JP3823043B2 - Power amplifier - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power amplifier mainly used in a mobile communication base station such as a mobile phone.
[0002]
[Prior art]
In recent years, a transmitter of a base station of a mobile communication device has required a power amplifier having high efficiency and linear characteristics as much as possible in order to amplify a large number of signal channels at once. . In order to make the characteristics of the power amplifier as linear as possible, for example, it is indispensable to reduce distortion of the power amplifier itself in addition to employing distortion compensation such as a feed forward method.
[0003]
FIG. 31 is a diagram showing a conventional power amplifier 600.
[0004]
The power amplifying apparatus 600 includes an input terminal 601, an output terminal 602, baluns 603 and 604, and amplifiers 605 and 606. The amplifiers 605 and 606 include amplification elements 611 and 612, input-side matching circuits 613 and 614, output-side matching circuits 615 and 616, input-side bias circuit capacitors 617 and 618, and output-side bias circuit capacitors. 619, 620. Amplifiers 605 and 606 operate as push-pull amplifiers. Each of capacitors 619 and 620 is actually composed of a plurality of capacitors. That is, a capacitor having a low impedance at a predetermined signal frequency and a capacitor having a low impedance at a frequency corresponding to a frequency difference (frequency interval) when a plurality of signals are input. By providing the output-side bias circuit capacitors 619 and 620, the intermodulation distortion generated in the amplifier can be suppressed, and the characteristics of the power amplifier can be made as close to linear as possible.
[0005]
[Problems to be solved by the invention]
However, in the conventional power amplifying apparatus 600, capacitors 619 and 620 must be provided in the bias circuit of each push-pull amplifier 605 and 606, which increases the number of components. In addition, since the capacitors 619 and 620 generally need to have a large capacity and a low resistance, an increase in the number of components increases the overall circuit scale. Furthermore, the degree of suppression of intermodulation distortion varies depending on the frequency interval of a plurality of signals input to the amplifier.
[0006]
An object of the present invention is to provide a power amplifier that reduces intermodulation distortion generated in an amplifier while reducing the number of components.
[0007]
[Means for Solving the Problems]
The power amplifier of the present invention includes an input unit that inputs a combined signal obtained by combining two signals having different frequencies, a first output unit that outputs a first signal having a first phase, and the first phase. A first balun having a second output for outputting a second signal having a second phase opposite to that of the first signal, and receiving and amplifying the first signal, thereby obtaining a frequency difference between the two signals. A first amplifier that outputs a first amplified signal including a frequency component comprising: a second amplifier including a frequency component comprising a frequency difference between the two signals by receiving and amplifying the second signal; A second amplifier for outputting an amplified signal, an output having a first input unit and a second input unit, and outputting a combined signal of signals input from the first input unit and the second input unit A second balun having a portion; An impedance element connected between an output of the first amplifier and an output of the second amplifier and having a self-resonant frequency as an absolute value of a frequency difference between the two signals; A frequency component included in the second amplified signal, Impedance element To the first amplification path that reaches the first input of the second balun Shi , The frequency component included in the first amplified signal is Impedance element To the second amplification path reaching the second input section of the second balun The This achieves the above object.
[0008]
[0009]
[0010]
The impedance element is connected in series and is included in the first amplified signal. Lap Wavenumber component, Said Included in the second amplified signal Lap There may be further provided a phase shifter that receives the wave number component, adjusts the phase of each frequency component, and outputs the frequency component in opposite phases.
[0011]
[0012]
[0013]
[0014]
[0015]
[0016]
[0017]
[0018]
[0019]
[0020]
[0021]
[0022]
[0023]
[0024]
[0025]
[0026]
[0027]
[0028]
[0029]
[0030]
[0031]
[0032]
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0034]
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a power amplifier 100 according to the first embodiment. The power amplifier 100 includes an input terminal 101, a first balun 103 having an input 103a, a first output 103b, and a second output 103c, an amplifier 105 having an input 105a and an output 105b, and an input 106a and an output 106b. An amplifier 106, a capacitor 107 as an impedance element, a second balun 104 having a first input 104b, a second input 104c, and an output 104a, and an output terminal 102.
[0035]
The connection relationship in the power amplifier 100 is as follows. The input terminal 101 is connected to the input 103a of the balun 103, and the first output 103b and the second output 103c of the balun 103 are connected to the input 105a of the amplifier 105 and the input 106a of the amplifier 106, respectively. The output 105b of the amplifier 105 and the output 106b of the amplifier 106 are connected to the first input 104b and the second input 104c of the second balun 104, respectively. The output 104 a of the balun 104 is connected to the output terminal 102. Further, the capacitor 107 is connected between the output 105b of the amplifier 105 and the output 106b of the amplifier 106. Hereinafter, a path from the first output 103b of the balun 103 to the first input 104b of the balun 104 via the amplifier 105 is referred to as a first amplification path 161. A path from the second output 103 c of the balun 103 to the second input 104 c of the balun 104 via the amplifier 106 is defined as a second amplification path 162.
[0036]
FIG. 2 shows a specific circuit configuration of the power amplifier 100. The amplifier 105 includes an amplifying element 111 composed of a transistor, an input side matching circuit 113 that matches the impedance on the input side, an output side matching circuit 115 that matches the impedance on the output side, and an input side bias circuit that applies a bias to the input side. 131 and an output side bias circuit 133 that applies a bias to the output side. An input side matching circuit 113 and an input side bias circuit 131 are connected to the gate of the amplifying element 111. Further, the output side matching circuit 115 and the output side bias circuit 133 are connected to the drain of the amplifying element 111. The input side bias circuit 131 includes a transmission line 121 and an input side bias circuit capacitor 117. The output side bias circuit 133 includes a transmission line 123 and a capacitor 119 for the output side bias circuit. The transmission line 121 and the transmission line 123 are, for example, quarter wavelength lines of the input signal frequency. Capacitors 117 and 119 are capacitors having low impedance at the input signal frequency.
[0037]
On the other hand, the amplifier 106 of the power amplifier 100 includes an amplifying element 112 made of a transistor, an input side matching circuit 114, an output side matching circuit 116, an input side bias circuit 132, and an output side bias circuit 134. An input side matching circuit 114 and an input side bias circuit 132 are connected to the gate of the amplifying element 112. Further, the output side matching circuit 116 and the output side bias circuit 134 are connected to the drain of the amplifying element 112. The input side bias circuit 132 includes a transmission line 122 and an input side bias circuit capacitor 118. The output side bias circuit 134 includes a transmission line 124 and a capacitor 120 for the output side bias circuit.
