Doherty amplifier circuit

Abstract

Provided is a Doherty amplifier circuit capable of suppressing the size of the circuit and suppressing the influence of intermodulation distortion. The Doherty amplifier circuit includes: a 90-degree hybrid coupler; a first output terminal that outputs a first output signal on the basis of the first input signal; and a second output terminal that outputs a second output signal having a phase difference of 90 degrees from the first output signal on the basis of the first input signal. And an isolation terminal which ensures isolation from 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 being a terminal to which a second harmonic of a frequency band of the second harmonic of the first input signal is input.

Description

Technical Field

[0001] This invention relates to Doherty amplifier circuits. Background Technology

[0002] Mobile communication devices such as portable phones incorporate power amplifiers to amplify the power of transmitted signals. For example, when multiple signals with similar frequencies are supplied to such a power amplifier, intermodulation distortion (IMD) can occur from these signals, potentially leading to linear degradation. Therefore, to suppress the effects of such intermodulation distortion, techniques have been proposed to eliminate intermodulation distortion components by intentionally injecting higher harmonics into the signal path. For instance, Patent Document 1 discloses a distortion-compensating power amplifier that divides the output of a primary amplifier into a fundamental frequency and a second harmonic, adjusts the phase and amplitude of the second harmonic, adds it to the fundamental frequency, and inputs it to a subsequent amplifier stage, thereby compensating for intermodulation distortion.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-318373 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] The device described in Patent Document 1 uses the second harmonic extracted by a filter circuit to compensate for intermodulation distortion. In recent years, the following problems have arisen: due to 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 the Doherty amplifier circuit needs to correspond to has increased. Consequently, the number of filter circuits has increased, leading to larger circuit sizes. Furthermore, when applying the structure of the device described in Patent Document 1 to a Doherty amplifier circuit, it is necessary to ensure isolation between the device described in Patent Document 1 and the Doherty amplifier circuit to avoid affecting its operation. Therefore, multiple λ / 4 lines must be added. This results in the problem of larger circuit sizes.

[0008] The present invention was made in view of the following circumstances, and its object is to provide a Doherty amplifier circuit that can suppress circuit size and the effects of intermodulation distortion.

[0009] Technical solutions for solving the problem

[0010] To achieve this objective, one aspect of the present invention relates to a Doherty amplifier circuit comprising: a 90-degree hybrid coupler including an input terminal for inputting a first input signal, a first output terminal for outputting a first output signal based on the first input signal, a second output terminal for outputting a second output signal based on the first input signal with a phase difference of 90 degrees from the first output signal, and an isolation terminal ensuring isolation from the input terminal; a carrier amplifier for amplifying the first output signal to output a first amplified signal; and a peak amplifier for amplifying the second output signal to output a second amplified signal, wherein the isolation terminal is a terminal for inputting the second harmonic of the second harmonic band of the first input signal.

[0011] Invention Effects

[0012] According to the present invention, a Doherty amplifier circuit capable of suppressing circuit size and the effects of intermodulation distortion can be provided. Attached Figure Description

[0013] Figure 1 This is a diagram illustrating a structural example of the Doherty amplifier circuit according to the first embodiment.

[0014] Figure 2 This is a graph showing the spectrum of the input signal RFin supplied to the driver amplifier.

[0015] Figure 3 This is a diagram showing the cancellation of the third intermodulation distortion of the signal RF10 output from the driver amplifier.

[0016] Figure 4 This is a graph showing the signal throughput characteristics from the Tiso isolation terminal of the 90-degree hybrid coupler.

[0017] Figure 5 This is a diagram illustrating a structural example of the Doherty amplifier circuit involved in the first modified example.

[0018] Figure 6 This is a diagram illustrating a structural example of the Doherty amplifier circuit involved in the second variation.

[0019] Figure 7 This is a diagram illustrating the structural example of the Doherty amplifier circuit involved in the third variation.

[0020] Figure 8 This is a diagram illustrating a structural example of the Doherty amplifier circuit according to the second embodiment.

[0021] Figure 9 This is a diagram illustrating the structural example of the Doherty amplifier circuit involved in the fourth variation.

[0022] Explanation of reference numerals in the attached figures

[0023] 100, 100a, 100b, 100c, 100d, 100e… Doherty amplifier circuits,

[0024] 110, 110b… Distributor,

[0025] 110c… demultiplexer,

[0026] 120… drive amplifier,

[0027] 130…90 degree hybrid coupler,

[0028] 140…carrier amplifier,

[0029] 150… peak amplifier,

[0030] 160…phase shifter,

[0031] 170… Second harmonic generator,

[0032] 170d, 170e… higher harmonic generation part,

[0033] 171d…distributor,

[0034] 172d… Second harmonic generator,

[0035] 171e… demultiplexer,

[0036] 172e… Second Harmonic Amplifier

[0037] 180… Second harmonic amplifier. Detailed Implementation

[0038] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the same reference numerals are used for the same elements, and repeated descriptions are omitted.

