency of 48% is also maintained. As Figure 10A shown, it is the effect of reducing ΔZc21.

[0070] In addition, in the above example, the electrical length of the first transmission line 40 is set to 1 / 10 wavelength. However, if the electrical length of the first transmission line 40 is less than 1 / 4 wavelength, the same effect is achieved. As an example, the electrical length of the first transmission line 40 is set to 1 / 8 wavelength, and the other circuit constants are adjusted to the optimum to verify the dispersion of Zc21. If ΔZc21 from the frequency of 4.3 GHz to 4.7 GHz is observed, then for when the PA is turned on, ΔZc21 = 1.2 Ω + j4.5 Ω, and for when the PA is turned off, ΔZc21 = 0.3 Ω + j4.8 Ω. In the case where the electrical length of the first transmission line 40 is set to 1 / 8 wavelength, compared with Figure 4A and Figure 5AThe dispersion of the high-frequency amplifier 10 according to the comparative example shown is also reduced. For the cases where the electrical length of the first transmission line 40 is set to 1 / 10 wavelength, 1 / 8 wavelength, and 1 / 4 wavelength, the respective values of ΔZc21 are summarized in Table 1.

[0071] [Table 1]

[0072]

[0073] By setting the electrical length of the first transmission line 40 to be less than 1 / 4 wavelength, in terms of ΔZc21 when the PA is turned on and when the PA is turned off, compared with the high-frequency amplifier 10 according to the comparative example having the first transmission line 20 with an electrical length of 1 / 4 wavelength, ΔZc21 is reduced. As a result, the high-frequency amplifier 30 according to the present embodiment can achieve a wider bandwidth, higher efficiency, and smaller size compared with the high-frequency amplifier 10 according to the comparative example.

[0074] As described above, the high-frequency amplifier 30 according to the present embodiment is an amplifier that amplifies a first signal and a second signal in a specified frequency band and outputs a signal from the output terminal 22. It includes: a first amplifier that amplifies the first signal; a second amplifier that amplifies the second signal; a first matching circuit 33 connected to the output terminal of the first amplifier; a second matching circuit 36 connected to the output terminal of the second amplifier; a first transmission line 40 connected between the output terminal of the first matching circuit 33 and the output terminal of the second matching circuit 36 and having an electrical length less than 1 / 4 wavelength of the center frequency of the specified frequency band; a second transmission line 39 connected to the input terminal of one of the first amplifier and the second amplifier (in the present embodiment, the second amplifier) and having an electrical length less than 1 / 4 wavelength of the center frequency of the specified frequency band; and a third transmission line 21 connected between one end of the first transmission line 40 and the output terminal 22 and having an electrical length of 1 / 4 wavelength of the center frequency of the specified frequency band, and the phase rotation caused by the first matching circuit 33 or the second matching circuit 36 (in the present embodiment, the first matching circuit 33) connected to the output terminal of the other of the first amplifier and the second amplifier has a direction opposite to the phase rotation caused by the first transmission line 40.

[0075] Accordingly, the electrical length of the first transmission line 40 is less than 1 / 4 wavelength. Therefore, the loss of high-frequency power in the first transmission line 40 is reduced, the efficiency of the high-frequency amplifier 30 is improved, and the high-frequency amplifier 30 can be miniaturized. Furthermore, the phase rotation caused by the first matching circuit 33 or the second matching circuit 36 (in this embodiment, the first matching circuit 33) connected to the output terminal of the other of the first amplifier and the second amplifier is in the opposite direction to the phase rotation caused by the first transmission line 40. Therefore, the phase rotation caused by the first transmission line 40 is compensated (i.e., used to cancel) by the first matching circuit 33 or the second matching circuit 36 (in this embodiment, the first matching circuit 33). Specifically, the sum of the phase rotation amount caused by the first matching circuit 33 or the second matching circuit 36 (in this embodiment, the first matching circuit 33) connected to the output terminal of the other of the first amplifier and the second amplifier and the phase rotation amount caused by the first transmission line 40 is less than 90°. Therefore, the first matching circuit 33 or the second matching circuit 36 (in this embodiment, the first matching circuit 33) connected to the output terminal of the other of the first amplifier and the second amplifier can reduce the frequency dependence (i.e., dispersion) of the impedance when viewed from the output terminal of the first amplifier to the output side caused by the first transmission line 40, and the broadband characteristics of the high-frequency amplifier are improved.

[0076] Here, the first amplifier is the carrier amplifier 11, and the second amplifier is the peak amplifier 12. Accordingly, a Doherty amplifier with a wider bandwidth, higher efficiency, and smaller size than in the prior art is realized.

[0077] In addition, the first matching circuit 33 and the second matching circuit 36 each have a fourth transmission line and a fifth transmission line with one end grounded. Here, at least one (in this embodiment, both) of the fourth transmission line and the fifth transmission line is constituted by an inductor (parallel inductors 35 and 38). Accordingly, the first matching circuit 33 or the second matching circuit 36 (in this embodiment, the first matching circuit 33) that generates a phase rotation in the opposite direction to the phase rotation caused by the first transmission line 40 is simply realized using an inductor.