[0038]
Next, the basic operation of the power amplifier 100 will be described with reference to FIG. FIG. 3 is a block diagram showing signal waveforms in each part of the power amplifier 100. The unbalanced signal input from the input terminal 101 is converted into a first signal and a second signal by the balun 103 and output from the first output 103b and the second output 103c, respectively. At this time, balanced signals having the same amplitude and a phase difference of 180 ° are output from the two outputs. That is, the balun 103 converts one input signal into two signals whose phases are shifted from each other by 180 °, and outputs each of them. The first signal and the second signal are amplified by an amplifier 105 and an amplifier 106 that operate as push-pull amplifiers, respectively. The amplified first signal and second signal are input to the balun 104 from the first input 104b and the second input 104c of the balun 104, respectively, and converted into an amplified signal that is an unbalanced signal. In other words, the balun 104 amplifies and converts two input signals whose phases are shifted from each other by 180 ° into one signal, and outputs it. The converted amplified signal is output from the output terminal 102. As a result, the signal input from the input terminal 101 is output as an amplified signal at the output terminal 102.
[0039]
When viewed from the input signal line to the amplifier 105, the bias circuit 131 (FIG. 2) and the bias circuit 133 (FIG. 2) of the amplifier 105 have high impedance at the input signal frequency. That is, the bias circuit 131 (FIG. 2) and the bias circuit 133 (FIG. 2) do not affect the signal operation. The same applies to the bias circuit of the amplifier 106.
[0040]
Consider a case where two signals having a sufficiently small frequency interval with respect to the signal frequency are input to the input terminal 101. Even when two signals are input, the power amplifier 100 performs the basic operation described above. However, in this case, intermodulation distortion occurs due to the nonlinearity of the amplifier. Now, assume that the frequencies of two input signals are f1 and f2 (for example, f1 is 2000 MHz and f2 is 2010 MHz). FIG. 4A is a waveform diagram of signals of frequencies f1 and f2. Next, FIG. 4B is a waveform diagram of a synthesized signal obtained by synthesizing signals of the frequency f1 and the frequency f2. FIG. 4C shows the waveforms of the first signal and the second signal converted and output by the balun 103 (FIG. 3). The converted first signal and second signal are amplified by amplifier 105 and amplifier 106, respectively.
[0041]
Consider the case where the first signal is amplified. For example, assume that the amplifier 105 (FIG. 3) has a characteristic of amplifying the amplitude twice. With reference to (a) of FIG. 5, if the signal waveform of the input signal is F, the ideal signal waveform of the amplified signal is indicated as F ′. However, the signal waveform of the actual amplified signal is not represented as F ′, but becomes a signal waveform as indicated by F ″ in FIG. This is due to distortion caused by the nonlinearity of the amplifier 105. As the signal waveform F ″ approaches the vertex of the envelope, linear amplification cannot be obtained, and the phase also shifts.
[0042]
FIG. 6 shows a spectral distribution obtained by component analysis of the signal waveform of F ′ ((a) of FIG. 5). FIG. 6A shows the frequency spectrum of two signal waves of frequencies f1 and f2 before amplification. Let Δf be the absolute value of the difference between the frequencies f1 and f2 (= | f1-f2 |). Hereinafter, | f1-f2 | or Δf is referred to as a frequency interval.
[0043]
Of the intermodulation distortion, the third problem is the most problematic. As shown in FIG. 6B, the third-order distortion occurs at the frequencies 2f1-f2 and 2f2-f1. One of the factors that cause this third-order intermodulation distortion is that the frequency Δf component (FIG. 6B) generated by the nonlinearity of the amplifier 105 and the signal frequency f1 (or f2) component are once again a push-pull amplifier. Is considered to be mixed. Therefore, if the generated frequency Δf component can be kept small as shown in FIG. 6D, the generated third-order intermodulation distortion can be reduced. The frequency Δf component is equal to the frequency interval Δf shown in FIG.
[0044]
Therefore, in the first embodiment, the capacitor 107 (FIG. 1) is connected between the output 105b of the amplifier 105 (FIG. 1) and the output 106b of the amplifier 106 (FIG. 1). Then, the capacitor 107 (FIG. 1) is given a characteristic of having a low impedance with respect to the frequency Δf. In other words, the self-resonant frequency of the capacitor 107 (FIG. 1) is set to Δf. Thereby, the Δf component from the output 105b of the amplifier 105 (FIG. 1) and the Δf component of the output 106b of the amplifier 106 (FIG. 1) can be reduced. The reason will be described below.
[0045]
Referring again to FIG. 1, in the two balanced outputs 105b and 106b of the push-pull amplifiers 105 and 106, the respective Δf components have the same amplitude and the same phase. As described above, in this embodiment, the capacitor 107 having a low impedance with respect to the frequency Δf is provided. The capacitor 107 transmits the Δf component substantially as it is. Here, paying attention to the output 105b of the amplifier 105, a Δf component is output, and a Δf component of the same amplitude and phase transmitted from the output 106b of the amplifier 106 is input. The opposite is true at the output 106b of the amplifier 106. In theory, in the outputs 105b and 106b, Δf components do not cancel each other.
[0046]
However, in practice, the circuit wiring includes an impedance component, and a phase shift of the Δf component occurs, so the Δf component partially cancels and decreases. Thereby, it is possible to eliminate the mixing of the frequency Δf component and the signal frequency (f1 or f2) component, and to reduce the third-order intermodulation distortion generated in the amplifier. In addition, the number of parts can be reduced as compared with the prior art. In addition, since it is not necessary to use two capacitors having the same characteristics, there is an excellent effect that it is not necessary to consider deterioration of characteristics due to individual differences of capacitors. As described so far, according to the first embodiment, it is possible to realize a power amplifier in which intermodulation distortion is reduced and the number of components is reduced.
[0047]
In the first embodiment, the input signals are two sine wave signals having frequencies f1 and f2. However, if the two sides of the modulation wave component curve shown in FIG. 6C are set to f1 and f2, the same effect can be obtained for the modulation wave.
[0048]
In the first embodiment, the capacitor 107 (FIG. 1) is connected to the output side of the output side matching circuits 115 and 116. However, the same effect can be obtained even if the configuration is different from this configuration. FIG. 7 is a circuit diagram of another example of the power amplifier 100. The power amplifier 100 may be connected to the amplification element side of the output side matching circuits 115 and 116, that is, between the output side matching circuits 115 and 116 and the drain terminals of the amplification elements 111 and 112. The capacitor 107 only needs to be connected between the first amplification path 161 and the second amplification path 162.
