Power amplifier

Abstract

Suppresses oscillation in power amplifiers. [Solution] The power amplifier comprises a balanced amplifier and a control amplifier. The balanced amplifier includes a first amplifier and a second amplifier and amplifies the input power. The control amplifier, together with the balanced amplifier, forms a load-modulated balanced amplifier and outputs a control signal containing the fundamental wave component or harmonic component of the input power to each of the first and second amplifiers. The control amplifier is positioned between the first and second amplifiers.

Description

Technical Field

[0001] This disclosure relates to power amplifiers.

Background Art

[0002] U.S. Patent Application Publication No. 2018 / 0205348 (Patent Document 1), Japanese Patent Publication No. 2022-506367 (Patent Document 2), and U.S. Patent Application Publication No. 2022 / 0255506 (Patent Document 3) all disclose power amplifiers that perform load modulation. Such power amplifiers are also called load modulated balanced amplifiers (LMBAs).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Non-Patent Documents

[0004]

Non-Patent Document 1

[0005] The power amplifiers (load-modulated balanced amplifiers) disclosed in Patent Documents 1, 2, 3, etc., comprise a balanced amplifier (BA) and a control amplifier. The inventors have focused on the fact that, depending on the embodiment, the balanced amplifier may oscillate in such power amplifiers. It is desirable to suppress oscillation in power amplifiers.

[0006] One of the purposes of this disclosure is to suppress oscillation in power amplifiers. [Means for solving the problem]

[0007] The power amplifier according to this disclosure comprises a balanced amplifier and a control amplifier. The balanced amplifier includes a first amplifier and a second amplifier and amplifies the input power. The control amplifier, together with the balanced amplifier, forms a load-modulated balanced amplifier (LMBA) and outputs a control signal including the fundamental wave component or harmonic component of the input power to each of the first and second amplifiers. The control amplifier is positioned between the first and second amplifiers. [Effects of the Invention]

[0008] According to this disclosure, oscillation in a power amplifier can be suppressed. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a circuit block diagram showing an example of the application of the power amplifier according to Embodiment 1. [Figure 2] Figure 2 is a circuit block diagram showing the configuration of a power amplifier in a comparative example. [Figure 3] Figure 3 shows the configuration of the distributor in the comparative example. [Figure 4] Figure 4 is a circuit block diagram showing the basic configuration of the power amplifier according to Embodiment 1. [Figure 5] FIG. 5 is a diagram showing a first example of the configuration of the coupler in Embodiment 1. [Figure 6] FIG. 6 is a diagram showing a second example of the configuration of the coupler in Embodiment 1. [Figure 7] FIG. 7 is a layout diagram showing an example of the arrangement of the components of the power amplifier according to the comparative example. [Figure 8] FIG. 8 is a layout diagram showing an example of the arrangement of the components of the power amplifier according to Embodiment 1. [Figure 9] FIG. 9 is a circuit block diagram showing a first example of the configuration of the power amplifier according to Example 1 of Embodiment 1. [Figure 10] FIG. 10 is a diagram for explaining a first condition regarding the input power to the rat-race coupler. [Figure 11] FIG. 11 is a diagram for explaining the case where the phase control circuit is not provided. [Figure 12] FIG. 12 is a diagram for explaining a second condition regarding the phase relationship between the power and the control signal. [Figure 13] FIG. 13 is a diagram for explaining a second example of the arrangement of the phase control circuit. [Figure 14] FIG. 14 is a diagram for explaining a third example of the arrangement of the phase control circuit. [Figure 15] FIG. 15 is a Smith chart showing an example of the simulation result regarding the impedance matching of the power amplifier according to Example 1 of Embodiment 1. [Figure 16] FIG. 16 is a diagram showing an example of the simulation result regarding the power efficiency of the power amplifier according to Example 1 of Embodiment 1. [Figure 17] FIG. 17 is a circuit block diagram showing an example of the configuration of the power amplifier according to Example 1 of Embodiment 2. [Figure 18] FIG. 18 is a diagram showing an example of the configuration of the branch-line coupler. [Figure 19] FIG. 19 is a circuit block diagram showing an example of the configuration of the power amplifier according to Example 2 of Embodiment 2. [Figure 20] FIG. 20 is a diagram for explaining the configuration of a distributed coupling type coupler.

Embodiment for Carrying out the Invention

[0010] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0011] (1) The power amplifier according to the present disclosure includes a balanced amplifier including a first amplifier and a second amplifier for amplifying input power, and a control amplifier that forms a load modulation balanced amplifier together with the balanced amplifier and outputs a control signal including a harmonic component of the input power to each of the first amplifier and the second amplifier, and the control amplifier is disposed between the first amplifier and the second amplifier.

[0012] According to the configuration of (1) above, the control amplifier is disposed between the first amplifier and the second amplifier. Therefore, the distance between the first amplifier and the second amplifier is ensured, and the control amplifier functions as a shield between the first amplifier and the second amplifier. As a result, positive feedback due to a part of the power output from one of the first amplifier and the second amplifier returning to the other is less likely to occur (details will be described later). As a result, oscillation in the power amplifier can be suppressed.

[0013] (2) In (1) above, the balanced amplifier may include a directional coupler having a plurality of ports with a phase difference of 180°. The plurality of ports include a first port that receives the power amplified by the first amplifier, a second port that receives the power amplified by the second amplifier, a third port that receives the control signal, and may have a fourth port coupled to a load. The third port may be positioned between the first port and the second port along the outer circumference of the directional coupler with a phase difference of 180°.

[0014] According to the configuration described in (2) above, by using a directional coupler with a phase difference of 180°, the control amplifier can be placed between the first amplifier and the second amplifier without crossing the wiring.

[0015] (3) In (2) above, The directional coupler with a phase difference of 180° may also be a rat-race coupler having a distribution circuit. The first port, the third port, the second port, and the fourth port may be arranged in this order along the distribution circuit. The power amplifier may further include one or more phase control circuits that control the phase of the power amplified by the second amplifier with respect to the phase of the power amplified by the first amplifier.

[0016] According to the configuration described in (3) above, by appropriately controlling the phase with the phase control circuit, it is possible to efficiently supply power to the load while suppressing unnecessary power supply to the control amplifier.

