Balun and power amplifier circuit

Abstract

This invention provides a balun and power amplifier circuit that enables the amplifier to operate in Class F while suppressing an increase in circuit size. [Solution] The balun comprises: a first wiring having one end connected to a first balanced line through which one of the balanced signals is transmitted and the other end connected to a first reference potential; a second wiring having one end connected to a second balanced line through which the other of the balanced signals is transmitted and the other end connected to the first reference potential; a third wiring having one end and an open other end, and electromagnetically coupled to the first wiring; a fourth wiring having one end connected to the one end of the third wiring and the other end connected to an unbalanced line through which an unbalanced signal is transmitted, and electromagnetically coupled to the second wiring; a first capacitor connected in parallel with a portion of the first wiring; and a second capacitor connected in parallel with a portion of the second wiring.

Description

Technical Field

[0001] The present invention relates to a balun and a power amplification circuit.

Background Art

[0002] A differential amplifier used as a power amplification device for wireless communication and the like is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The transformer described in Patent Document 1 includes an input-side inductor and an output-side inductor. One end of the input-side inductor is connected to the output terminal of the first amplifier. The other end of the input-side inductor is connected to the output terminal of the second amplifier. One end of the output-side inductor is connected to the output terminal through a matching circuit. The other end of the output-side inductor is connected to the reference potential.

[0005] Although the transformer of Patent Document 1 magnetically couples the input-side inductor and the output-side inductor, for example, in a high-frequency band such as the sub-terahertz band, when a transformer in which the input-side inductor and the output-side inductor are constituted by coils is used, the influence of the parasitic capacitance between the lines becomes large. For this reason, the original performance of the transformer may not be exhibited. When a merchant balun is used instead of the transformer, this problem can be addressed, but a new problem occurs in that the amplifier operates in reverse class F.

[0006] Furthermore, in order to operate the amplifier connected to the merchant balun as a Class F amplifier, a configuration in which an LC series circuit is connected in parallel after the amplifier is conceivable. However, this is undesirable because it increases the circuit size due to the addition of the LC series circuit.

[0007] This invention has been made in view of these circumstances, and aims to provide a balun and power amplifier circuit that can operate the amplifier in Class F while suppressing an increase in circuit size. [Means for solving the problem]

[0008] A balun according to one aspect of the present invention comprises: a first wiring having one end connected to a first balanced line through which one of the balanced signals is transmitted and the other end connected to a first reference potential; a second wiring having one end connected to a second balanced line through which the other of the balanced signals is transmitted and the other end connected to the first reference potential; a third wiring having one end and an open other end, and electromagnetically coupled to the first wiring; a fourth wiring having one end connected to the one end of the third wiring and the other end connected to an unbalanced line through which an unbalanced signal is transmitted, and electromagnetically coupled to the second wiring; a first capacitor connected in parallel with a portion of the first wiring; and a second capacitor connected in parallel with a portion of the second wiring.

[0009] A power amplifier circuit according to another aspect of the present invention includes: a first amplifier that amplifies a first signal and outputs a first amplified signal from a first output terminal; a second amplifier that amplifies a second signal having a different phase from the first signal and outputs a second amplified signal from a second output terminal; a first wiring having one end connected to the first output terminal and the other end connected to a first reference potential; a second wiring having one end connected to the second output terminal and the other end connected to the first reference potential; a third wiring having one end and an open other end, and electromagnetically coupled with the first wiring; a fourth wiring having one end connected to the one end of the third wiring and the other end connected to an output terminal, and electromagnetically coupled with the second wiring; a first capacitor connected in parallel with a part of the first wiring; and a second capacitor connected in parallel with a part of the second wiring. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a balun and power amplifier circuit that can operate the amplifier in Class F while suppressing an increase in circuit size. [Brief explanation of the drawing]

[0011] [Figure 1] This is the circuit diagram of power amplifier circuit 201. [Figure 2] This is a circuit diagram of power amplifier circuit 291, which is an example. [Figure 3] This figure shows the simulation results of the frequency change of S11 in the power amplifier circuit 291, which is an example, on a Smith chart. [Figure 4] This is a circuit diagram of power amplifier circuit 292, which is an example. [Figure 5] This figure shows the simulation results of the frequency change of S11 in the power amplifier circuit 201 on a Smith chart. [Figure 6] This figure shows the simulation results of the frequency change of S21 in the power amplifier circuit 291, which is an example. [Figure 7] This figure shows the simulation results of the frequency change of S21 in the power amplifier circuit 201. [Figure 8] This is a plan view of the Balun 101 from above. [Figure 9] This is a plan view of the area around the capacitor 121 in the balun 101, seen from above. [Figure 10] This is a perspective view of the area around the capacitor 121 in the balun 101. [Figure 11] This is the circuit diagram of power amplifier circuit 202. [Figure 12] This is the circuit diagram of power amplifier circuit 203. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same elements are denoted by the same reference numerals, and redundant descriptions will be omitted as much as possible.

[0013] [First Embodiment] The power amplifier circuit 201 according to the first embodiment will be described. FIG. 1 is a circuit diagram of the power amplifier circuit 201. As shown in FIG. 1, the power amplifier circuit 201 includes a differential pair 51, capacitors 62p, 62m, and 63, a balun 101, wirings 303a and 304a, and capacitors 303b and 304b.

[0014] The differential pair 51 includes amplifiers 51p (first amplifier) and 51m (second amplifier). The amplifiers 51p and 51m include amplification transistors (not shown). The balun 101 includes wirings 111 (first wiring), 112 (second wiring), 113 (third wiring), and 114 (fourth wiring), and capacitors 121 (first capacitor) and 122 (second capacitor).

[0015] In this embodiment, the transistor is composed of a bipolar transistor such as a heterojunction bipolar transistor (HBT), for example. Note that the transistor may be composed of other transistors such as a metal-oxide-semiconductor field-effect transistor (MOSFET). In that case, the base, collector, and emitter may be read as the gate, drain, and source, respectively.