[0078] Furthermore, the first matching circuit 33 and the second matching circuit 36 each have a series inductor 34 and a series inductor 37. Accordingly, both the first matching circuit 33 and the second matching circuit 36 that generate a phase rotation in the opposite direction to the phase rotation caused by the first transmission line 40 can be constituted by at least two inductors.

[0079] (Embodiment 2)

[0080] Figure 11 is a circuit diagram of the high-frequency amplifier 50 according to Embodiment 2. As withFigure 6 The description will be centered around the differences in the high-frequency amplifier 30 according to Embodiment 1 shown in the figure. In the high-frequency amplifier 50 shown in the same figure, instead of Figure 6 the parallel inductor 35 shown, a fourth transmission line 55 with one end grounded is provided, and similarly, instead of the parallel inductor 38, a fifth transmission line 58 with one end grounded is provided. For the fourth transmission line 55 and the fifth transmission line 58, at a frequency of 4.5 GHz, desired characteristics can be obtained if the line lengths are set to 1 / 15 wavelength respectively. In addition, in the high-frequency amplifier 50 shown in the same figure, instead of Figure 6 the series inductors 34 and 37 shown, an eighth transmission line 54 and a ninth transmission line 57 having equivalent impedance transformation are used respectively. In addition, the fourth transmission line 55, the fifth transmission line 58, the eighth transmission line 54, and the ninth transmission line 57 are all microstrip lines or strip lines in this embodiment.

[0081] The phase rotation caused by the fourth transmission line 55 with one end grounded is equivalent to that of the parallel inductor 35 with one end grounded, and the same transformation as Figure 7 and Figure 8 can be obtained. In this way, the inductor can be treated as a type of transmission line. In addition, the high-frequency amplifier 50 can obtain the same efficiency characteristics as Figure 9A , Figure 9B , Figure 10A and Figure 10B shown.

[0082] As described above, in the high-frequency amplifier 50 according to this embodiment, the first matching circuit 53 and the second matching circuit 56 respectively have a fourth transmission line 55 and a fifth transmission line 58 with one end grounded. As a result, the first matching circuit 53 that generates a phase rotation in the opposite direction to the phase rotation caused by the first transmission line 40 is simply implemented using the fourth transmission line 55 such as a microstrip line.

[0083] (Embodiment 3)

[0084] Figure 12 is the circuit diagram of the high-frequency amplifier 60 according to Embodiment 3. Generally, sometimes the Figure 6 shown high-frequency amplifier 30 is classified as a forward Doherty amplifier, and the Figure 12The high-frequency amplifier 60 shown is divided into a reverse Doherty amplifier. An explanation will be given centering on the differences from the high-frequency amplifier 30. In the same figure, the connection point of the first transmission line 40 and the first matching circuit 33 is set as terminal Y. The third transmission line 21 is connected between terminal Y and the output terminal 22. The second transmission line 39 is connected to the input side of the carrier amplifier 11 and is set to have the same electrical length as the first transmission line 40 in order to compensate for the phase rotation caused by the first transmission line 40.

[0085] Regarding the first transmission line 40, in the conventional reverse Doherty amplifier, a transmission line of 1 / 4 wavelength is required, but in the high-frequency amplifier 60 according to the present embodiment, it can be shortened to less than 1 / 4 wavelength. Furthermore, the second matching circuit 36 compensates for the phase difference of the first transmission line 40, and the shunt inductor 38, one end of which is grounded as a structural element of the second matching circuit 36, has a phase rotation in the opposite direction to the phase rotation caused by the first transmission line 40, and the inductance of the series inductor 37 is smaller than that of the conventional reverse Doherty amplifier. There are the same characteristics as the content described Figure 7 and Figure 8 described above. As a result of these, in the high-frequency amplifier 60, the first matching circuit 33, the second matching circuit 36, the first transmission line 40, and the second transmission line 39 are optimized, so that the same efficiency characteristics as those of Figure 9A , Figure 9B , Figure 10A and Figure 10B shown can be obtained.

[0086] As described above, the high-frequency amplifier 60 according to the present embodiment is a reverse Doherty amplifier. And, similar to Embodiment 1, since the electrical length of the first transmission line 40 is less than 1 / 4 wavelength, the loss of high-frequency power in the first transmission line 40 is small, the efficiency of the high-frequency amplifier 60 is improved, and the high-frequency amplifier 60 can be miniaturized. Furthermore, the phase rotation caused by the first matching circuit 33 or the second matching circuit 36 (in the present embodiment, the second matching circuit 36) connected to the output terminal of the other of the first amplifier and the second amplifier is in the opposite direction to the phase rotation of the first transmission line 40. Therefore, the phase rotation caused by the first transmission line 40 is compensated (that is, eliminated) by the first matching circuit 33 or the second matching circuit 36 (in the present embodiment, the second matching circuit 36). Therefore, the first matching circuit 33 or the second matching circuit 36 (in the present embodiment, the second matching circuit 36) connected to the output terminal of the other of the first amplifier and the second amplifier can reduce the frequency dependence (i.e., dispersion) of the impedance when viewed from the output terminal of the second amplifier to the output side caused by the first transmission line 40, and the broadband characteristics of the high-frequency amplifier are improved.

