Multi-stage amplifier

Abstract

The present invention provides a multi-stage amplifier, which is used for amplifying a multi-carrier signal including two carrier frequencies (f1, f2). The multi-stage amplifier (1) comprises: N (N is an integer greater than 2) amplifiers, wherein the amplifier of the k+1th stage is cascade-connected to the amplifier of the kth stage, respectively amplifying the multi-carrier signal; and an extraction circuit (9), whose input is connected to the output of the amplifier of the jth stage, and whose output provides a compensation signal to the input of the amplifier of the j+1th stage or the output of the amplifier of the j+1th stage, wherein the extraction circuit comprises: a filter circuit (11) connected to the output of the amplifier of the jth stage, extracting a deformed frequency component of n times (n is an integer greater than 1) the differential frequency f2-f1; a phase shifter (13) connected in series to the filter circuit, shifting the phase of the deformed frequency component; and a gain adjustment circuit (15) connected in series to the phase shift circuit, adjusting the amplitude of the deformed frequency component, and generating a compensation signal.

Description

Technical Field

[0001] The present disclosure relates to a multi-stage amplifier that amplifies a signal containing a carrier frequency. Background Art

[0002] Conventionally, in equipment such as base stations constituting mobile phone systems, amplifiers that amplify multi-carrier signals including multiple carrier frequencies are used, and the amplifiers are provided with means for compensating for deformations generated by the amplifiers. For example, Patent Document 1: Japanese Patent Publication No. 1-302901 discloses a structure that minimizes deformation components of the output of the amplifier. Furthermore, Patent Document 2: Japanese Patent Publication No. 2000-252765 discloses a structure in which a passive filter circuit is added to the output side of the amplifier, and the filter circuit reduces the level of noise generated as a modulation product with the multi-carrier signal. Furthermore, Patent Document 3: Japanese Patent Publication No. 2008-48032 discloses a structure in which a plurality of signal generating circuits that output deformation compensation signals of different orders are provided on the input side of the amplifier. Similarly, Patent Document 4: Japanese Patent Publication No. 2008-271289 discloses a structure in which a plurality of signal generating circuits that output different deformation compensation signals are provided on the input side of the amplifier, and deformations of odd orders are generated by these generating circuits.

[0003] In the above-mentioned conventional amplifier structure, it is not possible to sufficiently reduce the hybrid modulation based on the secondary intermodulation deformation or its higher harmonics, and there is a tendency that the quality of the output signal is reduced. In particular, when the bandwidth of the multi-carrier signal is wide, there is a situation where the relatively low-order higher harmonic deformation enters the bandwidth and the quality of the output signal is reduced. Therefore, it is desired to sufficiently reduce the hybrid modulation based on the secondary intermodulation deformation or its higher harmonics to improve the quality of the output signal. Summary of the invention

[0004] A multi-stage amplifier according to one aspect of the present disclosure is used to amplify a multi-carrier signal, the multi-carrier signal including a first component having a first frequency f1 and a second component having a second frequency f2, the multi-stage amplifier comprising: N (N is an integer greater than or equal to 2) amplifiers, each of which is divided into an i-th stage (i is an integer from 1 to N) amplifier, a k+1-th stage (1≤k≤N-1) amplifier cascade-connected to the k-th stage amplifier, each amplifier amplifying the multi-carrier signal; and a compensation circuit having an input and an output, the input being connected to the output of the j-th (j is an integer from 1 to N-1) amplifier, and the output providing a compensation signal to the input of the j+1-th amplifier or the output of the j+1-th amplifier, the compensation circuit comprising: a filter circuit connected to the output of the j-th amplifier, extracting a deformed frequency component of n times (n is an integer greater than or equal to 1) the differential frequency f2-f1; a phase shift circuit connected in series to the filter circuit, shifting the phase of the deformed frequency component; and an amplitude adjustment circuit connected in series to the phase shift circuit, adjusting the amplitude of the deformed frequency component, and generating a compensation signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 1 is a block diagram showing a schematic configuration of a multi-stage amplifier 1 according to the embodiment.

[0006] Figure 2 Yes means Figure 1 The amplifiers M1 to M1 in the multi-stage amplifier 1 n A circuit diagram of the connection structure between stages and the connection structure on the input side and the output side.

[0007] Figure 3 : is a graph showing the frequency spectrum of a multi-carrier signal amplified by a multi-stage amplifier without using a distortion compensation unit.

[0008] Figure 4 : is a graph showing the frequency spectrum of a multi-carrier signal amplified by a multi-stage amplifier without using a distortion compensation unit.

[0009] Figure 5 This is a diagram showing an actual waveform of the frequency spectrum of a multi-carrier signal amplified by a multi-stage amplifier that does not include a distortion compensation unit.

[0010] Figure 6 1 is a diagram showing an example of a circuit configuration for extracting a signal in the extraction circuit 9 .