[0017] (4) In (3) above, The rat race coupler may be a ring-type loosely coupled rat race coupler in which the distribution circuit has a ring shape.

[0018] According to the configuration described in (4) above, the cost of the power amplifier can be reduced by using a ring-type loosely coupled rat-race coupler.

[0019] (5) In (3) above, The rat race coupler may be a coupling line type rat race coupler having two coupling lines arranged to connect with each other between the first port and the fourth port.

[0020] According to the configuration described in (5) above, the cost of the power amplifier can be reduced by using a coupled line type rat race coupler. In addition, a high-bandwidth and compact power amplifier can be realized.

[0021] (6) In (1) above, The balanced amplifier may include a directional coupler with a phase difference of 90° having multiple ports. The aforementioned multiple ports are, A first port that receives power amplified by the first amplifier, A second port that receives power amplified by the second amplifier, A third port that receives the aforementioned control signal, It may also have a fourth port that is coupled to a load.

[0022] According to the configuration described in (6) above, even when using a directional coupler with a phase difference of 90°, the control amplifier can be placed between the first amplifier and the second amplifier.

[0023] (7) In the above (6), The aforementioned directional coupler with a phase difference of 90° may also be a branch line coupler having a distribution circuit. The first port, the second port, the fourth port, and the third port may be arranged in this order along the distribution circuit. The first port may be coupled to the first amplifier by a first transmission line. The second port may be coupled to the second amplifier by a second transmission line. The third port may be coupled to the control amplifier by a third transmission line. The first transmission line, the second transmission line, and the third transmission line may be mounted on a multilayer substrate including multiple conductor layers. The first transmission line and the third transmission line may be mounted on different conductor layers among the plurality of conductor layers and intersect three-dimensionally, such that the control amplifier is positioned between the first amplifier and the second amplifier.

[0024] According to the configuration described in (7) above, by crossing the first transmission line and the third transmission line in a three-dimensional manner, a control amplifier can be placed between the first amplifier and the second amplifier using a directional coupler with a phase difference of 90°.

[0025] (8) In (6) above, The aforementioned directional coupler with a phase difference of 90° may also be a distributed coupling type coupler. The first port, the fourth port, the second port, and the third port may be arranged in this order along the outer circumference of the distributed coupling type coupler. The distributed coupling type coupler may have a multilayer structure including a first conductive layer and a second conductive layer. The first port and the fourth port may be connected by a first wiring arranged in the first conductive layer. The second port and the third port may be connected by a second wiring arranged in the second conductive layer. The first wiring and the second wiring may be arranged so as to at least partially overlap when the distributed coupling type coupler is viewed from above.

[0026] According to the configuration of (8) above, by arranging the first wiring and the second wiring to partially overlap inside the distributed coupling type coupler, a control amplifier can be placed between the first amplifier and the second amplifier using a directional coupler with a phase difference of 90°.

[0027] (9) In (1) to (8) above, The power amplifier may further include a divider that divides the input power into the first amplifier, the second amplifier, and the control amplifier.

[0028] According to the configuration described in (9) above, a circuit configuration that distributes the input power to the first amplifier, the second amplifier, and the control amplifier can be easily realized by using a divider.

[0029] (10) In (9) above, The divider may include a first Wilkinson divider and a second Wilkinson divider. The first Wilkinson divider may divide the input power between the first amplifier and the second Wilkinson divider. The second Wilkinson divider may further divide the input power divided by the first Wilkinson divider between the second amplifier and the control amplifier.

[0030] According to the configuration described in (10) above, isolation and impedance matching between the first amplifier, the second amplifier, and the control amplifier can be easily achieved by using a Wilkinson divider as a divider.

[0031] [Details of the embodiments of this disclosure] Next, details of embodiments of this disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated. At least some of the embodiments described below may be combined in any way.

[0032] <Explanation of Terms> In this disclosure and its embodiments, "high frequency" means electromagnetic waves in the MHz band or GHz band (frequency band of 1 MHz or more and less than 1 THz). High frequency includes microwaves. "Microwaves" are electromagnetic waves in the band of 300 MHz or more and less than 300 GHz.

[0033] <Embodiment 1> ≪Overall Structure≫ Figure 1 is a circuit block diagram showing an application example of the power amplifier according to Embodiment 1. In this example, the power amplifier 100 is applied to a base station. The base station 90 is, for example, a massive MIMO (Massive Multiple Input Multiple Output) base station used in 5G (fifth-generation mobile communication system). The base station 90 includes an arithmetic processing unit 91, a transmission unit 92, and an antenna unit 93.

[0034] The arithmetic processing unit 91 performs digital signal processing (such as baseband processing) of information transmitted from the base station 90 during communication between the base station 90 and communication equipment (not shown).

[0035] The transmitting unit 92 includes multiple RF (Radio Frequency) chains 921. Each of the RF chains 921 includes a power amplifier 100 in addition to filters, switches, mixers, D / A converters, etc. (none of which are shown). The configuration of the power amplifier 100 will be described in detail in Figure 2 and subsequent figures.

[0036] The antenna section 93 includes multiple antennas 931. Each of the multiple antennas 931 is connected to a multiple RF chain 921.

[0037] The base station 90 is merely an example of the applications of the power amplifier 100, and the applications of the “power amplifier” in this disclosure are not limited to this. The “power amplifier” in this disclosure may be applied to various devices (such as mobile terminals) used in mobile communication systems, for example.

[0038] <Power amplifier configuration> ≪Comparative Example≫ To facilitate understanding of the power amplifier 100 according to Embodiment 1, we will first briefly describe the configuration of a power amplifier according to a comparative example.

[0039] Figure 2 is a circuit block diagram showing the configuration of a power amplifier in a comparative example. The power amplifier 900 is a load-modulated balanced amplifier (LMBA). The power amplifier 900 includes a first amplifier 1, a second amplifier 2, a control amplifier (CA) 3, a divider 4, a distributor 51, and a combiner 52.

[0040] The divider 4 splits the input power Pin from the AC power supply 901 into two. The input power Pin is a high frequency (typically microwave) with frequency f0. A portion of the input power Pin is supplied to the distributor 51. The distributor 51 distributes the input power Pin to the first amplifier 1 and the second amplifier 2. Each of the first amplifier 1 and the second amplifier 2 amplifies the input power Pin distributed to it and outputs the amplified power to the combiner 52. The combiner 52 combines the power amplified by the first amplifier 1 and the power amplified by the second amplifier 2 and supplies the combined power to the load 902. In the comparative example, the first amplifier 1 and the second amplifier 2, together with the distributor 51 and the combiner 52, form a balanced amplifier.