[0049]
Subsequently, a configuration for further reducing the Δf component will be described. FIG. 8 is a block diagram showing the configuration of the power amplifier 110 that reduces the Δf component. Hereinafter, only components different from the power amplifier 100 (FIG. 3) in the power amplifier 110 will be described, and description of the same components will be omitted.
[0050]
The power amplifier 110 differs from the power amplifier 100 (FIG. 3) in that a phase shifter 81 is provided in series with the capacitor 107. The phase shifter 81 can change the phase of the input signal. Specifically, the phase shifter 81 outputs the Δf component input signal output from the amplifier 105 in a phase opposite to the phase of the Δf component signal output from the amplifier 106. Further, the phase shifter 81 outputs the Δf component input signal output from the amplifier 106 in a phase opposite to the phase of the Δf component signal output from the amplifier 105. That is, the Δf component has almost the same phase with the same amplitude, and is reduced at both the output 105 b of the amplifier 105 and the output 106 b of the amplifier 106. As a result, third-order intermodulation distortion generated in the amplifier can be significantly reduced. Furthermore, by changing the phase in consideration of the phase shift due to the impedance of the circuit wiring, it is possible to cancel the Δf component so that it becomes substantially zero.
[0051]
The phase shifter 81 may be provided in series connection with the capacitor 107 described with reference to FIG. 7, or may be provided so as to connect between the output of the amplifier 105 and the output of the amplifier 106 in FIG. 7.
[0052]
(Embodiment 2)
FIG. 9 is a circuit diagram of the power amplifier 100 according to the second embodiment. The same components as those described in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
[0053]
The power amplifier 100 shown in FIG. 9 differs from the power amplifier according to the first embodiment not only between the outputs of the amplifiers 105 and 106, in other words, between the first input and the second input of the balun 104. A capacitor is also connected between the drains of the amplifying elements 111 and 112. A capacitor between the drains of the amplifying elements 111 and 112 is 107a, and a capacitor between the inputs of the balun 104 is 107b.
[0054]
In general, an actual capacitor has a unique self-resonant frequency, and the impedance at that frequency is close to 0Ω. For this reason, by providing the capacitor 107b, it is possible to reduce intermodulation distortion due to the Δf component corresponding to the self-resonant frequency of the capacitor. However, the impedance becomes high at frequencies away from the self-resonant frequency. FIG. 10 is a graph showing an example of the resonance characteristics of the capacitor. As is clear from FIG. 10A, in a capacitor, the frequency band showing low impedance characteristics is generally narrow.
[0055]
The frequency of the signal input to the power amplifier has a certain bandwidth, and which frequency of the carrier signal is used varies depending on the case. Therefore, the frequency interval Δf also has a predetermined width. As described above, since a capacitor generally has a narrow frequency band that exhibits low impedance characteristics, if the value of the frequency interval Δf is different from the self-resonant frequency of the capacitor 107b (FIG. 9), the intermodulation distortion cannot be reduced. There is.
[0056]
Therefore, it is necessary to be able to reduce intermodulation distortion even when the value of the signal frequency interval Δf changes. In the second embodiment, a capacitor 107a having a self-resonance frequency different from that of the capacitor 107b is further connected. The frequency band in which the impedance of the capacitor 107a is small and the frequency band in which the impedance of the capacitor 107b is small have an overlapping portion. Thereby, the intermodulation distortion corresponding to a wide frequency interval Δf can be reduced. That is, the intermodulation distortion can be reduced according to the change in the frequency interval Δf between the two input signals. For example, as shown in FIG. 10B, a capacitor 107a having a self-resonant frequency of 5 MHz and a capacitor 107b having a self-resonant frequency of 20 MHz are provided. Thereby, it is possible to reduce intermodulation distortion when a plurality of signals are amplified over a frequency interval Δf ranging from 5 MHz to 20 MHz.
[0057]
In the second embodiment, as in the case of the first embodiment, it is possible to realize a power amplifier in which the number of parts is reduced and the intermodulation distortion is reduced as compared with the conventional case.
[0058]
Furthermore, in the second embodiment, one of the two capacitors is connected between the drains of the amplifying element 111 and the amplifying element 112, and the other is the output after passing through the matching circuits 115 and 116. A connection was made between the two inputs of the side balun 104. This point is not limited to the above, and both may be connected between the drain terminals of the push-pull amplifier. Alternatively, both may be connected between the first input and the second input of the output balun 104. Even in these cases, the same effects as those of the second embodiment can be obtained.
[0059]
In the second embodiment, two types of capacitors having different self-resonant frequencies are used. However, three or more types of capacitors having different self-resonant frequencies may be used. Further, the connection position can be freely set as long as it is between the first amplification path 151 and the second amplification path 152. Even in this case, the same effect as that of the second embodiment can be obtained.
[0060]
Furthermore, by providing the phase shifter described with reference to FIG. 8, it is possible to greatly reduce intermodulation distortion when a plurality of signals are amplified. The phase shifter may be provided at a position where a Δf component signal is transmitted through each capacitor. The number of phase shifters corresponding to the number of capacitors may be provided, or may be provided only for a specific capacitor.
[0061]
(Embodiment 3)
FIG. 11 is a circuit diagram of the power amplifier 100 according to the third embodiment. The same components as those described in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
[0062]
The power amplifier 100 shown in FIG. 11 is different from the power amplifier according to the first embodiment in that an inductor 108 is connected instead of a capacitor between the outputs of the push-pull amplifiers 105 and 106. The inductor 108 is also an impedance element.
[0063]
The meaning of providing the inductor 108 is the same as that of the capacitor 107 in the first and second embodiments. In the third embodiment, consider a case where two signals having frequencies f1 and f2 are input to the power amplifier 100. It is assumed that the frequency interval Δf is sufficiently smaller than the signal frequency. Further, it is assumed that the inductor 108 has a low impedance around the frequency Δf. At this time, the Δf components appearing at the output 105b of the amplifier 105 and the output 106b of the amplifier 106 cancel each other for the same reason as described in the first embodiment. As a result, mixing between the Δf component and the signal frequency (f1 or f2) in the amplifier does not occur, and the third-order intermodulation distortion generated in the amplifier can be reduced as in the first embodiment. In addition, a power amplifier with a reduced number of parts compared to the conventional one can be realized.
