Power amplifier, amplification method, and transmitter

Abstract

The present invention provides a power amplifier, amplification method, and transmitter that can be miniaturized. [Solution] According to one embodiment, the power amplifier comprises a power amplifier core 4 capable of discrete integer amplitude control and a variable attenuator 5. The power amplifier core 4 regenerates the RF signal envelope by amplitude control, and the variable attenuator 5 changes the amount of attenuation. The average transmit power is controlled by the combination of the amplitude control of the power amplifier core 4 and the amount of attenuation of the variable attenuator 5.

Description

Technical Field

[0001] The present disclosure relates to a power amplifier, an amplification method, and a transmitter.

Background Art

[0002] Non-Patent Document 1 describes an envelope elimination and restoration (referred to as EER) technique.

[0003] Non-Patent Document 2 describes a switched capacitor power amplifier (referred to as SCPA) technique.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] It is desired to increase the efficiency of a power amplifier (sometimes referred to as PA).

[0006] Other challenges and novel features will become apparent from the description and accompanying drawings in this specification. [Means for solving the problem]

[0007] According to one embodiment, the power amplifier comprises a power amplifier core capable of discrete integer amplitude control and a variable attenuator.

[0008] According to one embodiment, the amplification method comprises the steps of performing discrete integer amplitude control in the power amplifier core and changing the amount of attenuation with a variable attenuator.

[0009] According to one embodiment, the transmitter includes a phase-amplitude separation circuit that separates a baseband signal into a phase signal which is the phase component of the baseband signal and an amplitude signal which is the amplitude component of the baseband signal; a phase modulation block that generates a phase-modulated first RF signal by modulating an RF carrier signal with the phase signal; a power amplifier core section capable of discrete integer gradation amplitude control; and a variable attenuator. The power amplifier core section generates a second RF signal that has a gradation envelope including multiple steps by modulating the phase-modulated first RF signal with the amplitude signal, and controls the average value of the transmission power of the amplitude-modulated second RF signal to be a predetermined integer number of values. The variable attenuator can change the amount of attenuation by a value smaller than the maximum value obtained by expressing the difference between adjacent values ​​in decibels when the integer number of values ​​are arranged in descending order. [Effects of the Invention]

[0010] According to the above embodiment, it is possible to provide a power amplifier, amplification method, and transmitter that can achieve high efficiency. [Brief explanation of the drawing]

[0011] [Figure 1]This is a conceptual diagram illustrating a transmitter using EER technology according to Comparative Example 1. [Figure 2] (a) to (d) are conceptual diagrams illustrating an amplification method using the SCPA technology related to Comparative Example 2. [Figure 3] This graph illustrates polar modulation using the SCPA technology described in Comparative Example 3. The horizontal axis represents time, and the vertical axis, from top to bottom, shows the rectangular RF carrier signal before modulation, the PM baseband signal (referred to as the PM signal in the figure), the phase-modulated RF signal, the AM baseband signal (referred to 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] This graph illustrates polar modulation using the SCPA technology described in Comparative Example 3. The horizontal axis represents time, and the vertical axis, from top to bottom, shows the rectangular 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. [Figure 5] This is a block diagram illustrating a transmitter related to Comparative Example 3. [Figure 6] This figure illustrates the design results for the transmitter according to Comparative Example 3. [Figure 7] This figure illustrates an alternative design result for the transmitter according to Comparative Example 3. [Figure 8] This graph illustrates the error in the case of the second amplitude control for the transmission power of the power amplifier core section of the transmitter according to Comparative Example 3, comparing the case with 2048 gradations and the case with 1024 gradations. The horizontal axis shows the ideal value of the attenuation (ATT), and the vertical axis shows the error. [Figure 9] This is a block diagram illustrating a power amplifier according to Embodiment 1. [Figure 10] This figure illustrates the design results for a power amplifier according to Embodiment 1. [Figure 11] This figure illustrates the design results for a power amplifier according to Embodiment 1. [Figure 12] This flowchart illustrates an amplification method using a power amplifier according to Embodiment 1. [Figure 13] It is a block diagram illustrating a transmitter according to Embodiment 2. [Figure 14] It is a block diagram illustrating a transmitter according to Modification 1 of Embodiment 2. [Figure 15] It is a block diagram illustrating a transmitter according to Modification 2 of Embodiment 2. [Figure 16] It is a block diagram illustrating a matching circuit in a transmitter according to Modification 2 of Embodiment 2. [Figure 17] It is a block diagram illustrating the configuration of a power amplifier core section according to Embodiment 3. [Figure 18] It is a block diagram illustrating the operation of a power amplifier core section according to Embodiment 3. [Figure 19] It is a block diagram illustrating a power amplifier core section and a variable attenuator according to Embodiment 3. [Figure 20] It is a diagram illustrating a design result in a power amplifier including a power amplifier core section and a variable attenuator according to Embodiment 3. ]> [Figure 21] It is a graph illustrating the average value of transmission power in a power amplifier according to Embodiment 3, where the horizontal axis represents time and the vertical axis represents transmission power.

Modes for Carrying Out the Invention

[0012] For clarity of explanation, the following description and drawings are appropriately omitted and simplified. In each drawing, the same reference numerals are assigned to the same elements, and redundant explanations are omitted as necessary. Some reference numerals may be omitted so that the drawings do not become complicated.