[0016] The differential pair 51 in the power amplifier circuit 201 amplifies signals RFp2 (first signal) and RFm2 (second signal) which are balanced signals. The frequency of the balanced signal is included in, for example, the sub-terahertz band. Specifically, the frequency of the balanced signal is included in 90 GHz to 300 GHz.

[0017] Signal RFm2 has a different phase from signal RFp2. In this embodiment, for example, signal RFm2 has a phase difference of approximately 180° from signal RFp2.

[0018] In detail, the amplifier 51p in the differential pair 51 amplifies the signal RFp2 supplied from the preceding circuit and outputs the amplified signal RFp3 (first amplified signal) from the output terminal 51pa (first output terminal). The amplifying transistor included in amplifier 51p is operated by the power supply voltage VDD supplied through the wiring 303a, which functions as an inductor, and the output terminal 51pa. Capacitor 303b is a bypass capacitor and has one end to which the power supply voltage VDD is supplied and the other end connected to ground. Here, the potential of ground is an example of a first reference potential.

[0019] Amplifier 51m amplifies the signal RFm2 supplied from the preceding circuit and outputs the amplified signal RFm3 (second amplified signal) from output terminal 51ma (second output terminal). The amplifying transistor included in amplifier 51m is operated by the power supply voltage VDD supplied through the wiring 304a, which functions as an inductor, and the output terminal 51ma. Capacitor 304b is a bypass capacitor and has one end to which the power supply voltage VDD is supplied and the other end connected to ground.

[0020] The balanced transmission line 501p (first balanced transmission line) has one end connected to the output terminal 51pa of amplifier 51p and the other end, and one of the balanced signals, i.e., the amplified signal RFp3, is transmitted through it.

[0021] The balanced transmission line 501m (second balanced transmission line) has one end connected to the output terminal 51ma of the amplifier 51m, and the other end, through which the other half of the balanced signal, i.e., the amplified signal RFm3, is transmitted.

[0022] Capacitors 62p and 62m, for example, have a DC blocking function and are provided in the balanced transmission lines 501p and 501m, respectively. Capacitors 62p and 62m may also have a function of matching the impedance between the differential pair 51 and the balun 101.

[0023] In detail, capacitor 62p has one end connected to the output terminal 51pa of amplifier 51p through a portion of the balanced transmission line 501p, and the other end connected to wiring 111 through the other portion of the balanced transmission line 501p.

[0024] Capacitor 62m has one end connected to the output terminal 51ma of amplifier 51m through a portion of the balanced transmission line 501m, and the other end connected to wiring 112 through another portion of the balanced transmission line 501m.

[0025] The balun 101 converts the amplified signals RFp3 and RFm3 supplied from the differential pair 51 into an unbalanced signal, i.e., a single-ended signal, which is the output signal RFout. The balun 101 also matches the impedance between the differential pair 51 and the circuit downstream of the output terminal 32, such as an antenna.

[0026] In detail, the wiring 111 in the balun 101 has one end connected to the other end of the balanced line 501p and the other end connected to ground.

[0027] The wiring 112 has one end connected to the other end of the balanced line 501m and the other end connected to ground.

[0028] Each of the wirings 111 and 112 is a quarter-wavelength line. More specifically, the time required for the amplified signal RFp3 or RFm3 to be transmitted from one end of wiring 111 or 112 to the other is approximately one-quarter of the period of the amplified signal RFp3 or RFm3. In other words, the electrical length of each of the wirings 111 and 112 is approximately one-quarter of the wavelength of the amplified signal RFp3 or RFm3.

[0029] Wiring 113 has one end and an open end. Wiring 113 is electromagnetically coupled to wiring 111.

[0030] Wiring 114 has one end connected to one end of wiring 113 and the other end connected to the unbalanced line 502 through which the output signal RFout is transmitted. Wiring 114 is electromagnetically coupled to wiring 112.

[0031] The unbalanced transmission line 502 has one end connected to the other end of the wiring 114 and the other end connected to the output terminal 32.

[0032] The capacitor 63 is provided in the unbalanced transmission line 502. More specifically, the capacitor 63 has one end connected to the other end of the wiring 114 through a portion of the unbalanced transmission line 502, and the other end connected to the output terminal 32 through another portion of the unbalanced transmission line 502.

[0033] The combined wiring of wires 113 and 114 is a half-wavelength line. More specifically, the time required for the output signal RFout to be transmitted from the other end of wire 113 to the other end of wire 114 is approximately half the period of the output signal RFout. In other words, the electrical length from the other end of wire 113 to the other end of wire 114 is approximately half the wavelength of the output signal RFout.

[0034] Capacitor 121 is connected in parallel with a portion 111a of wiring 111. More specifically, portion 111a is located between one end and the other end of wiring 111. Note that portion 111a may include either one of the ends of wiring 111.

[0035] Capacitor 122 is connected in parallel with a portion 112a of wiring 112. More specifically, portion 112a is located between one end and the other end of wiring 112. Note that portion 112a may include either one of the ends of wiring 112. The electrical length of portion 111a and the electrical length of portion 112a are approximately the same.

[0036] [Reference example] The power amplifier circuit 291, which is an example, will be described. Figure 2 is a circuit diagram of the power amplifier circuit 291, which is an example. In the power amplifier circuit 291, a balun 901 is provided instead of a balun 101, compared to the power amplifier circuit 201 (see Figure 1). Compared to the balun 101 (see Figure 1), the balun 901 does not have capacitors 121 and 122.

[0037] Figure 3 shows the simulation results of the frequency change of S11 in the power amplifier circuit 291, which is a reference example, on a Smith chart. Here, S11 is the S-parameter of the signal incident from amplifier 51p to capacitor 62p. The same applies to the signal incident from amplifier 51m to capacitor 62m, but below we will explain the signal incident from amplifier 51p to capacitor 62p as a representative example.