[0064]
A further feature of the inductor 108 is that it exhibits a low impedance characteristic even at a frequency lower than the frequency Δf. Thereby, by connecting the inductor 108 between the outputs of the push-pull amplifier, the intermodulation distortion can be reduced even when the frequency interval Δf of a plurality of signals input to the amplifier changes.
[0065]
In the third embodiment, the inductor 108 is used as the impedance element having a low impedance at the frequency Δf. However, the configuration shown in FIG. 12 may be used instead.
[0066]
FIG. 12 is a circuit diagram showing another example of the power amplifier 100 according to the third embodiment. In the power amplifier 100, instead of the inductor 108, an inductor 109a connected between the outputs of the push-pull amplifier, a low-pass filter 109, a capacitor 109b connected between the output 105b of the amplifier 105 and the ground 109d, And a low-pass filter 109 constituted by a capacitor 109c connected between the output 106b of the amplifier 106 and the ground 109e. By using the low-pass filter 109 instead of the inductor 108, it is possible to widen the bandwidth for low impedance.
[0067]
Needless to say, the same effects as those of the present embodiment can be obtained even with a low-pass filter having a configuration different from the configuration described above. Further, as described with reference to FIG. 8 in the first embodiment, a phase shifter may be provided to reduce the frequency interval Δf more reliably.
[0068]
( Reference example 1 )
FIG. Reference example 1 2 is a block diagram showing a configuration of a power amplifier 200 according to FIG. The power amplifier 200 has the same function as the power amplifier described in the first to third embodiments. That is, when a plurality of signals having a sufficiently small frequency interval with respect to the signal frequency are input, the power amplifier 200 reduces intermodulation distortion (particularly third-order intermodulation distortion) and shifts the phase with respect to the input signal. Amplified signal without noise is output.
[0069]
First, the configuration of the power amplifier 200 will be described. The power amplifier 200 includes an input terminal 201, a first balun 203 having an input 203a, a first output 203b and a second output 203c, an amplifier 205 having an input 205a and an output 205b, and an input 206a and an output 206b. An amplifier 206, a second balun 204 having an input 204a, a first output 204b and a second output 204c, and a first directional coupler 2 51 and a second directional coupler 2 52 and an output terminal 202 are provided.
[0070]
Directional coupler 2 51, 2 For the transmission line 52, a known directional coupler that couples only a signal propagating in a specific direction to the secondary line in the transmission line can be used. The degree of attenuation received when a signal passes through the directional coupler and enters the secondary line is called the degree of coupling and is expressed in decibels. First directional coupler of power amplifier 200 2 51 includes a first terminal 251a, a second terminal 251b, a third terminal 251c, and a fourth terminal 251d. Second directional coupler 2 52 includes a first terminal 252a, a second terminal 252b, a third terminal 252c, and a fourth terminal 252d.
[0071]
The connection relationship in the power amplifier 200 is as follows. The input terminal 201 is connected to the input 203a of the balun 203, and the first output 203b and the second output 203c of the balun 203 are connected to the input 205a of the amplifier 205 and the input 206a of the amplifier 206, respectively. The output 205 b of the amplifier 205 is connected to the first terminal 251 a of the first directional coupler 251, and the output 206 b of the amplifier 206 is connected to the first terminal 252 a of the second directional coupler 252. .
[0072]
The connection relationship of the directional coupler is as follows. With respect to the first directional coupler 251, the second terminal 251b is connected to the first input 204b of the balun 204. The third terminal 251c is connected to the fourth terminal 252d of the second directional coupler 252. The fourth terminal 251d is connected to the third terminal 252c of the second directional coupler 252. On the other hand, the second terminal 252 b of the second directional coupler 252 is connected to the second input 204 c of the balun 204. The third terminal 252c and the fourth terminal 252d are as described above.
[0073]
Hereinafter, a path from the first output 203b of the balun 203 to the first input 204b of the balun 204 via the amplifier 205 and the first directional coupler 251 is referred to as a first amplification path 261. A path from the second output 203c of the balun 203 to the second input 204c of the balun 204 via the amplifier 206 and the second directional coupler 252 is referred to as a second amplification path 262.
[0074]
FIG. 14 shows a specific circuit configuration of the power amplifier 200. As is apparent from the figure, the functions and configurations of the amplifiers 205 and 206 of the power amplifier 200 are the same as the configurations of the amplifiers 105 and 106 (FIG. 7). Therefore, the description is omitted.
[0075]
As described above, the basic function of power amplifier 200 is the same as that of the power amplifiers of the first to third embodiments. Hereinafter, the principle by which the power amplifier 200 can reduce intermodulation distortion (particularly third-order intermodulation distortion) will be described with reference to FIG.
[0076]
FIG. 15 is a diagram illustrating the principle of reducing intermodulation distortion. Two signals with a frequency interval sufficiently small with respect to the signal frequency are input to the input terminal 201. The frequencies of the two input signals are f1 and f2 (for example, f1 is 2000 MHz and f2 is 2010 MHz). The frequency interval (| f1-f2 |) is defined as Δf. As described in the first embodiment, Reference example 1 However, the purpose is to reduce Δf in order to reduce intermodulation distortion, particularly third-order intermodulation distortion.
[0077]
Therefore, Reference example 1 Then, for example, a directional coupler having a coupling degree of 3 dB with respect to a frequency Δf representing a frequency interval between two signals and hardly coupling with respect to a signal frequency is used. That is, only the Δf component is extracted from the third terminal 251 c of the first directional coupler 251 and the third terminal 252 c of the second directional coupler 252. The Δf component extracted from the third terminal 251 c of the first directional coupler 251 is input to the fourth terminal 252 d of the second directional coupler 252 and combined with the output of the amplifier 206. The output signal of the amplifier 206 includes a Δf component. It should be noted that the Δf component and the Δf component input to the fourth terminal 252d are out of phase. This is because the circuit wiring includes an impedance component, and therefore when the circuit wiring length is different, the phase shift amount is also different. As a result, the Δf components cancel each other and the Δf component is reduced. Similarly, in the first directional coupler 251, the Δf component included in the output signal of the amplifier 205 is the Δf component extracted from the third terminal 252 c of the second directional coupler 252 out of phase. And cancel each other out.
[0078]
As described above, since the Δf component generated in each amplifier constituting the push-pull amplifier is canceled, mixing between the Δf component and the signal frequency (f1 or f2) does not occur. Therefore, the third-order intermodulation distortion generated in the amplifier can be reduced. In addition, Reference example 1 Then, although the coupling degree of the directional coupler is 3 dB, even if the value is different, an effect of suppressing intermodulation distortion can be obtained.
