Power amplifier, amplification method and transmitter

Abstract

The present disclosure relates to a power amplifier, an amplification method, and a transmitter. According to an embodiment, the power amplifier includes a power amplifier core unit capable of performing amplitude control in discrete integer steps and a variable attenuator. The power amplifier core unit performs amplitude control to reproduce an envelope of an RF signal. The variable attenuator changes an attenuation amount, and controls average transmission power by using a combination of the amplitude control performed by the power amplifier core unit and the attenuation amount of the variable attenuator.

Description

Cross-reference to related applications

[0001] The entire disclosure of Japanese Patent Application No. 2024-225142, filed on December 20, 2024, including the specification, drawings and abstract, is incorporated herein by reference. Technical Field

[0002] This disclosure relates to power amplifiers, amplification methods, and transmitters. Background Technology

[0003] The disclosed technologies are listed below.

[0004] [Non-Patent Literature 1] F. Raab, “Intermodulation distortion in Khan-technique transmitters”, IEEE Transactions on Microwave Theory and Technology, Vol. 44, pp. 2273-2278, December 1996.

[0005] [Non-Patent Literature 2] SM. Yoo et al., “A switched-capacitor RF power amplifier”, IEEE Solid State Circuits Journal, Vol. 46, No. 12, pp. 2977-2987, December 2011.

[0006] Non-patent document 1 discloses an envelope elimination and recovery (referred to as EER) technique.

[0007] Non-patent document 2 discloses a switched capacitor power amplifier (SCPA) technology. Summary of the Invention

[0008] The goal is to improve the efficiency of power amplifiers (sometimes referred to as PAs).

[0009] Other issues and novel features will become clear from the description of this specification and the accompanying drawings.

[0010] According to an embodiment, a power amplifier includes a power amplifier core unit capable of performing amplitude control in discrete integer steps and a variable attenuator.

[0011] According to an embodiment, an amplification method includes the steps of performing amplitude control in discrete integer steps using a power amplifier core unit, and changing the attenuation amount using a variable attenuator.

[0012] According to an embodiment, a transmitter includes: a phase-amplitude separation circuit that separates a baseband signal into a phase signal and an amplitude signal, the phase signal being the phase component of the baseband signal and the amplitude signal being the amplitude component of the baseband signal; a phase modulation block that modulates an RF carrier signal with the phase signal to generate a phase-modulated RF carrier signal; a power amplifier core unit capable of performing amplitude control in discrete integer steps; and a variable attenuator. The power amplifier core unit performs: modulating the phase-modulated RF carrier signal with the amplitude signal to generate a second RF signal that is amplitude-modulated to have an envelope comprising multiple levels; and controlling the average value of the transmitted power of the amplitude-modulated second RF signal to a value having a predetermined integer number. When the predetermined integer number of values ​​are arranged in descending order, the variable attenuator can change the attenuation by a value smaller than the maximum value representing the difference between adjacent values ​​(in decibels).

[0013] According to the above embodiments, a power amplifier, amplification method, and transmitter that can achieve high efficiency can be provided. Attached Figure Description

[0014] Figure 1 The illustration shows a conceptual diagram of a transmitter using EER technology according to the first comparative example.

[0015] Figures 2A to 2D This is a conceptual diagram illustrating a magnification method using SCPA technology based on the second comparative example.

[0016] Figure 3 The diagram illustrates polar modulation using SCPA technology according to the third comparative example. The horizontal axis indicates time, and the vertical axis from top to bottom indicates the square RF carrier signal before modulation, the PM baseband signal (illustrated as PM signal in the diagram), the phase-modulated RF signal, the AM baseband signal (illustrated as AM signal in the diagram), the RF output signal, and the product of the AM baseband signal and the PM baseband signal.

[0017] Figure 4 It is a diagram illustrating polar modulation using SCPA technology according to the third comparative example, with the horizontal axis indicating time and the vertical axis from top to bottom indicating the square RF carrier signal before modulation, the PM baseband signal, the phase-modulated RF signal, the AM baseband signal, the RF output signal, and the product of the AM baseband signal and the PM baseband signal.

[0018] Figure 5 The diagram illustrates a transmitter based on the third comparative example.

[0019] Figure 6 It is a diagram illustrating the design results in the transmitter according to the third comparative example.

[0020] Figure 7 This is a diagram illustrating another design result in the transmitter based on the third comparative example.

[0021] Figure 8 It is a graph illustrating the error between level 2049 and level 1025 in the second amplitude control of the transmitted power performed by the power amplifier core unit in the transmitter according to the third comparative example. The horizontal axis indicates the ideal value of the attenuation amount (ATT), and the vertical axis indicates the error.

[0022] Figure 9 This is a block diagram illustrating a power amplifier according to the first embodiment.

[0023] Figure 10 This is a diagram illustrating the design results in a power amplifier according to the first embodiment.

[0024] Figure 11 This is a diagram illustrating the design results in a power amplifier according to the first embodiment.

[0025] Figure 12 This is a flowchart illustrating an amplification method using a power amplifier according to a first embodiment.

[0026] Figure 13 The diagram illustrates a block diagram of a transmitter according to a second embodiment.

[0027] Figure 14 This is a block diagram illustrating a first modified transmitter according to the second embodiment.

[0028] Figure 15 This is a block diagram illustrating a second modified transmitter according to the second embodiment.

[0029] Figure 16 This is a block diagram illustrating the matching circuit in a second modified transmitter according to the second embodiment.

[0030] Figure 17 This is a block diagram illustrating the configuration of the power amplifier core unit according to the third embodiment.

[0031] Figure 18 This is a block diagram illustrating the operation of the power amplifier core unit according to the third embodiment.

[0032] Figure 19 This is a block diagram illustrating the power amplifier core unit and the variable attenuator according to the third embodiment.

[0033] Figure 20 This is a diagram illustrating the design results of a power amplifier including a power amplifier core unit and a variable attenuator according to a third embodiment.