[0013] First, in <Comparative Example 1> to <Comparative Example 3>, the power amplifier, amplification method, and transmitter according to Comparative Examples 1 to 3 will be described. Then, in <Problems Newly Identified by the Inventor>, the problems newly identified by the inventor in relation to the power amplifier, amplification method, and transmitter of Comparative Examples 1 to 3 will be described. Finally, in <Embodiment 1> to <Embodiment 3>, the power amplifier, amplification method, and transmitter according to Embodiments 1 to 3 will be described in comparison with the comparative examples. This will further clarify the power amplifier, amplification method, and transmitter according to this embodiment. Note that Comparative Examples 1 to 3 and the problems newly identified by the inventor are also within the scope of the technical concept of the embodiment.

[0014] <Comparative Example 1> Figure 1 is a conceptual diagram illustrating a transmitter 100 using EER technology according to Comparative Example 1. As shown in Figure 1, the transmitter 100 of Comparative Example 1 is related to the EER technology described in Non-Patent Literature 1. The transmitter 100 of Comparative Example 1 uses EER technology or polar modulation technology. EER technology or polar modulation technology is a technology that includes the following operations (1) to (4) in an RF (Radio Frequency) transmitter: (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 with the amplitude component of the baseband signal. (4) An RF output signal is obtained by combining the phase modulation component and the amplitude modulation component again.

[0015] Specifically, the transmitter 100 of Comparative Example 1 first separates the input AF baseband signal into a phase component cos[wit+φ(t)] and an amplitude component E(t). The lower module in Figure 1 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. The upper module in Figure 1 amplifies the RF carrier signal modulated with the phase component using a power amplifier that controls the output amplitude with the amplitude component of the baseband signal. The upper module includes an envelope detector and a Class S modulator, etc.

[0016] Then, an RF output signal is output, which is a composite of the phase and amplitude components. Furthermore, as with the EER technology described in Non-Patent Document 1, a highly efficient Class D amplifier may be used as the power amplifier. EER technology allows the quadrature modulator to be omitted from the transmitter. Also, EER technology allows the use of a highly efficient non-linear amplifier or switching amplifier for the power amplifier, which consumes the most power. Therefore, EER technology can improve the power efficiency of the transmitter. It is also possible to use a power amplifier that digitally controls the amplitude. In that case, the amplitude data is input to the power amplifier as digital data. In Comparative Example 1, the output amplitude is controlled by varying the power supply voltage VDRF of the Class D amplifier. The power supply voltage VDRF is an analog value.

[0017] <Comparative Example 2> Figures 2(a) to 2(d) are conceptual diagrams illustrating an amplification method using SCPA technology according to Comparative Example 2. As shown in Figures 2(a) to 2(d), the amplification method of Comparative Example 2 is related to the SCPA technology described in Non-Patent Literature 2. The amplification method of Comparative Example 2 is a technology that digitizes the control of the output amplitude in EER technology or polar modulation technology. SCPA technology applies an RF carrier signal or a phase-modulated RF carrier signal as a square wave to one end of n of the N capacitor elements arranged in a row. The other ends of the remaining (Nn) capacitor elements are fixed at a fixed potential. This divides the amplitude of the RF carrier signal from 0 to VDD by n / N times. By changing the value of n, the output amplitude can be controlled with high precision.

[0018] Specifically, for example, as shown in Figures 2(a) and (b), in the case of full power, the output amplitude is controlled by applying an RF carrier signal or a phase-modulated RF carrier signal as a square wave to all N=4 capacitive elements, i.e., by setting n=4. On the other hand, when reducing the power, as shown in Figures 2(c) and (d), the output amplitude may be controlled by applying an RF carrier signal or a phase-modulated RF carrier signal as a square wave to two of the N=4 capacitive elements, i.e., n=2, etc. Note that the signal with controlled output amplitude may be made high-output by matching the impedance through a matching circuit such as a matching network.

[0019] <Comparative Example 3> Figures 3 and 4 are graphs illustrating polar modulation using SCPA technology according to Comparative Example 3. The horizontal axis represents time, and the vertical axis, from top to bottom, shows the rectangular RF carrier signal before modulation, the phase signal (referred to as the PM baseband signal; denoted as PM signal in the figures), the phase-modulated RF carrier signal, the amplitude signal (referred to as the AM baseband signal; denoted as AM signal in the figures), the RF output signal, and the product of the AM baseband signal and the PM baseband signal. Figure 4 is an enlarged view of a part of Figure 3. In Figures 3 and 4, the AM baseband signal is shown as a numerical value corresponding to the amplitude of the amplitude control signal provided by the digital signal of SCPA technology for easier understanding, and does not exist as an actual analog signal.

[0020] As shown in Figures 3 and 4, the amplitude control signal (AM baseband signal) of SCPA technology is actually a digital signal existing in the digital domain. In the example shown in Figure 3, the AM baseband signal has 9 values ​​from 0 to 8. Since there is also a phase inversion effect, this is equivalent to modulating the amplitude of the output RF signal in 17 steps from -8 to 8. This corresponds to a modulation resolution of approximately 4 bits. The actual required modulation resolution depends on the communication standard. Typically, a modulation resolution of 4 to 8 bits or more is required.

[0021] Figure 5 is a block diagram illustrating a transmitter 300 according to Comparative Example 3. Figure 5 shows the correspondence with each of the signals described above. As shown in Figure 5, the transmitter 300 includes a phase amplitude separation circuit 10, a local signal generation circuit 20, a phase modulation block 30, a power amplifier core section 40, and a matching circuit 60. The transmitter 300 may further include an antenna 70. The transmitter 300 may also further include a control unit 80. The transmitter 300 may be configured to be connected to an externally provided antenna 70. Furthermore, the transmitter 300 does not need to include a control unit 80; the functions of the control unit 80 may be handled by software running on a CPU (Central Processing Unit) mounted on the same chip or a separate chip.