[0011] Figure 7 Yes means Figure 6 A coordinate diagram of an example of calculation of signal transmission characteristics in a structure of FIG.

[0012] Figure 8 1 is a diagram showing an example of a circuit configuration for combining signals in the extraction circuit 9.

[0013] Fig. 9 Yes means Figure 8 A coordinate diagram of an example of calculation of signal transmission characteristics in a structure of FIG.

[0014] Fig.10 1 is a diagram showing an example of a circuit configuration for combining signals in the extraction circuit 9.

[0015] Fig.11 Yes means Fig.10 A coordinate diagram of an example of calculation of signal transmission characteristics in a structure of FIG.

[0016] Fig.12 1 is a block diagram showing a schematic configuration of a multi-stage amplifier 1A according to a modified example.

[0017] Fig.13 1 is a diagram showing an example of a circuit configuration for combining signals in the extraction circuit 9.

[0018] Fig.14 Yes means Fig.13 A coordinate diagram of an example of calculation of signal transmission characteristics in a structure of FIG.

[0019] Fig.15 1 is a diagram showing an example of a circuit configuration for combining signals in the extraction circuit 9.

[0020] Fig.16 Yes means Fig.15 A coordinate diagram of an example of calculation of signal transmission characteristics in a structure of FIG. DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that in the description of the drawings, the same elements are denoted by the same reference numerals, and repeated descriptions are omitted.

[0022] [Structure of multi-stage amplifier]

[0023] Figure 1 1 is a block diagram showing the structure of a multi-stage amplifier 1 according to an embodiment. The multi-stage amplifier 1 is used in a base station or other equipment constituting a mobile phone system to amplify an analog signal (multi-carrier signal) including multiple carrier frequencies. For example, the multi-carrier signal input to the multi-stage amplifier 1 is a signal including at least a first carrier frequency f1 and a second carrier frequency f2. The first carrier frequency f1 and the second carrier frequency f2 are not limited to specific values, and are, for example, frequencies in the 2 GHz band, that is, f1 = 1810 MHz and f2 = 2160 MHz.

[0024] like Figure 1 As shown, the multi-stage amplifier 1 includes an input terminal P to which a multi-carrier signal is input. IN , output terminal P for outputting the amplified multi-carrier signalOUT , at the input terminal P IN With output terminal P OUT The amplifiers M1, M2, ..., M1 of the first to nth stages (n is a natural number greater than 2) are connected in cascade. n-1 、M n The amplifier M1 will be input from the terminal P IN The input multi-carrier signal is amplified and the amplified multi-carrier signal is output to the amplifier M2 of the next stage. n-1 The amplifiers M1, ...M n-2 The input multi-carrier signal is amplified and the amplified multi-carrier signal is sent to the next stage amplifier M3, ...M n Output. The final amplifier M n The amplifier M from the previous level n-1 The input multi-carrier signal is amplified and the amplified multi-carrier signal is output through the output terminal P OUT Through such a multi-stage structure, the multi-stage amplifier 1 can amplify the multi-carrier signal at a high gain.

[0025] Figure 2 The amplifiers M1 to M2 in the multi-stage amplifier 1 are shown. n The connection structure between the stages and the connection structure between the input side and the output side. n The output of is connected to a bias circuit composed of an inductor L1 and a capacitor C1. The M bias circuits constitute a DC bias supply circuit 3. In each bias circuit, a bias voltage V is applied to one end of the inductor L1 and one end of the capacitor C1. C In each bias circuit, the other end of the inductor L1 is connected to each amplifier M1 to M2. n The DC bias supply circuit 3 is connected to the output of each amplifier M1 to M2. n Supply DC bias voltage. IN An input matching circuit 5 composed of a capacitor C2 and an inductor L2 is connected between the input of the amplifier M1 at the first stage. n With output terminal P OUT An output matching circuit 7 composed of capacitors C3, C4 and an inductor L3 is connected between them. In the input matching circuit 5, one end of the capacitor C2 is connected to the input terminal P IN The other end of the capacitor C2 and one end of the inductor L2 are connected to the input of the primary amplifier M1, and the other end of the inductor L2 is grounded. In the output matching circuit 7, one end of the capacitor C3 and one end of the inductor L3 are connected to the input of the final amplifier M1. nThe other end of the inductor L3 and one end of the capacitor C4 are connected to the output terminal P OUT , the other ends of capacitors C3 and C4 are grounded.