[0087] (Embodiment 4)

[0088] Figure 13 is a circuit diagram of the high-frequency amplifier 70 according to Embodiment 4. In the high-frequency amplifier 70, the fourth transmission line 55 and the fifth transmission line 58 are respectively connected to the power supply terminal 75 and the power supply terminal 76. A first capacitor 72 for grounding, with one end grounded, is connected between the power supply terminal 75 and the fourth transmission line 55. In addition, a second capacitor 74 for grounding, with one end grounded, is connected between the power supply terminal 76 and the fifth transmission line 58. Thus, with respect to the fourth transmission line 55 and the fifth transmission line 58, one end is grounded at high frequency, so that in the high-frequency amplifier 70, the same characteristics as those of the high-frequency amplifier 30 according to Embodiment 1 can also be obtained. In this way, by using the fourth transmission line 55 and the fifth transmission line 58 for both impedance matching and supplying power from the power supply, miniaturization of the circuit can be achieved.

[0089] As described above, the high-frequency amplifier 70 according to the present embodiment, in addition to the structure of the high-frequency amplifier 50 according to Embodiment 2, further includes a first capacitor 72 for grounding one end of the fourth transmission line 55 and connected between one end of the fourth transmission line 55 and the reference potential, and a second capacitor 74 for grounding one end of the fifth transmission line 58 and connected between one end of the fifth transmission line 58 and the reference potential. Thus, the fourth transmission line 55 and the fifth transmission line 58 are grounded at high frequency, and the high-frequency amplifier 70 can exhibit the same effects as those of the high-frequency amplifier 50 according to Embodiment 2.

[0090] In addition, in the high-frequency amplifier 70 according to the present embodiment, at least one (both in the present embodiment) of the fourth transmission line 55 and the fifth transmission line 58 is used not only for impedance transformation but also for supplying power from the power supply. Thus, the circuit elements required for the high-frequency amplifier 70 can be reduced, and miniaturization of the circuit can be performed.

[0091] (Embodiment 5)

[0092] Figure 14 is a circuit diagram of the high-frequency amplifier 77 according to Embodiment 5. As compared with Figure 13The difference of the high frequency amplifier 70 according to the fourth embodiment shown in FIG. 1 is that in the high frequency amplifier 77, the first power supply inductor 78 is connected between the point S, which is the connection point between the fourth transmission line 55 and the first capacitor 72, and the power supply terminal 75. In the high frequency amplifier 70 according to the fourth embodiment, the length of the fourth transmission line 55 is selected with priority given to impedance matching. When the length of the fourth transmission line 55 is short, leakage of the high frequency signal from the power supply terminal 75 to the power supply side becomes a problem. In this embodiment, as shown in FIG. Figure 14 As shown, leakage of high-frequency signals can be prevented by using the first power supply inductor 78. Similarly, the second power supply inductor 79 is connected between the point S', which is the connection point between the fifth transmission line 58 and the second capacitor 74, and the power supply terminal 76. By using the second power supply inductor 79, leakage of high-frequency signals to the power supply side can be prevented.

[0093] As described above, the high-frequency amplifier 77 according to the present embodiment includes, in addition to the configuration of the high-frequency amplifier 70 according to the fourth embodiment, a first power supply inductor 78 connected between the connection point between the fourth transmission line 55 and the first capacitor 72 and the power supply, and a second power supply inductor 79 connected between the connection point between the fifth transmission line 58 and the second capacitor 74 and the power supply. Thus, leakage of the high-frequency signal from the high-frequency amplifier 77 to the power supply side can be prevented.

[0094] (for load impedance)

[0095] For the purpose of this disclosure, use Figure 15 The Smith chart showing the region of the load impedance in the high frequency amplifier according to the first to fifth embodiments will be described. Here, the description will be made with reference to the first embodiment. Figure 6 The high frequency amplifier 30 shown in FIG. 1 is characterized in that parallel inductors 35 and 38 with one end grounded are used for the first matching circuit 33 and the second matching circuit 36, respectively. The reason why such first matching circuit 33 and second matching circuit 36 ​​can be used is that the load impedance of the carrier amplifier 11 and the peak amplifier 12 is limited to Figure 15 In the case of the matching region (hatched region) shown in FIG. 1 , the matching region (hatched region) is located within the region excluding the circle passing through the point R=50Ω and the short-circuit point (that is, passing through the equal admittance circle of R=50Ω) with the midpoint of the point R=50Ω and the short-circuit point as the center. In the Doherty amplifier studied so far for high-output applications, the load of the amplifier is located within the above circle due to the large size of the transistors used, and the first matching circuit 33 and the second matching circuit 36 ​​provided in the high-frequency amplifier 30 cannot be used.

[0096] In the fifth-generation communication (commonly known as 5G) expected to develop in the future, the number of antennas used in radio base station devices has increased significantly (for example, from 4 in the past to 256). In such a radio base station device, an array antenna is used to output high-frequency signals output from multiple high-frequency amplifiers through beamforming, so each high-frequency amplifier tends to have a lower output. Moreover, the broadband, high efficiency, and miniaturization of the amplifiers used are more important than ever. To solve this problem, the high-frequency amplifier related to the present disclosure is designed.