[0079]
Next, a configuration that can further reduce intermodulation distortion will be described. FIG. 16 is a block diagram illustrating another example of the power amplifier 200. In this example, one or more capacitors 207 having a low impedance at a frequency Δf, which is a frequency interval between two signals, as described in the first to third embodiments, are added. By shifting the frequency at which the degree of coupling of the directional coupler increases and the self-resonant frequency of the capacitor, intermodulation distortion corresponding to a wider frequency interval Δf can be suppressed.
[0080]
Instead of the capacitor 207, one or more inductors having a low impedance at the frequency Δf, which is the frequency interval of two signals, as described in the third embodiment, may be added. By shifting the frequency at which the degree of coupling of the directional coupler increases and the frequency at which the inductor has a low impedance, intermodulation distortion can be suppressed over a wider range of frequency intervals Δf. Note that the connection position of the capacitor 207 and the inductor can be freely set as long as it is between the first amplification path 261 and the second amplification path 262.
[0081]
Furthermore, according to the power amplifier 200 shown in FIG. 17, the intermodulation distortion when a plurality of signals are amplified can be greatly reduced. FIG. 17 shows a power amplifier 210 provided with two phase shifters. A difference from the power amplifier 200 (FIG. 13) is that two phase shifters 171 are provided on the wiring between the first directional coupler 251 and the second directional coupler 252 that transmit a signal of Δf component. , 172 are provided. For the Δf component input signal output from the amplifier 205, the phase shifter 171 outputs the phase of the Δf component signal output from the amplifier 206 in the opposite phase. Further, the phase shifter 172 outputs the Δf component input signal output from the amplifier 206 in a phase opposite to the phase of the Δf component signal output from the amplifier 205. As a result, the Δf component has substantially the opposite phase with the same amplitude and is reduced. Thereby, the third-order intermodulation distortion generated in the amplifier can be greatly reduced. Furthermore, by changing the phase in consideration of the phase shift due to the impedance of the circuit wiring, it is possible to cancel the Δf component so that it becomes substantially zero. Note that the phase shifter may be provided at a position where the signal of the Δf component is transmitted via each capacitor, and is not limited to the position shown in FIG.
[0082]
( Reference example 2 )
FIG. Reference example 2 2 is a block diagram showing a configuration of a power amplifier 220 according to FIG. The power amplifier 220 is the same as in Embodiments 1 3 and Reference Example 1 It has the same function as the power amplifier described in (1). That is, when a plurality of signals having a sufficiently small frequency interval with respect to the signal frequency are input, the power amplifier 220 reduces intermodulation distortion (particularly third-order intermodulation distortion) and shifts the phase with respect to the input signal. Amplified signal without noise is output.
[0083]
The power amplifier 220 is different from the power amplifier 110 (FIG. 8) in that a first inductor 181, a phase shifter 182 and a second inductor 183 are connected in series between the outputs of the push-pull amplifiers 105 and 106. It is a point. The configuration of power amplifier 220 is similar to the configuration of power amplifier 110 (FIG. 8). Therefore, the same reference numerals are assigned to the same components as those already described, and the description thereof is omitted.
[0084]
Both the inductors 181 and 183 have a high impedance with respect to the frequency of the signal output from the amplifiers 105 and 106, while the impedance is low with respect to the frequency of the signal of the Δf component. By connecting the inductors 181 and 183 between the outputs of the amplifier, the intermodulation distortion can be reduced even when the frequency interval Δf of a plurality of signals input to the amplifier changes. The inductor is, for example, a choke coil, and is shared with a bias line of a bias power source 184 that applies a bias voltage.
[0085]
For the Δf component input signal output from the amplifier 105, the phase shifter 182 outputs the signal in a phase opposite to the phase of the Δf component signal output from the amplifier 106. In addition, the phase shifter 182 outputs the Δf component input signal output from the amplifier 106 in a phase opposite to the phase of the Δf component signal output from the amplifier 105. That is, the Δf components are substantially opposite in phase with the same amplitude, and are reduced from each other. Thereby, the third-order intermodulation distortion generated in the amplifier can be greatly reduced. Furthermore, by changing the phase in consideration of the phase shift due to the impedance of the circuit wiring, it is possible to cancel the Δf component so that it becomes substantially zero.
[0086]
Next, a power amplifier 230 using the above-described series connection of the first inductor 181, the phase shifter 182 and the second inductor 183 will be described with reference to FIG. The characteristics of the inductors 181 and 183 and the operation of the phase shifter 182 are as described above.
[0087]
The configuration of the power amplifier 100 (FIG. 7) is similar to the configuration of the power amplifier 230. FIG. 19 is a block diagram showing a configuration of the power amplifier 230. The power amplifier 230 is different from the power amplifier 100 (FIG. 7) in that instead of the capacitor 107 (FIG. 7), a first inductor 181, a phase shifter 182 and a second inductor 183 are connected in series. And a bias power source 184 for applying a bias voltage is connected between the phase shifter 182 and the second inductor 183. Furthermore, by providing the bias power supply 184, the matching circuits 131 to 134 can be omitted.
[0088]
By configuring in this way, the Δf component is reduced by being made substantially antiphase with the same amplitude by the phase shifter, so that third-order intermodulation distortion caused by the Δf component can be greatly reduced.
[0089]
( Reference example 3 )
FIG. Reference example 3 2 is a block diagram showing a configuration of a power amplifier 300 according to FIG. The power amplifier 300 includes an input terminal 301, a first balun 303 having an input 303a, a first output 303b, and a second output 303c, first to fourth directional couplers 353 to 356, and an input 305a. An amplifier 305 for amplifying an input signal, an input 306a and an output 306b, an amplifier 306 for amplifying the input signal, an input 304a, a first output 304b, and a second output 304c. 2 baluns 304 and an output terminal 302 are provided.
[0090]
The connection relationship in the power amplifier 300 is as follows. The input terminal 301 is connected to the input 303 a of the balun 303. The first output 303b and the second output 303c of the balun 303 are connected to the first terminal 353a of the first directional coupler 353 and the first terminal 354a of the second directional coupler 354, respectively. . The second terminal 353b of the first directional coupler 353 is connected to the input 305a of the amplifier 305, and the second terminal 354b of the second directional coupler 354 is connected to the input 306a of the amplifier 306. . The output 305b of the amplifier 305 is connected to the first terminal 355a of the third directional coupler 355, and the output 306b of the amplifier 306 is connected to the first terminal 356a of the fourth directional coupler 356. . The second terminal 355b of the third directional coupler 355 and the second terminal 356b of the fourth directional coupler 356 are connected to the first input 304b and the second input 304c of the balun 304. The output 304 a of the balun 304 is connected to the output terminal 302.