[0022] The phase-amplitude separation circuit 10 separates the baseband signal into a PM baseband signal, which is the phase component of the baseband signal, and an AM baseband signal, which is the amplitude component of the baseband signal. 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 section 40. The AM baseband signal separated by the phase-amplitude separation circuit 10 is used in the power amplifier core section 40 for amplitude control of the RF signal (sometimes called first amplitude control) to obtain an amplitude-modulated RF output signal.

[0023] 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 rectangular waveforms.

[0024] The phase modulation block 30 generates a phase-modulated RF signal by modulating the RF carrier signal with a PM baseband signal. The phase modulation block 30 outputs the phase-modulated RF signal to the power amplifier core 40.

[0025] The power amplifier core section 40 includes, for example, a power amplifier having SCPA technology. The power amplifier core section 40 forms an envelope having multiple steps as shown in Figures 3 and 4. The power amplifier core section 40 recombines the PM baseband signal and the AM baseband signal to generate an RF output signal in which phase modulation components and amplitude modulation components are combined.

[0026] The matching circuit 60 generates an RF signal with matched impedances, etc. The RF output signal generated by the matching circuit 60 is output from the antenna 70.

[0027] The control unit 80 performs amplitude control of the RF output signal (sometimes called second amplitude control) to control the average transmission power from the antenna 70.

[0028] <New challenges identified by the inventor> The transmitter 300, such as an RF transmitter, requires not only a first amplitude control to obtain an RF signal amplitude-modulated with a baseband signal, but also a second amplitude control to control the average transmission power from the antenna 70. Here, we will consider a specific numerical example.

[0029] For example, the first amplitude control for amplitude modulation controls the RF carrier signal to have an amplitude with 17 steps, ranging from 0 to 16 at 1-step intervals. Including the phase inversion, the first amplitude control controls the amplitude to have 33 steps, ranging from -16 to 16 at 1-step intervals. The amplitude controlled in this way corresponds to a modulation accuracy of approximately 5 bits. Now consider the case where a second amplitude control is performed in a transmitter 300 with such modulation accuracy to control the average transmit power up to a maximum of 24 dB at 1 dB step intervals. In order to accommodate both the first amplitude control for amplitude modulation and the second amplitude control for average transmit power, it is necessary to increase the number of steps in the gradation of the output amplitude of the power amplifier core 40.

[0030] Figure 6 is an example of the design results for the transmitter 300 according to Comparative Example 3. As shown in Figure 6, the amplitude control of the power amplifier core 40 in the transmitter 300 has a gradation with 2049 steps from 0 to 2048. Here, a gradation with 2049 steps is sometimes simply referred to as 2049 gradation.

[0031] In the case of maximum output, i.e., when the attenuation is 0 dB, the amplitude of the RF carrier signal is controlled to 17 gradations, with 128 codes in the first amplitude control signal representing one unit (×1), and values ​​ranging from 0 to 2048 at 128-step intervals. That is, the amplitude of the RF carrier signal is controlled to 17 gradations: 0 / 128 / 256 / 384 / ... / 2048. This reproduces the envelope of the RF carrier signal. Here, the attenuation amount is sometimes called ATT or ATT amount, taking the three letters of Attenuation Amount or Attenuator. For example, ATT may be used when referring to a quantity. ATT amount may be used when referring to the amount of attenuation.

[0032] In the case of a 24dB attenuator (ATT), the amplitude of the RF carrier signal is controlled in 17 gradations, with 8 codes in the first amplitude control signal treated as one unit (×1), and values ​​from 0 to 128 spaced at 8-step intervals. This reproduces the envelope of the RF carrier signal. The ratio of this to the amplitude of the transmit power at maximum output is 8 / 128. Converting this to dB, it is 20log(8 / 128) = -24.08dB. The absolute value of the error relative to the design target of 24dB is 0.08dB. Looking at each of the attenuators from 0 to 24dB, the maximum absolute value of the error is 0.32dB when the ATT = 21dB.

[0033] Figure 7 illustrates an example of a different design result for the transmitter 300 according to Comparative Example 3. Figure 7 shows an example in which the amplitude control of the power amplifier core section 40 is reduced by approximately half to 1025 gradations from 0 to 1024. As shown in Figure 7, in this case, the resolution of the output amplitude of the transmitted power at low output is insufficient. For example, when ATT = 24dB, 23dB, 22dB, and 21dB, one unit of the amplitude control code becomes 4, 5, 5, and 6, respectively. Therefore, the output amplitude when ATT = 22dB must be the same as the output amplitude when ATT = 23dB.

[0034] Figure 8 is a graph illustrating the error in average transmit power control for the transmitter 300 according to Comparative Example 3, when the amplitude control of the power amplifier core 40 is 2049 levels and when it is 1025 levels. The horizontal axis shows the ideal value of ATT, and the vertical axis shows the error. As shown in Figure 8, in both the 2049 level and 1025 level cases, the absolute value of the error tends to increase in the region where the ATT amount is large. Furthermore, the error is larger in the 1025 level case, where the resolution of the output amplitude is lower. Thus, generally speaking, when attempting to perform accurate second amplitude control of the average transmit power in the region where the ATT amount is large, the required resolution of the output amplitude deteriorates.