[0038] As shown in Figure 3, S11 at frequencies of 120 GHz, 130 GHz, and 140 GHz, which are included in the fundamental frequency band of the amplified signal RFp3, is represented by Lchr, Mchr, and Hchr, respectively.

[0039] S11 for frequencies of 240 GHz, 260 GHz, and 280 GHz, which are included in the second harmonic bandwidth of the amplified signal RFp3, is denoted by HDLchr, HDMchr, and HDHchr, respectively.

[0040] The impedance between the differential pair 51 and the circuit after the output terminal 32 is matched, suppressing the reflection of the fundamental wave of the amplified signal RFp3. On the other hand, because a shorted quarter-wavelength line is connected to the output terminal 51ma of amplifier 51p, the impedance of the second harmonic of the amplified signal RFp3 becomes large. For this reason, in the power amplifier circuit 291, amplifier 50p can only operate in inverse-F class.

[0041] Figure 4 is a circuit diagram of a power amplifier circuit 292, which is a reference example. Compared to the power amplifier circuit 291 (see Figure 2), the power amplifier circuit 292 further includes LC series circuits 311 and 312.

[0042] The LC series circuit 311 includes a capacitor 311a and an inductor 311b connected in series between the output terminal 51pa of the amplifier 51p and ground.

[0043] The LC series circuit 312 includes a capacitor 312a and an inductor 312b connected in series between the output terminal 51ma of the amplifier 51m and ground.

[0044] By adjusting the circuit constants of the LC series circuits 311 and 312 so that they short-circuit at the second harmonic of the amplified signal RFp3, and by making the LC series circuits 311 and 312 function as notch filters, it is possible to operate amplifiers 50p and 50m in Class F.

[0045] However, if the Q values ​​of the LC series circuits 311 and 312 are not high, the loss in the fundamental frequency band of the amplified signal RFp3 will increase, which may lead to a degradation in output power and efficiency.

[0046] Furthermore, the inclusion of LC series circuits 311 and 312 increases the circuit size. If a subterahertz band antenna is constructed using patch antennas, the size of the patch antenna is approximately 1.1 mm, so methods that increase the circuit size are undesirable.

[0047] Furthermore, it is difficult to form a high-Q notch filter within a semiconductor chip that amplifies signals in the subterahertz band.

[0048] Figure 5 shows the simulation results of the frequency change of S11 in the power amplifier circuit 201 on a Smith chart.

[0049] As shown in Figure 5, S11 at frequencies of 120 GHz, 130 GHz, and 140 GHz, which are included in the fundamental frequency band of the amplified signal RFp3, is shown for Lch, Mch, and Hch, respectively.

[0050] S11 for frequencies of 240 GHz, 260 GHz, and 280 GHz, which are included in the second harmonic band of the amplified signal RFp3, is shown as HDLch, HDMch, and HDHch, respectively.

[0051] As shown in Figures 1 and 5, in the power amplifier circuit 201, a capacitor 121 is provided in parallel with a portion 111a of the wiring 111. In the bandwidth of the fundamental wave of the amplified signal RFp3, the portion 111a of the wiring 111 and the capacitor 121 function as an LC tank circuit, allowing for good impedance matching between the differential pair 51 and the circuit downstream of the output terminal 32. This suppresses the reflection of the fundamental wave of the amplified signal RFp3.

[0052] In the second harmonic bandwidth of the amplified signal RFp3, the parallel circuit of part 111a of wiring 111 and capacitor 121 exhibits significant capacitive properties, so wiring 111 and capacitor 121 as a whole become close to a series LC circuit.

[0053] In other words, the wiring 111 and capacitor 121 can function as a notch filter that shorts in the second harmonic band of the amplified signal RFp3. This reduces the impedance in the second harmonic band of the amplified signal RFp3, allowing the amplifier 50pF to operate in Class F.

[0054] Therefore, the 50pF amplifier can be operated in Class F while suppressing an increase in circuit size. The same applies to the 50m amplifier.

[0055] Figure 6 shows the simulation results of the frequency change of S21 in the power amplifier circuit 291, which is a reference example. Here, S21 is the S-parameter of the signal passing from amplifier 51p through balun 901. The vertical axis shows S21 in units of "dB". The horizontal axis shows frequency in units of "GHz".

[0056] Figure 7 shows the simulation results of the frequency change of S21 in the power amplifier circuit 201. Here, S21 is the S-parameter of the signal passing from amplifier 51p through balun 101. Note that Figure 7 can be interpreted in the same way as Figure 6.

[0057] As shown in Figures 6 and 7, in the second harmonic bandwidth of the amplified signal RFp3, the impedance of power amplifier circuit 201 is close to zero compared to power amplifier circuit 291, resulting in a larger S21 value.

[0058] [Layout of Balan 101] This section describes the layout of Balun 101. Each drawing may show the x, y, and z axes. The x, y, and z axes form a right-handed three-dimensional Cartesian coordinate system. Hereinafter, the direction of the arrow on the x axis may be referred to as the x-axis+ side, and the direction opposite to the arrow may be referred to as the x-axis- side, and the same applies to the other axes. The z-axis+ side and z-axis- side may also be referred to as the "upper side" and "lower side," respectively. Furthermore, the planes perpendicular to the x, y, or z axes may be referred to as the yz plane, zx plane, or xy plane, respectively. Here, the direction of rotation clockwise when viewed from the upper side to the lower side is defined as the clockwise direction cw. The direction of rotation counterclockwise when viewed from the upper side to the lower side is defined as the counterclockwise direction ccw.

[0059] Figure 8 is a plan view of the balun 101 from above. As shown in Figure 8, the wirings 111, 112, 113, and 114 are formed by metal electrodes 611 (first conductive member), 612 (second conductive member), 613 (third conductive member), and 614 (fourth conductive member), respectively.