[0091]
Further, the third terminal 355c of the third directional coupler 355 and the fourth terminal 354d of the second directional coupler 354 are connected, and the third terminal 356c of the fourth directional coupler 356 is connected. And the fourth terminal 353d of the first directional coupler 353 are connected.
[0092]
In the following, the path from the first output 303b of the balun 303 to the first input 304b of the balun 304 via the first directional coupler 353, the amplifier 305, and the third directional coupler 355 will be described. 1 amplification path 361. In addition, the second path 303c from the second output 303c of the balun 303 to the second input 304c of the balun 304 via the second directional coupler 354, the amplifier 306, and the fourth directional coupler 356 The amplification path 362 of FIG.
[0093]
FIG. 21 shows a specific circuit configuration of the power amplifier 300. The configurations of the amplifiers 305 and 306 are the same as the configurations of the amplifiers 105 and 106 described in the first embodiment. Therefore, the description is omitted. The basic function of power amplifier 300 is the same as that in the first embodiment. Amplifiers 305 and 306 function as push-pull amplifiers.
[0094]
Reference example 3 Let us consider a case where two signals of frequencies f 1 and f 2 are input to the power amplifier 300. It is assumed that the frequency interval Δf is sufficiently smaller than the signal frequency. As described in the first embodiment, Reference example 3 However, the purpose is to reduce Δf in order to reduce intermodulation distortion, in particular third-order intermodulation distortion.
[0095]
Therefore, Reference example 3 Then, for example, a directional coupler having a coupling degree of 3 dB with respect to a frequency Δf representing a frequency interval between two signals and hardly coupling with respect to a signal frequency is used. A more specific description will be given with reference to FIG. 20 again. First, the signal of the frequency Δf component generated by the nonlinearity of the amplifier 305 is taken out from the third terminal 355c of the third directional coupler 355, and the fourth terminal 354d of the second directional coupler 354 is connected. Then, it is input to the amplifier 306. Similarly, the signal of the frequency Δf component generated by the nonlinearity of the amplifier 306 is taken out from the third terminal 356c of the fourth directional coupler 356, and the fourth terminal 353d of the first directional coupler 353 is obtained. Then, the signal is input to the amplifier 305.
[0096]
With this configuration, the Δf component having the same amplitude that is out of phase with the Δf component generated by the nonlinearity of the amplifier 305 is input to the amplifier 305, and as a result, the Δf component generated in the amplifier 305. Reduce. In addition, a Δf component having the same amplitude that is out of phase with the Δf component generated by the nonlinearity of the amplifier 306 is input to the amplifier 306, and as a result, the Δf component generated in the amplifier 306 is reduced. As a result, mixing between the Δf component and the signal frequencies (f1 and f2) does not occur, and third-order intermodulation distortion generated in the amplifiers 305 and 306 can be reduced.
[0097]
In addition, Reference example 3 Then, although the coupling degree of the directional coupler is 3 dB, even if the value is different, an effect of suppressing intermodulation distortion can be obtained.
[0098]
As shown in FIG. 22, at least one capacitor 307 having a low impedance at a frequency Δf, which is a frequency interval between two signals, is added between the first amplification path 361 and the second amplification path 362. You can also. Furthermore, instead of the capacitor 307 (FIG. 19), at least one inductor (not shown) having a low impedance at the frequency Δf, which is the frequency interval of two signals, may be added. By shifting the frequency at which the coupling degree of the directional coupler increases and the self-resonance frequency of the capacitor, or by shifting the frequency at which the coupling degree of the directional coupler increases and the frequency at which the inductor has low impedance, a wider range can be obtained. Intermodulation distortion can be suppressed with respect to Δf.
[0099]
Note that the position where the capacitor 307 or the inductor (not shown) is connected can be freely set as long as it is between the first amplification path 361 and the second amplification path 362. Even in that case book Reference example It goes without saying that the same effect as in the case of can be obtained.
[0100]
( Reference example 4 )
Next, another example to which the present invention can be applied will be described with reference to FIGS. Both examples aim to reduce a signal having a frequency Δf that is a frequency interval between two input signals, which causes third-order intermodulation distortion.
[0101]
FIG. Reference example 4 2 is a block diagram showing a configuration of a first power amplifier 400 according to FIG. The power amplifier 400 is Reference example 3 This is a modification of the power amplifier 300 (FIG. 20) described in FIG. Hereinafter, only components different from the power amplifier 300 (FIG. 20) in the power amplifier 400 will be described, and description of the same components will be omitted.
[0102]
The power amplifier 400 is different from the power amplifier 300 (FIG. 20) in that a phase shifter 371 is provided on the wiring from the fourth directional coupler 356 to the first directional coupler 353 that transmits a signal of Δf component. The phase shifter 372 is provided on the wiring from the third directional coupler 355 to the second directional coupler 354. The phase shifters 371 and 372 can change the phase of the input signal. More specifically, the phase shifter 371 outputs the Δf component signal output from the amplifier 306 with the phase of the Δf component signal output from the amplifier 305 reversed. In addition, for the Δf component input signal output from the amplifier 306, the phase shifter 372 outputs the Δf component signal output from the amplifier 305 with the phase reversed. As a result, the Δf component is substantially opposite in phase with the same amplitude as the Δf component generated in the amplifiers 305 and 306, and the Δf component generated in the amplifiers 305 and 306 is reduced. Thereby, the third-order intermodulation distortion generated in the amplifier can be greatly reduced. Furthermore, by changing the phase in consideration of the phase shift due to the impedance of the circuit wiring, it is possible to cancel the Δf component so that it becomes substantially zero.
[0103]
FIG. Reference example 4 2 is a block diagram showing a configuration of a second power amplifier 410 according to FIG. The power amplifier 410 is a modification of the above-described power amplifier 400 (FIG. 23). Hereinafter, only components different from the power amplifier 400 (FIG. 23) in the power amplifier 410 will be described, and description of the same components will be omitted.