[0035] However, in reality, it is difficult to design a power amplifier with a power amplifier core 40 capable of controlling the output amplitude in 2049 steps, as shown in Figure 6. First, dividing the power amplifier core 40 into numerous unit PAs leads to an increase in dead space in the layout. For example, a power amplifier core 40 capable of controlling the output amplitude in 2049 steps would require 2048 unit PAs.

[0036] Furthermore, dividing the power amplifier core 40 into numerous unit PAs (Power Amplifiers) results in a large amount of wiring required for the RF carrier signal and the on / off control signals of each unit PA. Consequently, dead space increases. As a result, such power amplifiers have long and complex signal lines, leading to larger timing errors in the signals. This degrades modulation accuracy. In addition, parasitic capacitance and inductance of the wiring increase, leading to increased power loss.

[0037] Another implementation method to solve the problems of dead space and wiring volume is to weight the size of the unit PAs binaryly as 1, 2, 4, ... However, in this case, it becomes difficult to maintain a proportional relationship between the performance of a unit PA corresponding to the maximum ×1024 gradation and a unit PA corresponding to ×1. Also, when reproducing a modulated signal, the on / off frequency of each unit PA increases, making it difficult to generate a low-distortion waveform. For example, in the configuration of arranging many ×1 unit PAs as described above, it is sufficient to turn on each unit PA sequentially. In contrast, in the case where the amplitude is increased linearly from 0, 1, 2, 3, 4, ..., in a binary configuration, the ×1 unit PAs will repeatedly be off, on, off, on, off, on. The ×2 unit PAs will repeatedly be off, off, on, on, off, off, on, on. Therefore, the on / off frequency increases.

[0038] As described above, in the transmitter 300, which uses EER technology or polar modulation technology to control amplitude with a digital signal, there are limitations on the number of gradations for the first amplitude control and second amplitude control of the power amplifier core section 40. Therefore, it is difficult to achieve both a wide output variable range and high modulation accuracy.

[0039] <Embodiment 1> Next, a power amplifier according to Embodiment 1 will be described. Figure 9 is a block diagram illustrating the power amplifier PA1 according to Embodiment 1. As shown in Figure 9, the power amplifier PA1 of this embodiment includes a power amplifier core 4 and a variable attenuator 5.

[0040] The power amplifier core section 4 is configured to allow discrete integer amplitude control. For example, the power amplifier core section 4 is configured to allow discrete amplitude control in (N+1) steps from 0 to N. The power amplifier core section 4 regenerates the RF signal envelope through amplitude control. The variable attenuator 5 changes the ATT amount. Therefore, the power amplifier PA1 of this embodiment controls the average transmit power by combining the amplitude control of the power amplifier core section 4 and the ATT amount of the variable attenuator 5.

[0041] The power amplifier core section 4 has an input terminal 4i, a first terminal 4a, a second terminal 4b, and an output terminal 4o. The input terminal 4i is the terminal to which the phase-modulated RF carrier signal is input. The first terminal 4a is the terminal to which the first amplitude control signal is input. The second terminal 4b is the terminal to which the second amplitude control signal is input. The output terminal 4o is the terminal to which the amplitude-modulated RF signal from the power amplifier core section 4 is output to the variable attenuator 5.

[0042] The variable attenuator 5 has an input terminal 5i, a first terminal 5a, and an output terminal 5o. The input terminal 5i is a terminal to which an amplitude-modulated RF signal is input. The first terminal 5a is a terminal to which an ATT control signal is input. The output terminal 5o is a terminal to which the RF signal to which a predetermined ATT amount is applied is output in the variable attenuator 5.

[0043] Figure 10 is a diagram illustrating the design results of the power amplifier PA1 according to Embodiment 1. As shown in Figure 10, the power amplifier PA1 of this embodiment can realize a second amplitude control for controlling the average transmit power in 145 gradations from 0 to 144. Specifically, the power amplifier PA1 of this embodiment controls the amplitude of the RF carrier signal to an output amplitude of 17 gradations, with intervals of 1 step from 0 to 16. Furthermore, the combination of the amplitude control of the power amplifier core 4 and the attenuation amount of the variable attenuator 5 controls the average transmit power within a range of 24 dB, with intervals of 1 dB. The amplitudes corresponding to each stage controlled by the first amplitude control may be equally spaced with respect to the control code, or partially unequally spaced, or entirely unequally spaced. The amplitudes corresponding to each stage controlled by the second amplitude control may be equally spaced with respect to the control code, or partially unequally spaced, or entirely unequally spaced.

[0044] Similar to the power amplifier PA1 of this embodiment, in order to control the transmitted power within a 24dB range divided into 1dB step intervals, the power amplifier of Comparative Example 3 described above requires a second amplitude control of a 2049-gradation power amplifier, as shown in Figure 6. The design example of this embodiment will be explained in more detail below.

[0045] Figure 11 is a diagram illustrating the design results of the power amplifier PA1 according to Embodiment 1. As shown in Figure 11, the power amplifier core 4 can control its output amplitude 1 from 17 levels of operation from 0 to 16, where "×1", to 9 levels of operation from 0 to 144, where "×9". When the variable attenuator 5 is not operating, the ATT amount is in 9 stages: ATT = 0dB, 1.0dB, 2.2dB, 3.5dB, 5.1dB, 7.0dB, 9.5dB, 13.1dB, and 19.1dB. As shown in Figure 10, the variable attenuator 5 combines this with an ATT amount of up to 6.0dB at 0.5dB step intervals. As a result, the power amplifier PA1 can achieve an ATT amount of up to 24dB with a maximum error of 0.18dB.