[0034] Figure 21 It is a graph illustrating the average value of the transmitted power in the power amplifier according to the third embodiment, with the horizontal axis indicating time and the vertical axis indicating the transmitted power. Detailed Implementation

[0035] To ensure clarity, the following description and figures have been appropriately omitted and simplified. In the figures, the same elements are represented by the same reference numerals, and repeated descriptions have been omitted where necessary. Some reference numerals have been omitted to avoid complicating the figures in certain situations.

[0036] First, in the sections "First Comparative Example" to "Third Comparative Example," the power amplifier, amplification method, and transmitter according to the first to third comparative examples will be described. Then, in the section "Problems Newly Discovered by the Inventor," problems newly discovered by the inventor regarding the power amplifier, amplification method, and transmitter according to the first to third comparative examples will be described. In the sections "First Embodiment" to "Third Embodiment," the power amplifier, amplification method, and transmitter according to the first to third embodiments will be described for comparison with the comparative examples. This will further clarify the power amplifier, amplification method, and transmitter according to embodiments of the present invention. It should be noted that the first to third comparative examples and the problems newly discovered by the inventor also fall within the scope of the technical concept of the embodiments.

[0037] <First Comparison Example>

[0038] Figure 1 This is a conceptual diagram illustrating a transmitter 100 using EER technology according to a first comparative example. (See diagram below.) Figure 1 The transmitter 100 illustrated in the figure, according to the first comparative example, relates to the EER technology described in Non-Patent Document 1. The transmitter 100 according to the first comparative example uses EER technology or polar modulation technology. EER technology or polar modulation technology is a technology in a radio frequency (RF) transmitter that includes the following operations (1) to (4): (1) The baseband signal is temporarily separated into a phase component and an amplitude component. (2) The RF carrier signal is modulated with the phase component of the baseband signal. (3) The RF signal modulated with the phase component is amplified by a power amplifier that controls the output amplitude by using the amplitude component of the baseband signal. (4) The RF output signal in which the phase modulation component and the amplitude modulation component are synthesized is acquired again.

[0039] Specifically, according to the transmitter 100 of the first comparison example, the input AF baseband signal is temporarily separated into phase components. And the amplitude component E(t). Figure 1The lower module shown in the figure modulates the RF carrier signal with the phase component of the baseband signal. The lower module of transmitter 100 includes, for example, a delay module, a limiter, a frequency converter, a Class B modulator, etc. Figure 1 The upper module illustrated in the diagram amplifies the RF carrier signal modulated by the phase component using a power amplifier, which controls the output amplitude using the amplitude component of the baseband signal. The upper module includes an envelope detector, a Class-S modulator, etc.

[0040] Then, the RF output signal, in which the phase and amplitude components are synthesized, is output again. It should be noted that, similar to the EER technology described in Non-Patent Document 1, a high-efficiency Class D amplifier can be used as the power amplifier. The EER technology can omit the quadrature modulator from the transmitter. Furthermore, in the EER technology, a high-efficiency nonlinear amplifier or switching amplifier can be used as the power amplifier consuming the maximum amount of power. Therefore, the EER technology can improve the power efficiency of the transmitter. As the power amplifier, a scheme that performs digital control of the amplitude can also be used. In this case, the amplitude data is input to the power amplifier as digital data. In the first comparative example, the output amplitude can be controlled by varying the supply voltage VDRF of the Class D amplifier. It should be noted that the supply voltage VDRF has an analog value.

[0041] <Second Comparison Example>

[0042] Figures 2A to 2D This is a conceptual diagram illustrating a magnified method using SCPA technology based on the second comparative example. (See diagram for example.) Figures 2A to 2D The amplification method illustrated in the figure, according to the second comparative example, relates to the SCPA technology described in Non-Patent Document 2. The amplification method according to the second comparative example is a technique for digitally controlling the output amplitude in EER technology or polarity modulation technology. In SCPA technology, an RF carrier signal or a phase-modulated RF carrier signal is applied in a square wave to one end of each of the n capacitive elements arranged in an array of N capacitive elements. The other ends of the remaining (Nn) capacitive elements are fixed to a fixed potential. As a result, the amplitude of the RF carrier signal from 0 to VDD is divided by n / N. By changing the value of n, the output amplitude is precisely controlled.

[0043] Specifically, for example, in the case of full power, such as Figure 2A and Figure 2B As illustrated, the output amplitude is controlled by applying a square wave RF carrier signal or a phase-modulated RF carrier signal to all N (=4) capacitive elements (that is, by satisfying n=4). On the other hand, in the case of reduced power, such as Figure 2C and Figure 2DAs illustrated, for example, the output amplitude is controlled by applying a square-wave RF carrier signal or a phase-modulated RF carrier signal (that is, by satisfying n=2) to two of all N (=4) capacitive elements. It should be noted that by using a matching circuit (such as a matching network) to match the impedance, the signal whose output amplitude is controlled can have a high output.

[0044] <Third Comparison Example>

[0045] Figure 3 and Figure 4 The diagram illustrates a polar modulation using SCPA technology according to the third comparative example. The horizontal axis indicates time, and the vertical axis from top to bottom indicates the pre-modulation square RF carrier signal, the phase signal (referred to as the PM baseband signal and illustrated as the PM signal in the figure), the phase-modulated RF carrier signal, the amplitude signal (referred to as the AM baseband signal and illustrated as the AM signal in the figure), the RF output signal, and the product of the AM baseband signal and the PM baseband signal. Figure 4 It's a diagram. Figure 3 A magnified view of a portion. Figure 3 and Figure 4 In this context, for ease of understanding, the AM baseband signal is represented as a value corresponding to the amplitude of the amplitude control signal provided as a digital signal in SCPA technology, and the AM baseband signal does not exist as a true analog signal.