[0039] ===Doherty amplifier circuit 100 according to the first embodiment===

[0040] Figure 1 This is a diagram showing a structural example of the Doherty amplifier circuit 100 according to the first embodiment. Figure 1The Doherty amplifier circuit 100 shown is used, for example, in mobile communication devices such as mobile phones to amplify the power of radio frequency (RF) signals transmitted to base stations. The Doherty amplifier circuit 100 amplifies the power of signals from 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). Furthermore, the frequency of the RF signal is, for example, in the range of several hundred MHz to tens of GHz. It should be noted that the communication standards and frequencies of the signals amplified by the Doherty amplifier circuit 100A are not limited to these.

[0041] The Doherty amplifier circuit 100 can suppress circuit size and compensate for third-order intermodulation distortion, improving linearity, without using filter circuitry to ensure isolation.

[0042] The Doherty amplifier circuit 100 includes, for example, a distributor 110, a driver 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.

[0043] Distributor 110, for example, distributes the input signal RFin into signal RF1 and signal RF2, which has a phase difference of approximately 180 degrees from signal RF1. Approximately 180 degrees includes, for example, a range of 135 to 225 degrees. Distributor 110 may be configured to include a balun. Distributor 110 may also have the function of impedance matching between its preceding circuitry (not shown) and the subsequent driver amplifier 120.

[0044] The driver amplifier 120 amplifies the signal RF1 input through the distributor 110 and outputs the signal RF10 to the input terminal T10 of the 90-degree hybrid coupler 130.

[0045] The 90-degree hybrid coupler 130 distributes the signal RF10 output from the driver amplifier 120 into two signals of equal power with a 90-degree phase difference. 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.

[0046] The 90-degree hybrid coupler 130 can also be configured as two transmission lines (e.g., λ / 4 lines) that include electromagnetic field coupling. The two transmission lines are, for example, striplines or microstrip lines disposed on a substrate. Each of the two transmission lines is configured to extend along a certain direction when the power amplifier 100 is viewed from above.

[0047] The signal RF10 is input to the input terminal T10, which serves as one end of the transmission line, via the driver amplifier 120. The second output terminal T30, serving as the other end of the transmission line, outputs the signal RF12, which distributes the signal RF10. The first output terminal T20, serving as the other end of the transmission line, outputs the signal RF11, which distributes the signal RF10. It should be noted that the phase of signal RF12 is approximately 90 degrees delayed relative to the phase of signal RF11.

[0048] The isolation terminal Tiso, which serves as the other end of another transmission line, is a terminal that ensures isolation from the input terminal T10. That is, even if the signal RF10 is input to the input terminal T10, no voltage is generated at the isolation terminal Tiso. The second harmonic RF20 output from the second harmonic generator 170 is input to the isolation terminal Tiso, which is isolated from other terminals.

[0049] The Doherty amplifier circuit 100 has a structure that provides isolation to the isolation terminal Tiso, which ensures isolation from the input terminal T10, so that the third-order intermodulation distortion can be compensated without using a filter circuit to ensure isolation. This allows for circuit miniaturization.

[0050] It should be noted that the 90-degree hybrid coupler 130 is not limited to being composed of two transmission lines coupled by electromagnetic fields; for example, it can also be formed by connecting four microstrip lines of length λ / 4 into a quadrilateral. It should also be noted that in this case, the Doherty amplifier circuit 100 is configured to input the second harmonic RF20 output from the second harmonic generator 170 to a terminal that is isolated from other terminals.

[0051] Carrier amplifier 140 amplifies the signal RF11 output from the first output terminal T20 of the 90-degree hybrid coupler 130, outputting signal RF110. Carrier amplifier 140 operates independently of the voltage level of signal RF11. That is, carrier amplifier 140 operates when the power level of signal RF11 is higher than zero.

[0052] Peak amplifier 150 amplifies signal RF12 output from the second output terminal T30 of 90-degree hybrid coupler 130, outputting signal RF120. Peak amplifier 150 operates in the region where the voltage level of signal RF12 is lower than the maximum level by a specified level. For example, peak amplifier 150 operates in the region where the power level of signal RF12 is more than 3dB lower than the maximum level.

[0053] Phase shifter 160 is, for example, a quarter-wavelength line connected to the output side of carrier amplifier 140. This allows for the efficient operation of the Doherty amplifier 100 by mitigating the load impedance variation observed at the output of carrier amplifier 140.

[0054] The second harmonic generator 170 is a circuit that generates a second harmonic RF20 as a second harmonic signal based on the signal RF2 distributed by the distributor 110. This second harmonic RF20 is used to compensate for third 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 has a structure that removes the fundamental frequency of the signal RF2 distributed by the distributor 110 and amplifies the frequency band of the second harmonic of the signal RF2. It should be noted that the second harmonic generator 170 can also generate the second harmonic RF20 by adjusting the phase and amplitude of the signal RF2. That is, the second harmonic generator 170 can also adjust the phase and amplitude of the signal RF2 to be suitable for compensating for third intermodulation distortion and output the second harmonic RF20.