[0046] The configuration of the power amplifier PA1 in this embodiment requires fewer gradations to control the output amplitude of the power amplifier core 4 compared to Comparative Example 3. Therefore, the layout becomes more compact and the control wiring is simpler. As a result, the power amplifier PA1 of this embodiment enables the realization of a small and highly efficient transmitter. In this way, the power amplifier PA1 of this embodiment achieves miniaturization and high power efficiency operation of the transmitter by realizing high-range and high-precision output power control with a power amplifier that has fewer amplitude control gradations.

[0047] On the other hand, if the ATT amount of the variable attenuator 5 is large, power dissipation of the RF carrier signal may occur, potentially reducing the efficiency of the transmitter. If this power dissipation is large, the overall power reduction of the transmitter will not be achieved. However, for the reasons described below, this is not a practical problem.

[0048] First, let's consider the range of ATT = 8dB or less, where the transmitted power is high. As shown in Figure 10, when the target setting is ATT = 0dB, 1dB, 2dB, 5dB, and 7dB, the variable attenuator 5 is set to 0dB. Therefore, the problem of power dissipation of the RF carrier signal does not occur. For other target setting values ​​of ATT = 3dB, 4dB, 6dB, and 8dB, the ATT setting of the variable attenuator 5 is minor, ranging from 0.5 to 1.0dB. The power dissipated as a result is 10% and 20% of the transmitted power, respectively. If the efficiency of the power amplifier is 50% when the target setting is ATT = 0dB, then the power consumption is only 10% × 50% = 5% and 20% × 50% = 10%. This is not enough to surpass the efficiency improvement of the standalone power amplifier core 4 in this embodiment.

[0049] When the ATT amount of the variable attenuator 5 is large, the dissipation rate of the RF carrier signal power increases. As shown in Figure 10, when the variable attenuator 5 is controlled to an ATT of 3 dB or more, that is, when more than 50% of the RF carrier signal power is dissipated, it is in the region of ATT = 16 dB or higher. However, in this region, the absolute value of the RF carrier signal's transmission power is small, so the absolute value of the transmission power dissipated by the variable attenuator 5 is also small. To give specific figures, when ATT = 16 dB, the transmission power of the power amplifier core 4 is 13 dB lower than when ATT = 0 dB. In other words, the transmission power is reduced to 1 / 20. Since the variable attenuator 5 is set to 3 dB, the RF power that is dissipated is only half of that.

[0050] Furthermore, the efficiency of a power amplifier is generally highest near its maximum output, and decreases in this low transmission power range. In other words, in the case of ATT=16dB, the efficiency of the power amplifier core also decreases, and the self-power consumption of the power amplifier core 4 alone is greater than the power dissipated by the variable attenuator 5. That is, the power dissipated by the variable attenuator 5 becomes even smaller in relative terms.

[0051] Thus, according to this embodiment, the layout of the power amplifier core section 4 becomes more compact, and the amount of control wiring is reduced to less than 1 / 10, from 2049 gradation control in Comparative Example 3 to 145 gradation control in Figure 11. As a result, the self-power consumption of the transmit power of the power amplifier PA1 of this embodiment is significantly reduced. Therefore, the power amplifier PA1 of this embodiment can reduce the overall power consumption of the transmitter.

[0052] Figure 12 is a flowchart illustrating an amplification method using the power amplifier PA1 according to Embodiment 1. As shown in Figure 12, the amplification method according to this embodiment comprises a step S10 for amplitude control and a step S20 for changing the ATT amount.

[0053] In step S10, the power amplifier core 4 performs discrete integer amplitude control. The power amplifier core 4 regenerates the envelope of the RF carrier signal through amplitude control. In step S20, the variable attenuator 5 changes the ATT amount. As a result, the power amplifier PA1 controls the average transmit power through a combination of the amplitude control of the power amplifier core 4 and the ATT amount of the variable attenuator 5.

[0054] <Embodiment 2> Next, a transmitter according to Embodiment 2 will be described. Figure 13 is a block diagram illustrating a transmitter TM1 according to Embodiment 2. As shown in Figure 13, in addition to the power amplifier core section 4 and the variable attenuator 5, the transmitter TM1 of this embodiment 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 further include an antenna 7. The transmitter TM1 may also further include a power control signal separation section 8. The transmitter TM1 may be configured to be connected to an externally provided antenna 7. Furthermore, the transmitter TM1 does not need to include the power control signal separation section 8, and the function of the power control signal separation section 8 may be handled by software running on a CPU mounted on the same chip or a separate chip.

[0055] The phase-amplitude separation circuit 1 separates the baseband signal into a PM baseband signal, which is the phase component of the baseband signal, and an AM baseband signal, which is the amplitude component of the baseband signal. In this embodiment, the PM baseband signal is called the phase control signal, and the AM baseband signal is called 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 section 4 via the first terminal 4a. The first amplitude control signal is used in the power amplifier core section 4 for first amplitude control of the RF signal to obtain an amplitude-modulated RF signal.

[0056] The local signal generation circuit 2, phase modulation block 3, and matching circuit 6 have the same functions as the local signal generation circuit 20, phase modulation block 30, and matching circuit 60 of Comparative Example 3. In this embodiment, the variable attenuator 5 is located between the power amplifier core 4 and the matching circuit 6.

[0057] 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 transmit power control signal is input to the power control signal separation unit 8. The power control signal separation unit 8 separates the transmit 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 in the power amplifier core unit 4 for second amplitude control, which controls the average transmit 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 for control of changing the ATT amount.