[0046] like Figure 3 and Figure 4 As illustrated in the diagram, in practice, the amplitude control signal (AM baseband signal) in SCPA technology is a digital signal existing in the digital domain. Figure 3 In the example illustrated, the AM baseband signal has nine values ​​from 0 to 8. There is also a phase inversion effect, so this corresponds to modulating the amplitude of the output RF signal to a total of 17 levels (-8 to 8). This approximately corresponds to a 4-bit modulation resolution. It should be noted that the actual required modulation resolution depends on the communication standard. Typically, a modulation resolution of approximately 4 to 8 bits or more is needed.

[0047] Figure 5 The diagram illustrates a block diagram of a transmitter 300 according to a third comparative example. Figure 5 The diagram illustrates the correspondence between each signal described above and the given signals. For example... Figure 5As illustrated, transmitter 300 includes a phase-amplitude separation circuit 10, a local signal generation circuit 20, a phase modulation block 30, a power amplifier core unit 40, and a matching circuit 60. Transmitter 300 may also include an antenna 70. Additionally, transmitter 300 may include a control unit 80. It should be noted that transmitter 300 can be configured to connect to the externally located antenna 70. Furthermore, the control unit 80 can be omitted from transmitter 300, and the functions of control unit 80 can be implemented by software running on a central processing unit (CPU) mounted on the same chip or another chip.

[0048] The phase-amplitude separation circuit 10 separates the baseband signal into a PM baseband signal (phase component) and an AM baseband signal (amplitude component). The phase-amplitude separation circuit 10 outputs the separated PM baseband signal to the phase modulation block 30. The phase-amplitude separation circuit 10 outputs the separated AM baseband signal to the power amplifier core unit 40. The AM baseband signal separated by the phase-amplitude separation circuit 10 is used by the power amplifier core unit 40 to perform amplitude control (in some cases referred to as first amplitude control) on the RF signal to obtain an amplitude-modulated RF output signal.

[0049] The local signal generation circuit 20 outputs an RF carrier signal to the phase modulation block 30. The RF carrier signal includes, for example, multiple square waves.

[0050] Phase modulation block 30 modulates the RF carrier signal with the PM baseband signal to generate a phase-modulated RF signal. Phase modulation block 30 outputs the phase-modulated RF signal to the power amplifier core unit 40.

[0051] The power amplifier core unit 40 includes, for example, a power amplifier with SCPA technology. The power amplifier core unit 40 forms a configuration having… Figure 3 and Figure 4 The diagram shows multiple step-size envelopes. The power amplifier core unit 40 resynthesizes the PM baseband signal and the AM baseband signal to generate the RF output signal in which the phase modulation component and the amplitude modulation component are synthesized.

[0052] Matching circuit 60 generates an RF signal with matched impedance, etc. The RF output signal generated by matching circuit 60 is output from antenna 70.

[0053] The control unit 80 performs amplitude control (in some cases referred to as second amplitude control) on the RF output signal to control the average transmitted power from the antenna 70.

[0054] <New Problem Discovered by the Inventor>

[0055] In addition to performing a first amplitude control to acquire an RF signal modulated with the baseband signal amplitude, the transmitter 300 (such as an RF transmitter) also performs a second amplitude control to control the average transmitted power from the antenna 70. Specific numerical examples will be considered here.

[0056] For example, in the first amplitude control for amplitude modulation, control is performed such that the amplitude of the RF carrier signal has 17 levels obtained by dividing 0 to 16 in step intervals of 1. When phase inversion levels are included, in the first amplitude control, control is performed to obtain an amplitude with 33 levels obtained by dividing -16 to 16 in step intervals of 1. The amplitude controlled as described above corresponds to a modulation accuracy of approximately 5 bits. Consider the case where a transmitter 300 with such modulation accuracy performs a second amplitude control, controlling the average transmitted power by up to 24 dB in step intervals of 1 dB. To support both the first amplitude control for amplitude modulation and the second amplitude control for average transmitted power, the number of levels in the output amplitude of the power amplifier core unit 40 needs to be increased.

[0057] Figure 6 This is a diagram illustrating the design results in transmitter 300 according to the third comparative example. (See diagram for example.) Figure 6 As illustrated, the amplitude control performed by the power amplifier core unit 40 in the transmitter 300 has 2049 levels (0 to 2048). Here, in some cases, the level with 2049 levels is simply referred to as the 2049 level.

[0058] At maximum output, that is, with an attenuation of 0 dB, the amplitude of the RF carrier signal is controlled with 17 levels, obtained by dividing 0 to 2048 in step intervals of 128, where 128 codes in the signal controlled by the first amplitude are used as a unit (×1). In other words, the amplitude of the RF carrier signal is controlled with 17 levels: 0 / 128 / 256 / 384 / ... / 2048. As a result, the envelope of the RF carrier signal is reproduced. Here, in some cases, the attenuation is referred to as ATT or ATT quantity, taking three letters from attenuation or attenuator. For example, ATT can be used to indicate quantity. ATT quantity can be used to refer to the amount of attenuation.

[0059] With an ATT of 24 dB, the amplitude of the RF carrier signal is controlled in 17 levels, obtained by dividing 0 to 128 into steps of 8, with 8 codes in the signal controlled by the first amplitude as a unit (×1). As a result, the envelope of the RF carrier signal is reproduced. The ratio between the amplitude of the transmitted power at this point and the amplitude of the transmitted power at the maximum output time is 8 / 128. In dB, 20log(8 / 128) = -24.08 dB. The absolute value of the error relative to the design target of 24 dB is 0.08 dB. The maximum absolute value of the error is 0.32 dB relative to the corresponding ATT from 0 to 24 dB when the ATT = 21 dB.

[0060] Figure 7 This is a diagram illustrating another design result in the transmitter 300 according to the third comparative example. Figure 7 The following example is illustrated: the power amplifier core unit 40 has implemented amplitude control to have 1025 levels (0 to 1024), which is approximately half the number of levels compared to 2049. Figure 7 As illustrated, in this case, the resolution of the output amplitude at low output power is insufficient. Therefore, for example, the amplitude control code units are 4, 5, 5, and 6 for ATT = 24 dB, 23 dB, 22 dB, and 21 dB, respectively. Thus, the output amplitude at ATT = 22 dB needs to be the same as the output amplitude at ATT = 23 dB.