[0041] The remaining portion of the input power Pin, divided by the divider 4, is supplied to the control amplifier 3. The control amplifier 3 generates a control signal Pctrl from the input power Pin. The control signal Pctrl contains the fundamental component (the component at frequency f0) or harmonic components (the component at frequency 2f0 or higher) of the input power Pin to the balanced amplifier. The control amplifier 3 load-modulates the balanced amplifier by supplying the fundamental component of the control signal Pctrl to the combiner 52. The control amplifier 3 may also inject the harmonic components of the control signal Pctrl into the combiner 52. This is called "harmonic injection." Harmonic injection can improve the power efficiency of the balanced amplifier.

[0042] Figure 3 shows the configuration of the combiner 52 in the comparative example. The combiner 52 is a directional coupler with a phase difference of 90°, and more specifically, a 90° hybrid coupler. In this example, the combiner 52 is a branch line coupler.

[0043] The combiner 52 has an input port 521, an isolation port (also called a cutoff port) 523, and two output ports. Hereafter, the two output ports will be referred to as the direct port (also called a through port) 522 and the coupled port 524. These four ports are arranged clockwise along the outer circumference of the branch line coupler in the order of input port 521, direct port 522, coupled port 524, and isolation port 523. Although not shown in the diagram, the configuration of the distributor 51 is equivalent to that of the combiner 52.

[0044] This embodiment Next, the configuration of the power amplifier 100 according to Embodiment 1 will be described in detail.

[0045] Figure 4 is a circuit block diagram showing the basic configuration of the power amplifier according to Embodiment 1. The power amplifier 100 is an LMBA, similar to the power amplifier 900 in the comparative example. The power amplifier 100 includes a first amplifier 1, a second amplifier 2, a control amplifier 3, a divider 4, and a coupler 6.

[0046] The divider 4 divides the input power Pin of frequency f0 from the AC power supply 901 into three parts in this example. The input power Pin is distributed to the first amplifier 1, the second amplifier 2, and the control amplifier 3. By using the divider 4, a circuit configuration that distributes the input power Pin to the first amplifier 1, the second amplifier 2, and the control amplifier 3 can be easily realized. Each of the first amplifier 1 and the second amplifier 2 amplifies the input power Pin distributed to them from the divider 4 and outputs the amplified power to the coupler 6.

[0047] The first amplifier 1 and the second amplifier 2 have equivalent size (layout area). The first amplifier 1 and the second amplifier 2 are implemented using, for example, gallium nitride (GaN) high electron mobility transistors (HEMTs). However, the implementation method of each amplifier is not limited to this. The first amplifier 1 and the second amplifier 2 may be implemented using IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) (for example, lateral MOSFETs (LDMOSFETs)). The materials for the first amplifier 1 and the second amplifier 2 may be silicon (Si), silicon carbide (SiC), etc.

[0048] The control amplifier 3 generates a control signal Pctrl by amplifying frequency f0 and outputs it to the coupler 6. The control signal Pctrl may include harmonic components of frequency 2f0 or higher, as described in this example. The control amplifier 3, like the first amplifier 1 and the second amplifier 2, is implemented using, for example, a GaN HEMT. The control amplifier 3 may also be implemented using a Si or SiC IGBT, or a Si or SiC MOSFET.

[0049] The first amplifier 1 and the second amplifier 2, together with the coupler 6, form a balanced amplifier. The balanced amplifier performs load modulation using the fundamental wave component of the control signal Pctrl from the control amplifier 3. Alternatively, the balanced amplifier may perform harmonic injection using the harmonic components of the control signal Pctrl. The balanced amplifier generates output power Pout from input power Pin by load modulation or harmonic injection. The balanced amplifier supplies output power Pout to the load 902.

[0050] In this example, the input power Pin from the AC power supply 901 is distributed to all three amplifiers. However, the power amplifier 100 may be configured to distribute the input power Pin to the first amplifier 1 and the second amplifier 2, while supplying a separate power (not shown) to the control amplifier 3.

[0051] Figure 5 shows a first example of the configuration of the coupler 6 in Embodiment 1. The coupler 6 in Embodiment 1 is a directional coupler with a phase difference of 180°, and more specifically, a 180° hybrid coupler. In this example, the coupler 6 is a rat-race coupler.

[0052] The rat-race coupler 61 has a ring-shaped distribution channel 610, an input port 611, a direct port 612, an isolation port 613, and a coupling port 614. These ports are arranged in this order counterclockwise along the distribution channel 610. These ports may also be arranged in the same order clockwise along the distribution channel 610.

[0053] Input port 611 is coupled to the output node of the first amplifier 1. Isolation port 613 is coupled to the output node of the second amplifier 2. Direct port 612 is coupled to the output node of the control amplifier 3. Coupling port 614 is coupled to the load 902.

[0054] The input port 611 corresponds to the "first port" in this disclosure. The direct port 612 corresponds to the "third port" in this disclosure. The isolation port 613 corresponds to the "second port" in this disclosure. The coupling port 614 corresponds to the "fourth port" in this disclosure.

[0055] Figure 6 shows a second example of the configuration of the coupler 6 in Embodiment 1. The coupler 6 may be a different type of rat-race coupler than the rat-race coupler 61 shown in Figure 5. The rat-race coupler 62 shown in Figure 6 differs from the rat-race coupler 61 in that it further has two coupling lines 625 arranged closely together between the input port 621 and the coupling port 624 to electromagnetically couple with each other. The other configurations of the rat-race coupler 62 are the same as those of the rat-race coupler 61 and will not be repeated in this description.

[0056] The rat race coupler 61 may also be called a ring-type loosely coupled rat race coupler. The rat race coupler 62 may also be called a coupled-line type rat race coupler. By using a ring-type loosely coupled rat race coupler, the cost of the power amplifier 100 can be reduced. By using a coupled-line type rat race coupler, in addition to reducing the cost of the power amplifier 100, a high-bandwidth and compact power amplifier 100 can be realized.