[0055] Each amplifier is configured to include bipolar transistors such as heterojunction bipolar transistors (HBTs). It should be noted that each amplifier can also be configured to include field-effect transistors (MOSFETs) instead of HBTs.

[0056] It should be noted that the above description refers to the case where the Doherty amplifier circuit 100 includes the second harmonic generator 170, but it is not limited to this. The Doherty amplifier circuit 100 may also omit the second harmonic generator 170. In this case, the Doherty amplifier circuit 100 can be configured to input the second harmonic RF20 from other circuits to the isolation terminal Tiso. Therefore, the Doherty amplifier circuit 100 can reduce the circuit size.

[0057] <<Compensation Actions for Three-Stage Intermodulation Distortion>>

[0058] Reference Figure 2and Figure 3 The operation of compensation for the three intermodulation distortions in the Doherty amplifier circuit 100 is explained. Figure 2 This is a graph 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 component in the signal RF12. Figure 3 This is a graph showing the cancellation of third-order intermodulation distortion in the signal RF120 output from peak amplifier 150. Figure 2 and Figure 3 In the diagram, the horizontal axis represents the signal frequency, and the vertical axis represents the power spectral density (PSD).

[0059] like Figure 2 As shown, a signal F containing the fundamental wave from signals RF11 and RF12 via a 90-degree hybrid coupler 130 is supplied to carrier amplifier 140 and peak amplifier 150. 01 and the signal 2F as the second harmonic 01 Here, the fundamental frequency signal F 01 This includes components with two closely spaced frequencies, f1 and f2 (f1 < f2). That is, the Doherty amplifier circuit 100 is supplied with a signal F that represents frequencies f1 and f2. 01 Signal 2F with frequencies 2f1 and 2f2 01 The signal is synthesized.

[0060] like Figure 3 As shown, the nonlinear carrier amplifier 140 and peak amplifier 150 amplify the signal F at the fundamental frequency (frequency f1) through the fundamental frequency amplification operation. 01 The low-frequency side generates a third intermodulation distortion IM3 with a frequency of 2f1-f2. L The signal F at the fundamental frequency (f2) 01 The high-frequency side generates a third intermodulation distortion IM3 with a frequency of 2f2-f1. H .

[0061] IM3 with three-way intermodulation distortion L and IM3 H With the fundamental signal F 01 The frequencies f1 and f2 are quite close. Therefore, it is difficult to remove the third-order intermodulation distortion IM3 using filter circuits or similar methods. L and IM3 H IM3 with three-way intermodulation distortion L and IM3 H This is the main reason for the degradation of the characteristics of the Doherty amplifier circuit 100.

[0062] Therefore, in the Doherty amplifier circuit 100, as Figure 3As shown, in order to generate IM3 for compensating for third-order intermodulation distortion L IM3 H The compensation signals CL1 and CL2 intentionally combine the second harmonic RF20 with the fundamental signal F. 01 synthesis.

[0063] Specifically, the Doherty amplifier circuit 100 uses a carrier amplifier 140 and a peak amplifier 150 to amplify the fundamental signal F. 01 The signal is obtained by combining the second harmonic RF20 with the fundamental frequency RF20 through a 90-degree hybrid coupler 130. The Doherty amplifier circuit 100 generates a signal F with a frequency 2f1 from the second harmonic RF20 and the fundamental frequency. 01 The compensation signal CL1 is the frequency difference (2f1-f2) between another frequency f2 in the fundamental frequency. Additionally, the Doherty amplifier circuit 100 generates a signal F with another frequency 2f2 in the second harmonic RF20 and the fundamental frequency. 01 The compensation signal CL2 is the frequency difference (2f2-f1) between two frequencies, f1 and f1.

[0064] That is, in the Doherty amplifier circuit 100, the phase is adjusted to the third intermodulation distortion IM3 generated by the amplification operation of the carrier amplifier 140 and the peak amplifier 150. L IM3 H The phase of the signal is approximately 180 degrees out of phase with the phase of the compensation signals CL1 and CL2 in the outputs of the carrier amplifier 140 and the peak amplifier 150, resulting in the second harmonic RF20, which is input to the isolation terminal Tiso of the 90-degree hybrid coupler 130.

[0065] Furthermore, in the Doherty amplifier circuit 100, the amplitude is adjusted to the third intermodulation distortion IM3 generated in the carrier amplifier 140 and the peak amplifier 150. L IM3 H The second harmonic RF20, obtained by canceling out the amplitudes of the carrier amplifier 140 and the peak amplifier 150 with the amplitudes of the compensation signals CL1 and CL2, is input to the isolation terminal Tiso of the 90-degree hybrid coupler 130.