[0061] Figure 8 This is a graph illustrating the average transmitted power control error between level 2049 and level 1025 in amplitude control performed by the power amplifier core unit 40 in transmitter 300 according to the third comparative example. The horizontal axis indicates the ideal value of ATT, and the vertical axis indicates the error. Figure 8 As illustrated in the diagram, in both the 2049 and 1025 level cases, the absolute value of the error tends to increase in areas with large ATT values. Furthermore, the error is larger in the 1025 level case, where the output amplitude resolution is low. As described above, typically, when attempting to perform secondary amplitude control for accurate average transmission power in areas with large ATT values, the necessary output amplitude resolution deteriorates.

[0062] However, in practice, such as Figure 6As illustrated, it is difficult to design a power amplifier including a power amplifier core unit 40 capable of controlling the output amplitude to 2049 levels. First, dividing the power amplifier core unit 40 into a large number of unit PAs increases the dead space in the layout. For example, a power amplifier core unit 40 capable of controlling the output amplitude to 2049 levels requires 2048 unit PAs.

[0063] Furthermore, dividing the power amplifier core unit 40 into a large number of unit PAs increases the amount of wiring required to allocate the RF carrier signal or the on / off control signal of each unit PA. This leads to a further increase in dead time. As a result, in such a power amplifier, the signal lines become long and complex, and the signal timing error increases. Therefore, the modulation accuracy deteriorates. In addition, the parasitic capacitance and inductance of the wiring also increase, which leads to increased power loss.

[0064] As an alternative approach to addressing dead-zone and wiring issues, it is conceivable to binary-weight the size of unit PAs to 1, 2, 4, ... However, in this case, it is difficult to maintain a proportional relationship between the performance of a unit PA corresponding to ×1 and that of a unit PA corresponding to the maximum ×1024 level. Furthermore, when reproducing a modulated signal, the on / off frequency of each unit PA increases, making it difficult to generate low-distortion waveforms. For example, in the configuration described above with a large number of ×1 unit PAs, it is sufficient to sequentially put one unit PA into the on state at a time. In contrast, with the amplitude linearly increasing to 0, 1, 2, 3, 4, ..., in a binary configuration, the ×1 unit PAs repeatedly switch on / off states, such that they are off, on, off, on, off. The ×2 unit PAs also repeatedly switch on / off states, such that they are off, off, on, on, off, off, on, on. Therefore, the on / off frequency increases.

[0065] As described above, in the transmitter 300 that uses digital signals to control amplitude using EER technology or polarity modulation technology, the number of levels in the first and second amplitude control performed by the power amplifier core unit 40 is limited. Therefore, it is difficult to ensure both a wide output variable range and modulation accuracy.

[0066] <First Embodiment>

[0067] Next, the power amplifier according to the first embodiment will be described. Figure 9 This is a block diagram illustrating the power amplifier PA1 according to the first embodiment. Figure 9 As illustrated in the figure, the power amplifier PA1 according to this embodiment includes a power amplifier core unit 4 and a variable attenuator 5.

[0068] The power amplifier core unit 4 is configured to perform amplitude control in discrete integer steps. For example, the power amplifier core unit 4 is configured to perform discrete amplitude control in (N+1) steps from 0 to N. The power amplifier core unit 4 performs amplitude control to reproduce the envelope of the RF signal. The variable attenuator 5 changes the ATT amount. Therefore, according to this embodiment, the power amplifier PA1 controls the average transmitted power by using a combination of amplitude control performed by the power amplifier core unit 4 and the ATT amount of the variable attenuator 5.

[0069] The power amplifier core unit 4 includes an input terminal 4i, a first terminal 4a, a second terminal 4b, and an output terminal 4o. The input terminal 4i is for receiving a phase-modulated RF carrier signal. The first terminal 4a is for receiving a first amplitude control signal. The second terminal 4b is for receiving a second amplitude control signal. The output terminal 4o outputs the RF signal, amplitude-modulated by the power amplifier core unit 4, to the variable attenuator 5.

[0070] The variable attenuator 5 includes an input terminal 5i, a first terminal 5a, and an output terminal 5o. The input terminal 5i is the terminal for receiving an amplitude-modulated RF signal. The first terminal 5a is the terminal for receiving an ATT control signal. The output terminal 5o is the terminal from which an RF signal is output, to which a predetermined ATT amount has been applied by the variable attenuator 5.

[0071] Figure 10 This is a diagram illustrating the design results of the power amplifier PA1 according to the first embodiment. (See diagram for example.) Figure 10 As illustrated, the power amplifier PA1 according to this embodiment can implement a second amplitude control to control the average transmission power at 145 levels (0 to 144). Specifically, the power amplifier PA1 according to this embodiment controls the amplitude of the RF carrier signal to obtain 17 levels of output amplitude obtained by dividing 0 to 16 in step intervals of 1. Furthermore, by using a combination of amplitude control performed by the power amplifier core unit 4 and the attenuation amount of the variable attenuator 5, the average transmission power is controlled within a range of 24 dB obtained by dividing in step intervals of 1 dB. The amplitude corresponding to each controlled level in the first amplitude control can be set with equal intervals relative to the control code or partially with unequal intervals. Alternatively, the entire portion can be set with completely unequal intervals. The amplitude corresponding to each controlled level in the second amplitude control can be set with equal intervals relative to the control code or partially with unequal intervals. Alternatively, the entire portion can be set with completely unequal intervals.

[0072] In order to control the transmitted power within a 24 dB range divided in 1 dB increments, similar to the power amplifier PA1 according to this embodiment, the power amplifier described above according to the third comparative example requires a second amplitude control performed by a 2049-level power amplifier, such as... Figure 6 As illustrated in the figure. A design example according to this embodiment will be described in more detail below.