[0104]
The power amplifier 410 is different from the power amplifier 400 (FIG. 23) in that inductors 413 to 416 are provided instead of the directional couplers 353 to 356. The inductors 413 to 416 are, for example, choke coils and have a low impedance at the frequency Δf. Thereby, also in the power amplifier 410, the Δf component is extracted and reduced similarly to the power amplifier 400 (FIG. 23). Thereby, the third-order intermodulation distortion generated in the amplifier can be greatly reduced. Furthermore, by changing the phase in consideration of the phase shift due to the impedance of the circuit wiring, it is possible to cancel the Δf component so that it becomes substantially zero.
[0105]
FIG. Reference example 4 4 is a block diagram showing a configuration of a third power amplifier 420 according to FIG. The power amplifier 420 is a modification of the power amplifier 300 (FIG. 22). Hereinafter, only components different from the power amplifier 300 (FIG. 23) in the power amplifier 420 will be described, and description of the same components will be omitted.
[0106]
The power amplifier 420 is different from the power amplifier 300 (FIG. 22) in that diplexers 421 and 422 are provided instead of the directional couplers 353 to 356. The diplexers 421 and 422 separate the signals according to the frequency. More specifically, the diplexers 421 and 422 pass the fundamental wave components of the frequencies f1 and f2 to the balun 304, and pass the difference frequency component of the frequency Δf to the amplifiers 305 and 306 on the opposite path.
[0107]
The diplexers 421 and 422 include bandpass filters (BPF) 425 and 427 including frequencies f1 and f2 (for example, GHz band) in the passband, and frequencies Δf (for example, MHz band) in the passband, and the frequency f1. , F2 include low-pass filters (low-pass filters (LPF)) 426, 428 not included. The low-pass filters (LPF) 426 and 428 can be said to be impedance elements like the capacitor 107 (FIG. 1), the inductor 108 (FIG. 11) and the like.
[0108]
An output signal from the amplifier 306 is input to the diplexer 422. The diplexer 422 passes the fundamental wave components of the frequencies f1 and f2 through the balun 304 by the band pass filter 427, and outputs the difference frequency component of the frequency Δf to the amplifier 305 by the low pass filter 428. It should be noted that the phase of the signal that has passed through the low-pass filter 428 gives a predetermined deviation from the phase of the input signal. If the amount of deviation is designed to be, for example, about 180 degrees, the Δf component input to the amplifier 305 has the same amplitude and almost opposite phase with respect to the Δf component generated by the amplifier 305. Thereby, the Δf component generated in the amplifier 305 can be reduced. The function of the diplexer 421 is the same as that of the diplexer 422. In other words, the fundamental wave components of the frequencies f 1 and f 2 are passed through the balun 304 by the band pass filter 425, and the difference frequency component of the frequency Δf is output to the amplifier 306 by the low pass filter 426. The Δf component input to the amplifier 306 reduces the Δf component generated in the amplifier 306. As a result, the third-order intermodulation distortion generated in the amplifier can be greatly reduced.
[0109]
FIG. Reference example 4 4 is a block diagram showing a configuration of a fourth power amplifier 430 according to FIG. The power amplifier 430 is a modification of the power amplifier 420 shown in FIG. The power amplifier 430 is different from the power amplifier 420 (FIG. 25) in that the Δf component is not reduced by the amplifiers 305 and 306, but is performed between the outputs of the diplexer 421 and the diplexer 422. Further, since the phase of the Δf component is adjusted by the phase shifter 431, the phase characteristics of the low-pass filter included in the diplexer need not be particularly problematic.
[0110]
More specifically, the Δf component generated by the amplifier 306 is extracted by the low-pass filter 428 and input to the phase shifter 431. The phase shifter 431 adjusts the phase of the input Δf component so as to be opposite in phase to the Δf component input to the diplexer 422, and outputs it to the low pass filter 426. The low-pass filter 426 passes the Δf component whose phase is shifted by 180 degrees. On the other hand, an amplified signal including the Δf component generated by the amplifier 305 is also input from the amplifier 305. As a result, the Δf component generated in the amplifier 305 is reduced by the Δf component received from the phase shifter. This is a process performed by the diplexer 421, but the diplexer 422 also performs a process in which the Δf component is simultaneously reduced. In this process, the diplexer 421 and the diplexer 422 may be interchanged in the above description, and the description thereof is omitted. Through the above processing, a signal in which the Δf component is reduced and the third-order intermodulation distortion is greatly reduced is input from the bandpass filters 425 and 427 to the balun 304.
[0111]
FIG. Reference example 4 7 is a block diagram showing a configuration of a fifth power amplifier 440 according to FIG. A feature of the power amplifier 440 is that phase amplifiers 441 and 442 are provided at the outputs of the amplifiers 305 and 306, respectively, and two inputs of the balun 444 are electrically connected by an inductor 445. The phase shifters 441 and 442 are each designed to shift the phase by 90 degrees. Further, it is assumed that the inductor 445 has a characteristic of having a low impedance with respect to the frequency Δf, which is a frequency interval between two input signals. The balun 444 has a function of amplifying, converting, and outputting two input signals whose phases are shifted from each other by 180 °, and is the same as the balun 104 (FIG. 1). .
[0112]
The principle that the power amplifier 440 configured as described above reduces the Δf component will be described. First, the phase of the Δf component generated by the amplifier 306 is shifted by 90 degrees in the phase shifter 442. Then, the phase is shifted by 90 degrees by the phase shifter 441 through the inductor 445 of the balun 444 that has a low impedance with respect to the frequency Δf. Since the phase shifter 441 shifts the phase in the same direction as the phase shifter 442 shifts, the phase of the Δf component generated by the amplifier 306 is finally shifted by 180 degrees. The Δf component is input to the amplifier 305, and the Δf component generated by the amplifier 305 is reduced. In the amplifier 306 as well, the Δf component is simultaneously reduced by the same process as described above. As a result, a signal in which the Δf component is reduced and the third-order intermodulation distortion is significantly reduced is input to the balun 444.
[0113]
FIG. Reference example 4 6 is a block diagram showing a configuration of a sixth power amplifier 450 according to FIG. The power amplifier 450 is characterized in that a power supply 451 that outputs a signal having a frequency Δf, which is a frequency interval between two input signals, is provided. The frequency Δf of the signal to be output can be obtained by extracting from the output terminal of the amplifier 305 or 306. Alternatively, it may be generated by detecting the signal on the input side. The signal having the frequency Δf output from the power source 451 is input to the midpoint of the transformer side port (inductor 445) of the balun 444 through the inductor 452 having a low impedance with respect to the frequency Δf. The inductor 445 also has a characteristic of having a low impedance with respect to the frequency Δf. A signal having a frequency Δf is input from the inductor 445 to the amplifiers 305 and 306. The phase of the signal having the frequency Δf input to the amplifiers 305 and 306 is changed by passing through the inductors 452 and 445. As a result, the Δf component generated in the amplifiers 305 and 306 can be reduced. In consideration of the phase shift caused by the inductors 452 and 445, the power supply 451 outputs so that the signal of the frequency Δf input to the amplifiers 305 and 306 is 180 degrees out of phase with the generated Δf component. The phase of the signal may be adjusted. Thereby, the Δf component generated in the amplifiers 305 and 306 can be more reliably reduced.