[0066] Through the aforementioned effects, the Doherty amplifier circuit 100 can suppress the third intermodulation distortion IM3 caused by the amplification operation of the carrier amplifier 140 and the peak amplifier 150 without using a filter circuit to ensure isolation. L IM3 H The effect of this is that, according to the Doherty amplifier circuit 100, linear degradation in the Doherty amplifier circuit can be suppressed.

[0067] <<Details on the compensation operation for peak amplifier 150>>

[0068] Next, refer to Figure 4 The following describes the case in which the linearity of the peak amplifier 150 can be improved by using a 90-degree hybrid coupler 130 in the Doherty amplifier circuit 100. Figure 4 This is a graph showing the signal throughput characteristics from the Tiso input of the 90-degree hybrid coupler 130 isolation terminal. Figure 4 In the diagram, the horizontal axis represents the signal frequency, and the vertical axis represents the signal strength. Additionally, in... Figure 4 In the example, the signal passing through the first output terminal T20 is represented by a dashed line, and the signal passing through the second output terminal T30 is represented by a solid line.

[0069] In the Doherty amplifier circuit, the peak amplifier 150, which operates in the region of higher input voltage levels, exhibits linear degradation compared to the carrier amplifier 140. In the Doherty amplifier circuit 100, the peak amplifier 150, which significantly degrades linearity, allows more second harmonic RF20 to pass than the carrier amplifier 140. Therefore, the Doherty amplifier circuit 100 can suppress the linear degradation in the Doherty amplifier circuit. The following example illustrates the operation of the 90-degree hybrid coupler 130 as a 3dB coupler for a 1GHz signal.

[0070] like Figure 4 As shown, the 90-degree hybrid coupler 130, for example, when a 1 GHz signal is input to the isolation terminal Tiso, outputs a signal of the same signal strength from the first output terminal T20 connected to the carrier amplifier 140 and the second output terminal T30 connected to the peak amplifier 150. Figure 4 (P1).

[0071] Furthermore, when the 90-degree hybrid coupler 130, for example, inputs a 2GHz signal as the second harmonic of 1GHz to the isolation terminal Tiso, the signal output from the first output terminal T20 of the connected carrier amplifier 140 has a power of -6.990dB. Figure 4 The power ratio of “P2” to the signal input to the isolation terminal Tiso is 0.2. In contrast, the signal output from the second output terminal T30 connected to the peak amplifier 150 has a power of -0.969dB. Figure 4 The power ratio of “P3” to the signal input to the isolation terminal Tiso is 0.8.

[0072] That is, in the 90-degree hybrid coupler 130, the second harmonic output to the peak amplifier 150 shows four times the power of the second harmonic output to the carrier amplifier 140.

[0073] Through the aforementioned effects, the Doherty amplifier circuit 100 can further suppress the third intermodulation distortion IM3 caused by the significantly degraded linearity of the peak amplifier 150 without using a filter circuit to ensure isolation. L IM3 H This has an impact. Thus, in the Doherty amplifier circuit 100, the linearity of the Doherty amplifier circuit can be improved.

[0074] <<First Variation>>

[0075] Reference Figure 5 The Doherty amplifier circuit 100a involved in the first modified example will be described. Figure 5 This is a diagram illustrating a structural example of the Doherty amplifier circuit 100a according to the first modified example. It should be noted that, below, descriptions 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, the same effects produced by the same structure will not be mentioned repeatedly.

[0076] Doherty amplifier circuit 100a and Figure 1 Compared to the Doherty amplifier circuit 100, the distributor 160 is positioned after the driver amplifier 120. Specifically, the driver amplifier 120 outputs a signal amplified from the input signal RFin to the distributor 110. The distributor 160, for example, distributes the signal amplified by the driver amplifier 120 into a signal RF10 and a signal RF2 with a phase difference of approximately 180 degrees from signal RF10. Signal RF10 is input to the input terminal T10 of the 90-degree hybrid coupler 130, and signal RF2 is input to the isolation terminal Tiso via the second harmonic generator 170.

[0077] Thus, in the Doherty amplifier circuit 100a, compared to the Doherty amplifier circuit 100, a higher power second harmonic RF20 can be input to the isolation terminal Tiso of the 90-degree hybrid coupler 130. Consequently, in the Doherty amplifier circuit 100a, the circuit can be miniaturized without using a filter circuit to ensure isolation, and the third intermodulation distortion IM3 generated in the carrier amplifier 140 and the peak amplifier 150 can be suppressed more reliably. L IM3 H The effect of improving linearity.

[0078] <<Second Variation>>

[0079] Reference Figure 6 The Doherty amplifier circuit 100b involved in the second variation will be described. Figure 6This is a diagram illustrating a structural example of the Doherty amplifier circuit 100b involved in the second modification. It should be noted that, below, descriptions of matters common to the Doherty amplifier circuit 100 involved in the first embodiment will be omitted, and only the differences will be described. In particular, the same effects produced by the same structure will not be mentioned repeatedly.