[0097] Here, the relationship between the reduction in the output of the high-frequency amplifier and the high-frequency amplifier related to the present disclosure will be described in detail. Through the research of the inventors, in the case of using a GaN FET for a high-frequency transistor, in a FET with a total gate width of 5 mm or less, the optimal load clearly enters Figure 15 the possible matching region shown. The saturation power output from a GaN FET with a total gate width of 5 mm is 30 W. When it is used in the carrier amplifier 11 and the peak amplifier 12, the saturation output of the high-frequency amplifier 30 obtained is 60 W, and the high-frequency amplifier 30 can be used as a high-frequency amplifier for a radio base station device for fifth-generation communication. This can be said for the high-frequency amplifiers disclosed in all embodiments of this specification.

[0098] As described above, in the high-frequency amplifier according to this embodiment, at least one of the impedance observed from the output terminal of the first amplifier toward the output side and the impedance observed from the output terminal of the second amplifier toward the output side is outside the constant admittance circle on the Smith chart.

[0099] To satisfy this, the first amplifier and the second amplifier are composed of FETs using GaN, and preferably the maximum high-frequency output of the FET is set to 30 W or less. Thus, the high-frequency amplifier according to the embodiment can be used in a radio base station device for applications such as fifth-generation communication that uses an array antenna to output high-frequency signals.

[0100] (Embodiment 6)

[0101] Figure 16 is a layout diagram of the high-frequency amplifier 80 according to Embodiment 6. The high-frequency amplifier 80 according to this embodiment has the same circuit as Figure 14 the high-frequency amplifier 77 according to Embodiment 5 shown. Therefore, Figure 16 is equivalent to a diagram showing the specific layout on the substrate 80a for the circuit diagram of the high-frequency amplifier 77 according to Figure 14 Embodiment 5 shown.

[0102] Figure 14 and Figure 16 correspond as follows. That is,Figure 14 The eighth transmission line 54 in corresponds to Figure 16 Line AB. Similarly, Figure 14 The fourth transmission line 55 corresponds to Figure 16 In addition, Figure 14 The first transmission line 40 corresponds to Figure 16 Line BX. Figure 14 The first capacitor 72 for grounding is composed of Figure 16 The device capacitor 82 is composed of an element having one end connected to the ground portion 87 . Figure 14 The first power supply inductor 78 corresponds to Figure 16 The two connected devices are the element inductor 85 in the circuit AB and the line CD as an example of the sixth transmission line. Here, by using the line CD together, the inductance of the element inductor 85 can be reduced, and as a result, the Q value of the element inductor 85 can be improved. The output terminal (point P) of the carrier amplifier 11 and the input terminal (point A) of the line AB are connected by a bonding wire. In addition, the carrier amplifier 11 is formed on the semiconductor chip 80b.

[0103] same, Figure 14 The ninth transmission line 57 in corresponds to Figure 16 The line A'B'. Figure 14 The fifth transmission line 58 corresponds to Figure 16 Line B'C'. Figure 14 The second capacitor 74 for grounding corresponds to Figure 16 The element capacitor 84 has one end connected to the ground portion 88 . Figure 14 The second power supply inductor 79 corresponds to Figure 16 The two connected devices are the element inductor 86 in the circuit A'B' and the line C'D' as an example of the seventh transmission line. Here, by using the lines C'D' together, the inductance of the element inductor 86 can be reduced, and as a result, the Q value of the element inductor 86 can be improved. The output terminal (point P') of the peak amplifier 12 and the input terminal (point A') of the line A'B' are connected by a bonding wire. In addition, the peak amplifier 12 is formed on the semiconductor chip 80c.

[0104] from Figure 16It can be seen that in the layout of the high-frequency amplifier 80 according to this embodiment, the configuration from the carrier amplifier 11 to the power supply terminal 75, that is, the configuration of the chip 80b, the line AB corresponding to the eighth transmission line 54, the line BC corresponding to the fourth transmission line 55, the line CD corresponding to the sixth transmission line, the first capacitor 82, and the first power supply inductor 85; and the configuration from the peak amplifier 12 to the power supply terminal 76, that is, the configuration of the chip 80c, the line A'B' corresponding to the ninth transmission line 57, the line B'C' corresponding to the fifth transmission line 58, the line C'D' corresponding to the seventh transmission line, the second capacitor 84, and the second power supply inductor 86 are made line-symmetrically. In addition, the line BX is implemented with a 1 / 10 wavelength (about 3 mm at a frequency of 4.5 GHz on the substrate 80a), so it can be short.

[0105] As described above, in the high-frequency amplifier 80 according to this embodiment, instead of the first power supply inductor 78 in Embodiment 5, it is composed of the component inductor 85 and the line CD as an example of the sixth transmission line, and instead of the second power supply inductor 79 in Embodiment 5, it is composed of the component inductor 86 and the line C'D' as an example of the seventh transmission line. That is, the first power supply inductor 78 in Embodiment 5 includes the sixth transmission line (line CD), and the second power supply inductor 79 in Embodiment 5 includes the seventh transmission line (line C'D').