[0114]
When the frequency Δf of the signal to be output is extracted from the output terminal of the amplifier 305 or 306, the power supply 451 may not be provided. FIG. Reference example 4 7 is a block diagram showing a configuration of a seventh power amplifier 460 according to FIG. As is apparent from the figure, the power supply 451 (FIG. 28) is omitted, and the output of the amplifier 306 is input to the midpoint of the transformer side port (inductor 445) of the balun 444 via the inductor 452.
[0115]
Further, in the case where the frequency Δf of the signal to be output is generated by detecting the signal input from the input terminal 301, the configuration shown in FIG. 30 is effective. FIG. Reference example 4 FIG. 20 is a block diagram showing a configuration of an eighth power amplifier 470 according to FIG. The characteristic of the power amplifier 470 is that an envelope detector 471 is provided. The envelope detection unit 471 detects an envelope of the signal input from the input terminal 301, and detects and outputs a signal having a frequency Δf that is a frequency interval between two input signals.
[0116]
【The invention's effect】
As described above, the present invention reduces the component of the frequency interval Δf generated at the output terminal of the push-pull amplifier when a plurality of signals are input to the push-pull amplifier. As a result, the intermodulation distortion generated in the amplifier can be suppressed, and it is not necessary to provide a capacitor in the bias circuit as in the prior art, so that the number of components can be reduced. As a result, the linearity of the amplifier is improved, and a power amplifier that can amplify a large number of signal channels at once without distortion can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a power amplifier according to a first embodiment.
FIG. 2 shows a specific circuit configuration of a power amplifier.
FIG. 3 is a block diagram showing signal waveforms at various parts of the power amplifier.
FIG. 4A is a waveform diagram of signals of frequencies f1 and f2. (B) is a waveform diagram of a synthesized signal obtained by synthesizing signals of frequency f1 and frequency f2. (C) is a figure which shows the waveform of the 1st signal and the 2nd signal which were converted and output by the balun.
FIG. 5A is a diagram showing a combined signal waveform input to each amplifier constituting the push-pull amplifier and an ideal amplified signal waveform; (B) is a figure which shows the waveform of the input synthetic signal waveform and the actual amplified signal.
6 shows a spectral distribution obtained by analyzing the component of the signal waveform F ′ shown in FIG.
7 is a circuit diagram showing another example of the power amplifier of FIG. 1. FIG.
FIG. 8 is a block diagram showing the configuration of a power amplifier that reduces the Δf component.
FIG. 9 is a circuit diagram of a power amplifier according to a second embodiment.
FIG. 10 is a graph showing an example of resonance characteristics of a capacitor.
FIG. 11 is a circuit diagram of a power amplifier according to a third embodiment.
12 is a circuit diagram showing another example of the power amplifier of FIG.
FIG. 13 Reference example 1 It is a block diagram which shows the structure of the power amplifier by this.
FIG. 14 is a diagram showing a specific circuit configuration of a power amplifier.
FIG. 15 is a diagram illustrating the principle of reducing intermodulation distortion.
16 is a block diagram showing another example of the power amplifier of FIG.
FIG. 17 is a diagram showing a power amplifier provided with two phase shifters.
FIG. 18 Reference example 2 It is a block diagram which shows the structure of the power amplifier by this.
FIG. 19 is a block diagram showing a configuration of a power amplifier.
FIG. 20 Reference example 3 It is a block diagram which shows the structure of the power amplifier by this.
FIG. 21 shows a specific circuit configuration of the power amplifier.
22 is a block diagram showing another example of the power amplifier of FIG.
FIG. 23 Reference example 4 2 is a block diagram showing a configuration of a first power amplifier according to FIG.
FIG. 24 Reference example 4 It is a block diagram which shows the structure of the 2nd power amplifier by these.
FIG. 25 Reference example 4 It is a block diagram which shows the structure of the 3rd power amplifier by these.
FIG. 26 Reference example 4 It is a block diagram which shows the structure of the 4th power amplifier by these.
FIG. 27 Reference example 4 It is a block diagram which shows the structure of the 5th power amplifier by this.
FIG. 28 Reference example 4 It is a block diagram which shows the structure of the 6th power amplifier by these.
FIG. 29 Reference example 4 It is a block diagram which shows the structure of the 7th power amplifier by these.
FIG. 30 Reference example 4 It is a block diagram which shows the structure of the 8th power amplifier by.
FIG. 31 is a diagram showing a conventional power amplifier.
[Explanation of symbols]
101 Input terminal
102 Output terminal
103, 104 balun
105, 106 Amplifier
107 capacitor
161 First amplification path
162 Second amplification path

Claims (2)

An input unit that inputs a synthesized signal obtained by synthesizing two signals having different frequencies, a first output unit that outputs a first signal having a first phase, and a second phase opposite to the first phase A first balun having a second output for outputting a second signal having
A first amplifier that receives and amplifies the first signal to output a first amplified signal including a frequency component that is a frequency difference between the two signals;
A second amplifier that receives and amplifies the second signal to output a second amplified signal including a frequency component composed of a difference between the frequencies of the two signals;
A second balun having a first input unit and a second input unit, and having an output unit for outputting a combined signal of the signals input from the first input unit and the second input unit;
An impedance element connected between an output of the first amplifier and an output of the second amplifier and having a self-resonant frequency as an absolute value of a frequency difference between the two signals;
With
A frequency component included in said second amplified signal, via said impedance element is input to the first amplification path reaching the first input of the second balun,
The frequency component contained in the first amplified signal, to enter into the second amplification path reaching the second input of the second balun via the impedance element, the power amplifier. Connected to said impedance element in series, said a contained Ru frequency component to the first amplified signal, receives a frequency component that is part of the second amplified signal, adjusting the phase of each frequency component Te, further comprising a phase shifter output in opposite phase, the power amplifier according to claim 1.

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