[0080] Doherty amplifier circuit 100b and Figure 1 Compared to the Doherty amplifier circuit 100, the distributor 110b is positioned after the carrier amplifier 140 and the peak amplifier 150. Specifically, the driver amplifier 120 outputs the amplified input signal RF10 to the input terminal T10 of the 90-degree hybrid coupler 130. The distributor 110b distributes the signal obtained by combining 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 based on the signal RF2 and outputs it to the isolation terminal Tiso of the 90-degree hybrid coupler 130.

[0081] Thus, in the Doherty amplifier circuit 100b, compared to the Doherty amplifier circuit 100, a higher power second harmonic RF20 can be input to the isolation terminal Tiso of the 90-degree hybrid coupler 130. Consequently, in the Doherty amplifier circuit 100b, the circuit can be miniaturized without using a filter circuit to ensure isolation, and the third intermodulation distortion IM3 generated in the carrier amplifier 140 and the peak amplifier 150 can be suppressed more reliably. L IM3 H The effect of improving linearity.

[0082] <<Third Variation>>

[0083] Reference Figure 7 The Doherty amplifier circuit 100c involved in the third variation will be described. Figure 7 This is a diagram illustrating a structural example of the Doherty amplifier circuit 100c involved in the third modification. It should be noted that, below, descriptions of matters common to the Doherty amplifier circuit 100 involved in the first embodiment will be omitted, and only the differences will be described. In particular, the same effects produced by the same structure will not be mentioned repeatedly.

[0084] The Doherty amplifier circuit 100c is a... Figure 6 The circuit in which the distributor 110 in the Doherty amplifier circuit 100b is replaced with the demultiplexer 110c and the second harmonic generator 170 is replaced with the second harmonic amplifier 180.

[0085] Demultiplexer 110c is a unidirectional duplexer that separates the second harmonic component from the signal obtained by combining the signal RF110 output from carrier amplifier 140 and the signal RF120 output from peak amplifier 150. For example, demultiplexer 110c is a circuit composed of a low-pass filter and a band-pass filter. Demultiplexer 110c outputs the fundamental signal as the output signal RFout through output terminal 102, and outputs the separated second harmonic to second harmonic amplifier 180. Second harmonic amplifier 180 amplifies the second harmonic input from demultiplexer 110c and outputs it to the isolation terminal Tiso of 90-degree hybrid coupler 130.

[0086] Thus, in the Doherty amplifier circuit 100c, compared to the Doherty amplifier circuit 100, a higher power second harmonic RF20 can be input to the isolation terminal Tiso of the 90-degree hybrid coupler 130. Consequently, in the Doherty amplifier circuit 100c, the third intermodulation distortion IM3 generated in the carrier amplifier 140 and the peak amplifier 150 can be suppressed more reliably without using filter circuitry to ensure isolation. L IM3 H The impact.

[0087] It should be noted that the above description refers to the case where the Doherty amplifier circuit 100c includes the second harmonic amplifier 180, but it is not limited to this. The Doherty amplifier circuit 100c may also not include the second harmonic amplifier 180. In this case, the second harmonic input to the isolation terminal Tiso of the 90-degree hybrid coupler 130 can be designed by adjusting the design conditions of the drive amplifier 120, carrier amplifier 140, and peak amplifier 150. Therefore, the Doherty amplifier circuit 100 can be reduced in size.

[0088] ===The Doherty amplifier circuit 100d involved in the second embodiment===

[0089] Reference Figure 8 The Doherty amplifier circuit 100d according to the second embodiment will be described. Figure 8 This is a diagram illustrating a structural example of the Doherty amplifier circuit 100d according to the second embodiment. It should be noted that, below, descriptions of matters common to the Doherty amplifier circuit 100 according to the first embodiment will be omitted, and only the differences will be explained. In particular, the same effects produced by the same structure will not be mentioned repeatedly.

[0090] Doherty amplifier circuit 100d and Figure 1Compared to the Doherty amplifier circuit 100, a 90-degree hybrid coupler 160d is provided on the output side of the carrier amplifier 140 and the peak amplifier 150, replacing the phase shifter 160. Furthermore, the Doherty amplifier circuit 100d is configured such that a second harmonic RF310 is input from the higher harmonic generation section 170d to the isolation terminal Tiso2 in the 90-degree hybrid coupler 160d, which ensures isolation between the second harmonic and the output terminal T70. Thus, in the Doherty amplifier circuit 100d, a second harmonic is synthesized on the output side, suppressing the third intermodulation distortion IM3 generated in the carrier amplifier 140 and the peak amplifier 150. L IM3 H The impact.