[0026] return Figure 1 The multi-stage amplifier 1 further includes an amplifier M inserted into the n-1th stage. n-1 The output of the final amplifier M n The extraction circuit 9 includes a filter circuit 11, a shifter (phase shifter) 13, and a gain adjustment circuit 15. The filter circuit 11, the shifter (phase shifter) 13, and the gain adjustment circuit 15 are cascade-connected in this order. The input of the filter circuit 11 is connected to the amplifier M of the n-1th stage. n-1 The output of the final amplifier M n The transmission path between the filter circuit 11 is from the amplifier M of the n-1th stage. n-1 The output multi-carrier signal removes the fundamental wave components of the first carrier frequency f1 and the second carrier frequency f2, and extracts the frequency component (deformed frequency component) of the differential frequency (f2-f1) corresponding to the difference between the first carrier frequency f1 and the second carrier frequency f2. The filter circuit 11 is, for example, a low-pass filter that extracts the frequency component of the differential frequency (f2-f1). The transducer 13 adjusts the phase of the signal of the frequency component of the differential frequency (f2-f1) output from the filter circuit 11. The gain adjustment circuit 15 is composed of a variable gain amplifier or a variable attenuator. The input of the gain adjustment circuit 15 is connected to the output of the transducer 13, and the output of the gain adjustment circuit 15 is connected to the final stage amplifier M. n The signal output from the gain adjustment circuit 15 is connected to the output of the amplifier M of the final stage. n The gain adjustment circuit 15 adjusts the amplitude (strength) of the signal of the frequency component of the differential frequency (f2-f1) output from the transmitter 13, and outputs the adjusted signal.

[0027] The extraction circuit 9 of the above structure adjusts the n-1 The phase and amplitude of the frequency component of the differential frequency (f2-f1) extracted from the output multi-carrier signal are reduced from the final stage amplifier M n That is, in the extraction circuit 9, the shifter 13 performs phase adjustment, and the gain adjustment circuit 15 performs amplitude adjustment to generate a frequency component for the output multi-carrier signal (f2-f1). nThe output multi-carrier signal has the smallest frequency component of the differential frequency (f2-f1). By configuring in this way, it is possible to suppress not only the hybrid modulation based on the frequency component of the differential frequency (f2-f1) in the output of the multi-stage amplifier 1, but also the hybrid modulation based on the higher harmonics and the hybrid modulation based on the mutual modulation deformation caused by the above.

[0028] Here, hybrid modulation generated when a multi-carrier signal including a signal of a first carrier frequency f1 and a signal of a second carrier frequency f2 is amplified by a multi-stage amplifier without a distortion compensation circuit as a comparative example is shown. Next, the effects of the multi-stage amplifier 1 of this embodiment are described.

[0029] Figure 3 and Figure 4 FIG. 2 shows an example of the spectrum of a multi-carrier signal amplified by a multi-stage amplifier without a distortion compensation circuit. Figure 3 As shown in FIG. 1 , if a multi-carrier signal is input to a multi-stage amplifier, signal components of frequencies ±k1·f1±k2·f2 (k1 and k2 are natural numbers) generated by mutual modulation in addition to frequencies f1 and f2 also appear in the output. The above-mentioned frequency components other than frequencies f1 and f2 are caused by the fact that the gain of the multi-stage amplifier is nonlinear and the output signal is deformed relative to the input signal. k1+k2 is the order of mutual modulation (IM). Moreover, as Figure 4 As shown, at the output of the multi-stage amplifier, not only Figure 3 In addition to the intermodulation distortion shown, higher harmonic distortion having frequency components of integer multiples of the fundamental wave or the intermodulation distortion of frequencies f1, f2 is also generated.

[0030] Figure 5 An example of an actual waveform of the spectrum of a multi-carrier signal amplified by a multi-stage amplifier without a distortion compensation circuit is shown. Here, an example is shown when a multi-carrier signal including components of a first carrier frequency f1 = 1810 MHz and a second carrier frequency f2 = 2160 MHz is input. Thus, it can be seen that the output signal of the multi-stage amplifier includes the following frequency components.

[0031] ·Frequency components f1 and f2 of the fundamental wave

[0032] The frequency component of the third-order intermodulation deformation IM3_low: 2f1-f2

[0033] · Frequency component of third-order intermodulation deformation IM3_high: 2f2-f1

[0034] The frequency component of the fifth intermodulation deformation IM5_low: 3f1-2f2

[0035] ·Frequency component of fifth-order intermodulation deformation IM5_high: 3f2-2f1

[0036] · Frequency component of the seventh intermodulation deformation IM7_low: 4f1-3f2

[0037] · Frequency component of seventh-order intermodulation deformation IM7_high: 4f2-3f1

[0038] ·Frequency component IM2 of secondary complementary modulation deformation: f2-f1

[0039] Second harmonic of frequency component IM2, second intermodulation distortion, and other intermodulation distortion frequency components: 2×(f2-f1)

[0040] The third harmonic of the frequency component IM2, the second order intermodulation distortion, and other intermodulation distortion frequency components: 3×(f2-f1)

[0041] The fourth harmonic of the frequency component IM2, the second order intermodulation distortion, and other intermodulation distortion frequency components: 4×(f2-f1)

[0042] The fifth harmonic of the frequency component IM2, the second order intermodulation distortion, and the frequency components of other intermodulation distortions: 5×(f2-f1)

[0043] The sixth harmonic of the frequency component IM2, the second order intermodulation distortion, and other intermodulation distortion frequency components: 6×(f2-f1)

[0044] The seventh harmonic of the frequency component IM2, the second order intermodulation distortion, and the frequency components of other intermodulation distortions: 7×(f2-f1)

[0045] Frequency components of the second harmonic of the fundamental wave: 2×f1, 2×f2

[0046] The intended band of the multi-carrier signal is a band with a width of 640 MHz centered at 2 GHz. Figure 5 In the output signal shown above, the following deformation components (A1) to (A4) become problematic as deformations that affect the quality of the multi-carrier signal.

