Doherty amplifier circuit

Abstract

To provide a Doherty amplifier circuit capable of suppressing an influence of intermodulation distortion while suppressing a circuit scale.SOLUTION: A Doherty amplifier circuit includes: a 90-degree hybrid coupler including an input terminal to which a first input signal is input, a first output terminal that outputs a first output signal based on the first input signal, a second output terminal that outputs a second output signal having a phase different from that of the first output signal by 90 degrees based on the first input signal, and an isolation terminal that ensures isolation with the input terminal; a carrier amplifier that amplifies the first output signal and outputs a first amplified signal; and a peak amplifier that amplifies the second output signal and outputs a second amplified signal. The isolation terminal is a terminal to which a second harmonic of a frequency band of a second harmonic of the first input signal is input.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a Doherty amplifier circuit. [Background technology]

[0002] Mobile communication devices such as mobile phones are equipped with power amplifiers for amplifying the power of transmission signals. For example, when multiple signals with closely spaced frequencies are supplied to such a power amplifier, intermodulation distortion (IMD) occurs from these multiple signals, potentially degrading linearity. Therefore, in order to suppress the effects of such intermodulation distortion, a technique has been proposed in which harmonics are intentionally injected into the signal path to cancel out the intermodulation distortion components. For example, Patent Document 1 discloses a distortion-compensating power amplifier device that divides the output of a first-stage amplifier into a fundamental wave and a second harmonic, adjusts the phase and amplitude of the second harmonic, adds it to the fundamental wave, and inputs it to a subsequent amplifier, thereby compensating for intermodulation distortion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-318373 Summary of the Invention [Problem to be solved by the invention]

[0004] The device described in Patent Document 1 compensates for intermodulation distortion using second harmonics extracted by a filter circuit. In recent years, with the introduction of new communication standards such as 4G (fourth generation mobile communication system) and 5G (fifth generation mobile communication system), the number of frequency bands that Doherty amplifier circuits must support has increased, posing a problem of increased circuit size due to the corresponding increase in the number of filter circuits. Furthermore, when the configuration of the device described in Patent Document 1 is applied to a Doherty amplifier circuit, isolation between the device described in Patent Document 1 and the Doherty amplifier circuit must be ensured to avoid affecting the operation of the Doherty amplifier circuit, which necessitates the provision of multiple additional λ / 4 lines. This results in a problem of increased circuit size.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a Doherty amplifier circuit that can suppress the influence of intermodulation distortion while suppressing the circuit size. [Means for solving the problem]

[0006] To achieve this object, one aspect of the present invention provides a Doherty amplifier circuit comprising: a 90-degree hybrid coupler including an input terminal to which a first input signal is input; a first output terminal that outputs a first output signal based on the first input signal; a second output terminal that outputs a second output signal based on the first input signal, the second output signal having a phase difference of 90 degrees from the first output signal; and an isolation terminal that ensures isolation between the input terminals; a carrier amplifier that amplifies the first output signal and outputs a first amplified signal; and a peak amplifier that amplifies the second output signal and outputs a second amplified signal, wherein the isolation terminal is a terminal to which a second harmonic in a frequency band twice the frequency of the first input signal is input. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a Doherty amplifier circuit that can suppress the influence of intermodulation distortion while suppressing the circuit size. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a configuration example of a Doherty amplifier circuit according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing the spectrum of an input signal RFin supplied to a drive amplifier. [Figure 3] 10 is a diagram showing that third-order intermodulation distortion of a signal RF10 output from a drive amplifier is canceled out. FIG. [Figure 4] 10 is a graph showing the pass characteristics of a signal input from an isolation terminal Tiso of a 90-degree hybrid coupler. [Figure 5] FIG. 10 is a diagram illustrating a configuration example of a Doherty amplifier circuit according to a first modified example. [Figure 6] FIG. 10 is a diagram illustrating a configuration example of a Doherty amplifier circuit according to a second modification. [Figure 7] FIG. 10 is a diagram illustrating a configuration example of a Doherty amplifier circuit according to a third modification. [Figure 8] FIG. 10 is a diagram illustrating a configuration example of a Doherty amplifier circuit according to a second embodiment. [Figure 9] FIG. 10 is a diagram illustrating a configuration example of a Doherty amplifier circuit according to a fourth modification. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same elements are designated by the same reference numerals, and redundant description will be omitted.

[0010] Doherty Amplifier Circuit 100 According to the First Embodiment FIG. 1 is a diagram illustrating an example of the configuration of a Doherty amplifier circuit 100 according to a first embodiment. The Doherty amplifier circuit 100 illustrated in FIG. 1 is mounted on a mobile communication device such as a mobile phone and is used to amplify the power of a radio frequency (RF) signal to be transmitted to a base station. The Doherty amplifier circuit 100 amplifies the power of signals conforming to communication standards such as 2G (second-generation mobile communication system), 3G (third-generation mobile communication system), 4G (fourth-generation mobile communication system), 5G (fifth-generation mobile communication system), LTE (Long Term Evolution)-FDD (Frequency Division Duplex), LTE-TDD (Time Division Duplex), LTE-Advanced, LTE-Advanced Pro, and 6G (sixth-generation mobile communication system). The frequency of the RF signal is, for example, approximately several hundred MHz to several tens of GHz. Note that the communication standards and frequencies of the signals amplified by the Doherty amplifier circuit 100A are not limited to these.