[0091] It should be noted that, in Figure 8 The diagram shows the use of a 90-degree hybrid coupler 130d, but it is not limited to this. For example, the 90-degree hybrid coupler 130d can be a distributor that divides the signal RF10 into the signal RF11 and the signal RF12, which has a phase difference of 90 degrees from the signal RF11.

[0092] 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 has a phase difference of 90 degrees from the signal RF110. It should be noted that the 90-degree hybrid coupler 160d has... Figure 4 The characteristics shown are as follows. 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.

[0093] The 90-degree hybrid coupler 160d can also be configured as two transmission lines (e.g., λ / 4 lines) including electromagnetic field coupling. The two transmission lines are, for example, striplines or microstrip lines disposed on a substrate. Each of the two transmission lines is configured to extend along a certain direction when viewed from above in the Doherty amplifier circuit 100d.

[0094] Signal RF110 is input from carrier amplifier 140 to the first input terminal T50, which serves as one end of a transmission line. A composite signal RF30 is output from the output terminal T70, which serves as the other end of the transmission line. This composite signal RF30 is obtained by combining signal RF110 with RF120 output from peak amplifier 150. Signal RF120 is input from peak amplifier 150 to the second input terminal T60, which serves as the other end of a transmission line. It should be noted that in the 90-degree hybrid coupler 160d, the input signal RF110 is phase-delayed by approximately 90 degrees before being combined with signal RF120, and the composite signal RF30 is output from the output terminal T70.

[0095] The isolation terminal Tiso2, serving as the other end of another transmission line, is a terminal that ensures isolation from the output terminal T70. That is, even if signals RF110 and RF120 are input to the first input terminal T50 and the second input terminal T60, no voltage is generated at the isolation terminal Tiso2. The second harmonic RF310, output from the higher harmonic generation unit 170d (described later), is input to the isolation terminal Tiso2.

[0096] The higher harmonic generation unit 170d includes, for example, a distributor 171d and a second harmonic generator 172d. The distributor 171d is configured, for example, to include a balun. The distributor 171d, for example, distributes the synthesized signal RF30 into an output signal RFout and a signal RF31 whose phase differs from the output signal RFout by approximately 180 degrees. The second harmonic generator 172d is a circuit that generates a second harmonic RF310 based on the signal RF31 distributed by the distributor 171d. This second harmonic RF310 is a signal used to compensate for the second harmonic of the third intermodulation distortion in the Doherty amplifier circuit. The second harmonic generator 172d has the same structure as the second harmonic generator 170 of the Doherty amplifier circuit 100.

[0097] Therefore, in the Doherty amplifier circuit 100d, the third intermodulation distortion IM3 generated in the carrier amplifier 140 and the peak amplifier 150 can be suppressed without using a filter circuit to ensure isolation. L IM3 H The effect of improving linearity.

[0098] <<Fourth Variation>>

[0099] Reference Figure 9 The Doherty amplifier circuit 100e involved in the fourth variation will be explained. Figure 9 This is a diagram illustrating a structural example of the Doherty amplifier circuit 100e according to the fourth modification. It should be noted that, below, descriptions of matters common to the Doherty amplifier circuit 100d according to the second embodiment will be omitted, and only the differences will be explained. In particular, the same effects produced by the same structure will not be mentioned repeatedly.

[0100] Compared to the Doherty amplifier circuit 100d, the Doherty amplifier circuit 100e is, for example, a circuit in which the distributor 171d is replaced by the demultiplexer 171e and the second harmonic generator 172d is replaced by the second harmonic amplifier 172e.

[0101] Demultiplexer 171e is a unidirectional duplexer that separates the second harmonic component from a signal output from terminal T70 of 90-degree hybrid coupler 160e, and is obtained by combining signal RF110 output from carrier amplifier 140 and signal RF120 output from peak amplifier 150. For example, demultiplexer 171e is a circuit combining a low-pass filter and a band-pass filter. Demultiplexer 171e outputs the fundamental signal as output signal RFout through terminal 102, and separates the second harmonic and outputs it to second harmonic amplifier 172e. Second harmonic amplifier 172e amplifies the second harmonic input from demultiplexer 171e and outputs it to isolation terminal Tiso2 of 90-degree hybrid coupler 160e.

[0102] Therefore, in the Doherty amplifier circuit 100e, the third intermodulation distortion IM3 generated in the carrier amplifier 140 and the peak amplifier 150 can be suppressed without using a filter circuit to ensure isolation. L IM3 H The effect of improving linearity.

[0103] It should be noted that the above description refers to the case where the Doherty amplifier circuit 100e includes the second harmonic amplifier 172e, but it is not limited to this. The Doherty amplifier circuit 100e may also not include the second harmonic amplifier 172e. In this case, the Doherty amplifier circuit 100e designs the second harmonic input to the isolation terminal Tiso2 of the 90-degree hybrid coupler 160e by adjusting the design conditions of the carrier amplifier 140 and the peak amplifier 150. Therefore, the Doherty amplifier circuit 100e can reduce circuit size.