[0047] (A1) The fifth harmonic of the frequency component IM2, the second order intermodulation distortion, and the frequency components of other intermodulation distortions: 5×(f2-f1)

[0048] (A2) The sixth harmonic of the frequency component IM2, the secondary intermodulation distortion, and the frequency components of other intermodulation distortions: 6×(f2-f1)

[0049] (A3) The third-order mutual modulation between the frequency component f1 and the frequency component 5×(f2-f1) is the frequency component IM3 (5×(f2-f1) & f1)

[0050] (A4) The third-order mutual modulation between the frequency component f2 and the frequency component 6×(f2-f1) is the frequency component IM3 (6×(f2-f1) & f2)

[0051] In this way, when a multi-carrier signal including two carrier frequencies is amplified, the frequency of the frequency component IM2 of the secondary intermodulation deformation increases, and the higher harmonic components of relatively small orders enter the signal band. In addition, the higher harmonic components of the integral multiples of the frequency component IM2 produce a third-order intermodulation deformation between it and the fundamental wave, and this deformation enters the signal band. As a result, the quality of the multi-carrier signal is degraded and does not meet the standard of the multi-carrier signal.

[0052] In order to compensate for such deformation components, it is also possible to consider using the conventional digital distortion compensation system (DPD: Digital Pre-Distortion). However, if the frequency band that can be compensated by such a system does not cover the frequency of the deformation, the compensation of the deformation becomes insufficient, and the deformation compensation of the multi-carrier signal becomes difficult. For example, in the above-mentioned case (A1), in order to receive the frequencies 5f1 and 5f2 that are the source of the mutual modulation deformation, a band of 10 GHz, which is 5 times of 2 GHz, is required. Moreover, in the case of compensating for the fifth harmonic of the frequency component IM2, it is also necessary to receive the frequency f2-f1=2160MHz-1810MHz=350MHz that is the source of the generation. This case also requires a band of 2000-350MHz near 2 GHz, which is difficult to implement as a band of DPD for communication systems such as base stations. As DPD, it is necessary to process frequency components as small as 350MHz for 2 GHz (the center frequency of 2 carriers). That is, the DPD needs to impart distortion to the input signal input to the FET constituting the amplifier, and in order to compensate for the distortion, an operation in a band wider than the above-mentioned intended band is required.

[0053] On the other hand, according to the multi-stage amplifier 1 of this embodiment, the extracting circuit 9 extracts the amplifier M from the n-1 stage. n-1 The output signal of the first carrier frequency f1 is extracted from the frequency component IM2 of the differential frequency (f2-f1) equivalent to the difference between the first carrier frequency f1 and the second carrier frequency f2. This frequency component (compensation component) is adjusted in phase and intensity and then connected to the final amplifier M nThe output signal is combined. As a result, in the output of the final stage, the secondary mutual modulation deformation or the mixed modulation of its higher harmonics based on the components of the two fundamental waves can be sufficiently reduced. As a result, the quality of the output signal can be improved. Specifically, the frequency component IM2 of the secondary mutual modulation deformation can be reduced, and as a result, the higher harmonics and mutual modulation deformation based on the frequency component IM2 can also be reduced, so that the above-mentioned deformation components (A1) to (A4) in the output signal can be reduced. In particular, in the multi-stage amplifier 1, the transmitter 13 and the gain adjustment circuit 15 adjust the phase and amplitude in order to compensate for the frequency component IM2 contained in the output signal, so that the secondary mutual modulation deformation or the mixed modulation of its higher harmonics can be reliably reduced, and the quality of the output signal can be sufficiently improved.

[0054] As a structure for compensating for the distortion, a structure using a passive filter circuit as described in Japanese Patent Application Laid-Open No. 2000-252765 can be considered. In such a structure, a filter circuit needs to be added outside the device constituting the amplifier, which generates a parasitic resistance component. If the secondary intermodulation distortion component is attenuated, the fundamental wave component (carrier frequency component) may also be attenuated. In this embodiment, the amplifier M of the n-1th stage is made n-1 The output signal is branched and processed, and the processed signal is combined with the final amplifier M n The output of the DAC is combined, so this possibility does not exist.