[0011] The Doherty amplifier circuit 100 can compensate for third-order intermodulation distortion and improve linearity while suppressing the circuit size without using a filter circuit for ensuring isolation.

[0012] The Doherty amplifier circuit 100 includes, for example, a divider 110, a drive amplifier 120, a 90-degree hybrid coupler 130, a carrier amplifier 140, a peak amplifier 150, a phase shifter 160, a second harmonic generator 170, an input terminal 101, and an output terminal 102.

[0013] The divider 110 divides, for example, the input signal RFin into a signal RF1 and a signal RF2 that is approximately 180 degrees out of phase with the signal RF1. Approximately 180 degrees includes, for example, a range of 135 degrees to 225 degrees. The divider 110 is configured to include, for example, a balun transformer. The divider 110 may have a function of matching the impedance between a circuit (not shown) in the preceding stage and the drive amplifier 120 in the subsequent stage.

[0014] The drive amplifier 120 amplifies the signal RF1 input through the divider 110 and outputs a signal RF10 to an input terminal T10 of the 90-degree hybrid coupler .

[0015] The 90-degree hybrid coupler 130 splits the signal RF10 output from the drive amplifier 120 into two signals with equal power and a phase difference of 90 degrees. The 90-degree hybrid coupler 130 has an input terminal T10, a first output terminal T20, a second output terminal T30, and an isolation terminal Tiso.

[0016] The 90-degree hybrid coupler 130 may be configured to include, for example, two electromagnetically coupled transmission lines (e.g., λ / 4 lines). The two transmission lines are, for example, striplines or microstriplines provided on a substrate. When the power amplifier 100 is viewed from above, the two transmission lines are formed so as to extend together in a certain direction.

[0017] A signal RF10 is input to an input terminal T10, which is one end of one transmission line, via a drive amplifier 120. A second output terminal T30, which is the other end of one transmission line, outputs a signal RF12 obtained by dividing the signal RF10. A first output terminal T20, which is one end of the other transmission line, outputs a signal RF11 obtained by dividing the signal RF10. The phase of the signal RF12 lags behind the phase of the signal RF11 by approximately 90 degrees.

[0018] The other end of the other transmission line, isolation terminal Tiso, is a terminal that ensures isolation from input terminal T10. That is, even if signal RF10 is input to input terminal T10, no voltage is generated at isolation terminal Tiso. Second harmonic RF20 output from second harmonic generator 170 is input to isolation terminal Tiso, which ensures isolation from other terminals.

[0019] The Doherty amplifier circuit 100 is configured to input the second harmonic RF20 to the isolation terminal Tiso, which maintains isolation from the input terminal T10, and therefore can compensate for third-order intermodulation distortion without using a filter circuit to ensure isolation, thereby enabling the circuit to be miniaturized.

[0020] The 90-degree hybrid coupler 130 is not limited to being formed by two electromagnetically coupled transmission lines, and may be formed by, for example, four microstrip lines, each with a length of λ / 4, connected to form a rectangle. In this case, the Doherty amplifier circuit 100 is configured so that the second harmonic RF20 output from the second harmonic generator 170 is input to a terminal that is isolated from the other terminals.

[0021] The carrier amplifier 140 amplifies the signal RF11 output from the first output terminal T20 of the 90-degree hybrid coupler 130 and outputs the signal RF110. The carrier amplifier 140 operates regardless of the voltage level of the signal RF11. That is, the carrier amplifier 140 operates when the power level of the signal RF11 is higher than zero.

[0022] The peak amplifier 150 amplifies the signal RF12 output from the second output terminal T30 of the 90-degree hybrid coupler 130 and outputs the signal RF120. The peak amplifier 150 operates in a range where the voltage level of the signal RF12 is a predetermined level lower than the maximum level. For example, the peak amplifier 150 operates in a range where the power level of the signal RF12 is at least 3 dB lower than the maximum level.

[0023] The phase shifter 160 is, for example, a quarter-wave line connected to the output side of the carrier amplifier 140. This changes the load impedance seen at the output end of the carrier amplifier 140, thereby enabling the Doherty amplifier 100 to achieve high efficiency.

[0024] The second harmonic generator 170 is a circuit that generates, from the signal RF2 distributed by the divider 110, a second harmonic RF20, which is a second harmonic signal for compensating for third-order intermodulation distortion in the Doherty amplifier circuit. The second harmonic generator 170 outputs the generated second harmonic RF20 to the isolation terminal Tiso of the 90-degree hybrid coupler 130. For example, the second harmonic generator 170 is configured to remove the fundamental wave of the signal RF2 distributed by the divider 110 and amplify a signal in the frequency band of the second harmonic of the signal RF2. Note that the second harmonic generator 170 may generate the second harmonic RF20 by adjusting the phase and amplitude of the signal RF2. In other words, the second harmonic generator 170 may adjust the signal RF2 so that the phase and amplitude are suitable for compensating for third-order intermodulation distortion, and then output the second harmonic RF20.