[0057] ≪Contrast in Arrangement≫ Generally, oscillation in an amplifier can occur when a portion of the power (signal) output from its output node returns to the input node of the same amplifier (in other words, positive feedback occurs). The arrangement of the components can also affect the oscillation of an amplifier.

[0058] Figure 7 is a layout diagram showing an example of the arrangement of components of the power amplifier 900 in the comparative example. In the comparative example, a portion of the power output from the output node of the first amplifier 1 returns to the input node of the first amplifier 1. In addition, as shown in Figure 7, the first amplifier 1 and the second amplifier 2 are arranged adjacent to each other in the comparative example. In such an arrangement, the distance between the first amplifier 1 and the second amplifier 2 is short. Therefore, a portion of the power output from the output node of the first amplifier 1 can also return to the input node of the second amplifier 2. Similarly, a portion of the power output from the output node of the second amplifier 2 can return to the input node of the second amplifier 2, as well as to the input node of the first amplifier 1.

[0059] Thus, in the comparative example, not only is there positive feedback from the first amplifier 1 itself and positive feedback from the second amplifier 2 itself, but positive feedback from one of the first amplifier 1 and the second amplifier 2 to the other can also occur. Therefore, depending on conditions such as the input power bandwidth, oscillation of the power amplifier 900 may be likely to occur.

[0060] The adjacent placement of the first amplifier 1 and the second amplifier 2 is thought to originate from the port arrangement of the branch line coupler used as the combiner 52 in the comparative example. More specifically, as shown in Figure 3, the branch line coupler has input ports 521 and isolation ports 523 arranged consecutively along its outer circumference. When the output node of the first amplifier 1 is coupled to input port 521 and the output node of the second amplifier 2 is coupled to isolation port 523, the first amplifier 1 and the second amplifier 2 naturally end up adjacent to each other.

[0061] In contrast, in Embodiment 1, a rat-race coupler 61 is used instead of a branch-line coupler. In the rat-race coupler 61, as shown in Figure 5, the arrangement of the input port 611 and the isolation port 613 is discontinuous, and a direct port 612 is located between the input port 611 and the isolation port 613. The direct port 612 is coupled to the output node of the control amplifier 3. Therefore, as shown in Figures 4 and 5, the first amplifier 1 and the second amplifier 2 are arranged with the control amplifier 3 in between. In other words, in Embodiment 1, the control amplifier 3 is located between the first amplifier 1 and the second amplifier 2. The same applies to the rat-race coupler 62 shown in Figure 6.

[0062] Figure 8 is a layout diagram showing an example of the arrangement of components of the power amplifier 100 according to Embodiment 1. In the arrangement of Embodiment 1 shown in Figure 8, the first amplifier 1 and the second amplifier 2 are separated compared to the arrangement of the comparative example shown in Figure 7, and the space between the first amplifier 1 and the second amplifier 2 is shielded by the control amplifier 3. As a result, positive feedback from one of the first amplifier 1 and the second amplifier 2 to the other is less likely to occur. Therefore, according to Embodiment 1, oscillation in the power amplifier 100 can be suppressed.

[0063] <Example 1 of Embodiment 1> Circuit Configuration Figure 9 is a circuit block diagram showing a first example of the configuration of a power amplifier according to Embodiment 1 of Embodiment 1. The power amplifier 101 includes a first amplifier 1, a second amplifier 2, a control amplifier 3, a divider 4A, a rat-race coupler 61, a phase shifter 71, and a phase control circuit 72. The divider 4A includes a first Wilkinson divider 41, a second Wilkinson divider 42, a transmission line 431, and a transmission line 432. The power amplifier 101 may include a rat-race coupler 62 (see Figure 6) instead of the rat-race coupler 61.

[0064] The first Wilkinson divider 41 includes a branching section 411, a transmission line 412, an output port 413, a transmission line 414, an output port 415, and an isolation section 416.

[0065] The branching section 411 branches the transmission line from the input port coupled to the AC power supply 901 into a transmission line to transmission line 412 and a transmission line to transmission line 414. Transmission line 412 is a λ / 4 (λ is wavelength) transmission line that connects the branching section 411 and the output port 413. Transmission line 414 is a λ / 4 transmission line that connects the branching section 411 and the output port 413. The isolation section 416 matches the impedance between output port 413 and output port 415 and insulates output port 413 and output port 415 from each other.

[0066] The second Wilkinson divider 42 includes a branching section 421, a transmission line 422, an output port 423, a transmission line 424, an output port 425, and an isolation section 426.

[0067] The branching section 421 branches the transmission line from the transmission line 432 into a transmission line to transmission line 422 and a transmission line to transmission line 424. Transmission line 422 is a λ / 4 transmission line connecting the branching section 421 and output port 423. Transmission line 424 is a λ / 4 transmission line connecting the branching section 421 and output port 425. The isolation section 426 matches the impedance between output port 423 and output port 425 and insulates output port 423 and output port 425.

[0068] In this way, by using the first Wilkinson divider 41 and the second Wilkinson divider 42 as dividers, isolation and impedance matching between the first amplifier 1, the second amplifier 2, and the control amplifier 3 can be easily achieved. Furthermore, the phase difference between the power output from the first amplifier 1 and the power output from the second amplifier 2 can be set to a desired value (90° in the example described later).

[0069] The phase shifter 71 is coupled between the output port 423 of the second Wilkinson divider 42 and the input node of the control amplifier 3. The phase shifter 71 delays the phase of the signal supplied from the second Wilkinson divider 42 to the control amplifier 3. In this embodiment, the amount of phase delay by the phase shifter 71 can be adjusted so that the phase of the power supplied from the first amplifier 1 to the input port 611 of the rat race coupler 61 and the phase of the control signal Pctrl supplied from the control amplifier 3 to the direct port 612 of the rat race coupler 61 are in appropriate phase.

[0070] In this embodiment, the phase control circuit 72 is coupled between the output node of the second amplifier 2 and the isolation port 613 of the rat-race coupler 61. However, as will be described later, the phase control circuit 72 may be coupled between the output node of the first amplifier 1 and the input port 611 of the rat-race coupler 61 (see Figure 13). The phase control circuit 72 may be coupled between the output node and input port 611 of the first amplifier 1, and also between the output node of the second amplifier 2 and the isolation port 613 (see Figure 14).