[0106] Thus, near the carrier amplifier 11 and the peak amplifier 12, it is possible to arrange transmission lines with a shorter line length compared to the prior art, and miniaturization of the circuit of the high-frequency amplifier 80 is achieved.

[0107] In addition, in this embodiment, the semiconductor chip 80b on which the carrier amplifier 11 is formed and the semiconductor chip 80c on which the peak amplifier 12 is formed are different chips, but it is not limited thereto, and they may also be the same chip.

[0108] In addition, Figure 16 The exemplified eighth transmission line 54, ninth transmission line 57, fourth transmission line 55, fifth transmission line 58, first transmission line 40, second transmission line 39 ( Figure 16 not shown in the figure) and the third transmission line 21 may also be made of the same material (such as copper).

[0109] (Embodiment 7)

[0110] Figure 17 It is a layout diagram of the high-frequency amplifier 90 according to Embodiment 7. The high-frequency amplifier 90 according to this embodiment has the same circuit as the Figure 14 high-frequency amplifier 77 according to Embodiment 5 shown. Therefore,Figure 17 This is a diagram showing the specific layout on the substrate 90a corresponding to the circuit diagram of the high-frequency amplifier 77 related to Embodiment 5 shown below. Figure 14 In the high-frequency amplifier 90 according to this embodiment, on the semiconductor chip 90b on which the carrier amplifier 91 is formed, not only the FET serving as the carrier amplifier 91 is formed, but also the line PQ and the first capacitor 95 are formed. One end of the first capacitor 95 is connected to the ground on the back surface of the semiconductor chip 90b via a through hole (not shown in the figure). Similarly, on the semiconductor chip 90c on which the peak amplifier 92 is formed, not only the FET serving as the peak amplifier 92 is formed, but also the line P'Q' and the second capacitor 96 are formed. One end of the second capacitor 96 is connected to the ground on the back surface of the semiconductor chip 90c via a through hole (not shown in the figure).

[0111] In the high-frequency amplifier 90 according to this embodiment, on the semiconductor chip 90b on which the carrier amplifier 91 is formed, not only the FET serving as the carrier amplifier 91 is formed, but also the line PQ and the first capacitor 95 are formed. One end of the first capacitor 95 is connected to the ground on the back surface of the semiconductor chip 90b via a through hole ( Figure 17 not shown in the figure). Similarly, on the semiconductor chip 90c on which the peak amplifier 92 is formed, not only the FET serving as the peak amplifier 92 is formed, but also the line P'Q' and the second capacitor 96 are formed. One end of the second capacitor 96 is connected to the ground on the back surface of the semiconductor chip 90c via a through hole ( Figure 17 not shown in the figure).

[0112] Figure 14 and Figure 17 are corresponding as follows. That is, Figure 14 the eighth transmission line 54 in Figure 17 corresponds to the line PQ on the semiconductor chip and the part where the bonding wire is connected between point Q and point H in Figure 14 Similarly, the fourth transmission line 55 in Figure 17 corresponds to the line HJ in Figure 14 The first transmission line 40 in Figure 17 corresponds to the line HX in Figure 14 The first capacitor 72 for grounding in Figure 17 corresponds to the first capacitor 95 formed on the semiconductor chip 90b in Figure 14 Similarly, the ninth transmission line 57 in Figure 17 is composed of the line P'Q' on the semiconductor chip and the bonding wire between point Q' and point H' in Figure 14 The fifth transmission line 58 in Figure 17 corresponds to the line H'J' in Figure 14 The second capacitor 74 for grounding in Figure 17 corresponds to the second capacitor 96 formed on the conductor chip 90c in

[0113] In addition, Figure 17 the line between point J and the power supply terminal 75 in

[0114] In a high frequency band above the millimeter wave band, since the wavelength becomes shorter, transmission lines can be formed on a semiconductor chip. In addition, compared with the wavelength, the length of the bonding wire becomes significant, so the bonding wire can be used to form part of the matching circuit. Further, since a capacitor for grounding can be realized with a smaller capacitance value in a higher frequency band, it can be formed on the semiconductor chip.