[0055] In addition, as another structure, in order to compensate for the deformation, a compensation signal of the same amplitude and opposite phase as the harmonic of the frequency component IM2 generated by the device is injected into the circuit at the end of the amplifier device. In this case, a new signal source is required to generate the compensation signal, and it is also necessary to synchronize the compensation signal with the signal generated by the amplifier, which makes the structure of the amplifier complicated. In this embodiment, such a signal source is not required, nor is a mechanism for synchronizing them, and it is easy to implement with a simple structure and miniaturization.

[0056] Next, an example of a circuit configuration for extracting and combining the frequency component IM2 from the multi-carrier signal in the extraction circuit 9 of the multi-stage amplifier 1 is shown.

[0057] Figure 6 FIG. 2 shows an example of a configuration for extracting a signal in the extraction circuit 9. The extraction circuit 9 has an amplifier M formed at the n-1th stage. n-1 The output of the final amplifier M n The transmission path TP1 between the input and output is branched and connected to the inductor L Z and capacitor C ZThe structure of extracting the signal from port Port1 by a series circuit. The series circuit is an amplifier M from the n-1th stage n-1 The bandpass filter that extracts the frequency component IM2 from the output signal is an example of the filter circuit 11. This series circuit is configured to pass the frequency component IM2 but block the fundamental wave components f1 and f2 to avoid affecting the transmission characteristics of the carrier frequencies f1 and f2 in the transmission path TP1.

[0058] Figure 7 Show Figure 6 The calculation example of the signal transmission characteristic in the structure of is shown in FIG. The transmission characteristic A shows that the n-1th stage amplifier M n-1 The output goes to the final amplifier M n The input characteristics, transfer characteristics B show the n-1th stage amplifier M n-1 Here, for example, the inductor L Z The inductance is set to 39nH, the capacitor C Z The capacitance is set to 4.7 pF. Thus, in transmission characteristic A, the loss is sufficiently reduced to about 0.1 dB in the band including 2 GHz near the carrier frequency, and in transmission characteristic B, the loss at the frequency component IM2 of 350 MHz is the smallest, while on the other hand, the loss is sufficiently large near the carrier frequency of 2 GHz.

[0059] Figure 8 FIG. 2 shows an example of a configuration for combining the compensation signal of the frequency component IM2 in the extraction circuit 9. The extraction circuit 9 has a circuit structure in which the compensation signal of the frequency component IM2 is combined via an amplifier M formed in the final stage. n The output and output terminal P OUT The transmission path between the two branches forms a transmission path for bias voltage application, and the compensation signal of the frequency component IM2 is connected to the amplifier M n The output signal is combined into a structure. That is, in the final stage amplifier M n The output and output terminal P OUTIn between, two transmission paths TP2 and TP3 are formed in a straight line, and the two transmission paths TP2 and TP3 are connected by a capacitor C14 for DC isolation. In addition, three capacitors C11, C12, and C13 for output matching circuits are connected between the transmission path TP2 and the ground pattern GND, and a transmission path TP4 is formed by branching from the middle of the transmission path TP2 to the port Port2 for bias voltage application, and high-pass capacitors C15, C16, C17, and C18 are connected between the transmission path TP4 and the ground pattern GND. The port Port2 and the transmission path TP4 are also shared as a circuit for combining the compensation signal of the frequency component IM2. In this circuit, the transmission path TP4 has a transmission path length l from the branch point branched from the transmission path TP2 to the high-pass capacitor C15. The transmission path length l and the capacitance of the high-pass capacitors C15, C16, C17, and C18 are set in a manner that meets the following requirements: (1) The amplifier M n The transmission characteristic between the output and port Port2 allows the frequency component IM2 to pass through. (2) Amplifier M n The transmission characteristics between the output and port Port2 isolate the fundamental wave components f1 and f2, and (3) the transmission characteristics of the transmission path TP2 avoid attenuating the frequency components of the carrier frequencies f1 and f2 as much as possible.

[0060] Fig. 9 Show Figure 8 The signal transmission characteristic C is calculated from the final amplifier M. n Output to output terminal P OUT The transfer characteristic D represents the transfer characteristic from the final amplifier M n Thus, in the transmission characteristic C, the loss is sufficiently reduced to about 0.3 dB in the band including 2 GHz near the carrier frequency, and in the transmission characteristic D, the loss of the frequency component IM2 at the frequency of 350 MHz is the smallest, while on the other hand, near the carrier frequency of 2 GHz, the loss is sufficiently increased to prevent the carrier frequency component from flowing into the circuit for applying the bias.