[0073] Figure 11 This is a diagram illustrating the design results of the power amplifier PA1 according to the first embodiment. (See diagram for example.) Figure 11 As illustrated, the power amplifier core unit 4 can be controlled in nine levels, ranging from 17 levels (0 to 16) with "×1" as the output amplitude 1 to 17 levels (0 to 144) with "×9" as the output amplitude 9. When the variable attenuator 5 is not in operation, the ATT quantity has nine levels, such that ATT = 0 dB, 1.0 dB, 2.2 dB, 3.5 dB, 5.1 dB, 7.0 dB, 9.5 dB, 13.1 dB, and 19.1 dB. Figure 10 As illustrated, the variable attenuator 5 combines it with an ATT of up to 6.0 dB in step intervals of 0.5 dB. As a result, the power amplifier PA1 can achieve an ATT of up to 24 dB with a maximum error of 0.18 dB.

[0074] In this configuration of the power amplifier PA1 according to this embodiment, compared to the third comparative example, the number of levels in the power amplifier core unit 4 for controlling the output amplitude can be reduced. Therefore, the layout becomes compact, and the control wiring becomes simple. Thus, the power amplifier PA1 according to this embodiment enables a small and efficient transmitter. As described above, the power amplifier PA1 according to this embodiment achieves high-range and high-precision output power control by using a power amplifier with fewer levels in amplitude control, and this achieves a reduction in transmitter size and high power efficiency operation.

[0075] On the other hand, with a large ATT value for the variable attenuator 5, the transmitter efficiency may decrease due to power dissipation of the RF carrier signal. If the power dissipation is large, lower power consumption for the entire transmitter cannot be achieved. However, this is not a problem in practice for the reasons described below.

[0076] First, consider the range where ATT = 8 dB or lower and transmission power is high. For example... Figure 10As illustrated, with target values ​​ATT = 0 dB, 1 dB, 2 dB, 5 dB, and 7 dB, the variable attenuator 5 is set to 0 dB. Therefore, no power dissipation problem occurs for the RF carrier signal. In another case with target values ​​ATT = 3 dB, 4 dB, 6 dB, and 8 dB, the ATT of the variable attenuator 5 is set small (0.5 dB to 1.0 dB). The power dissipated is 10% or 20% of each transmitted power. Assuming the power amplifier efficiency is 50% with a target value ATT = 0 dB, the dissipated power is only 5% (= 10% × 50%) or 10% (= 20% × 50%) of the power consumption. This does not exceed the efficiency improvement of the single power amplifier core unit 4 according to this embodiment.

[0077] When the ATT value of the variable attenuator 5 is large, the power dissipation rate of the RF carrier signal increases. For example... Figure 10 As illustrated, in the region where ATT = 16 dB or greater, the variable attenuator 5 is controlled to have an ATT of 3 dB or greater, and in other words, 50% or more of the power of the RF carrier signal is dissipated. However, in this region, the absolute value of the transmitted power of the RF carrier signal is small, and therefore the absolute value of the transmitted power dissipated attributable to the variable attenuator 5 is also small. To give a specific value, when ATT = 16 dB, the transmitted power of the power amplifier core unit 4 is 13 dB lower than the transmitted power when ATT = 0 dB. In other words, the transmitted power is reduced to 1 / 20. The variable attenuator 5 has been set to 3 dB, so the dissipated RF power is only half of the transmitted power.

[0078] Typically, the efficiency of a power amplifier is highest near the maximum output time and decreases in this low-power transmission region. In other words, at ATT = 16 dB, the efficiency of the power amplifier core unit also decreases, and the self-dissipated power of a single power amplifier core unit 4 is greater than the power dissipated attributable to the variable attenuator 5. In other words, the power dissipated attributable to the variable attenuator 5 becomes relatively negligible.

[0079] As described above, according to this embodiment, the layout of the power amplifier core unit 4 becomes more compact, and the amount of control wiring is reduced from the 2049 level of control according to the third comparative example to 1 / 10 or less, becoming Figure 11 The control is illustrated at level 145. This has a significant effect on reducing the self-consuming transmission power of the power amplifier PA1 according to this embodiment. Therefore, the power amplifier PA1 according to this embodiment can reduce the power consumption of the entire transmitter.

[0080] Figure 12This is a flowchart illustrating an amplification method using power amplifier PA1 according to the first embodiment. Figure 12 As illustrated in the figure, the amplification method according to this embodiment includes a step S10 of performing amplitude control and a step S20 of changing the ATT amount.

[0081] In step S10, the power amplifier core unit 4 performs amplitude control in discrete integer steps. The power amplifier core unit 4 performs amplitude control to reproduce the envelope of the RF carrier signal. In step S20, the variable attenuator 5 changes the ATT amount. As a result, the power amplifier PA1 controls the average transmitted power by using a combination of amplitude control performed by the power amplifier core unit 4 and the ATT amount of the variable attenuator 5.

[0082] <Second Embodiment>

[0083] Next, the transmitter according to the second embodiment will be described. Figure 13 This is a block diagram illustrating the transmitter TM1 according to the second embodiment. Figure 13 As illustrated, in addition to the power amplifier core unit 4 and the variable attenuator 5, the transmitter TM1 according to this embodiment also includes a phase amplitude separation circuit 1, a local signal generation circuit 2, a phase modulation block 3, and a matching circuit 6. The transmitter TM1 may also include an antenna 7. Furthermore, the transmitter TM1 may also include a power control signal separation unit 8. It should be noted that the transmitter TM1 can be configured to connect to the externally located antenna 7. Additionally, the power control signal separation unit 8 can be omitted from the transmitter TM1, and its function can be assigned to software executing on a CPU installed on the same or another chip.

[0084] The phase-amplitude separation circuit 1 separates the baseband signal into a PM baseband signal (phase component) and an AM baseband signal (amplitude component). In this embodiment, the PM baseband signal is referred to as the phase control signal. The AM baseband signal is referred to as the first amplitude control signal. The phase-amplitude separation circuit 1 outputs the separated phase control signal to the phase modulation block 3. The phase-amplitude separation circuit 1 outputs the separated first amplitude control signal to the power amplifier core unit 4 via the first terminal 4a. The first amplitude control signal is used by the power amplifier core unit 4 to perform first amplitude control on the RF signal to obtain an amplitude-modulated RF signal.