[0025] Each amplifier is configured to include a bipolar transistor such as a heterojunction bipolar transistor (HBT). Note that each amplifier may be configured to include a field-effect transistor (MOSFET: Metal-oxide-semiconductor Field-Effect Transistor) instead of an HBT.

[0026] Although the Doherty amplifier circuit 100 has been described above as including the second harmonic generator 170, this is not limiting. The Doherty amplifier circuit 100 does not have to include the second harmonic generator 170. In this case, the Doherty amplifier circuit 100 only needs to be configured to input the second harmonic RF20 from another circuit to the isolation terminal Tiso. This allows the Doherty amplifier circuit 100 to be smaller in size.

[0027] <<Compensation operation for third-order intermodulation distortion>> Referring to FIGS. 2 and 3, the operation of compensating for third-order intermodulation distortion in the Doherty amplifier circuit 100 will be described. FIG. 2 is a diagram showing the spectrum of the input signal RFin supplied to the peak amplifier 150. Third-order intermodulation distortion is generated by the second-harmonic signal components in the signal RF12. FIG. 3 is a diagram showing that the third-order intermodulation distortion of the signal RF120 output from the peak amplifier 150 is canceled. In FIGS. 2 and 3, the horizontal axis represents the frequency of the signal, and the vertical axis represents the power spectral density (PSD).

[0028] As shown in FIG. 2, the carrier amplifier 140 and the peak amplifier 150 are supplied with the fundamental wave signals F , 01 , 01 , H , 01 , L , 01 , , H , 01 ,

[0029] , 01 , L , L , H , , ,

[0030] and the signal 2F which is the second harmonic 01 contained in the signals RF11 and RF12 via the 90-degree hybrid coupler 130. Here, let the fundamental wave signal F 01 include components of two frequencies f1 and f2 (f1 < f2) close to each other. That is, the Doherty amplifier circuit 100 is supplied with a signal synthesized from the signals F<00ooo004>at frequencies f1 and f2 and the signals 2F 01 at frequencies 2f1 and 2f2. <ooo00168>

[0029] As shown in FIG. 3, the carrier amplifier 140 and the peak amplifier 150 showing non-linearity generate, by the fundamental wave amplification operation, third-order intermodulation distortion IM3<ooo0006>at a frequency of 2f1 - f2 on the low-frequency side of the signal F 01 of the fundamental wave (frequency f1), and generate third-order intermodulation distortion IM3 H at a frequency of 2f2 - f1 on the high-frequency side of the signal F 01 of the fundamental wave (frequency f2). [[ID=2B]]

[0030] The third-order intermodulation distortions IM3 L and IM3 H are relatively close to the frequencies f1 and f2 of the fundamental wave signal F 01 . Therefore, the third-order intermodulation distortions IM3 L and IM3 HIt is difficult to remove third-order intermodulation distortion (IM3). L and IM3 H This can cause the characteristics of the Doherty amplifier circuit 100 to deteriorate.

[0031] Therefore, in the Doherty amplifier circuit 100, as shown in FIG. 3, the third-order intermodulation distortion IM3 L ,IM3 H In order to generate compensation signals CL1 and CL2 to cancel out the second harmonic RF20, the fundamental signal F 01 and combine it.

[0032] Specifically, the Doherty amplifier circuit 100 receives a fundamental wave signal F 01 and the second harmonic RF20 in a 90-degree hybrid coupler 130, and the resulting signal is amplified by a carrier amplifier 140 and a peak amplifier 150. The Doherty amplifier circuit 100 amplifies one frequency 2f1 of the second harmonic RF20 and the fundamental signal F 01 The Doherty amplifier circuit 100 generates a compensation signal CL1 having a frequency (2f1-f2) that is the difference between the other frequency 2f2 of the second harmonic RF20 and the fundamental wave signal F 01 A compensation signal CL2 having a frequency (2f2-f1) that is the difference between the frequency f1 and one of the frequencies f1 and f2 is generated.

[0033] That is, in the Doherty amplifier circuit 100, the third-order intermodulation distortion IM3 generated by the amplification operations of the carrier amplifier 140 and the peak amplifier 150 L ,IM3 H The second harmonic RF20 is adjusted so that the phase of the second harmonic RF20 differs by approximately 180 degrees from the phases of the compensation signals CL1 and CL2 at the outputs of the carrier amplifier 140 and the peak amplifier 150, and is input to the isolation terminal Tiso of the 90-degree hybrid coupler 130.