[0104] ===Summary===

[0105] <1> The Doherty amplifier circuit 100 according to the exemplary embodiment of this disclosure includes: a 90-degree hybrid coupler 130, which includes an input terminal T10 for inputting a signal RF1 (first input signal), a first output terminal T20 for outputting a signal RF11 (first output signal) based on the signal RF1 (first input signal), a second output terminal T30 for outputting a signal RF12 (second output signal) with a phase difference of 90 degrees from the signal RF11 (first output signal) based on the signal RF1 (first input signal), and an isolation terminal Tiso that ensures isolation from the input terminal T10; a carrier amplifier 140 that amplifies the signal RF11 (first output signal) and outputs a signal RF110 (first amplified signal); and a peak amplifier 150 that amplifies the signal RF12 (second output signal) and outputs a signal RF120 (second amplified signal), wherein the isolation terminal Tiso is a terminal for inputting the second harmonic RF20 of the second harmonic band of the signal RF1 (first input signal). Thus, the Doherty amplifier circuit 100 can suppress circuit size and compensate for third-order intermodulation distortion, improving linearity, without using filter circuitry to ensure isolation.

[0106] <2> The Doherty amplifier circuit 100 according to the exemplary embodiment of this disclosure further includes, in <1> the Doherty amplifier circuit described therein: a distributor 110, which is connected in series with the input terminal 101 (terminal) and the input terminal T10 for inputting the input signal, and distributes the input signal RFin into signal RF1 (first input signal) and signal RF2 (second input signal); and a second harmonic generator 170, which generates a second harmonic RF20 based on signal RF2 (second input signal) and outputs the second harmonic RF20 to the isolation terminal Tiso. Thus, the Doherty amplifier circuit 100 can suppress circuit size and compensate for third intermodulation distortion without using a filter circuit to ensure isolation, thereby improving linearity.

[0107] <3> The Doherty amplifier circuit 100 according to the exemplary embodiment of this disclosure further includes a driver amplifier 120 in the Doherty amplifier circuit described in <2>, which outputs the amplified signal RF1 (first input signal) to the input terminal T10. Thus, the Doherty amplifier circuit 100 can suppress circuit size and compensate for third-order intermodulation distortion without using a filter circuit to ensure isolation, thereby improving linearity.

[0108] <4> The Doherty amplifier circuit 100a according to the exemplary embodiment of this disclosure further includes, in <2>, a driver amplifier 120 that amplifies the input signal RFin and outputs a signal; and a distributor 110 that distributes the signal into signal RF10 (first input signal) and signal RF2 (second input signal). Therefore, in the Doherty amplifier circuit 100a, circuit size can be suppressed without using filter circuitry to ensure isolation, and the effects of third intermodulation distortion generated in the carrier amplifier 140 and peak amplifier 150 can be suppressed more reliably, improving linearity.

[0109] <5> The Doherty amplifier circuit 100b according to the exemplary embodiment of this disclosure further includes, in <1> the Doherty amplifier circuit: a distributor 110b, which distributes the synthesized signal obtained by combining the signal RF110 (first amplified signal) and the signal RF120 (second amplified signal) into an output signal RFout and an output signal RFout to be output to the output terminal 102. Figure 6 The signal RF2 (third input signal) shown; and the second harmonic generator 170, which is based on Figure 6 The signal RF2 (third input signal) is shown to generate a second harmonic RF20, which is then output to the isolation terminal Tiso. Thus, in the Doherty amplifier circuit 100b, circuit size can be reduced without using a filter circuit to ensure isolation, and the effects of third intermodulation distortion generated in the carrier amplifier 140 and peak amplifier 150 can be suppressed more reliably, improving linearity.

[0110] <6> The Doherty amplifier circuit 100c according to the exemplary embodiment of this disclosure further includes a splitter 110c in the Doherty amplifier circuit described in <1>, which separates the second harmonic RF20 component from the synthesized signal obtained by combining the signal RF110 (first amplified signal) and the signal RF120 (second amplified signal), and outputs the second harmonic RF20 to the isolation terminal Tiso. Therefore, in the Doherty amplifier circuit 100c, the circuit size can be suppressed without using a filter circuit to ensure isolation, and the effects of third intermodulation distortion generated in the carrier amplifier 140 and the peak amplifier 150 can be suppressed more reliably.

[0111] <7> The Doherty amplifier circuit 100c according to the exemplary embodiment of this disclosure further includes a second harmonic amplifier 180 in the Doherty amplifier circuit described in <6>, which amplifies the second harmonic RF20 output from the demultiplexer and outputs it to the isolation terminal Tiso. Therefore, in the Doherty amplifier circuit 100c, circuit size can be suppressed without using filter circuitry to ensure isolation, and the effects of third intermodulation distortion generated in the carrier amplifier 140 and the peak amplifier 150 can be suppressed more reliably.