[0060] In detail, wiring 111 is formed by a metal electrode 611 extending from one end of wiring 111 to the other end of wiring 111. Wiring 112 is formed by a metal electrode 612 extending from one end of wiring 112 to the other end of wiring 112. Wiring 113 is formed by a metal electrode 613 extending from one end of wiring 113 to the other end of wiring 113. Wiring 114 is formed by a metal electrode 614 extending from one end of wiring 114 to the other end of wiring 114.

[0061] The metal electrodes 611, 612, 613, and 614 are provided along the first surface. In this embodiment, the first surface is substantially parallel to the xy plane. The first surface is, for example, the surface of a semiconductor chip. The first surface may also be the surface of an insulating layer provided inside the semiconductor chip.

[0062] The metal electrodes 611 and 612 have a shape symmetrical with respect to a plane parallel to the zx plane (hereinafter sometimes referred to as the plane of symmetry Ps). The capacitors 62p and 62m have a shape symmetrical with respect to the plane of symmetry Ps. The equilibrium lines 501p and 501m have a shape symmetrical with respect to the plane of symmetry Ps. The capacitors 121 and 122 have a shape symmetrical with respect to the plane of symmetry Ps.

[0063] The metal electrode 611 includes an extended portion 611a (first extended portion) and 611b (second extended portion), and a corner portion 611c (first corner portion). The corner portion 611c forms a part 111a of the wiring 111, and the direction of extension changes.

[0064] In this embodiment, the extension direction of the metal electrode 611, which extends from one end of the wiring 111 to the other end of the wiring 111, changes from the y-axis + direction to the x-axis + direction at the corner portion 611c.

[0065] The metal electrode 612 includes an extended portion 612a (third extended portion) and 612b (fourth extended portion), and a corner portion 612c (second corner portion). The corner portion 612c forms a part 112a of the wiring 112, and the direction of extension changes.

[0066] In this embodiment, the extension direction of the metal electrode 612, which extends from one end of the wiring 112 to the other end of the wiring 112, changes from the y-axis direction to the x-axis direction at the corner portion 612c.

[0067] The extended portion 611a and the extended portion 612a extend from the corner portion 611c and the corner portion 612c, respectively, so as to move closer to each other.

[0068] Specifically, the extension portion 611a extends from the corner portion 611c in the y-axis direction. A balanced line 501p is connected to the x-axis side of the extension portion 611a. A capacitor 62p is provided on the balanced line 501p. The balanced line 501p electrically connects the extension portion 611a and the amplifier 51p.

[0069] The extension 612a extends from the corner 612c in the y-axis direction. A balanced line 501m is connected to the x-axis side of the extension 612a. A capacitor 62m is provided on the balanced line 501m. The balanced line 501m electrically connects the extension 612a and the amplifier 51m.

[0070] The extended portion 611b and the extended portion 612b extend in the same direction from the corner portion 611c and the corner portion 612c, respectively.

[0071] Specifically, the extended portion 611b extends from the corner portion 611c in the x-axis+ direction. A portion of the extended portion 611b on the x-axis+ side is electrically connected to an electrode having the potential of ground through an interlayer via 701p.

[0072] The extended portion 612b extends from the corner portion 612c in the x-axis+ direction. A portion of the extended portion 612b on the x-axis+ side is electrically connected to an electrode having the potential of ground through an interlayer via 701m.

[0073] The metal electrode 613 includes extended portions 613a and 613b and a corner portion 613c (third corner portion). The corner portion 613c is located inside the corner portion 611c and extends parallel to the corner portion 611c.

[0074] In this embodiment, the extension direction of the metal electrode 613, which extends from one end of the wiring 113 to the other end of the wiring 113, changes from the y-axis + direction to the x-axis + direction at the corner portion 613c.

[0075] The metal electrode 614 includes extended portions 614a and 614b and a corner portion 614c (fourth corner portion). The corner portions 613c and 614c have a shape symmetrical with respect to the plane of symmetry Ps. The corner portion 614c is located inward from the corner portion 612c and extends parallel to the corner portion 612c.

[0076] In this embodiment, the extension direction of the metal electrode 614, which extends from one end of the wiring 114 to the other end of the wiring 114, changes from the y-axis direction to the x-axis direction at the corner portion 614c.

[0077] The extensions 613a and 614a extend from the corners 613c and 614c, respectively, moving closer to each other. Specifically, extension 613a is located on the x-axis+ side of extension 611a and extends parallel to extension 611a in the y-direction from corner 613c. Extension 614a is located on the x-axis+ side of extension 612a and extends parallel to extension 612a in the y-direction from corner 614c, connecting with extension 613a.

[0078] The extensions 613b and 614b extend in the same direction from the corners 613c and 614c, respectively. Specifically, the extension 613b is located on the y-axis-side of the extension 611b and extends parallel to the extension 611b from the corner 613c in the x-axis-direction. The extension 614b is located on the y-axis-side of the extension 612b and extends parallel to the extension 612b from the corner 614c in the x-axis-direction.

[0079] Figure 9 is a plan view of the area around the capacitor 121 in the balun 101, viewed from above. Figure 10 is a perspective view of the area around the capacitor 121 in the balun 101.

[0080] As shown in Figures 9 and 10, the capacitor 121 is located outside the corner portion 611c.

[0081] In detail, the outer edge of corner section 611c is cut off at an angle. Hereafter, the portion of corner section 611c that is cut off at an angle may be referred to as corner section 611ca.

[0082] The x-axis- and y-axis- ends of the cut-off portion 611ca are connected to a metal electrode 621a that extends in the y-axis-positive direction. A portion of the y-axis-positive side of the metal electrode 621a forms the lower electrode of the capacitor 121.

[0083] The ends of the cut-off portion 611ca on the x-axis + and y-axis + sides are connected to a metal electrode 621b that extends in the x-axis - direction.

[0084] A bridge portion 621c is provided at the x-axis-side end of the metal electrode 621b. A metal electrode 621ca, which will be the upper electrode of the capacitor 121, is provided on the x-axis-side of the bridge portion 621c. The metal electrode 621ca faces a portion of the y-axis-+ side of the metal electrode 621a, separated by an insulator.