[0034] Furthermore, in the Doherty amplifier circuit 100, third-order intermodulation distortion IM3 generated in the carrier amplifier 140 and the peak amplifier 150 L ,IM3 Hand the amplitudes of the compensation signals CL1 and CL2 cancel each other out at the outputs of the carrier amplifier 140 and the peak amplifier 150. The second harmonic RF20 is input to the isolation terminal Tiso of the 90-degree hybrid coupler 130.

[0035] Due to the above-described action, the Doherty amplifier circuit 100 can suppress the third-order intermodulation distortion IM3 generated by the amplification operations of the carrier amplifier 140 and the peak amplifier 150 without using a filter circuit to ensure isolation. L ,IM3 H The Doherty amplifier circuit 100 can suppress the degradation of linearity in the Doherty amplifier circuit.

[0036] <<Details of the compensation operation for the peak amplifier 150>> Next, with reference to FIG. 4, it will be described how the linearity of the peak amplifier 150 can be improved by using the 90-degree hybrid coupler 130 in the Doherty amplifier circuit 100. FIG. 4 is a graph showing the pass characteristics of a signal input from the isolation terminal Tiso of the 90-degree hybrid coupler 130. In FIG. 4, the horizontal axis represents the signal frequency, and the vertical axis represents the signal strength. Also, in FIG. 4, as an example, the pass characteristics of a signal passing through the first output terminal T20 are shown by a dashed line, and the pass characteristics of a signal passing through the second output terminal T30 are shown by a solid line.

[0037] In a Doherty amplifier circuit, the peak amplifier 150, which operates in a region where the input voltage level is high, has worse linearity than the carrier amplifier 140. In the Doherty amplifier circuit 100, the peak amplifier 150, which has a significant deterioration in linearity, passes more second harmonic RF20 than the carrier amplifier 140. This allows the Doherty amplifier circuit 100 to suppress degradation of linearity in the Doherty amplifier circuit. As an example, the following description will be given assuming that the 90-degree hybrid coupler 130 operates as a 3 dB coupler for a 1 GHz signal.

[0038] As shown in FIG. 4, when a 1 GHz signal, for example, is input to the isolation terminal Tiso of the 90-degree hybrid coupler 130, a signal of the same signal strength is output from the first output terminal T20 to which the carrier amplifier 140 is connected and the second output terminal T30 to which the peak amplifier 150 is connected ("P1" in FIG. 4).

[0039] When a 2 GHz signal, which is the second harmonic of 1 GHz, is input to the isolation terminal Tiso of the 90-degree hybrid coupler 130, for example, the signal output from the first output terminal T20 to which the carrier amplifier 140 is connected has a power of −6.990 dB (represented by “P2” in FIG. 4, and the power ratio to the signal input to the isolation terminal Tiso is 0.2), while the signal output from the second output terminal T30 to which the peak amplifier 150 is connected has a power of −0.969 dB (represented by “P3” in FIG. 4, and the power ratio to the signal input to the isolation terminal Tiso is 0.8).

[0040] That is, in the 90-degree hybrid coupler 130, the second harmonic output to the peak amplifier 150 exhibits four times higher power than the second harmonic output to the carrier amplifier 140.

[0041] Due to the above-described action, the Doherty amplifier circuit 100 does not use a filter circuit for ensuring isolation, and the third-order intermodulation distortion IM3 generated by the amplification operation of the peak amplifier 150, which has a significant deterioration in linearity, is reduced. L ,IM3 H In this way, the Doherty amplifier circuit 100 can improve the linearity of the Doherty amplifier circuit.

[0042] <<First Modification>> A Doherty amplifier circuit 100a according to a first modification will be described with reference to Fig. 5. Fig. 5 is a diagram showing an example configuration of the Doherty amplifier circuit 100a according to the first modification. Note that, below, a description of matters common to the Doherty amplifier circuit 100 according to the first embodiment will be omitted, and only differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned one by one.

[0043] 1, the Doherty amplifier circuit 100a has a divider 160 arranged after the drive amplifier 120. Specifically, the drive amplifier 120 amplifies the input signal RFin and outputs the amplified signal to the divider 110. The divider 160 divides the signal amplified by the drive amplifier 120 into a signal RF10 and a signal RF2 that is approximately 180 degrees out of phase with the signal RF10, for example. The signal RF10 is input to an input terminal T10 of the 90-degree hybrid coupler 130, and the signal RF2 is input to the isolation terminal Tiso via a second-order harmonic generator 170.

[0044] In this way, in the Doherty amplifier circuit 100a, a second harmonic RF20 with a higher power can be input to the isolation terminal Tiso of the 90-degree hybrid coupler 130 compared to the Doherty amplifier circuit 100. As a result, the Doherty amplifier circuit 100a does not use a filter circuit to ensure isolation, thereby reducing the circuit size and reducing the third-order intermodulation distortion IM3 generated in the carrier amplifier 140 and the peak amplifier 150. L ,IM3 H The influence of the above can be more reliably suppressed, thereby improving linearity.