[0071] The phase control circuit 72 is configured to control the phase difference between the power amplified by the first amplifier 1 and the power amplified by the second amplifier 2, and to control the phase difference between the power amplified by the first amplifier 1 and / or the power amplified by the second amplifier 2 and the control signal Pctrl from the control amplifier 3. In this example, the phase control circuit 72 is configured to delay the phase of the power amplified by the second amplifier 2 by 90°, and to delay the phase of the control signal Pctrl transmitted from the control amplifier 3 to the second amplifier 2 by 90°.

[0072] The phase delay amount by the phase shifter 71 and the phase control circuit 72 should preferably be determined so as to satisfy the following two conditions.

[0073] ≪First condition for phase control≫ The first condition is a phase condition relating to the input power to the rat-race coupler 61. More specifically, the first condition is a condition for efficiently combining the input power from the first amplifier 1 to the input port 611 of the rat-race coupler 61 and the input power from the second amplifier 2 to the isolation port 613 of the rat-race coupler 61.

[0074] Figure 10 is a diagram illustrating the first condition regarding the input power to the rat-race coupler 61. For simplicity, the phase control circuit 72 is not provided. It is also assumed that a resistor R1 is coupled to the direct port 612 of the rat-race coupler 61 in place of the control amplifier 3, and a resistor R2 is coupled to the coupling port 614 of the rat-race coupler 61 in place of the load 902.

[0075] The phase difference between input port 611 and direct port 612, the phase difference between direct port 612 and isolation port 613, and the phase difference between isolation port 63 and coupling port 614 are all 90°. The phase difference between input port 611 and coupling port 614 is 270°.

[0076] The phase of the power transmitted from the first amplifier 1 to the input port 611 (indicated by the white arrow) is denoted as φ1. The phase of the power transmitted from the second amplifier 2 to the isolation port 613 (indicated by the hatched arrow) is denoted as φ2. These two powers have the same amplitude.

[0077] The first condition is that the phase φ1 at the input port 611 and the phase φ2 at the isolation port 613 are in opposite phases. In this example, we assume that phase φ1 = 0° and phase φ2 = 180°.

[0078] First, let's explain the power supplied to the rat-race coupler 61 from the input port 611 or the isolation port 613 and output from the direct port 612. As power with phase φ1 = 0° is transmitted from the input port 611 to the direct port 612, a phase delay of 90° is added to this power, so the phase φ1 at the direct port 612 is 90°. On the other hand, as power with phase φ2 = 180° is transmitted from the isolation port 613 to the direct port 612, a phase delay of 90° is added to this power, so the phase φ2 at the direct port 612 is 270°. Therefore, the power transmitted from the input port 611 to the direct port 612 and the power transmitted from the isolation port 613 to the direct port 612 are in opposite phase and have the same amplitude. Since these two powers cancel each other out, no power is output from the direct port 612 and supplied to the resistor R1 (a substitute for the control amplifier 3).

[0079] Next, we will describe the power supplied to the rat-race coupler 61 from the input port 611 or the isolation port 613 and output from the coupling port 614. As power with phase φ1 = 0° is transmitted from the input port 611 to the coupling port 614, a phase delay of 270° is added to this power, so the phase φ1 at the coupling port 614 is 270°. On the other hand, as power with phase φ2 = 180° is transmitted from the isolation port 613 to the coupling port 614, a phase delay of 90° is added to this power, so the phase φ2 at the coupling port 614 is 270°. Therefore, the power transmitted from the input port 611 to the coupling port 614 and the power transmitted from the isolation port 613 to the coupling port 614 are in phase and have the same amplitude. The combined power of these two powers is output from the coupling port 614 and supplied to the resistor R2 (a substitute for the load 902) as output power Pout.

[0080] In this way, by making the input power to input port 611 (phase φ1) and the input power to isolation port 613 (phase φ2) out of phase, it is possible to efficiently supply power to the load 902 while suppressing unnecessary power supply to the control amplifier 3.

[0081] ≪Second condition for phase control≫ The second condition is a phase condition for matching the timing of load modulation operation between the first amplifier 1 and the second amplifier 2. More specifically, the second condition is a condition for appropriately setting the relationship between the phase of the power output from each amplifier and the phase of the control signal Pctrl transmitted to each amplifier.

[0082] Figure 11 illustrates the case where the phase control circuit 72 is not provided. As indicated by the black arrows, of the control signal Pctrl output from the control amplifier 3 to the direct port 612, a portion is transmitted to the first amplifier 1 via the input port 611, and another portion is transmitted to the second amplifier 2 via the isolation port 613.

[0083] The phase of the control signal Pctrl is denoted as φctrl. A 90° phase delay is added when the control signal Pctrl is transmitted from the direct port 612 to the input port 611. Similarly, a 90° phase delay is added when the control signal Pctrl is transmitted from the direct port 612 to the isolation port 613.

[0084] The phase difference between the input power from the first amplifier 1 to the input port 611 (indicated by the white arrow) with respect to the control signal Pctrl output from the input port 611 to the first amplifier 1 is denoted as Δφ1. That is, phase difference Δφ1 = φ1 - φctrl. The phase difference between the input power from the second amplifier 2 to the isolation port 613 (indicated by the arrow with hatched diagonal lines) with respect to the control signal Pctrl output from the isolation port 613 to the second amplifier 2 is denoted as Δφ2. That is, phase difference Δφ2 = φ2 - φctrl.

[0085] The second condition is that the phase difference Δφ1 with respect to the first amplifier 1 is equal to the phase difference Δφ2 with respect to the second amplifier 2. In this example, the phase of the control signal Pctrl at the direct port 612 is assumed to be φctrl = 0°.

[0086] As in Figure 10, if the phase φ1 of the input power to input port 611 is set to 0° and the phase φ2 of the input power to isolation port 613 is set to 180°, the first condition is satisfied.

[0087] On the other hand, the phase φctrl of the control signal Pctrl in the first amplifier 1 is 90°. If the phase control circuit 72 is not provided, the phase φctrl of the control signal in the second amplifier 2 is also 90°. In that case, the phase difference Δφ1 = φ1 - φctrl = 0° - 90° = -90°, and the phase difference Δφ2 = φ2 - φctrl = 180° - 90° = 90°. That is, the phase difference Δφ1 in the first amplifier 1 and the phase difference Δφ2 in the second amplifier 2 are different. Therefore, the second condition is not satisfied.