[0058] The transmitter TM1 of this embodiment uses a power amplifier PA1 that can control the amplitude of the RF signal with fewer gradations, thereby achieving high-range and high-precision output power control. As a result, the transmitter TM1 achieves miniaturization and high power-efficient operation. Specifically, when the specifications are the same as the transmitter 300 of Comparative Example 3, i.e., when the average transmit power control is set to a range of 24 dB in 1 dB step intervals, fewer gradations can be achieved than the transmitter 300 of Comparative Example 3. In other words, the transmitter TM1 can realize the output amplitude of the RF output signal with 17 gradations, divided into 1 step intervals from 0 to 16.

[0059] <Example 1> Figure 14 is a block diagram illustrating a transmitter TM2 according to a modified example 1 of Embodiment 2. As shown in Figure 14, the transmitter TM2 of this embodiment is connected in the following order: power amplifier core 4, matching circuit 6, variable attenuator 5, and antenna 7. Compared to the configuration of the transmitter TM1 of Embodiment 2 described above, the positions of the variable attenuator 5 and the matching circuit 6 are swapped. The RF carrier signal output from the output terminal 4o of the power amplifier core 4 is input to the matching circuit 6. The RF signal output from the matching circuit 6 is then input to the variable attenuator 5. The transmitter TM2 of this embodiment includes a power amplifier PA2. The power amplifier PA2 includes a matching circuit 6 between the power amplifier core 4 and the variable attenuator 5. The same effects as in Embodiment 2 can be obtained with this configuration as well.

[0060] <Modification 2> Figure 15 is a block diagram illustrating a transmitter TM3 according to a modification 2 of Embodiment 2. As shown in Figure 15, the transmitter TM3 of this embodiment has a matching circuit 9 in which the variable attenuator 5 and the matching circuit 6 are integrated, instead of a variable attenuator 5 and a matching circuit 6. Therefore, the power amplifier PA3 of the transmitter TM3 includes a power amplifier core section 4 and a matching circuit 9. The matching circuit 9, which matches the output impedance, has the function of a variable attenuator. In other words, the variable attenuator of this modification is a matching circuit 9 equipped with the function of an attenuator, 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 section 4. The matching circuit 9 receives an ATT control signal from the power control signal isolation section 8.

[0061] Figure 16 is a block diagram illustrating a matching circuit 9 in a transmitter TM3 according to a modified example 2 of Embodiment 2. As shown in Figure 16, the matching circuit 9 of this modified example 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 of the variable capacitor 9a can be controlled by a digital code. One end of each variable capacitor 9a is connected to the power amplifier core section 4. The other end of each variable capacitor 9a is connected to a fixed potential such as ground. Coils 9b may be appropriately placed between the variable capacitors 9a and between the variable capacitors 9a and the power amplifier core section 4.

[0062] Generally, a matching circuit 9 equipped with a variable capacitor 9a, as shown in Figure 16, is often used as a means of tuning the difference between the design characteristics and the actual characteristics. The function of such a variable capacitor 9a is also used as a means of realizing a variable attenuator in the transmission power control of this modified example. The variable capacitor 9a in this modified example may be one that is originally provided as a means of absorbing design errors. This makes it unnecessary to add a new variable attenuator 5.

[0063] <Embodiment 3> Next, the power amplifier core section according to Embodiment 3 will be described. Figure 17 is a block diagram illustrating the configuration of the power amplifier core section 4X according to Embodiment 3. Figure 18 is a block diagram illustrating the operation of the power amplifier core section 4X according to Embodiment 3. As shown in Figures 17 and 18, the power amplifier core section 4X includes a plurality of unit power amplifier groups 4g. The power amplifier core section 4X includes, for example, L unit power amplifier groups 4g. The plurality of unit power amplifier groups 4g are connected in parallel.

[0064] The unit power amplifier group 4g includes multiple capacitors and a logic circuit that switches the capacitors between an operating state and a dormant state. Each unit power amplifier group 4g can be amplitude-controlled to have multiple levels of gradation. Each unit power amplifier group 4g can be controlled to have, for example, an amplitude of (M+1) gradation from 0 to M. Thus, the power amplifier core section 4X is configured by connecting L unit power amplifier groups 4g in parallel, each capable of amplitude controllable to (M+1) gradation including zero output. In other words, L × M (the product of L and M) is a value corresponding to N in the N+1 gradation from 0 to N that the power amplifier core section 4X controls. Here, L, M, and N are integers. Each unit power amplifier group 4g may also include a switched-capacitor PA (SCPA) consisting of M unit amplifiers. Thus, the power amplifier core section 4X may include a switched-capacitor power amplifier.

[0065] As shown in Figure 18, the control of the average transmit power of the RF signal is achieved by a combination of controlling the number of active (l) units out of the L unit power amplifier groups 4g and the ATT control of the variable attenuator 5. The remaining (Ll) unit power amplifier groups 4g are always in a dormant state and are in the RF carrier signal transmission off state. Thus, the power amplifier of this embodiment controls the average transmit power by a combination of controlling the number of operating unit power amplifier groups 4g out of the L parallel units and the ATT amount of the variable attenuator 5.

[0066] Each of the 4g unit power amplifier groups is capable of (M+1) degree amplitude control. Focusing on each of the 1 active unit power amplifier groups 4g, instantaneously, m unit amplifiers are active and (Mm) unit amplifiers are in a dormant state. By controlling the value of m over time, the power amplifier core 4X can regenerate the RF carrier signal envelope with (M+1) degree control. The 1 unit power amplifier groups 4g operate in the same way.