[0045] <<Second Modification>> A Doherty amplifier circuit 100b according to a second modification will be described with reference to Fig. 6. Fig. 6 is a diagram showing an example configuration of the Doherty amplifier circuit 100b according to the second modification. Note that, below, a description of matters common to the Doherty amplifier circuit 100 according to the first embodiment will be omitted, and only differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned one by one.

[0046] 1, the Doherty amplifier circuit 100b has a divider 110b arranged after the carrier amplifier 140 and the peak amplifier 150. Specifically, the drive amplifier 120 amplifies the input signal RFin to generate a signal RF10, which is output to the input terminal T10 of the 90-degree hybrid coupler 130. The divider 110b divides the combined signal of the signal RF110 output from the carrier amplifier 140 and the signal RF120 output from the peak amplifier 150 into an output signal RFout output to the output terminal 102 and a signal RF2 input to the second-harmonic generator 170. The second-harmonic generator 170 generates a second-harmonic RF20 from the signal RF2 and outputs it to the isolation terminal Tiso of the 90-degree hybrid coupler 130.

[0047] In this way, in the Doherty amplifier circuit 100b, a second harmonic RF20 with a higher power can be input to the isolation terminal Tiso of the 90-degree hybrid coupler 130 compared to the Doherty amplifier circuit 100. As a result, the Doherty amplifier circuit 100b does not use a filter circuit to ensure isolation, thereby reducing the circuit size and reducing the third-order intermodulation distortion IM3 generated in the carrier amplifier 140 and the peak amplifier 150. L ,IM3 H The influence of the above can be more reliably suppressed, thereby improving linearity.

[0048] <<Third Modification>> A Doherty amplifier circuit 100c according to a third modification will be described with reference to Fig. 7. Fig. 7 is a diagram showing an example configuration of the Doherty amplifier circuit 100c according to the third modification. Note that, below, a description of matters common to the Doherty amplifier circuit 100 according to the first embodiment will be omitted, and only differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned one by one.

[0049] The Doherty amplifier circuit 100c is a circuit in which the distributor 110 in the Doherty amplifier circuit 100b in FIG. 6 is replaced with a demultiplexer 110c and the second harmonic generator 170 is replaced with a second harmonic amplifier 180.

[0050] The demultiplexer 110c is a diplexer that separates the second harmonic component from a signal obtained by combining the signal RF110 output from the carrier amplifier 140 and the signal RF120 output from the peak amplifier 150. For example, the demultiplexer 110c is a circuit that combines a low-pass filter and a band-pass filter. The demultiplexer 110c passes the fundamental signal to the output terminal 102 as the output signal RFout, separates the second harmonic, and outputs it to the second harmonic amplifier 180. The second harmonic amplifier 180 amplifies the second harmonic input from the demultiplexer 110c and outputs it to the isolation terminal Tiso of the 90-degree hybrid coupler 130.

[0051] In this way, in the Doherty amplifier circuit 100c, a second harmonic RF20 with a higher power can be input to the isolation terminal Tiso of the 90-degree hybrid coupler 130 compared to the Doherty amplifier circuit 100. As a result, in the Doherty amplifier circuit 100c, the third-order intermodulation distortion IM3 generated in the carrier amplifier 140 and the peak amplifier 150 can be reduced without using a filter circuit for ensuring isolation. L ,IM3 H The influence of the above can be more reliably suppressed.

[0052] Although the Doherty amplifier circuit 100c has been described above as including the second harmonic amplifier 180, this is not limiting. The Doherty amplifier circuit 100c does not have to include the second harmonic amplifier 180. In this case, the Doherty amplifier circuit 100c only needs to adjust the design conditions of the drive amplifier 120, carrier amplifier 140, peak amplifier 150, etc. to design the second harmonic to be input to the isolation terminal Tiso of the 90-degree hybrid coupler 130. This allows the Doherty amplifier circuit 100 to be compact.

[0053] Doherty Amplifier Circuit 100d According to the Second Embodiment A Doherty amplifier circuit 100d according to the second embodiment will be described with reference to Fig. 8. Fig. 8 is a diagram showing an example of the configuration of the Doherty amplifier circuit 100d according to the second embodiment. Note that, below, a description of matters common to the Doherty amplifier circuit 100 according to the first embodiment will be omitted, and only the differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned one by one.

[0054] 1, the Doherty amplifier circuit 100d includes a 90-degree hybrid coupler 160d instead of the phase shifter 160 on the output side of the carrier amplifier 140 and the peak amplifier 150. The Doherty amplifier circuit 100d is also configured so that a second harmonic RF310 is input from a harmonic generator 170d to an isolation terminal Tiso2 in the 90-degree hybrid coupler 160d, which is isolated from the output terminal T70. In this way, the Doherty amplifier circuit 100d combines second harmonics on the output side to generate third-order intermodulation distortion IM3 L ,IM3 H Suppress the effects of

[0055] Although FIG. 8 shows the use of a 90-degree hybrid coupler 130d, this is not limiting, and the 90-degree hybrid coupler 130d may be, for example, a divider that divides the signal RF10 into a signal RF11 and a signal RF12 that is 90 degrees out of phase with the signal RF11.