[0088] Figure 12 is a diagram illustrating the second condition regarding the phase relationship between power and control signals. In Figure 12, a phase control circuit 72 is provided between the output node of the second amplifier 2 and the isolation port 613. In this embodiment, the phase φ2 of the power output from the second amplifier 2 to the phase control circuit 72 is set to 90°. The phase delay amount by the phase control circuit 72 is set to 90°.

[0089] First, let's explain the first condition. The phase φ2 of the input power from the second amplifier 2 to the isolation port 613 is 180° because a 90° phase delay is added by the phase control circuit 72. On the other hand, the phase φ1 of the input power from the first amplifier 1 to the input port 611 is 0°, just as in the case where the phase control circuit 72 is not provided. That is, the input power to the input port 611 and the input power to the isolation port 613 are in opposite phase. Therefore, the first condition is satisfied.

[0090] Next, let's explain the second condition. The phase φctrl of the control signal Pctrl output from isolation port 613 is 90°. A 90° phase delay is added to this signal component by the phase control circuit 72, so the phase φctrl of the control signal Pctrl in the second amplifier 2 is 180°. Thus, the phase difference in the second amplifier 2 is calculated as Δφ2 = φ2 - φctrl = 90° - 180° = -90°. On the other hand, the phase φctrl of the control signal Pctrl output from input port 611 is also 90°. For this signal component, the phase difference in the first amplifier 1 is calculated as Δφ1 = φ1 - φctrl = 0° - 90° = -90°, similar to the case where the phase control circuit 72 is not provided. That is, the phase difference Δφ1 in the first amplifier 1 is equal to the phase difference Δφ2 in the second amplifier 2. Therefore, the second condition is also satisfied.

[0091] When the second condition is met, the phase relationship (phase difference Δφ1 and phase difference Δφ2) between the output power from each amplifier and the control signal Pctrl to each amplifier is aligned between the first amplifier 1 and the second amplifier 2, so that the timing of the load modulation operation is matched. Therefore, it becomes possible to appropriately perform load modulation operation on the first amplifier 1 and the second amplifier 2 using the control signal Pctrl.

[0092] Thus, in this embodiment, by using the divider 4A (first Wilkinson divider 41 and second Wilkinson divider 42) to set the phase φ2 of the power output from the second amplifier 2 to the phase control circuit 72 to 90° relative to the phase φ1 = 0° of the power output from the first amplifier 1, and by setting the phase delay amount by the phase control circuit 72 to 90°, the first and second conditions can be satisfied simultaneously.

[0093] <<Other layout examples>> The arrangement of the phase control circuit 72 is not limited to the arrangements shown in Figures 9 and 12. The phase control circuit 72 can be placed in other positions as well. The amount of phase delay by the phase control circuit 72 should be appropriately set according to the arrangement of the phase control circuit 72.

[0094] Figure 13 illustrates a second example of the arrangement of the phase control circuit 72. In this example, the phase control circuit 72 is coupled between the output node of the first amplifier 1 and the input port 611. The phase φ2 of the power output from the second amplifier 2 is set to 90°. The phase delay amount by the phase control circuit 72 is set to 270°. Although a detailed explanation will not be repeated, both the first and second conditions can be satisfied simultaneously with this configuration.

[0095] Figure 14 is a diagram illustrating a third example of the arrangement of the phase control circuit 72. As shown in Figure 14, two or more phase control circuits 72 may be provided. In this example, the first phase control circuit 72A is coupled between the output node of the first amplifier 1 and the input port 611, and the second phase control circuit 72B is coupled between the output node of the second amplifier 2 and the isolation port 613. In this case, for example, the phase φ2 of the power output from the second amplifier 2 to the second phase control circuit 72B may be set to 90°, the phase delay amount by the first phase control circuit 72A may be set to 90°, and the phase delay amount by the second phase control circuit 72B may be set to 180°. This also satisfies both the first and second conditions simultaneously.

[0096] <Simulation> Figure 15 is a Smith chart showing an example of the simulation results regarding impedance matching of the power amplifier 101 according to Embodiment 1 of Embodiment 1. In Figure 15, from top to bottom, the impedance changes of the control amplifier 3, the first amplifier 1, and the second amplifier when load modulation is performed by the fundamental wave component of the control signal Pctrl are shown. These were obtained from simulations using the circuit configuration shown in Figure 9. The same applies to the simulation in Figure 16, which will be described later.

[0097] As shown in Figure 15, it was confirmed that the control amplifier 3 was not load-modulated. In addition, it was confirmed that the impedance of the first amplifier 1 and the impedance of the second amplifier 2 were equal, in other words, that the first amplifier 1 and the second amplifier 2 were impedance-matched by load modulation. This indicates that the power amplifier 101 was operating with load modulation correctly.

[0098] Figure 16 shows an example of simulation results regarding the power efficiency of the power amplifier 101 according to Embodiment 1 of Embodiment 1. The horizontal axis represents the output power of the power amplifier 101, and the vertical axis represents the power efficiency of the power amplifier 101. For comparison, the output power dependence (trend) of the power efficiency of a typical single power amplifier (single amplifier) ​​is shown by a dashed line.

[0099] Figure 16 shows that, compared to a single-ended amplifier, the power efficiency of the power amplifier 101 in the back-off region is improved by the load modulation operation of the power amplifier 101.

[0100] <Summary> As described above, in Embodiment 1, the first amplifier 1 and the second amplifier 2 form a balanced amplifier together with a directional coupler with a phase difference of 180°. When the directional coupler with a phase difference of 180° is the rat-race coupler 61 shown in Figure 5, the input port 611 coupled to the first amplifier 1 and the isolation port 613 coupled to the second amplifier 2 are not adjacent. A direct port 612 is located between the input port 611 and the isolation port 613. Therefore, by coupling the control amplifier 3 to the direct port 612, the control amplifier 3 is positioned between the first amplifier 1 and the second amplifier 2. The same applies when the directional coupler with a phase difference of 180° is the rat-race coupler 62 shown in Figure 6.