[0067] In the configuration of the power amplifier core section 4X of this embodiment, the first amplitude control signal for regenerating the envelope of the RF carrier signal and the second amplitude control signal for controlling the average transmit power are separated. Therefore, the decoder for the gradation control of the power amplifier core section 4X can be simplified. Depending on the wireless system, the bandwidth of the baseband signal ranges from about 100 MHz to several hundred MHz. In that case, the timing error allowed for the first amplitude control signal and the second amplitude control signal must be smaller than 1 / signal bandwidth = 10 ns or less. Simplifying the decoder is advantageous in reducing timing errors and improving the modulation accuracy of the envelope component of the RF carrier signal. Furthermore, it is possible to use the same design for all unit power amplifier groups 4g. In that case, the design is simply to first design one unit power amplifier group 4g and then arrange L of them in a row. Thus, the design of the power amplifier core section 4X becomes easier.

[0068] Furthermore, the amplitude changes of the RF carrier signal corresponding to each gradation in the (N+1) and (M+1) gradation control may be equally spaced, partially unequal, or completely unequal. This is a design consideration. Also, the sizes of the L parallel-connected unit power amplifier groups 4g may all be equal, binaryly weighted, or arbitrarily unequal. This is a design consideration. Moreover, the unit power amplifier groups 4g may be SCPA as shown in this embodiment, other switching amplifiers, or other configurations. This is a design consideration.

[0069] Figure 19 is a block diagram illustrating a power amplifier core section 4X and a variable attenuator 5X according to Embodiment 3. As shown in Figure 19, the variable attenuator 5X is connected to the output terminal 4o of the power amplifier core section 4X. The variable attenuator 5X may include a capacitance bank 5B. One end of the capacitance bank 5B is connected to the output terminal 4o of the power amplifier core section 4X. The other end of the capacitance bank 5B is connected to a fixed potential node such as ground. Thus, the variable attenuator 5X may include a capacitance bank 5B in which one end is connected to a signal line through which an RF carrier signal passes, and the other end is connected to a fixed potential line.

[0070] Let C0 be the capacitance value of one SCPA unit in the power amplifier core section 4X. The total capacitance of the SCPA in the power amplifier core section 4X is L × M × C0. When the number of parallel SCPAs to be activated is 1, the instantaneous value of the amplitude control signal for modulation is m, and the capacitance of capacitance bank 5B is Cbank, the output amplitude of the RF output signal is proportional to equation (1) below.

[0071] 1 × m × C0 / (L × M × C0 + Cbank) (1)

[0072] In other words, the variable capacitance Cbank effectively functions as a variable attenuator. Converting equation (1) to dB yields equation (2) below.

[0073] 20log{1×m×C0 / (L×M×C0+Cbank)} =20log(m / M)+20log(l / L)-20log{1+Cbank / (L×M×C0)} (2)

[0074] The first term on the right-hand side is related to the envelope reproduction of the RF carrier signal. The second term on the right-hand side shows the control value of the average transmit power of the RF carrier signal by the number l of the active unit power amplifier group 4g. The third term shows the control value of the transmit power of the RF signal by the capacitance Cbank of the capacitance bank 5B, which functions as a variable attenuator 5X.

[0075] Figure 20 is a diagram illustrating the design results for a power amplifier including a power amplifier core 4X and a variable attenuator 5X according to Embodiment 3. As shown in Figure 20, the capacitance Cbank of capacitance bank 5B is controlled by 4 bits. The capacitances that each bit turns on / off 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 capacitance bank 5B is as shown in Figure 20. In this case, the ATT amount (attenuation) is in 0.5 dB steps from 0 dB to 3.0 dB. The ATT amount is in 1.0 dB steps from 3 dB to 6.0 dB. Thus, the variable attenuator 5X of this embodiment can achieve amplitude control with a maximum error of 0.1 dB in ATT from 0 dB to 6.0 dB.

[0076] Figure 21 is a graph illustrating the average value of the transmitted power in the power amplifier according to Embodiment 3, where the horizontal axis represents time and the vertical axis represents the transmitted power. In Figure 21, the phase inversion portion is omitted. As shown in Figure 21, the power amplifier core 4X generates an amplitude-modulated RF output signal having a gradient envelope including multiple stages by modulating the phase-modulated RF carrier signal with an amplitude signal.

[0077] For example, the power amplifier core section 4X may consist of L units of power amplifiers 4g, each controllable to (M+1) gradations, connected in parallel, where L and M are integers. The power amplifier core section 4X may also generate envelopes with (M+1) gradations.

[0078] Furthermore, the power amplifier core section 4X may be controlled so that the average value of the transmitted power of the RF output signal is L values. In Figure 21, the amplitude of the transmitted power for L=9, L=5, and L=4 is shown by solid lines. The transmitted power for L=9 corresponds to ATT=0dB. The transmitted power for L=5 corresponds to ATT=5dB. The average transmitted power for L=4 corresponds to ATT=7dB. However, the power amplifier core section 4 alone cannot make the transmitted power correspond to ATT=6dB. In other words, the power amplifier core section 4 alone cannot make the ATT correspond to the values ​​between L=5 and L=4.

[0079] Therefore, the variable attenuator 5X can change the attenuation amount by a value smaller than the maximum value obtained by expressing the difference between adjacent values ​​in decibels when the average values ​​of an integer number of transmit powers are arranged in descending order. For example, the variable attenuator 5X may attenuate the transmit power so that the average value of the transmit power falls between at least one of the arranged integer values ​​when L values ​​are arranged in descending order. Specifically, as shown by the dotted line in Figure 21, the variable attenuator 5X attenuates the transmit power to dB=6, which is between dB=7 at L=4 and dB=5 at L=5. In this way, the power amplifier core 4X and the variable attenuator 5X can perform highly accurate amplitude control while keeping the number of unit power amplifier groups 4g to a minimum. Thus, the power amplifier and transmitter TM3 can be miniaturized and made more efficient.