[0085] The local signal generation circuit 2, phase modulation block 3, and matching circuit 6 have functions similar to those of the local signal generation loop 20, phase modulation module 30, and matching circuit 60 according to the third comparative example. In this embodiment, the variable attenuator 5 is disposed between the power amplifier core unit 4 and the matching circuit 6.

[0086] The power control signal separation unit 8 is connected to the second terminal 4b of the power amplifier core unit 4 and the first terminal 5a of the variable attenuator 5. The power control signal separation unit 8 receives the transmitted power control signal. It separates the transmitted power control signal into a second amplitude control signal and an ATT control signal. The power control signal separation unit 8 outputs the separated second amplitude control signal to the power amplifier core unit 4 via the second terminal 4b. The second amplitude control signal is used by the power amplifier core unit 4 to perform second amplitude control, thereby controlling the average transmitted power output from the antenna 7. The power control signal separation unit 8 outputs the separated ATT control signal to the variable attenuator 5 via the first terminal 5a. The ATT control signal is used in the variable attenuator 5 to control the change in the ATT amount.

[0087] The transmitter TM1 according to this embodiment uses a power amplifier PA1 capable of controlling the amplitude of the RF signal in a small number of levels, thus achieving high-range and high-precision output power control. As a result, the transmitter TM1 achieves reduced size and high power-efficiency operation. As a specific example, when using the same specifications as the transmitter 300 of the third comparative example, that is, when controlling the average transmitted power within a range of 24 dB with a step interval of 1 dB, the number of levels can be less than that of the transmitter 300 according to the third comparative example. In other words, the transmitter TM1 can achieve an output amplitude of 17 levels (0 to 16) of RF output signal, which is obtained by dividing it with a step interval of 1.

[0088] <First Revision>

[0089] Figure 14 This is a block diagram illustrating the first modified transmitter TM2 according to the second embodiment. (See diagram below.) Figure 14 As illustrated, in the transmitter TM2 according to this modification, the power amplifier core unit 4, matching circuit 6, variable attenuator 5, and antenna 7 are connected in this order. Compared to the configuration of the transmitter TM1 according to the second embodiment described above, the positions of the variable attenuator 5 and matching circuit 6 are changed. The RF carrier signal output from the output terminal 4o of the power amplifier core unit 4 is input to the matching circuit 6. Then, the RF signal output from the matching circuit 6 is input to the variable attenuator 5. The transmitter TM2 according to this modification includes a power amplifier PA2. The power amplifier PA2 includes the matching circuit 6 between the power amplifier core unit 4 and the variable attenuator 5. This configuration can also achieve effects similar to those of the second embodiment.

[0090] <Second Revision>

[0091] Figure 15This is a block diagram illustrating a second modified transmitter TM3 according to the second embodiment. (See diagram below.) Figure 15 As illustrated, the transmitter TM3 according to this modification includes a matching circuit 9 in which the variable attenuator 5 and the matching circuit 6 are integrated, instead of including the variable attenuator 5 and the matching circuit 6 separately. Therefore, the power amplifier PA3 of the transmitter TM3 includes a power amplifier core unit 4 and a matching circuit 9. The matching circuit 9, which matches the output impedance, functions as a variable attenuator. In other words, the variable attenuator according to this modification includes a matching circuit 9 with attenuator functionality and includes a matching circuit 9 that matches the output impedance. The matching circuit 9 is connected to the output terminal 4o of the power amplifier core unit 4. The matching circuit 9 receives an ATT control signal from the power control signal separation unit 8.

[0092] Figure 16 This is a block diagram illustrating the matching circuit 9 in the second modified transmitter TM3 according to the second embodiment. (See diagram below.) Figure 16 As illustrated, the matching circuit 9 according to this modification includes two variable capacitors 9a. Each variable capacitor 9a includes a capacitive element and a switch. The capacitance value between the two terminals of the capacitive element can be controlled by a digital code. One end of each variable capacitor 9a is connected to the power amplifier core unit 4. The other end of each variable capacitor 9a is connected to a fixed potential, such as ground. A coil 9b may be suitably disposed between the variable capacitors 9a and between the variable capacitors 9a and the power amplifier core unit 4.

[0093] Typically, as a component to adjust for the difference between the designed characteristics and the actual characteristics, a matching circuit 9, including a variable capacitor 9a, is usually used, such as... Figure 16 As illustrated in the diagram. According to this modification, the variable capacitor 9a also functions as a component for implementing a variable attenuator when controlling the transmitted power. The variable capacitor 9a according to this modification can initially be provided as a component to absorb design errors. This eliminates the need to add a new variable attenuator 5.

[0094] <Third Embodiment>

[0095] Next, the core unit of the power amplifier according to the third embodiment will be described. Figure 17 This is a block diagram illustrating the configuration of the power amplifier core unit 4X according to the third embodiment. Figure 18 This is a block diagram illustrating the operation of the power amplifier core unit 4X according to the third embodiment. Figure 17 and Figure 18As illustrated, the power amplifier core unit 4X includes multiple unit power amplifier groups 4g. The power amplifier core unit 4X includes, for example, L unit power amplifier groups 4g. These multiple unit power amplifier groups 4g are connected in parallel with each other.

[0096] The unity power amplifier group 4g includes multiple capacitors and logic circuitry for switching the capacitors to an operating or inactive state. Each unity power amplifier group in the unity power amplifier group 4g can perform amplitude control to have multiple levels. Each unity power amplifier group in the unity power amplifier group 4g can perform control to have an amplitude of (M+1) levels (e.g., 0 to M). As a result, the power amplifier core unit 4X has the following configuration: L unity power amplifier groups 4g capable of performing amplitude control of (M+1) levels including zero output are connected in parallel. In other words, L×M (the product of L and M) is the value corresponding to N in the N+1 levels (from 0 to N) of amplitude control used for the power amplifier core unit 4X. Here, L, M, and N are integers. Each unity power amplifier group in the unity power amplifier group 4g may include a switched capacitor PA (SCPA) comprising M unity amplifiers. As described above, the power amplifier core unit 4X may include a switched capacitor power amplifier.