[0101] By placing a control amplifier 3 between the first amplifier 1 and the second amplifier 2, a sufficient distance is maintained between them, and the control amplifier 3 acts as a shield between them. This makes positive feedback less likely to occur between the first amplifier 1 and the second amplifier 2. As a result, oscillation in power amplifiers 100, 101, and 102 can be suppressed.

[0102] <Embodiment 2> Embodiment 1 described a configuration in which the coupler 6 is a directional coupler with a phase difference of 180° (asymmetric directional coupler). Embodiment 2 describes a configuration in which the coupler 6 is a directional coupler with a phase difference of 90° (symmetric directional coupler).

[0103] <Example 1 of Embodiment 2> Figure 17 is a circuit block diagram showing an example of the configuration of a power amplifier according to Embodiment 1 of Embodiment 2. Power amplifier 201 differs from power amplifier 101 according to Embodiment 1 of Embodiment 1 (see Figure 9) in that it includes a branch line coupler 63 instead of a rat race coupler 61.

[0104] Figure 18 shows an example of the configuration of a branch line coupler 63. Referring to Figures 17 and 18, the branch line coupler 63 has a rectangular distribution channel 630, an input port 631, a direct port 632, an isolation port 633, and a coupling port 634. These ports are arranged counterclockwise along the outer circumference of the branch line coupler 63 or along the distribution channel 630 in the order of input port 631, isolation port 633, coupling port 634, and direct port 632. The above four ports may also be arranged in the same order clockwise.

[0105] The input port 631 corresponds to the "first port" in this disclosure. The isolation port 633 corresponds to the "second port" in this disclosure. The coupling port 634 corresponds to the "fourth port" in this disclosure. The direct port 632 corresponds to the "third port" in this disclosure.

[0106] Input port 631 is coupled to the output node of the first amplifier 1 by transmission line 81. Direct port 632 is coupled to the output node of the control amplifier 3 by transmission line 83. Isolation port 633 is coupled to the output node of the second amplifier 2 by transmission line 82. Coupling port 634 is coupled to load 902.

[0107] Transmission lines 81, 82, and 83 are mounted on a multilayer substrate containing multiple conductor layers. Such mounting techniques may include, for example, the technology of multilayer monolithic microwave integrated circuits (MMICs). The multilayer substrate may include a double-sided substrate.

[0108] Transmission lines 81 and 83 are mounted on different conductor layers among multiple conductor layers and intersect three-dimensionally. Therefore, it is possible to place the control amplifier 3 between the first amplifier 1 and the second amplifier 2 while employing a branch line coupler 63 in which the input port 631 and the isolation port 633 are adjacent to each other. Transmission lines 81, 82, and 83 correspond to the "first transmission line," "second transmission line," and "third transmission line" respectively in this disclosure.

[0109] Alternatively, a general commercially available coupler may be used instead of the branch line coupler 63. Even when using a commercially available coupler, the control amplifier 3 can be placed between the first amplifier 1 and the second amplifier 2 by using a multilayer circuit board.

[0110] <Example 2 of Embodiment 2> Figure 19 is a circuit block diagram showing an example of the configuration of a power amplifier according to Embodiment 2 of Embodiment 2. Power amplifier 202 differs from power amplifier 201 according to Embodiment 1 of Embodiment 2 (see Figure 17) in that it includes a distributed coupling type coupler 64 instead of a branch line coupler 63.

[0111] The distributed coupling coupler 64 has an input port 641, a direct port 642, an isolation port 643, and a coupling port 644. These ports are arranged clockwise along the outer circumference of the distributed coupling coupler 64 in the order of input port 641, coupling port 644, isolation port 643, and direct port 642. In other words, the arrangement order of the four ports differs between the branch line coupler 63 and the distributed coupling coupler 64.

[0112] The input port 641 corresponds to the "first port" in this disclosure. The coupling port 644 corresponds to the "fourth port" in this disclosure. The isolation port 643 corresponds to the "second port" in this disclosure. The direct port 642 corresponds to the "third port" in this disclosure.

[0113] Input port 641 is coupled to the output node of the first amplifier 1 by transmission line 81. Direct port 642 is coupled to the output node of the control amplifier 3 by transmission line 83. Isolation port 643 is coupled to the output node of the second amplifier 2 by transmission line 82. Coupling port 644 is coupled to load 902.

[0114] Unlike Example 1, Example 2 does not involve crossing between transmission line 81 and transmission line 83. This is due to the use of a distributed coupling type coupler 64.

[0115] Figure 20 is a diagram illustrating the configuration of the distributed coupling type coupler 64. Figure 20 shows a perspective view of the distributed coupling type coupler 64 when viewed from above (see upper figure) and a cross-sectional view of the distributed coupling type coupler 64 along the line XXII-XXII (see lower figure).

[0116] The distributed coupling type coupler 64 has a rectangular flat plate shape extending in the XY plane direction when viewed from above along the Z direction in the figure. The Z direction is the thickness direction of the distributed coupling type coupler 64. The distributed coupling type coupler 64 has a multilayer structure in which a first conductive layer 651, an insulating layer 653, and a second conductive layer 652 are stacked in this order in the thickness direction.

[0117] The input port 641 and the direct port 642 are located on the same side of the rectangle in the first conductive layer 651. The isolation port 643 and the coupling port 644 are located on the same side of the rectangle (the side opposite to the input port 641 and the direct port 642) in the second conductive layer 652. The input port 641 and the direct port 642 are coupled by wiring 661 in the first conductive layer 651, and the isolation port 643 and the coupling port 644 are coupled by wiring 662 in the second conductive layer 652.

[0118] Wires 661 and 662 are arranged close to each other so as to be electromagnetically coupled to each other via the insulating layer 653. In this example, wires 661 and 662 are arranged so as to at least partially overlap when the distributed coupling coupler 64 is viewed from above. In this way, since wires 661 and 662 intersect three-dimensionally inside the distributed coupling coupler 64, it is not necessary to cross the transmission lines outside the distributed coupling coupler 64. Wires 661 and 662 correspond to the "first wiring" and "second wiring" as described herein.