[0085] The bridge portion 621c electrically connects the metal electrode 621ca and the x-axis-side end of the metal electrode 621b through the metal electrode 621cb, which is included in the conductive layer above the conductive layer containing the metal electrodes 621a and 621b.

[0086] As shown in Figure 8, the capacitor 122 is located outside the corner portion 612c. The structure of the capacitor 122 is the same as that of the capacitor 121, so a detailed explanation is omitted.

[0087] [Second Embodiment] The power amplifier circuit 202 according to the second embodiment will now be described. In the second embodiment and subsequent embodiments, descriptions of matters common to the first embodiment will be omitted, and only the differences will be described. In particular, similar effects and advantages due to similar configurations will not be mentioned sequentially for each embodiment.

[0088] Figure 11 is a circuit diagram of the power amplifier circuit 202. As shown in Figure 11, the power amplifier circuit 202 differs from the power amplifier circuit 201 according to the first embodiment in that the power supply voltage VDD (first reference potential) is supplied from the other end of wiring 111 and the other end of wiring 112.

[0089] Compared to the power amplifier circuit 201 shown in Figure 1, the power amplifier circuit 202 does not include capacitors 62p and 62m, nor wiring 303a and 304a.

[0090] One end of the wiring 111 is connected to the output terminal 51pa of the amplifier 51p via the balanced line 501p. The other end of the wiring 111 is supplied with the power supply voltage VDD. The capacitor 303b has one end connected to the other end of the wiring 111 and the other end connected to ground.

[0091] One end of wiring 112 is connected to the output terminal 51ma of amplifier 51m via balanced line 501m. The other end of wiring 112 is supplied with power supply voltage VDD. Capacitor 304b has one end connected to the other end of wiring 112 and the other end connected to ground.

[0092] This configuration allows wirings 111 and 112 to function as choke coils. Furthermore, the DC-blocking capacitors 62p and 62m can be reduced. This allows the power amplifier circuit 202 to be smaller in scale compared to the power amplifier circuit 201.

[0093] [Third Embodiment] A power amplifier circuit according to the third embodiment will now be described. Figure 12 is a circuit diagram of the power amplifier circuit 203. As shown in Figure 12, the power amplifier circuit 203 differs from the power amplifier circuit 201 according to the first embodiment in that a differential pair of driver stages and an antenna are further shown.

[0094] Compared to the power amplifier circuit 201 shown in Figure 1, the power amplifier circuit 203 further includes a differential pair 50, a capacitor 60, interstage matching circuits 61p and 61m, a patch antenna 64, a balun 151, wiring 301a and 302a, and capacitors 301b and 302b.

[0095] The differential pair 50 includes amplifiers 50p and 50m. Amplifiers 50p and 50m include amplifying transistors (not shown). The balun 151 includes wiring 161, 162, 163 and 164.

[0096] The balun 151 converts the single-ended input signal RFin into balanced signals RFp1 and RFm1. The balun 151 also matches the impedance between the circuit preceding the input terminal 31 and the differential pair 50.

[0097] In detail, the wirings 161, 162, 163, and 164 in balun 151 are the same as the wirings 111, 112, 113, and 114 in balun 101, respectively.

[0098] Wiring 163 has one end and the other end is open. Wiring 164 has one end connected to one end of wiring 163 and the other end to which an input signal RFin is supplied from input terminal 31 through capacitor 60.

[0099] Wiring 161 has one end that supplies the signal RFp1 to amplifier 50p and the other end that is connected to ground, and is electromagnetically coupled to wiring 163.

[0100] Wiring 162 has one end that supplies the signal RFm1 to amplifier 50m and the other end that is connected to ground, and is electromagnetically coupled to wiring 164.

[0101] In the differential pair 50, amplifier 50p amplifies the signal RFp1 supplied from the other end of wiring 161 and outputs the amplified signal RFp2 from output terminal 50pa. The amplifying transistor included in amplifier 50p is operated by the power supply voltage VDD supplied through wiring 301a, which functions as an inductor, and output terminal 50pa. Capacitor 301b is a bypass capacitor and has one end to which the power supply voltage VDD is supplied and the other end connected to ground.

[0102] Amplifier 50m amplifies the signal RFm1 supplied from the other end of wiring 162 and outputs the amplified signal RFm2 from output terminal 50ma. The amplifying transistor included in amplifier 50m is operated by the power supply voltage VDD supplied through wiring 302a, which functions as an inductor, and output terminal 50ma. Capacitor 302b is a bypass capacitor and has one end to which the power supply voltage VDD is supplied and the other end connected to ground.

[0103] Interstage matching circuit 61p is provided between amplifier 51p and amplifier 50p to match the impedance between amplifier 51p and amplifier 50p. Interstage matching circuit 61m is provided between amplifier 51m and amplifier 50m to match the impedance between amplifier 51m and amplifier 50m.

[0104] The patch antenna 64 is connected to the output terminal 32. The patch antenna 64 functions as a load for the power amplifier circuit 203.

[0105] In this embodiment, a configuration in which a balun 151 is provided on the input side has been described, but the system is not limited to this configuration. A configuration in which a balun 101 including a capacitor connected in parallel with part of the wiring is also provided on the input side is also possible.

[0106] The above describes exemplary embodiments of the present invention. In the balun 101, wiring 111 has one end connected to a balanced line 501p through which one of the balanced signals is transmitted, and the other end connected to a first reference potential. Wiring 112 has one end connected to a balanced line 501m through which the other of the balanced signals is transmitted, and the other end connected to a first reference potential. Wiring 113 has one end and an open other end, and is electromagnetically coupled to wiring 111. Wiring 114 has one end connected to one end of wiring 113, and the other end connected to an unbalanced line 502 through which an unbalanced signal is transmitted, and is electromagnetically coupled to wiring 112. Capacitor 121 is connected in parallel to a portion 111a of wiring 111. Capacitor 122 is connected in parallel to a portion 112a of wiring 112.