[0097] like Figure 18 As illustrated, the average transmission power of the RF signal is controlled by combining the activation of one (lowercase L) of the L unity power amplifier groups 4g with the control of ATT performed by the variable attenuator 5. The remaining (Ll) unity power amplifier groups 4g are always inactive and are in an off state for transmitting RF carrier signals. As described above, the power amplifier according to this embodiment controls the average transmission power by combining the control of the number of unity power amplifier groups 4g operating in parallel with the ATT amount of the variable attenuator 5.

[0098] Each unit power amplifier group in the unity power amplifier group 4g can perform amplitude control at a level of (M+1). Focusing on the active l unit power amplifier groups 4g, m unit amplifiers are momentarily active, and (Mm) unit amplifiers are inactive. By controlling the value of m over time, the power amplifier core unit 4X can perform control at a level of (M+1) to reproduce the envelope of the RF carrier signal. The l unit power amplifier groups 4g perform the same operation.

[0099] In the configuration of the power amplifier core unit 4X according to this embodiment, the first amplitude control signal for reproducing the envelope of the RF carrier signal and the second amplitude control signal for controlling the average transmission power are separated. Therefore, the decoder performing graded control in the power amplifier core unit 4X can be simplified. Depending on the radio scheme, the baseband signal bandwidth ranges from approximately 100 MHz to several hundred MHz. In this case, the permissible timing error between the first and second amplitude control signals needs to be equal to or less than 1 / (signal bandwidth), i.e., 10 ns or less. Simplifying the decoder helps reduce timing errors and improve the modulation accuracy of the envelope component of the RF carrier signal. Furthermore, all unit power amplifier groups 4g can have the same design. As a design in this case, it is sufficient to design one unit power amplifier group 4g and then arrange L such groups. Therefore, the power amplifier core unit 4X can be easily designed.

[0100] It should be noted that the amplitude variation of the RF carrier signal corresponding to each level in the (N+1) and (M+1) level control can be set at equal intervals, partially unequal intervals, or completely unequal intervals. This is a design issue. Furthermore, the dimensions of the L unity power amplifier groups 4g connected in parallel can all be equal, can be binary weighted, or can be arbitrarily set at unequal intervals. This is a design issue. Additionally, the unity power amplifier group 4g can be an SCPA as described in this embodiment, can be another switching amplifier, or can have another configuration. This is a design issue.

[0101] Figure 19 This is a block diagram illustrating the power amplifier core unit 4X and the variable attenuator 5X according to a third embodiment. Figure 19 As illustrated, the variable attenuator 5X is connected to the output terminal 4o of the power amplifier core unit 4X. The variable attenuator 5X may include a capacitor bank 5B. One end of the capacitor bank 5B is connected to the output terminal 4o of the power amplifier core unit 4X. The other end of the capacitor bank 5B is connected to a fixed potential node, such as ground. As described above, the variable attenuator 5X may include a capacitor bank 5B, one end of which is connected to the signal line through which the RF carrier signal passes and the other end is connected to a fixed potential line.

[0102] Assume that the capacitance of one cell of the SCPA in the power amplifier core unit 4X is C0. The total capacitance of the SCPA in the power amplifier core unit 4X is L×M×C0. When assuming that the number of parallel SCPA to be activated is 1, the instantaneous value of the amplitude control signal used for modulation is m, and the capacitance of capacitor bank 5B is Cbank, the output amplitude of the RF output signal is proportional to the formula (1) described below. (1)

[0103] In other words, Cbank, which is used as a variable capacitor, is essentially used as a variable attenuator. When equation (1) is converted to dB, the following equation (2) is obtained. (2)

[0104] The first item on the right is related to the reproduction of the envelope of the RF carrier signal. The second item on the right indicates the control value of the average transmitted power of the RF carrier signal relative to the number l of the unity power amplifier group 4g in the active state. The third item indicates the control value of the transmitted power of the RF signal relative to the capacitor Cbank of the capacitor group 5B, which is essentially used as a variable attenuator 5X.

[0105] Figure 20 This is a diagram illustrating the design results in a power amplifier including a power amplifier core unit 4X and a variable attenuator 5X according to a third embodiment. Figure 20 As shown in the diagram, capacitor Cbank of capacitor bank 5B is controlled by 4 bits. Assume the capacitors that turn on / off at the corresponding bits are 0.066×L×M×C0, 0.132×L×M×C0, 0.264×L×M×C0, and 0.510×L×M×C0. The truth table for capacitor bank 5B is as follows: Figure 20 As illustrated in the diagram. In this case, the ATT (attenuation) varies from 0 dB to 3.0 dB in steps of 0.5 dB. The ATT varies from 3 dB to 6.0 dB in steps of 1.0 dB. As described above, the variable attenuator 5X according to this embodiment can achieve amplitude control with a maximum error of 0.1 dB in the ATT range from 0 dB to 6.0 dB.

[0106] Figure 21 This is a graph illustrating the average transmitted power in the power amplifier according to the third embodiment, with the horizontal axis indicating time and the vertical axis indicating transmitted power. Figure 21 In this context, the phase reversal part is omitted. For example... Figure 21 As illustrated, the power amplifier core unit 4X uses an amplitude signal to modulate a phase-modulated RF carrier signal to generate an RF output signal that has been amplitude-modulated into an envelope with multiple levels.

[0107] For example, in the power amplifier core unit 4X, when L and M are integers, L unit power amplifier groups 4g capable of performing (M+1) level control can be connected in parallel. The power amplifier core unit 4X can generate an envelope of (M+1) level.