[0061] Fig.10 The compensation signal of the frequency component IM2 in the extraction circuit 9 is shown to the amplifier M n Another configuration example for combining the output signals of Fig.10 In the structure shown, the circuit for signal combination and the circuit for bias application are provided separately. That is, a circuit connected by an inductor L is branched from the middle of the transmission path TP2 to the port Port3 for signal combination. Y and capacitor C YThe series circuit is a bandpass filter that allows the compensation signal of the frequency component IM2 to pass from the port Port3 to the transmission path TP2. In the series circuit, the inductor L Y The inductor and capacitor C Y The capacitance is set to a value that allows the frequency component IM2 to pass but blocks the fundamental wave components f1 and f2, thereby avoiding as much as possible the reduction of the frequency components of the carrier frequencies f1 and f2 in the transmission path TP2.

[0062] Fig.11 Show Fig.10 The signal transmission characteristic E is calculated from the final amplifier M. n Output to output terminal P OUT The transfer characteristic F represents the transfer characteristic from the final amplifier M n Here, for example, the inductor L Y The inductance is set to 15nH, the capacitor C Y The capacitance is set to 12pF. Thus, in the transmission characteristic E, the loss is sufficiently reduced to about 0.4dB in the band including 2GHz near the carrier frequency, and in the transmission characteristic F, the loss of the frequency component IM2 at the frequency of 350MHz is the smallest. On the other hand, in the vicinity of the carrier frequency of 2GHz, a sufficiently large loss is given to prevent the carrier frequency component from flowing into the circuit for signal combination.

[0063] The principles of the present disclosure are illustrated and described in the preferred embodiments above, but those skilled in the art will appreciate that the present invention may be modified in configuration and details without departing from such principles. The present invention is not limited to the specific structure of the present disclosure. Therefore, all modifications and changes within the scope of the claims and their subject matter are claimed.

[0064] In the above embodiment, the compensation signal of the frequency component IM2 is connected to the final amplifier M n The output of Fig.12 As in the multi-stage amplifier 1A of the modified example shown in FIG. 1 , the compensation signal of the frequency component IM2 is connected to the amplifier M at the final stage. n Specifically, in the multi-stage amplifier 1A, the output of the extraction circuit 9 is connected to the amplifier M of the final stage. n The output signal (compensation signal) of the extraction circuit 9 is combined with the input signal of the final amplifier Mn. Fig.12 The figure shows the amplifier M n-1 The output is directly connected to the amplifier M n input, but in reality, the amplifier M n-1The output of is connected to the amplifier M via a transmission path (transmission line) for example. n The input of amplifier M n The input signal does not n-1 The output signals are the same, with a delay (phase difference). Therefore, Fig.12 In the example, the amplifier M from the n-1th stage n-1 The output goes to the final amplifier M n The input through-line actually includes a transmission line or other structures similar to a transmission line. Therefore, Fig.12 The structure of the amplifier M n-1 The compensation signal of the frequency component IM2 generated by the output signal is connected to the amplifier M n For example, in the extraction circuit 9, the amplifier M n-1 The output signal propagates to the amplifier M n The input delay is adjusted by the amplifier M n-1 The output signal generates the phase of the compensation signal of the frequency component IM2.

[0065] Fig.13 FIG. 1 shows an example of a configuration for combining a compensation signal of the frequency component IM2 in the extraction circuit 9 provided in the multi-stage amplifier 1A. The extraction circuit 9 has a plurality of amplifiers IM2 formed in the n-1th stage. n-1 The output of the final amplifier M n The transmission path between the inputs of the amplifier M is branched to form a transmission path for bias voltage application, and the compensation signal of the frequency component IM2 is transmitted to the amplifier M n The input signal is combined into a wave structure. That is, in the n-1th stage amplifier M n-1 The output of the port Port4 is connected to the final stage amplifier M n Three transmission paths TP5, TP6, and TP7 are formed linearly between the inputs of the amplifier M1 and the outputs of the amplifier M2. The transmission paths TP5 and TP6 are connected by a resistor element R1 and a capacitor C21 constituting a high-pass filter, and the transmission paths TP6 and TP7 are connected by a capacitor C22 for DC blocking. In addition, two matching capacitors C23 and C24 are connected between the transmission path TP7 and the ground pattern GND. A transmission path TP8 is formed by branching from the middle of the transmission path TP7 to the port Port5 for applying the bias voltage. High-pass capacitors C25, C26, C27, and C28 are connected between the transmission path TP5 and the ground pattern GND. The port Port5 and the transmission path TP8 are also used as the input to the amplifier M2 of the compensation signal of the frequency component IM2. n In this circuit, the amplifier M nThe transmission characteristics between the input of the amplifier and the port Port5 are set by adjusting the transmission path length l from the branch point of the transmission path TP7 to the high-pass capacitor C25 and the capacitance values ​​of the high-pass capacitors C25, C26, C27, and C28 to meet the following requirements: (1) The amplifier M n-1 The frequency component IM2 of the output signal is passed through the amplifier M n-1 (3) the fundamental wave components f1 and f2 of the output signal are cut off, and the frequency components of the carrier frequencies f1 and f2 in the transmission path TP7 are avoided as much as possible.