[0107] In this configuration, the capacitor 121 is provided in parallel with a portion 111a of the wiring 111, allowing the portion 111a of the wiring 111 and the capacitor 121 to function as an LC tank circuit in the fundamental frequency band of the balanced signal. Similarly, the capacitor 122 is provided in parallel with a portion 112a of the wiring 112, allowing the portion 112a of the wiring 112 and the capacitor 122 to function as an LC tank circuit in the fundamental frequency band of the balanced signal. This allows for good impedance matching between the differential pair preceding the balun 101 and the circuit following the balun 101, thereby suppressing reflection of the fundamental frequency of the balanced signal. In the second harmonic frequency band of the balanced signal, the parallel circuit of the portion 111a of the wiring 111 and the capacitor 121 exhibits significant capacitive properties, so the wiring 111 and the capacitor 121 as a whole become close to a series LC circuit. Similarly, the parallel circuit of part 112a of wiring 112 and capacitor 122 exhibits significant capacitive properties, so wiring 112 and capacitor 122 as a whole become close to a series LC circuit. That is, wiring 111 and capacitor 121, and wiring 112 and capacitor 122 can function as notch filters that short-circuit in the second harmonic bandwidth of the balanced signal. This reduces the impedance of the second harmonic of the balanced signal, allowing the differential pair preceding the balun 101 to operate in Class F without the need for a separate notch filter. Therefore, the amplifier can be operated in Class F while suppressing an increase in circuit size.

[0108] Furthermore, in balun 101, each of the wires 111 and 112 is a quarter-wavelength line. The combined wires 113 and 114 form a half-wavelength line.

[0109] This configuration allows for efficient conversion from balanced signals to unbalanced signals, and vice versa.

[0110] Furthermore, in Balun 101, the frequency of the balanced signal falls within the subterahertz band.

[0111] For example, when using an MCT (Magnetic Coupled Transformer) balun in the subterahertz band, the parasitic capacitance between the transformer wirings is large, resulting in significant losses and preventing the MCT balun from performing to its full potential. In this way, the balun 101 in the subterahertz band allows for a reduction in the length of wirings 111-114, thereby suppressing an increase in circuit size. Furthermore, by using a balun 101 with a wide bandwidth and low loss due to line coupling, a balun 101 with good performance can be provided.

[0112] Furthermore, in balun 101, the electrical length of part 111a of wiring 111 and the electrical length of part 112a of wiring 112 are approximately the same.

[0113] This configuration suppresses imbalances between the electrical characteristics of wiring 111 and wiring 112, thereby enabling better conversion from balanced signals to unbalanced signals and from unbalanced signals to balanced signals.

[0114] In the balun 101, the wiring 111 is provided along the first surface and is formed by a metal electrode 611 extending from one end of the wiring 111 to the other end. The metal electrode 611 forms a portion 111a of the wiring 111 and includes a corner portion 611c where the direction of extension changes. The capacitor 121 is provided outside the corner portion 611c.

[0115] With this configuration, for example, by cutting off the outside of the corner portion 611c, space for the capacitor 121 can be easily secured, thus simplifying the design of the balun 101 layout on the semiconductor chip. Furthermore, since space can be used effectively, the integration density of the semiconductor chip can be improved.

[0116] In the balun 101, the wiring 112 is provided along the first surface and is formed by a metal electrode 612 extending from one end of the wiring 112 to the other end. The metal electrode 612 forms a portion 112a of the wiring 112 and includes a corner portion 612c where the direction of extension changes. The capacitor 122 is provided outside the corner portion 612c.

[0117] With this configuration, for example, by cutting off the outside of the corner portion 612c, space for the capacitor 122 can be easily secured, thus simplifying the design of the balun 101 layout on the semiconductor chip. Furthermore, since space can be used effectively, the integration density of the semiconductor chip can be improved.

[0118] Furthermore, in the balun 101, the wiring 113 is provided along the first surface and is formed by a metal electrode 613 extending from one end of the wiring 113 to the other end. The metal electrode 613 is provided inside the corner portion 611c and includes a corner portion 613c that extends parallel to the corner portion 611c.

[0119] In this configuration, by providing the corner portion 613c on the opposite side of the capacitor 121, the capacitor 121 does not obstruct the routing of the corner portion 613c while maintaining a constant distance from the corner portion 611c. This allows for good electromagnetic coupling between the corner portions 611c and 613c.

[0120] Furthermore, in the balun 101, the wiring 114 is provided along the first surface and is formed by a metal electrode 614 extending from one end of the wiring 114 to the other end. The metal electrode 614 is provided inside the corner portion 612c and includes a corner portion 614c that extends parallel to the corner portion 612c.

[0121] In this configuration, by providing the corner portion 614c on the opposite side of the capacitor 122, the capacitor 122 does not obstruct the routing of the corner portion 614c while maintaining a constant distance from the corner portion 612c. This allows for good electromagnetic coupling between the corner portions 612c and 614c.

[0122] In the balun 101, the wiring 111 is formed by a metal electrode 611 that is provided along the first surface and extends from one end of the wiring 111 to the other end. The metal electrode 611 forms a portion 111a of the wiring 111 and includes a corner portion 611c where the direction of extension changes. The wiring 112 is formed by a metal electrode 612 that is provided along the first surface and extends from one end of the wiring 112 to the other end. The metal electrode 612 forms a portion 112a of the wiring 112 and includes a corner portion 612c where the direction of extension changes. The metal electrode 611 includes extensions 611a and 611b that are connected to the corner portion 611c. The metal electrode 612 includes extensions 612a and 612b that are connected to the corner portion 612c. The extensions 611a and 612a extend from the corner portions 611c and 612c, respectively, so as to move toward each other. Furthermore, the extended portions 611b and 612b extend in the same direction from the corner portions 611c and 612c, respectively.