[0115] As described above, the high frequency amplifier 90 according to the seventh embodiment is an amplifier that amplifies a first signal and a second signal in a specified frequency band and outputs a signal from the output terminal 22. The high frequency amplifier 90 includes: a substrate 90a; one or two semiconductor chips (in this embodiment, semiconductor chips 90b and 90c) mounted on the substrate 90a; a first amplifier formed on the semiconductor chip 90b that amplifies the first signal; a second amplifier formed on the semiconductor chip 90c that amplifies the second signal; a part (line PQ) of the eighth transmission line 54 formed on the semiconductor chip 90b, one end of which is connected to the output terminal of the first amplifier; a part (line P'Q') of the ninth transmission line 57 formed on the semiconductor chip 90c, one end of which is connected to the output terminal of the second amplifier; a first capacitor 95 formed on the semiconductor chip 90b; a second capacitor 96 formed on the semiconductor chip 90c; a fourth transmission line 55 (line HJ) formed on the substrate 90a, one end of which is connected to the other end of a part (line PQ) of the eighth transmission line 54; a fifth transmission line 58 (line H'J') formed on the substrate 90a, one end of which is connected to the other end of a part (line P'Q') of the ninth transmission line 57; a first transmission line 40 (line HX) formed on the substrate 90a, which is connected between one end (point H) of the fourth transmission line 55 and one end (point H') of the fifth transmission line 58 and has an electrical length less than 1 / 4 wavelength of the center frequency of the specified frequency band; a second transmission line 39 ( Figure 17 not shown in the figure) connected to the input terminal of one of the first amplifier or the second amplifier and having an electrical length less than 1 / 4 wavelength of the center frequency of the specified frequency band; and a third transmission line 21 (the transmission line between point X and the output terminal 22) connected between one end of the first transmission line 40 (line HX) and the output terminal 22 and having an electrical length of 1 / 4 wavelength of the center frequency of the specified frequency band. The other end of the fourth transmission line 55 and the first capacitor 95 are connected, and the other end of the fifth transmission line 58 and the second capacitor 96 are connected. More specifically, the other end of the fourth transmission line 55 and the first capacitor 95 are connected by a first bonding wire 97, and the other end of the fifth transmission line 58 and the second capacitor 74 are connected by a second bonding wire 98.

[0116] Accordingly, a bonding wire can be used to form a part of the matching circuit, and the length of the transmission line of the matching circuit needs to be shortened. In addition, a grounding capacitor is formed on the semiconductor chip on which the amplifier is formed, so that the amplifier and the capacitor can be designed as components independent of other circuits.

[0117] In addition, in the present embodiment, the semiconductor chip 90b on which the carrier amplifier 91 is formed and the semiconductor chip 90c on which the peak amplifier 92 is formed are different chips, but this is not limited thereto, and they may also be the same chip. In addition, Figure 17 the eighth transmission line 54, the ninth transmission line 57, the fourth transmission line 55, the fifth transmission line 58, the first transmission line 40, the second transmission line 39 ( Figure 17 not shown in the figure) and the third transmission line 21 may also be made of the same material (for example, copper).

[0118] (Embodiment 8)

[0119] Figure 18 is a layout diagram of the semiconductor chip 101 for a carrier amplifier according to Embodiment 8 ( Figure 18 (a)), and a layout diagram of the semiconductor chip 102 for a peak amplifier ( Figure 18 (b)). In Figure 18 the semiconductor chip 101 for a carrier amplifier shown in (a), not only an amplifying FET is formed, but also a line PQ and a first capacitor 105 are formed. In addition, bumps are formed at the connection point Q between the semiconductor chip 101 and the external transmission line, the upper electrode 106 as one end of the first capacitor 105, and the lower electrode 107 as the other end. Similarly, in Figure 18 the semiconductor chip 102 for a peak amplifier shown in (b), not only an amplifying FET is formed, but also a line P'Q' and a second capacitor 108 are formed. In addition, bumps are formed at the connection point Q' between the semiconductor chip 102 and the external transmission line, the upper electrode 109 as one end of the second capacitor 108, and the lower electrode 110 as the other end.

[0120] Figure 19 is a layout diagram of the high-frequency amplifier 100 according to Embodiment 8. The high-frequency amplifier 100 according to the present embodiment has the same circuit as the Figure 14 high-frequency amplifier 77 according to Embodiment 5 shown in the figure. Therefore, Figure 19 it is a diagram showing the specific layout on the substrate 100a with respect to the circuit diagram of the high-frequency amplifier 77 according to Embodiment 5 shown in Figure 14 the figure.

[0121] As shown in this figure,Figure 18 The semiconductor chip 101 for a carrier amplifier and the semiconductor chip 102 for a peak amplifier are mounted on the substrate 100a in a face-down form. Here, the mounting is such that the bump at point Q overlaps with point H, the bump of the upper electrode 106 overlaps with point J, the bump at point Q' overlaps with point H', and the bump of the upper electrode 109 overlaps with point J'. Further, the bumps of the lower electrodes 107 and 110, which are the other ends of the first capacitor 105 and the second capacitor 108, are grounded via the substrate 100a, respectively.

[0122] Figure 14 and Figure 19 The correspondence with is as follows. That is, Figure 14 the eighth transmission line 54 in corresponds to the line PQ in Figure 19 . Further, Figure 14 the fourth transmission line 55 in corresponds to Figure 19 the line HJ in Figure 14 the first transmission line 40 in corresponds to Figure 19 the line HX in Figure 14 Similarly, the ninth transmission line 57 in is constituted by the line P'Q' in Figure 19 . Further, Figure 14 the fifth transmission line 58 in corresponds to Figure 19 the line H'J' in

[0123] In this way, the semiconductor chip 101 for a carrier amplifier has bumps as the first conductor, and the bumps as the first conductor are formed in a region where at least a part of the semiconductor chip 101 overlaps with the other end (that is, point J) of the fourth transmission line 55 in a plan view. Similarly, the semiconductor chip 102 for a peak amplifier has bumps as the second conductor, and the bumps of the second conductor are formed in a region where at least a part of the semiconductor chip 102 overlaps with the other end (that is, point J') of the fifth transmission line 58 in a plan view. And, the other end (that is, point J) of the fourth transmission line 55 and the first capacitor 72 are connected via the bumps as the first conductor. Similarly, the other end (that is, point J') of the fifth transmission line 58 and the second capacitor 74 are connected via the bumps as the second conductor.