[0056] The 90-degree hybrid coupler 160d combines the signal RF110 output from the carrier amplifier 140 and the signal RF120 output from the peak amplifier 150, which is 90 degrees out of phase with the signal RF110. The 90-degree hybrid coupler 160d has the pass characteristics shown in Fig. 4. The 90-degree hybrid coupler 160d has a first input terminal T50, a second input terminal T60, an output terminal T70, and an isolation terminal Tiso2.

[0057] The 90-degree hybrid coupler 160d may be configured to include, for example, two electromagnetically coupled transmission lines (e.g., λ / 4 lines). The two transmission lines are, for example, striplines or microstriplines provided on a substrate. When the Doherty amplifier circuit 100d is viewed from above, the two transmission lines are formed so as to extend together in a certain direction.

[0058] A signal RF110 is input from the carrier amplifier 140 to a first input terminal T50, which is one end of one of the transmission lines. A combined signal RF30, which is a combination of the signal RF110 and RF150 output from the peak amplifier 150, is output from an output terminal T70, which is the other end of the one of the transmission lines. A signal RF120 is input from the peak amplifier 150 to a second input terminal T60, which is one end of the other of the transmission lines. Note that the 90-degree hybrid coupler 160d delays the phase of the input signal RF110 by approximately 90 degrees, combines it with the signal RF120, and outputs the combined signal RF30 from the output terminal T70.

[0059] The other end of the other transmission line, i.e., isolation terminal Tiso2, is a terminal that ensures isolation from output terminal T70. That is, even if signals RF110 and RF120 are input to first input terminal T50 and second input terminal T60, no voltage is generated at isolation terminal Tiso2. A second harmonic RF310 output from harmonic generator 170d (described later) is input to isolation terminal Tiso2.

[0060] The harmonic generation unit 170d includes, for example, a divider 171d and a second-harmonic generator 172d. The divider 171d includes, for example, a balun transformer. The divider 171d divides, for example, the combined signal RF30 into an output signal RFout and a signal RF31 that is approximately 180 degrees out of phase with the output signal RFout. The second-harmonic generator 172d is a circuit that generates, from the signal RF31 divided by the divider 171d, a second-harmonic signal RF310 that is a double wave signal for compensating for third-order intermodulation distortion in the Doherty amplifier circuit. The second-harmonic generator 172d has a configuration similar to that of the second-harmonic generator 170 of the Doherty amplifier circuit 100.

[0061] As a result, the Doherty amplifier circuit 100d can reduce the third-order intermodulation distortion IM3 generated in the carrier amplifier 140 and the peak amplifier 150 without using a filter circuit to ensure isolation. L ,IM3 H The influence of the above can be suppressed to improve the linearity.

[0062] <<Fourth Modification>> A Doherty amplifier circuit 100e according to a fourth modification will be described with reference to Fig. 9. Fig. 9 is a diagram showing an example of the configuration of the Doherty amplifier circuit 100e according to the fourth modification. Note that, below, a description of matters common to the Doherty amplifier circuit 100d according to the second embodiment will be omitted, and only the differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned one by one.

[0063] The Doherty amplifier circuit 100e is a circuit in which, compared to the Doherty amplifier circuit 100d, for example, the distributor 171d is replaced with a branching filter 171e and the second harmonic generator 172d is replaced with a second harmonic amplifier 172e.

[0064] The branching filter 171e is a diplexer that separates a second harmonic component from a signal that is output from the output terminal T70 of the 90-degree hybrid coupler 160e and is a combination of the signal RF110 output from the carrier amplifier 140 and the signal RF120 output from the peak amplifier 150. For example, the branching filter 171e is a circuit that combines a low-pass filter and a band-pass filter. The branching filter 171e passes the fundamental signal to the output terminal 102 as an output signal RFout, separates the second harmonic, and outputs it to the second harmonic amplifier 172e. The second harmonic amplifier 172e amplifies the second harmonic input from the branching filter 171e and outputs it to the isolation terminal Tiso2 of the 90-degree hybrid coupler 160e.

[0065] As a result, the Doherty amplifier circuit 100e can reduce the third-order intermodulation distortion IM3 generated in the carrier amplifier 140 and the peak amplifier 150 without using a filter circuit to ensure isolation. L ,IM3 H The influence of the above can be suppressed to improve the linearity.

[0066] Although the Doherty amplifier circuit 100e has been described above as including the second-harmonic amplifier 172e, this is not limiting. The Doherty amplifier circuit 100e does not necessarily have to include the second-harmonic amplifier 172e. In this case, the second-harmonic to be input to the isolation terminal Tiso2 of the 90-degree hybrid coupler 160e is designed by adjusting the design conditions of the carrier amplifier 140, the peak amplifier 150, and the like. This allows the Doherty amplifier circuit 100e to be compact.