[0119] <Summary> As described above, in Embodiment 2, the first amplifier 1 and the second amplifier 2 form a balanced amplifier together with a directional coupler with a phase difference of 90°. When the directional coupler with a phase difference of 90° is a branch line coupler 63 (see Figures 17 and 18), the input port 611 and the isolation port 613 are adjacent to each other. However, by crossing the transmission line 81 and the transmission line 83 three-dimensionally outside the branch line coupler 63 using a multilayer substrate, the control amplifier 3 can be placed between the first amplifier 1 and the second amplifier 2.

[0120] By placing a control amplifier 3 between the first amplifier 1 and the second amplifier 2, a sufficient distance is maintained between them, and the control amplifier 3 acts as a shield between them. This makes positive feedback less likely to occur between the first amplifier 1 and the second amplifier 2. As a result, oscillation in the power amplifier 201 can be suppressed.

[0121] On the other hand, if the directional coupler with a phase difference of 90° is a distributed coupling type coupler 64 (see Figures 19 and 20), the input port 641 and the isolation port 643 are not adjacent, and the direct port 642 is located between the input port 641 and the isolation port 643. Therefore, by coupling the control amplifier 3 to the direct port 612, the control amplifier 3 is positioned between the first amplifier 1 and the second amplifier 2.

[0122] In the distributed coupling type coupler 64, the wiring 661 and wiring 662 are coupled to each other even though they are arranged on different conductive layers inside the coupler, so it is not necessary to cross the transmission lines three-dimensionally outside the coupler. When using the distributed coupling type coupler 64, oscillation in the power amplifier 202 can be suppressed in the same way as when using the branch line coupler 63.

[0123] Embodiment 1, Embodiment 2, and the configurations described in their respective examples can be combined as appropriate.

[0124] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the embodiments described above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0125] 100, 101, 102, 201, 202, 900 Power Amplifier 1. First Amplifier 2. Second Amplifier 3. Control Amplifier 4,4A,4B divider 41. Wilkinson Divider No. 1 42 Wilkinson Divider No. 2 44 Rat Race Coupler 51 Distributor 52 Synthesizer 6 Combiner 61,62 Rat Race Coupler 63 Branch Line Coupler 64 Distributed Coupler 651 First conductive layer 652 Second conductive layer 653 Insulating layer 661,662 Wiring 71 Phase Shifter 72 Phase control circuit 72A First Phase Control Circuit 72B Second Phase Control Circuit 73 Phase Shifter 81, 82, 83 transmission lines 411,421 Branch 412,414,422,424 transmission lines Output ports 413, 415, 423, 425 416,426 Isolation section 431,432 transmission lines 440,610 distribution line 441, 521, 611, 631, 641 Input Ports 442,522,612,632,642 Direct Ports 443,523,613,633,643 Isolation Ports 444,524,614,634,644 combined ports 90 base station 91 Arithmetic Processing Unit 92 Transmitter 93 Antenna section 901 AC power supply 902 load 921 RF chain 931 Antenna R1,R2 resistance

Claims

1. A balanced amplifier that includes a first amplifier and a second amplifier to amplify the input power, The system includes a control amplifier that, together with the balanced amplifier, forms a load-modulated balanced amplifier and outputs a control signal including the fundamental wave component or harmonic component of the input power to the first amplifier and the second amplifier, respectively. The control amplifier is a power amplifier located between the first amplifier and the second amplifier.

2. The balanced amplifier includes a directional coupler with a phase difference of 180° having multiple ports. The aforementioned multiple ports are, A first port that receives power amplified by the first amplifier, A second port that receives power amplified by the second amplifier, A third port that receives the aforementioned control signal, It has a fourth port which is coupled to the load, The power amplifier according to claim 1, wherein the third port is located between the first port and the second port along the outer circumference of the directional coupler with a phase difference of 180°.

3. The aforementioned directional coupler with a phase difference of 180° is a rat-race coupler having a distribution circuit. The first port, the third port, the second port, and the fourth port are arranged in this order along the distribution circuit. The power amplifier according to claim 2, further comprising one or more phase control circuits for controlling the phase of the power amplified by the second amplifier with respect to the phase of the power amplified by the first amplifier.

4. The power amplifier according to claim 3, wherein the rat race coupler is a ring-type loosely coupled rat race coupler having a ring-shaped distribution circuit.

5. The power amplifier according to claim 3, wherein the rat-race coupler is a coupled-line type rat-race coupler having two coupled lines arranged to couple with each other between the first port and the fourth port.

6. The balanced amplifier includes a directional coupler with a phase difference of 90° having multiple ports. The aforementioned multiple ports are, A first port that receives power amplified by the first amplifier, A second port that receives power amplified by the second amplifier, A third port that receives the aforementioned control signal, The power amplifier according to claim 1, further comprising a fourth port coupled to a load.

7. The aforementioned directional coupler with a phase difference of 90° is a branch line coupler having a distribution circuit, The first port, the second port, the fourth port, and the third port are arranged in this order along the distribution circuit. The first port is coupled to the first amplifier by a first transmission line. The second port is coupled to the second amplifier by a second transmission line. The third port is coupled to the control amplifier by a third transmission line. The first transmission line, the second transmission line, and the third transmission line are mounted on a multilayer substrate including multiple conductor layers. The power amplifier according to claim 6, wherein the first transmission line and the third transmission line are mounted on different conductor layers among the plurality of conductor layers and intersect three-dimensionally, such that the control amplifier is positioned between the first amplifier and the second amplifier.

8. The aforementioned directional coupler with a phase difference of 90° is a distributed coupling type coupler. The first port, the fourth port, the second port, and the third port are arranged in this order along the outer circumference of the distributed coupling type coupler. The distributed coupling type coupler has a multilayer structure including a first conductive layer and a second conductive layer. The first port and the fourth port are connected by a first wiring arranged in the first conductive layer. The second port and the third port are connected by a second wiring arranged in the second conductive layer. The power amplifier according to claim 6, wherein the first wiring and the second wiring are arranged to overlap at least partially when the distributed coupling type coupler is viewed from above.

9. The power amplifier according to any one of claims 1 to 8, further comprising a divider for dividing the input power into the first amplifier, the second amplifier, and the control amplifier.

10. The divider includes a first Wilkinson divider and a second Wilkinson divider. The first Wilkinson divider divides the input power between the first amplifier and the second Wilkinson divider. The power amplifier according to claim 9, wherein the second Wilkinson divider further divides the input power divided by the first Wilkinson divider into the second amplifier and the control amplifier.

Images