[0124] In Embodiment 7, a part of the matching circuit is constituted by using the first bonding wire 97 and the second bonding wire 98. However, if the frequency becomes further higher, the inductance of the bonding wire becomes too large to achieve matching. In this case, since the inductance of the bump is much smaller than that of the bonding wire, as in this embodiment, it is sufficient to use the bump instead of the bonding wire to make contact with the external circuit.

[0125] As described above, the high-frequency amplifier according to the present disclosure has been described based on Embodiments 1 to 8. However, the present disclosure is not limited to these Embodiments 1 to 8. As long as it does not deviate from the gist of the present disclosure, various modifications conceivable by those skilled in the art applied to each embodiment, and other configurations constructed by combining some structural elements in each embodiment are also included in the scope of the present disclosure.

[0126] For example, in the above-described embodiment, the high-frequency amplifier is designed for a 50-Ω load, but the load impedance of the target is not limited to 50 Ω, and it may be designed for other loads such as 75 Ω. In this case, it is only necessary to make the characteristic impedance of each transmission line constituting the high-frequency amplifier consistent with the load impedance of the target.

[0127] Industrial Applicability

[0128] The high-frequency amplifier according to the present disclosure can be used, for example, as a small, high-efficiency, and broadband Doherty amplifier and inverse Doherty amplifier used in wireless communication. More specifically, it can be used as a high-frequency amplifier for a wireless base station device of the fifth-generation communication.

[0129] Reference Signs Explanation

[0130] 11, 91 Carrier Amplifier

[0131] 12, 92 Peak Amplifier

[0132] 21 Third Transmission Line

[0133] 22 Output Terminal

[0134] 23 First Input Terminal

[0135] 24 Second Input Terminal

[0136] 30, 50, 60, 70, 77, 80, 90, 100 High-Frequency Amplifier

[0137] 33, 53 First Matching Circuit

[0138] 34, 37 Series Inductor

[0139] 35, 38 Parallel Inductor

[0140] 36, 56 Second Matching Circuit

[0141] 39 Second Transmission Line

[0142] 40 First Transmission Line

[0143] 54 Eighth Transmission Line

[0144] 55 Fourth Transmission Line

[0145] 57 Ninth transmission line

[0146] 58 Fifth transmission line

[0147] 72, 95, 105 First capacitor

[0148] 74, 96, 108 Second capacitor

[0149] 75, 76 Power supply terminal

[0150] 78 First power supply inductor

[0151] 79 Second power supply inductor

[0152] 80a, 90a, 100a Substrate

[0153] 80b, 80c, 90b, 90c, 101, 102 Semiconductor chip

[0154] 82, 84 Component capacitor

[0155] 97 First bonding wire

[0156] 98 Second bonding wire

[0157] 106, 109 Upper electrode

[0158] 107, 110 Lower electrode

[0159] Line CD Seventh transmission line

[0160] Line C’D’ Eighth transmission line

Claims

1. A high-frequency amplifier is a high-frequency amplifier that amplifies a first signal and a second signal in a specified frequency band and outputs a signal from an output terminal, wherein, Comprising: A first amplifier for amplifying the first signal; A second amplifier for amplifying the second signal; A first matching circuit connected to the output terminal of the first amplifier; A second matching circuit connected to the output terminal of the second amplifier; A first transmission line connected between the output terminal of the first matching circuit and the output terminal of the second matching circuit and having an electrical length less than 1 / 4 wavelength of the center frequency of the specified frequency band; A second transmission line connected to the input terminal of the second amplifier and having an electrical length less than 1 / 4 wavelength of the center frequency of the specified frequency band; And A third transmission line connected between one end of the first transmission line and the output terminal of the high-frequency amplifier and having an electrical length of 1 / 4 wavelength of the center frequency of the specified frequency band, The first matching circuit has: A series inductor with one end connected to the output terminal of the first amplifier; and A parallel inductor as a fourth transmission line with one end connected to the other end of the series inductor and the other end grounded, The sum of the phase rotation amount brought by the first matching circuit and the phase rotation amount brought by the first transmission line is less than 90°.

2. The high-frequency amplifier according to claim 1, wherein, The electrical length of the first transmission line is 1 / 8 wavelength or less of the center frequency of the specified frequency band.

3. The high-frequency amplifier according to claim 1, wherein, The impedance observed from the output terminal of the first amplifier towards the output side is outside the constant admittance circle passing through R = 50Ω on the Smith chart.

4. The high-frequency amplifier according to claim 1, wherein, The first amplifier is composed of a field effect transistor (FET) using GaN, and the maximum high-frequency output of the FET using GaN is 30W or less.

5. The high-frequency amplifier according to claim 4, is used in a radio base station device that uses an array antenna to output a high-frequency signal.

6. The high-frequency amplifier according to claim 1, wherein, Comprising: A capacitor connected between the other end of the fourth transmission line and the ground potential.