[0067] ===Summary=== <1> The Doherty amplifier circuit 100 according to the exemplary embodiment of the present disclosure ensures isolation between an input terminal T10 to which a signal RF1 (first input signal) is input, a first output terminal T20 that outputs a signal RF11 (first output signal) based on the signal RF1 (first input signal), and a second output terminal T30 that outputs a signal RF12 (second output signal) that is 90 degrees out of phase with the signal RF11 (first output signal) based on the signal RF1 (first input signal). The Doherty amplifier circuit 100 includes a 90-degree hybrid coupler 130 including an isolation terminal Tiso that is connected to the input of the signal RF11 (first output signal) and a carrier amplifier 140 that amplifies a signal RF110 (first amplified signal) and outputs the signal RF110 (first amplified signal), and a peak amplifier 150 that amplifies a signal RF12 (second output signal) and outputs the signal RF120 (second amplified signal), where the isolation terminal Tiso is a terminal to which a second harmonic RF20 in a frequency band that is twice the frequency of the signal RF1 (first input signal) is input. This enables the Doherty amplifier circuit 100 to compensate for third-order intermodulation distortion and improve linearity while suppressing the circuit size without using a filter circuit to ensure isolation.

[0068] <2> The Doherty amplifier circuit 100 according to an exemplary embodiment of the present disclosure further includes a divider 110 connected in series to an input terminal 101 (terminal) to which an input signal is input and an input terminal T10, the divider 110 dividing the input signal RFin into a signal RF1 (first input signal) and a signal RF2 (second input signal), and a second harmonic generator 170 generating a second harmonic RF20 based on the signal RF2 (second input signal) and outputting the second harmonic RF20 to an isolation terminal Tiso. <1> The Doherty amplifier circuit according to claim 1, wherein the Doherty amplifier circuit 100 compensates for third-order intermodulation distortion while suppressing the circuit size without using a filter circuit for ensuring isolation, thereby improving linearity.

[0069] <3> The Doherty amplifier circuit 100 according to the exemplary embodiment of the present disclosure further includes a drive amplifier 120 that amplifies a signal RF1 (first input signal) and outputs the amplified signal to an input terminal T10. <2> The Doherty amplifier circuit according to claim 1, wherein the Doherty amplifier circuit 100 compensates for third-order intermodulation distortion while suppressing the circuit size without using a filter circuit for ensuring isolation, thereby improving linearity.

[0070] <4> The Doherty amplifier circuit 100a according to an exemplary embodiment of the present disclosure further includes a drive amplifier 120 that outputs a signal obtained by amplifying an input signal RFin, and a divider 110 that divides the signal into a signal RF10 (first input signal) and a signal RF2 (second input signal). <2> As a result, the Doherty amplifier circuit 100a can reduce the circuit size without using a filter circuit for ensuring isolation, and can more reliably suppress the effects of third-order intermodulation distortion generated in the carrier amplifier 140 and the peak amplifier 150, thereby improving linearity.

[0071] <5> The Doherty amplifier circuit 100b according to an exemplary embodiment of the present disclosure further includes a divider 110b that divides a composite signal, obtained by combining a signal RF110 (first amplified signal) and a signal RF120 (second amplified signal), into an output signal RFout output to the output terminal 102 and a signal RF2 (third input signal) shown in FIG. 6 , and a second harmonic generator 170 that generates a second harmonic RF20 based on the signal RF2 (third input signal) shown in FIG. 6 and outputs the second harmonic RF20 to the isolation terminal Tiso. <1> As a result, the Doherty amplifier circuit 100b can reduce the circuit size without using a filter circuit for ensuring isolation, and can more reliably suppress the effects of third-order intermodulation distortion generated in the carrier amplifier 140 and the peak amplifier 150, thereby improving linearity.

[0072] <6> The Doherty amplifier circuit 100c according to the exemplary embodiment of the present disclosure further includes a duplexer 110c that separates a second harmonic RF20 component from a combined signal obtained by combining the signal RF110 (first amplified signal) and the signal RF120 (second amplified signal) and outputs the second harmonic RF20 to an isolation terminal Tiso. <1> As a result, the Doherty amplifier circuit 100c can more reliably suppress the effects of third-order intermodulation distortion generated in the carrier amplifier 140 and the peak amplifier 150 while reducing the circuit size without using a filter circuit for ensuring isolation.

[0073] <7> The Doherty amplifier circuit 100c according to the exemplary embodiment of the present disclosure further includes a second harmonic amplifier 180 that amplifies the second harmonic RF20 output from the duplexer and outputs the amplified second harmonic RF20 to the isolation terminal Tiso. <6> As a result, the Doherty amplifier circuit 100c can more reliably suppress the effects of third-order intermodulation distortion generated in the carrier amplifier 140 and the peak amplifier 150 while reducing the circuit size without using a filter circuit for ensuring isolation.