[0123] With this configuration, the metal electrodes can be routed in a roughly U-shape from the extended portion 611b through the corner portion 611c, extended portion 611a, extended portion 612a, and corner portion 612c to the extended portion 612b, thus providing space for the wiring 113 and 114 inside the U-shape.

[0124] Furthermore, in the power amplification circuit 201, amplifier 51p amplifies the signal RFp2 and outputs the amplified signal RFp3 from output terminal 51pa. Amplifier 51m amplifies the signal RFm2, which has a different phase from the signal RFp2, and outputs the amplified signal RFm3 from output terminal 51ma. Wiring 111 has one end connected to output terminal 50pa and the other end connected to the first reference potential. Wiring 112 has one end connected to output terminal 50ma and the other end connected to the first reference potential. Wiring 113 has one end and the other end is open and is electromagnetically coupled to wiring 111. Wiring 114 has one end connected to one end of wiring 113 and the other end connected to output terminal 32 and is electromagnetically coupled to wiring 112. Capacitor 121 is connected in parallel with a part 111a of wiring 111. Capacitor 122 is connected in parallel with a part 112a of wiring 112.

[0125] In this configuration, the capacitor 121 is provided in parallel with a portion 111a of the wiring 111, allowing the portion 111a of the wiring 111 and the capacitor 121 to function as an LC tank circuit in the fundamental frequency band of the signals RFp2 and RFm2. Similarly, the capacitor 122 is provided in parallel with a portion 112a of the wiring 112, allowing the portion 112a of the wiring 112 and the capacitor 122 to function as an LC tank circuit in the fundamental frequency band of the signals RFp2 and RFm2. This allows for good impedance matching between the amplifiers 51p and 51m and the circuit downstream of the balun 101, thereby suppressing reflection of the fundamental frequencies of the signals RFp2 and RFm2. In the second harmonic frequency band of the signals RFp2 and RFm2, the parallel circuit of the portion 111a of the wiring 111 and the capacitor 121 exhibits significant capacitive properties, so the wiring 111 and the capacitor 121 as a whole become close to a series LC circuit. Similarly, the parallel circuit of part 112a of wiring 112 and capacitor 122 exhibits significant capacitive properties, so wiring 112 and capacitor 122 as a whole become close to a series LC circuit. That is, wiring 111 and capacitor 121, and wiring 112 and capacitor 122 can function as notch filters that short-circuit in the second harmonic bandwidth of signals RFp2 and RFm2. This reduces the impedance of the second harmonics of signals RFp2 and RFm2, allowing amplifiers 51p and 51m to operate in Class F without the need for a separate notch filter. Therefore, the amplifiers can be operated in Class F while suppressing an increase in circuit size.

[0126] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The present invention can be modified or improved without departing from its spirit, and equivalents thereof are also included. That is, any design modifications made to each embodiment by those skilled in the art are also included within the scope of the present invention, as long as they retain the features of the present invention. For example, the elements and their arrangement, materials, conditions, shapes, sizes, etc., of each embodiment are not limited to those exemplified and can be modified as appropriate. Furthermore, each embodiment is illustrative, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible, and these are also included within the scope of the present invention as long as they retain the features of the present invention.

[0127] <1> A first wiring having one end connected to a first balanced line through which one of the balanced signals is transmitted, and the other end connected to a first reference potential, A second wiring having one end connected to a second balanced line through which the other side of the balanced signal is transmitted, and the other end connected to the first reference potential, A third wiring having one end and an open other end, which is electromagnetically coupled to the first wiring, A fourth wiring having one end connected to the one end of the third wiring and the other end connected to an unbalanced line through which an unbalanced signal is transmitted, and which is electromagnetically coupled to the second wiring, A first capacitor connected in parallel with a portion of the first wiring, A second capacitor connected in parallel with a portion of the second wiring, Balan.

[0128] <2> <1> The balance described above, Each of the first and second wirings is a quarter-wavelength line, The combined third and fourth wiring is a half-wavelength transmission line. Balan.

[0129] <3> <1> or <2> The balance described above, The frequency of the balanced signal is included in the subterahertz band. Balan.

[0130] <4> <1> from <3> A balance described in any one of the following: The electrical length of the portion of the first wiring and the electrical length of the portion of the second wiring are approximately the same. Balan.

[0131] <5> <1> from <4> A balance described in any one of the following: The first wiring is provided along the first surface and is formed by a first conductive member extending from one end of the first wiring to the other end of the first wiring. The first conductive member forms a portion of the first wiring and includes a first corner portion where the direction of extension changes, The first capacitor is provided outside the first corner portion, Balan.

[0132] <6> <1> from <5> A balance described in any one of the following: The second wiring is provided along the first surface and is formed by a second conductive member extending from one end of the second wiring to the other end of the second wiring. The second conductive member forms a portion of the second wiring and includes a second corner portion where the direction of extension changes, The second capacitor is provided outside the second corner portion, Balan.

[0133] <7> <5> The balance described above, The third wiring is provided along the first surface and is formed by a third conductive member extending from one end of the third wiring to the other end of the third wiring. The third conductive member is provided inward from the first corner portion and includes a third corner portion that extends parallel to the first corner portion. Balan.

[0134] <8> <6> The balance described above, The fourth wiring is provided along the first surface and is formed by a fourth conductive member extending from one end of the fourth wiring to the other end of the fourth wiring. The fourth conductive member is provided inward from the second corner portion and includes a fourth corner portion that extends parallel to the second corner portion. Balan.