[0080] Although the present invention has been specifically described above based on embodiments, it goes without saying that the present invention is not limited to the above embodiments and can be modified in various ways without departing from its essence. For example, combinations of Comparative Examples 1 to 3, Embodiments 1 to 3 and each of their modified forms are also within the scope of the technical concept of the embodiments. [Explanation of Symbols]

[0081] 1. Phase-amplitude separation circuit 2. Local signal generation circuit 3 Phase Modulation Block 4. Power amplifier core section 4a 1st terminal 4b Second terminal 4i input terminals 4g Unit Power Amplifier Group 40 Output terminal 4X Power Amplifier Core 5. Variable Attenuator 5a 1st terminal 5B Capacity Bank 5i input terminal 50 Output terminal 5X Variable Attenuator 6 Matching circuit 7 Antennas 8 Power control signal separation unit 9 Matching circuit 9a Variable Capacity 9b Coil 10 Phase-amplitude separation circuit 20 Local signal generation circuit 30 Phase Modulation Block 40 Power amplifier core section 60 matching circuit 70 Antenna 80 Control Unit 100, 300 Transmitters PA1, PA2, PA3 Power Amplifiers TM1, TM2, TM3 Transmitters

Claims

1. A power amplifier core section capable of discrete integer amplitude control, Variable attenuator, Equipped with, Power amplifier.

2. The power amplifier core section regenerates the RF signal envelope by the amplitude control, The aforementioned variable attenuator changes the amount of attenuation, The average transmitted power is controlled by a combination of the amplitude control of the power amplifier core and the attenuation amount of the variable attenuator. The power amplifier according to claim 1.

3. The power amplifier core section includes a switched-capacitor power amplifier. The variable attenuator includes a capacitance bank, with one end connected to a signal line through which the RF signal output from the power amplifier core passes, and the other end connected to a fixed potential line. The power amplifier according to claim 1.

4. When L and M are integers, The power amplifier core section consists of L parallel-connected unit amplifier groups, each capable of controlling (M+1) gradations, including zero output. The power amplifier according to claim 1.

5. The power amplifier core section regenerates the RF signal envelope by controlling the (M+1) gradations. The average transmit power is controlled by a combination of controlling the number of operating unit amplifier groups among the L parallel units and the attenuation amount of the variable attenuator. The power amplifier according to claim 4.

6. The amplitude changes of the RF signal corresponding to each gradation include portions that are not equally spaced. The power amplifier according to claim 1.

7. The amplitude changes of the RF signals corresponding to each of the (M+1) gradations of the aforementioned gradation control include portions that are not equally spaced. The power amplifier according to claim 4.

8. The variable attenuator is a matching circuit that has the function of an attenuator, and includes the matching circuit that matches the output impedance. The power amplifier according to claim 1.

9. The power amplifier core performs discrete integer amplitude control, The steps include changing the amount of attenuation with a variable attenuator, Equipped with, Amplification method.

10. In the step of performing the amplitude control, The power amplifier core section regenerates the RF signal envelope by the amplitude control, The average transmit power is controlled by a combination of the amplitude control of the power amplifier core and the attenuation amount of the variable attenuator. The amplification method according to claim 9.

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

12. When L and M are integers, The power amplifier core section consists of L parallel connections of (M+1) controllable unit amplifier groups. The amplification method according to claim 9.

13. In the step of performing the amplitude control, The power amplifier core section regenerates the RF signal envelope by controlling the (M+1) gradations. The average transmit power is controlled by controlling the number of operating unit amplifier groups among the L parallel units and the attenuation amount of the variable attenuator. The amplification method according to claim 12.

14. The amplitude changes of the RF signal corresponding to each gradation include portions that are not equally spaced. The amplification method according to claim 9.

15. The amplitude changes of the RF signals corresponding to each of the (M+1) gradations of the aforementioned gradation control include portions that are not equally spaced. The amplification method according to claim 12.

16. The variable attenuator includes an output impedance matching circuit that provides the function of an attenuator. The amplification method according to claim 9.

17. A phase-amplitude separation circuit separates a baseband signal into a phase signal, which is the phase component of the baseband signal, and an amplitude signal, which is the amplitude component of the baseband signal. A phase modulation block that generates a phase-modulated RF carrier signal by modulating the RF carrier signal with the phase signal, A power amplifier core section capable of discrete integer amplitude control, Variable attenuator, Equipped with, The aforementioned power amplifier core section is By modulating the phase-modulated RF carrier signal with the amplitude signal, an amplitude-modulated RF signal is generated that has a gradient envelope including multiple stages. The average value of the transmission power of the amplitude-modulated RF signal is controlled to be one of a predetermined integer value. The aforementioned variable attenuator is When the average values ​​of the integers of the transmitted power are arranged in descending order, the attenuation can be changed by a value smaller than the maximum value obtained by expressing the difference between adjacent values ​​in decibels. Transmitter.

18. The aforementioned power amplifier core section is When L and M are integers, (M+1) units of controllable gradations are connected in L parallel. The average value of the transmitted power is controlled to be L values, The aforementioned variable attenuator is The transmission power is attenuated so that the average value of the transmission power falls within the range of at least one of the L values ​​in a sequence. The transmitter according to claim 17.

Images