[0066] Fig.14 Show Fig.13 The signal transmission characteristic G is calculated in the structure of the final amplifier M. n The transmission characteristic H represents the final amplifier M n The characteristic between the input of and port Port5. Thus, in the transmission characteristic G, the loss is sufficiently reduced to about 0.2 dB in the band including 2 GHz near the carrier frequency, and in the transmission characteristic H, the loss of the frequency component IM2 at the frequency of 350 MHz is the smallest. On the other hand, near the carrier frequency of 2 GHz, the loss is sufficiently increased to prevent the carrier frequency component from flowing into the circuit for applying the bias.

[0067] Fig.15 FIG. 10 shows the input of the compensation signal of the frequency component IM2 in the extraction circuit 9 provided in the multi-stage amplifier 1A to the amplifier M. n Another structure used to combine signals. Fig.15 In the structure shown, the circuit for signal combination and the circuit for bias application are provided separately. That is, a signal combination circuit is branched and connected between the transmission path TP7 and the port Port6 for signal combination. X and capacitor C X The series circuit is a bandpass filter that allows the signal of the frequency component IM2 to pass from the port Port6 to the transmission path TP7. The series circuit is connected to the transmission path TP7 by an inductor L X The inductor and capacitor C X The capacitor allows the frequency component IM2 to pass through and isolates the fundamental wave components f1 and f2, thereby avoiding affecting the transmission characteristics at the carrier frequencies f1 and f2 in the transmission path TP7.

[0068] Fig.16 Show Fig.15 The signal transmission characteristic calculation example in the structure of FIG. The transmission characteristic I represents the final stage amplifier M n The transmission characteristic J represents the final amplifier Mn Here, for example, the inductor L X The inductance is set to 39nH, the capacitor C X The capacitance is set to 4.7pF. Thus, in the transmission characteristic I, the loss is sufficiently reduced to about 0.4dB in the band including 2GHz near the carrier frequency, and in the transmission characteristic J, the loss of the frequency component IM2 at the frequency of 350MHz is the smallest. On the other hand, near the carrier frequency of 2GHz, the loss is sufficiently increased to prevent the carrier frequency component from flowing into the circuit for signal combination.

[0069] In the above-mentioned multi-stage amplifier 1, 1A, it is not limited to the amplifier M in the n-1th stage. n-1 The output of the final amplifier M n The structure of the extraction circuit 9 can be configured between the input or output of the amplifier M of the i-th stage (i is a natural number satisfying 1≤i≤n-1). i The output of the i+1th stage amplifier M i+1 An extraction circuit 9 is configured between the input or output. In such a structure, also in the output of the i+1th stage, the secondary mutual modulation deformation based on the components of the two fundamental waves or the mixed modulation of their higher harmonics can be sufficiently reduced, resulting in the improvement of the quality of the output signal of the final stage.

[0070] In addition, the filter circuit 11 of the extraction circuit 9 extracts the frequency component IM2 of the differential frequency (f2-f1) corresponding to the difference between the first carrier frequency f1 and the second carrier frequency f2 from the multi-carrier signal, but it is also possible to extract the frequency component of m times (an integer satisfying 2≤m≤5) of the differential frequency (f2-f1). In this case, the mixed modulation of the higher harmonics of the secondary mutual modulation deformation can be sufficiently reduced, and the quality of the output signal can be improved. In this structure, the frequency component of 5 times the differential frequency (f2-f1) in the output signal of the final stage is reduced by the phase adjustment of the transmitter 13 and the amplitude adjustment of the gain adjustment circuit 15. As a result, the mutual modulation deformation between the deformation component of m times the frequency component IM2 injected by the extraction circuit 9 and the (5-m)th harmonic of the frequency component IM2 is generated, and the fifth harmonic of the frequency component IM2 can be compensated. Therefore, the above-mentioned deformation components (A1) and (A3) that affect the signal quality can be reduced, and the quality of the output signal can be sufficiently improved.

[0071] In particular, it is preferred that the filter circuit 11 of the extraction circuit 9 extracts a frequency component of five times the differential frequency (f2-f1) from the multi-carrier signal, and the frequency component of five times the differential frequency (f2-f1) in the output signal of the final stage is reduced as much as possible through phase adjustment of the transmitter 13 and amplitude adjustment of the gain adjustment circuit 15. In this case, the above-mentioned deformation components (A1) and (A3) that affect the signal quality can be reduced, and the quality of the output signal can be improved.