[0135] <9> <1> from <8> A balance described in any one of the following: The first wiring is provided along the first surface and is formed by a first conductive member extending from one end of the first wiring to the other end of the first wiring. The first conductive member forms a portion of the first wiring and includes a first corner portion where the direction of extension changes, The second wiring is provided along the first surface and is formed by a second conductive member extending from one end of the second wiring to the other end of the second wiring. The second conductive member forms a portion of the second wiring and includes a second corner portion where the direction of extension changes, The first conductive member includes a first extension and a second extension connected to the first corner portion, The second conductive member includes a third extension and a fourth extension connected to the second corner portion, The first extension and the third extension extend from the first corner and the second corner, respectively, so as to move closer to each other. The second extension and the fourth extension extend in the same direction from the first corner and the second corner, respectively. Balan.

[0136] <10> A first amplifier that amplifies the first signal and outputs the first amplified signal from the first output terminal, A second amplifier that amplifies a second signal having a different phase from the first signal and outputs the second amplified signal from the second output terminal, A first wiring having one end connected to the first output terminal and the other end connected to the first reference potential, A second wiring having one end connected to the second output terminal and the other end connected to the first reference potential, A third wiring having one end and an open other end, which is electromagnetically coupled to the first wiring, A fourth wiring having one end connected to the one end of the third wiring and the other end connected to the output terminal, and electromagnetically coupled to the second wiring, A first capacitor connected in parallel with a portion of the first wiring, A second capacitor connected in parallel with a portion of the second wiring, Power amplifier circuit. [Explanation of symbols]

[0137] 31…Input terminals 32…Output terminals 50, 51... Differential pairs 50p, 50m, 51p, 51m… Amplifier 50pa, 50ma, 51pa, 51ma… Output terminals 60…Capacitor 61p, 61m...Interstage matching circuit 62p, 62m, 63...capacitor 64... Patch antenna 101... Balan 111, 112, 113, 114… wiring 111a, 112a...some 121, 122… Capacitors 151... Balan 161, 162, 163, 164… wiring 201, 202, 203… Power Amplifier Circuits 301a, 302a, 303a, 304a… wiring 301b, 302b, 303b, 304b… Capacitors 311, 312…LC series circuits 311a, 312a... Capacitors 311b, 312b... Inductors 501p, 501m...balanced line 502…Unbalanced line 611, 612, 613, 614...metal electrode 611a, 611b, 612a, 612b, 613a, 613b, 614a, 614b...extension part 611c, 612c, 613c, 614c... corner section 611ca...Corner cut section 621a, 621b...metal electrode 621c...Bridge section 621ca…metal electrode 701p, 701m... Interlayer vias

Claims

1. A first wiring having one end connected to a first balanced line through which one of the balanced signals is transmitted, and the other end connected to a first reference potential, A second wiring having one end connected to a second balanced line through which the other of the balanced signals is transmitted, and the other end connected to the first reference potential, A third wiring having one end and an open other end, which is electromagnetically coupled to the first wiring, A fourth wiring having one end connected to the one end of the third wiring and the other end connected to an unbalanced line through which an unbalanced signal is transmitted, and which is electromagnetically coupled to the second wiring, A first capacitor connected in parallel with a portion of the first wiring, A second capacitor is connected in parallel with a portion of the second wiring, Balan.

2. A balance according to claim 1, Each of the first and second wirings is a quarter-wavelength line, The combined wiring of the third and fourth wirings is a half-wavelength line. Balan.

3. A balance according to claim 1, The frequency of the balanced signal is included in the subterahertz band. Balan.

4. A balance according to claim 1, The electrical length of the portion of the first wiring and the electrical length of the portion of the second wiring are approximately the same. Balan.

5. A balance according to claim 1, The first wiring is provided along the first surface and is formed by a first conductive member extending from one end of the first wiring to the other end of the first wiring. The first conductive member forms a part of the first wiring and includes a first corner portion where the direction of extension changes, The first capacitor is provided outside the first corner portion, Balan.

6. A balance according to claim 1, The second wiring is provided along the first surface and is formed by a second conductive member extending from one end of the second wiring to the other end of the second wiring. The second conductive member forms a portion of the second wiring and includes a second corner portion where the direction of extension changes, The second capacitor is provided outside the second corner portion, Balan.

7. A balance according to claim 5, The third wiring is provided along the first surface and is formed by a third conductive member extending from one end of the third wiring to the other end of the third wiring. The third conductive member is provided inward from the first corner portion and includes a third corner portion that extends parallel to the first corner portion. Balan.

8. A balance according to claim 6, The fourth wiring is provided along the first surface and is formed by a fourth conductive member extending from one end of the fourth wiring to the other end of the fourth wiring. The fourth conductive member is provided inward from the second corner portion and includes a fourth corner portion that extends parallel to the second corner portion. Balan.

9. A balance according to claim 1, The first wiring is provided along the first surface and is formed by a first conductive member extending from one end of the first wiring to the other end of the first wiring. The first conductive member forms a part of the first wiring and includes a first corner portion where the direction of extension changes, The second wiring is provided along the first surface and is formed by a second conductive member extending from one end of the second wiring to the other end of the second wiring. The second conductive member forms a portion of the second wiring and includes a second corner portion where the direction of extension changes, The first conductive member includes a first extension and a second extension connected to the first corner portion, The second conductive member includes a third extended portion and a fourth extended portion connected to the second corner portion, The first extension and the third extension extend from the first corner and the second corner, respectively, so as to move closer to each other. The second extension and the fourth extension extend in the same direction from the first corner and the second corner, respectively. Balan.

10. A first amplifier that amplifies the first signal and outputs the first amplified signal from the first output terminal, A second amplifier that amplifies a second signal having a different phase from the first signal and outputs the second amplified signal from the second output terminal, A first wiring having one end connected to the first output terminal and the other end connected to the first reference potential, A second wiring having one end connected to the second output terminal and the other end connected to the first reference potential, A third wiring having one end and an open other end, which is electromagnetically coupled to the first wiring, A fourth wiring having one end connected to the one end of the third wiring and the other end connected to the output terminal, and electromagnetically coupled to the second wiring, A first capacitor connected in parallel with a portion of the first wiring, A second capacitor is connected in parallel with a portion of the second wiring, Power amplifier circuit.

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