[0074] <8> The Doherty amplifier circuits 100d and 100e according to the exemplary embodiments of the present disclosure include a divider 130e that divides a signal RF10 (input signal) into a signal RF11 (first output signal) and a signal RF12 (second output signal) that is 90 degrees out of phase with the signal RF11 (first output signal), a carrier amplifier 140 that amplifies the signal RF11 (first output signal) and outputs a signal RF110 (first amplified signal), a peak amplifier 150 that amplifies the signal RF12 (second output signal) and outputs a signal RF120 (second amplified signal), and 90-degree hybrid couplers 160d and 160e. The Doherty amplifier circuit includes a first input terminal T50 to which a signal RF110 (first amplified signal) is input, a second input terminal T60 to which a signal RF120 (second amplified signal) is input, an output terminal T70 that combines the signal RF110 (first amplified signal) and the signal RF120 (second amplified signal) to output a combined signal RF30, and an isolation terminal Tiso2 that ensures isolation between the output terminal T70 and the harmonic generator 170e that outputs second harmonics RF310 and RF320 in a frequency band that is twice the frequency of the combined signal RF30 to the isolation terminal Tiso2 based on the combined signal RF30. This allows the Doherty amplifier circuits 100d and 100e to reduce the circuit size without using a filter circuit to ensure isolation, while suppressing the influence of third-order intermodulation distortion generated in the carrier amplifier 140 and the peak amplifier 150 and improving linearity.

[0075] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from its spirit, and equivalents are also included within the scope of the present invention. In other words, designs modified by those skilled in the art as appropriate are also encompassed within the scope of the present invention as long as they incorporate the characteristics of the present invention. For example, the elements of the embodiments, as well as their arrangement, materials, conditions, shapes, sizes, etc., are not limited to those exemplified and can be modified as appropriate. Furthermore, the elements of the embodiments can be combined to the extent technically possible, and such combinations are also encompassed within the scope of the present invention as long as they incorporate the characteristics of the present invention. [Explanation of symbols]

[0076] 100, 100a, 100a, 100c, 100d, 100e...Doherty amplifier circuit, 110, 110b...splitter, 110c...divder, 120...drive amplifier, 130...90-degree hybrid coupler, 140...carrier amplifier, 150...peak amplifier, 160...phase shifter, 170...second-harmonic generator, 170d, 170e...harmonic generation unit, 171d...splitter, 172d...second-harmonic generator, 171e...divder, 172e...second-harmonic amplifier, 180...second-harmonic amplifier.

Claims

1. an input terminal to which a first input signal is input; a first output terminal that outputs a first output signal based on the first input signal; a second output terminal that outputs a second output signal having a phase that is 90 degrees different from that of the first output signal based on the first input signal; an isolation terminal that ensures isolation between the input terminal and the isolation terminal; a 90-degree hybrid coupler including: a carrier amplifier that amplifies the first output signal and outputs a first amplified signal; a peak amplifier that amplifies the second output signal and outputs a second amplified signal; Equipped with the isolation terminal is a terminal to which a second harmonic in a frequency band of a second harmonic of the first input signal is input. Doherty amplifier circuit.

2. a divider connected in series to a terminal to which an input signal is input and the input terminal, the divider dividing the input signal into the first input signal and the second input signal; a second harmonic generator that generates the second harmonic based on the second input signal and outputs the second harmonic to the isolation terminal; The Doherty amplifier circuit of claim 1 further comprising:

3. 3. The Doherty amplifier circuit according to claim 2, further comprising a drive amplifier that amplifies the first input signal and outputs the amplified signal to the input terminal.

4. a drive amplifier that outputs a signal obtained by amplifying the input signal; a divider that divides the signal into the first input signal and the second input signal; The Doherty amplifier circuit of claim 2 further comprising:

5. a divider that divides a composite signal obtained by combining the first amplified signal and the second amplified signal into an output signal that is output to an output terminal and a third input signal; a second harmonic generator that generates the second harmonic based on the third input signal and outputs the second harmonic to the isolation terminal; The Doherty amplifier circuit of claim 1 further comprising:

6. 2. The Doherty amplifier circuit according to claim 1, further comprising a branching filter that separates the second harmonic component from a combined signal obtained by combining the first amplified signal and the second amplified signal, and outputs the second harmonic to the isolation terminal.

7. 7. The Doherty amplifier circuit according to claim 6, further comprising a second harmonic amplifier that amplifies the second harmonic output from the branching filter and outputs the amplified second harmonic to the isolation terminal.

8. a divider that divides an input signal into a first output signal and a second output signal that is 90 degrees out of phase with the first output signal; a carrier amplifier that amplifies the first output signal and outputs a first amplified signal; a peak amplifier that amplifies the second output signal and outputs a second amplified signal; A 90-degree hybrid coupler; Equipped with The 90-degree hybrid coupler is a first input terminal to which the first amplified signal is input; a second input terminal to which the second amplified signal is input; an output terminal that combines the first amplified signal and the second amplified signal and outputs a combined signal; an isolation terminal that ensures isolation from the output terminal; A Doherty amplifier circuit comprising: a harmonic generating unit configured to output a second harmonic in a frequency band of a second harmonic of the composite signal to the isolation terminal based on the composite signal; Doherty amplifier circuit.

Images