7. The high-frequency amplifier according to claim 6, wherein, Comprising: A power supply inductor connected between the connection point between the fourth transmission line and the capacitor and the power supply.

8. The high-frequency amplifier according to claim 7, wherein, The power supply inductor is composed of an element inductor and a transmission line.

9. A high-frequency amplifier is a high-frequency amplifier that amplifies a first signal and a second signal in a specified frequency band and outputs a signal from an output terminal, wherein, Comprising: A first amplifier for amplifying the first signal; A second amplifier for amplifying the second signal; A first matching circuit connected to the output terminal of the first amplifier; A second matching circuit connected to the output terminal of the second amplifier; A first transmission line connected between the output terminal of the first matching circuit and the output terminal of the second matching circuit and having an electrical length less than 1 / 4 wavelength of the center frequency of the specified frequency band; A second transmission line connected to the input terminal of the second amplifier and having an electrical length less than 1 / 4 wavelength of the center frequency of the specified frequency band; And A third transmission line connected between one end of the first transmission line and the output terminal of the high-frequency amplifier and having an electrical length of 1 / 4 wavelength of the center frequency of the specified frequency band, The first matching circuit has: A series inductor with one end connected to the output terminal of the first amplifier; and A parallel inductor as a fourth transmission line with one end connected to the other end of the series inductor and the other end grounded, The sum of the phase rotation amount brought by the first matching circuit and the phase rotation amount brought by the first transmission line is less than 90°. The high-frequency amplifier further includes: A substrate; One or two semiconductor chips, which are mounted on the substrate and form the first amplifier and the second amplifier; And A first capacitor and a second capacitor, which are formed in the semiconductor chip, The first matching circuit includes: an eighth transmission line, which is formed in the semiconductor chip and one end is connected to the output terminal of the first amplifier; and a fourth transmission line, which is formed on the substrate and one end is connected to the other end of the eighth transmission line; The second matching circuit has: a ninth transmission line, which is formed in the semiconductor chip and one end is connected to the output terminal of the second amplifier; and a fifth transmission line, which is formed on the substrate and one end is connected to the other end of the ninth transmission line, The first transmission line is formed on the substrate and is connected between one end of the fourth transmission line and one end of the fifth transmission line, The other end of the fourth transmission line is connected to the first capacitor, The other end of the fifth transmission line is connected to the second capacitor.

10. The high-frequency amplifier according to claim 9, wherein, The other end of the fourth transmission line and the first capacitor are connected by a first bonding wire, The other end of the fifth transmission line and the second capacitor are connected by a second bonding wire.

11. The high-frequency amplifier according to claim 9, wherein, The semiconductor chip has: a first conductor, which is formed in a region where at least a part of the semiconductor chip overlaps with the other end of the fourth transmission line in a plan view; And a second conductor, which is formed in a region where at least a part of the semiconductor chip overlaps with the other end of the fifth transmission line in a plan view, The other end of the fourth transmission line and the first capacitor are connected via the first conductor, The other end of the fifth transmission line and the second capacitor are connected via the second conductor.

12. A high-frequency amplifier that amplifies a first signal and a second signal in a specified frequency band and outputs a signal from an output terminal, wherein, It includes: A first amplifier, which amplifies the first signal; A second amplifier, which amplifies the second signal; A first matching circuit, which is connected to the output terminal of the first amplifier; A second matching circuit, which is connected to the output terminal of the second amplifier; A first transmission line, which is connected between the output terminal of the first matching circuit and the output terminal of the second matching circuit and has an electrical length of less than 1 / 4 wavelength of the center frequency of the specified frequency band; A second transmission line, which is connected to the input terminal of the second amplifier and has an electrical length of less than 1 / 4 wavelength of the center frequency of the specified frequency band; And A third transmission line, which is connected between one end of the first transmission line and the output terminal of the high-frequency amplifier and has an electrical length of 1 / 4 wavelength of the center frequency of the specified frequency band, The first matching circuit has: A series inductor, one end of which is connected to the output terminal of the first amplifier; and A parallel inductor as the fourth transmission line, one end of which is connected to the other end of the series inductor and the other end is grounded, The sum of the phase rotation amount brought by the first matching circuit and the phase rotation amount brought by the first transmission line is less than 90°. The high-frequency amplifier further includes: A substrate; One or two semiconductor chips, which are mounted on the substrate and form the first amplifier and the second amplifier; And A first capacitor and a second capacitor as component capacitors, which are mounted on the substrate, The first matching circuit includes: an eighth transmission line formed on the substrate, one end of which is connected to the output terminal of the first amplifier; and a fourth transmission line formed on the substrate, one end of which is connected to the other end of the eighth transmission line; The second matching circuit has: a ninth transmission line formed on the substrate, one end of which is connected to the output terminal of the second amplifier; and a fifth transmission line formed on the substrate, one end of which is connected to the other end of the ninth transmission line, The first transmission line is formed on the substrate and is connected between one end of the fourth transmission line and one end of the fifth transmission line, The other end of the fourth transmission line is directly connected to the first capacitor, The other end of the fifth transmission line is directly connected to the second capacitor.

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