Claims

1. A multi-stage amplifier for amplifying a multi-carrier signal, the multi-carrier signal comprising a first component having a first frequency f1 and a second component having a second frequency f2, The multi-stage amplifier has: N amplifiers are respectively divided into amplifiers of the i-th stage, and the amplifier of the k+1-th stage is cascade-connected to the amplifier of the k-th stage, and each amplifier amplifies the multi-carrier signal, wherein, N is an integer greater than 2, i is an integer from 1 to N, 1≤k≤N-1; and A compensation circuit having an input and an output, wherein the input is connected to the output of the j-th amplifier, and the output provides a compensation signal to the input of the j+1-th amplifier or the output of the j+1-th amplifier, wherein j is an integer from 1 to N-1, The compensation circuit has: a filter circuit connected to the output of the j-th amplifier, which is a series circuit of an inductor and a capacitor branched and connected from the middle of a transmission path between the output of the j-th amplifier and the input of the j+1-th amplifier, wherein the series circuit is configured to remove fundamental wave components of the first frequency f1 and the second frequency f2 from the multi-carrier signal output by the j-th amplifier and extract a deformed frequency component of n times the differential frequency f2-f1, wherein n is an integer greater than or equal to 1; a phase shifting circuit connected in series to the output of the series circuit to shift the phase of the deformed frequency component; and an amplitude adjustment circuit connected in series with the output of the phase shift circuit, adjusting the amplitude of the deformation frequency component to generate the compensation signal, The compensation circuit has a transmission path connected to the output branch of the j+1th amplifier and used to apply a bias voltage to the j+1th amplifier, and the output of the amplitude adjustment circuit is connected to the transmission path and combined with the output of the j+1th amplifier. A plurality of high-pass capacitors (C15, C16, C17, C18) are connected between the transmission path (TP4) and the ground pattern (GND), and a transmission path length (l) from a branch point to a high-pass capacitor (C15) closest to the branch point among the plurality of high-pass capacitors and capacitances of the plurality of high-pass capacitors (C15, C16, C17, C18) are set in a manner that satisfies the following requirements: a transmission characteristic between an output of the j+1th stage and a port (Port2) for applying a bias voltage allows the deformed frequency component to pass but cuts off a fundamental wave component.

2. A multi-stage amplifier for amplifying a multi-carrier signal, the multi-carrier signal comprising a first component having a first frequency f1 and a second component having a second frequency f2, The multi-stage amplifier has: N amplifiers are respectively divided into amplifiers of the i-th stage, and the amplifier of the k+1-th stage is cascade-connected to the amplifier of the k-th stage, and each amplifier amplifies the multi-carrier signal, wherein, N is an integer greater than 2, i is an integer from 1 to N, 1≤k≤N-1; and A compensation circuit having an input and an output, wherein the input is connected to the output of the j-th amplifier, and the output provides a compensation signal to the input of the j+1-th amplifier or the output of the j+1-th amplifier, wherein j is an integer from 1 to N-1, The compensation circuit has: a filter circuit connected to the output of the j-th amplifier, which is a series circuit of an inductor and a capacitor branched and connected from the middle of a transmission path between the output of the j-th amplifier and the input of the j+1-th amplifier, wherein the series circuit is configured to remove fundamental wave components of the first frequency f1 and the second frequency f2 from the multi-carrier signal output by the j-th amplifier and extract a deformed frequency component of n times the differential frequency f2-f1, wherein n is an integer greater than or equal to 1; a phase shifting circuit connected in series to the output of the series circuit to shift the phase of the deformed frequency component; and an amplitude adjustment circuit connected in series with the output of the phase shift circuit, adjusting the amplitude of the deformation frequency component to generate the compensation signal, The compensation circuit further includes a transmission path that branches and connects between the output of the j-th amplifier and the j+1-th amplifier and is used to apply a bias voltage to the j-th amplifier. The output of the amplitude adjustment circuit is connected to the bias voltage application transmission path and combined with the input of the j+1-th amplifier. A plurality of high-pass capacitors (C25, C26, C27, C28) are connected between the transmission path (TP8) to which the bias is applied and the ground pattern (GND), and a transmission path length (l) from a branch point to a high-pass capacitor (C25) closest to the branch point among the plurality of high-pass capacitors and capacitances of the plurality of high-pass capacitors (C25, C26, C27, C28) are set in a manner that satisfies the following requirements: a transmission characteristic between an input of the j+1th stage and a port (Port5) for applying a bias voltage allows the deformed frequency component to pass but cuts off a fundamental wave component.

3. The multi-stage amplifier according to claim 1 or 2, wherein: The phase shift circuit and the amplitude adjustment circuit minimize the deformation frequency component of n times the differential frequency f2-f1 included in the output of the multi-stage amplifier.

4. The multi-stage amplifier according to claim 1 or 2, wherein: The series circuit extracts a deformation frequency component that is 1 times the differential frequency f2-f1.

5. The multi-stage amplifier according to claim 1 or 2, wherein: The series circuit extracts a deformation frequency component that is five times the differential frequency f2-f1.

6. The multi-stage amplifier according to claim 1 or 2, wherein: The amplifier of the j+1th stage is the amplifier of the Nth stage, and the amplifier of the jth stage is the amplifier of the N-1th stage.

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