[0112] <8> The Doherty amplifier circuits 100d and 100e according to the exemplary embodiments of this disclosure include: a distributor 130e that distributes the signal RF10 (input signal) into a signal RF11 (first output signal) and a signal RF12 (second output signal) whose phase differs from that of the signal RF11 (first output signal) by 90 degrees; a carrier amplifier 140 that amplifies the signal RF11 (first output signal) and outputs a signal 110 (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, 90-degree hybrid coupler 1 60d and 160e include: a first input terminal T50 for inputting signal RF110 (first amplified signal); a second input terminal T60 for inputting signal RF120 (second amplified signal); an output terminal T70 for combining signal RF110 (first amplified signal) and signal RF120 (second amplified signal) to output a combined signal RF30; and an isolation terminal Tiso2 for ensuring isolation from the output terminal T70. They also include a higher harmonic generation unit 170e, which, based on the combined signal RF30, outputs the second harmonics RF310 and RF320 of the second harmonic band of the combined signal RF30 to the isolation terminal Tiso2. Therefore, in the Doherty amplifier circuits 100d and 100e, circuit size can be reduced without using filter circuits to ensure isolation, and the effects of third intermodulation distortion generated in the carrier amplifier 140 and peak amplifier 150 can be suppressed, improving linearity.

[0113] The embodiments described above are intended to facilitate understanding of the present invention and are not intended to limit the scope of the invention. The present invention can be modified or improved without departing from its spirit, and equivalents are also included. That is, any modifications made by those skilled in the art to the embodiments that possess the features of the present invention are also included within the scope of the present invention. For example, the elements, their configurations, materials, conditions, shapes, and dimensions in each embodiment are not limited to the examples shown and can be appropriately modified. Furthermore, the elements in each embodiment can be combined to a technically feasible extent, and any combination thereof that includes the features of the present invention is also included within the scope of the present invention.

Claims

1. A Doherty amplifier circuit, comprising: A 90-degree hybrid coupler includes an input terminal for receiving a first input signal, a first output terminal for outputting a first output signal based on the first input signal, a second output terminal for outputting a second output signal with a phase difference of 90 degrees from the first output signal based on the first input signal, and an isolation terminal that ensures isolation from the input terminal. A carrier amplifier that amplifies the first output signal to output a first amplified signal; and A peak amplifier that amplifies the second output signal to output a second amplified signal. The isolation terminal is a terminal that receives the second harmonic of the second harmonic frequency band of the first input signal.

2. The Doherty amplifier circuit according to claim 1, wherein, The Doherty amplifier circuit also features: A distributor, which is connected in series with a terminal that receives the input signal and the input terminal, distributes the input signal into a first input signal and a second input signal; as well as A second harmonic generator generates the second harmonic based on the second input signal and outputs the second harmonic to the isolation terminal.

3. The Doherty amplifier circuit according to claim 2, wherein, The Doherty amplifier circuit also includes a driver amplifier that outputs the amplified signal of the first input signal to the input terminal.

4. The Doherty amplifier circuit according to claim 2, wherein, The Doherty amplifier circuit also features: The driver amplifier amplifies the output signal of the input signal; and A distributor that distributes the signal into the first input signal and the second input signal.

5. The Doherty amplifier circuit according to claim 1, wherein, The Doherty amplifier circuit also features: A distributor that distributes the combined signal obtained by combining the first amplified signal and the second amplified signal into an output signal and a third input signal to be output to the output terminal; as well as A second harmonic generator generates the second harmonic based on the third input signal and outputs the second harmonic to the isolation terminal.

6. The Doherty amplifier circuit according to claim 1, wherein, The Doherty amplifier circuit also includes a demultiplexer that separates the second harmonic component from the composite signal obtained by combining the first amplified signal and the second amplified signal, and outputs the second harmonic to the isolation terminal.

7. The Doherty amplifier circuit according to claim 6, wherein, The Doherty amplifier circuit also includes a second harmonic amplifier that amplifies the second harmonic output from the demultiplexer and outputs it to the isolation terminal.

8. A Doherty amplifier circuit, comprising: A distributor that distributes an input signal into a first output signal and a second output signal whose phase differs from the first output signal by 90 degrees. A carrier amplifier that amplifies the first output signal to output a first amplified signal; A peak amplifier that amplifies the second output signal to output a second amplified signal; as well as 90-degree hybrid coupler The 90-degree hybrid coupler includes: The first input terminal receives the first amplified signal. The second input terminal receives the second amplified signal. The output terminal combines the first amplified signal and the second amplified signal to output a combined signal; and An isolation terminal, which ensures isolation from the output terminal. The Doherty amplifier circuit includes a high-order harmonic generation unit that outputs the second harmonic of the second harmonic frequency band of the synthesized signal to the isolation terminal based on the synthesized signal.

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