[0108] Furthermore, the power amplifier core unit 4X can perform control to ensure that the average value of the transmitted power of the RF output signal has L values. Figure 21 In the diagram, solid lines indicate the amplitude of the transmitted power at L=9, L=5, and L=4. The transmitted power at L=9 corresponds to ATT=0 dB. The transmitted power at L=5 corresponds to ATT=5 dB. The average transmitted power at L=4 corresponds to ATT=7 dB. However, control via the power amplifier core unit 4 alone cannot make the transmitted power correspond to ATT=6 dB. In other words, control via the power amplifier core unit 4 alone cannot make the transmitted power correspond to the ATT between L=5 and L=4.

[0109] Therefore, when an integer number of average transmission power values ​​are arranged in descending order, the variable attenuator 5X can change the attenuation by a value smaller than the maximum value representing the difference between adjacent values ​​(in decibels). For example, when an integer number (L) of values ​​are arranged in descending order, the variable attenuator 5X can attenuate the transmission power such that the average transmission power falls between at least one pair of arranged values. Specifically, as... Figure 21 As illustrated by the dashed line, the variable attenuator 5X attenuates the transmitted power to achieve a dB=6 between dB=7 at L=4 and dB=5 at L=5. In this way, the power amplifier core unit 4X and the variable attenuator 5X can perform high-precision amplitude control while minimizing the number of unit power amplifier groups 4g. Therefore, the size of the power amplifier and transmitter TM3 can be reduced, and their efficiency can be improved.

[0110] The invention made by the inventors has been specifically described above based on embodiments. However, it should be noted that the invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. For example, suitable combinations of the first to third comparative examples, the first to third embodiments, and modified corresponding configurations are also within the scope of the technical concept of the embodiments.

Claims

1. A power amplifier, comprising: A power amplifier core unit, which is capable of performing amplitude control in discrete integer steps; as well as Variable attenuator.

2. The power amplifier according to claim 1, The power amplifier core unit performs the amplitude control to reproduce the envelope of the RF signal. The variable attenuator changes the attenuation amount, and The average transmitted power is controlled by using a combination of amplitude control performed by the power amplifier core unit and attenuation of the variable attenuator.

3. The power amplifier according to claim 1, The power amplifier core unit mentioned above includes a switched capacitor power amplifier, and The variable attenuator includes a capacitor bank, one end of which is connected to a signal line and the other end of which is connected to a fixed potential line. The RF signal output from the power amplifier core unit passes through the signal line.

4. The power amplifier according to claim 1, Where L and M are integers. In the core unit of the power amplifier, L units of unit amplifiers are connected in parallel, and the L units of unit amplifiers are capable of performing M+1 level control, including zero output.

5. The power amplifier according to claim 4, The power amplifier core unit performs the control at level M+1 to reproduce the envelope of the RF signal, and The average transmission power is controlled by combining the control of a certain number of the L groups of unit amplifiers to be operated in parallel with the attenuation of the variable attenuator.

6. The power amplifier according to claim 1, The changes in the amplitude of the RF signal corresponding to each level include portions that are not set at equal intervals.

7. The power amplifier according to claim 4, The change in amplitude of the RF signal corresponding to each level in the control of the M+1 level includes portions that are not set at equal intervals.

8. The power amplifier according to claim 1, The variable attenuator includes a matching circuit that functions as an attenuator and matches the output impedance.

9. A method for magnification, comprising: Amplitude control is performed in discrete integer steps using a power amplifier core unit; as well as The step of changing the attenuation by using a variable attenuator.

10. The amplification method according to claim 9, In the step of performing the amplitude control, The power amplifier core unit performs the amplitude control to reproduce the envelope of the RF signal, and The average transmitted power is controlled by using a combination of amplitude control performed by the power amplifier core unit and attenuation of the variable attenuator.

11. The amplification method according to claim 9, The power amplifier core unit mentioned above includes a switched capacitor power amplifier, and The variable attenuator includes a capacitor bank, one end of which is connected to a signal line and the other end of which is connected to a fixed potential line. The RF signal output from the power amplifier core unit passes through the signal line.

12. The amplification method according to claim 9, Where L and M are integers. In the core unit of the power amplifier, L units of amplifiers are connected in parallel, and the L units of amplifiers are capable of performing M+1 level control.

13. The amplification method according to claim 12, In the step of performing the amplitude control, The power amplifier core unit executes the control at level M+1 to reproduce the envelope of the RF signal, and The average transmission power is controlled by combining the control of a certain number of the L groups of unit amplifiers to be operated in parallel with the attenuation of the variable attenuator.

14. The amplification method according to claim 9, The changes in the amplitude of the RF signal corresponding to each level include portions that are not set at equal intervals.

15. The amplification method according to claim 12, The change in amplitude of the RF signal corresponding to each level in the control of the M+1 level includes portions that are not set at equal intervals.

16. The amplification method according to claim 9, The variable attenuator includes an output impedance matching circuit, which functions as an attenuator.

17. A transmitter, comprising: A phase-amplitude separation circuit separates a baseband signal into a phase signal and an amplitude signal, wherein the phase signal is the phase component of the baseband signal and the amplitude signal is the amplitude component of the baseband signal. A phase modulation block, wherein the phase modulation block modulates the RF carrier signal with the phase signal to generate a phase-modulated RF carrier signal; A power amplifier core unit, which is capable of performing amplitude control in discrete integer steps; as well as Variable attenuator, The power amplifier core unit The amplitude signal is used to modulate the phase-modulated RF carrier signal to generate an amplitude-modulated RF signal with an envelope, the envelope comprising multiple levels. The average transmission power of the amplitude-modulated RF signal is controlled to any value among a predetermined integer number of averages, and When the average of the predetermined integer number is arranged in descending order, the variable attenuator can change the attenuation by a value smaller than the maximum value representing the difference between adjacent values, wherein the value is in decibels.

18. The transmitter according to claim 17, In the core unit of the power amplifier When L and M are integers L units of amplifiers are connected in parallel, and these L units of amplifiers are capable of performing M+1 level control. The average value of the transmission power is controlled to have L values, and The variable attenuator attenuates the transmitted power such that the average value of the transmitted power falls between at least one pair of the L values ​​arranged in order.

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