JPH0828619B2 - Feed forward amplifier - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feed-forward amplifier, and more particularly to a multi-frequency input which detects distortion in an amplified signal generated by simultaneously amplifying a multi-frequency input signal and suppresses the detected distortion to amplify it. The present invention relates to a feedforward amplifier that outputs a signal.

[0002]

2. Description of the Related Art In general, a feedforward amplifier is
The distortion detection loop detects the distortion in the amplified signal generated by simultaneously amplifying the multi-frequency input signal, suppresses the detected distortion by the distortion removal loop, and outputs the amplified multi-frequency input signal. However, because the characteristics of the amplifier fluctuate due to fluctuations in the ambient temperature, it is extremely difficult to maintain the balance of the two feedforward loops (the distortion detection loop and the distortion removal loop) in a timely manner. Therefore, the characteristics deteriorate due to the ambient temperature and the like.

Therefore, a feedforward amplifier provided with a means for injecting a pilot signal of a specific frequency into a distortion detection loop in order to perform a more stable operation with respect to fluctuations in ambient temperature and the like has been conventionally known (special feature: Kaihei 1-19
8809). FIG. 4 is a block diagram showing an example of this conventional feedforward amplifier. In the figure, the multi-frequency input signal from the input terminal 1 is input to the distortion detection loop A through the first directional coupler 2, amplified here, and
After the distortion component is detected, it is input to the distortion removal loop B via the power combiner 21.

A pilot signal of a specific frequency from the pilot oscillator 3 is injected into the distortion detection loop A through the directional coupler 2. The output signal of the distortion removal loop B is output to the output terminal 31 through the directional coupler 29.

The above distortion detection loop A is composed of the power distributor 4
Divides the input signal into two, one of which is the pilot oscillator 1
5 is input to the power combiner 21 through the second directional coupler 14 for applying the second pilot signal from the main amplifier 16 and the main amplifier 16, and the other is connected to the first delay line 18, the first variable attenuator 19, and In the configuration, the first variable phase shifter 13 is input to the power combiner 21 via the route sequentially arranged.

Further, the distortion elimination loop B is provided with a second delay line 22 for delaying the output signal of the main amplifier 16 and a third directional coupler 23 arranged in the transmission path of the power-combined signal. , Second variable attenuator 25, second variable phase shifter 26, auxiliary amplifier 27, and fourth directional coupler 28 to which both output signals of second delay line 22 and auxiliary amplifier 27 are input. Consists of. The output terminal of the fourth directional coupler 28 is connected to the output terminal 31 via the fifth directional coupler 29.

Further, a pilot receiver 24 for receiving a pilot signal from the signal extracted from the directional coupler 23, a pilot receiver 30 for receiving a pilot signal from the signal extracted from the directional coupler 29, Based on the outputs of these pilot receivers 24 and 30,
A control circuit 32 for controlling the first variable attenuator 19 and the first variable phase shifter 20 or the second variable attenuator 25 and the second variable phase shifter 26 is provided.

Next, the operation of this conventional feedforward amplifier will be described with reference to FIG. Here, for simplicity, the multi-frequency input signal input to the input terminal 1 is shown in FIG.
As shown in (A), a frequency-multiplexed signal of two waves with frequencies f ₁ and f ₂ is used. This multi-frequency input signal is multiplexed with the pilot signal p ₁ from the pilot oscillator 3 by the directional coupler 2 to be a signal having the frequency spectrum shown in FIG. 6 (B), and then divided by the power divider 4. .

One of the two split signals is a directional coupler 1.
4 to the main amplifier 16 where it is amplified to a specified value. The frequency spectrum of the output signal of the main amplifier 16 includes the third-order intermodulation distortion and the fifth-order intermodulation distortion due to amplification as shown in FIG. 6 (C). The pilot signal p ₁ is not shown in FIG. 6 (C). This is because the pilot signal p ₁ is multiplexed with the input signal at a predetermined time interval.

Further, the other signal divided into two is given a delay amount equivalent to the delay amount to the main amplifier 16 by the delay line 18, and then, by the output of the D / A converter which is a constituent element of the control circuit 32. Variable attenuator 19 and variable phase shifter 2 controlled
0 controls the level and phase.

The power combiner 21 is shown in FIG.
The amplified signal of the frequency spectrum shown in (C) and the signal of the frequency spectrum shown in FIG. 6 (B) from the variable attenuator 20 are input, and after passing through a certain level of attenuation, the amplified signal is directly output from the first output terminal. A signal obtained by canceling the multi-frequency input signals f ₁ and f ₂ as shown in FIG. 6 (E) by outputting and supplying to the delay line 22, and performing reverse phase synthesis of the amplified signal and the output signal of the variable attenuator 20. (That is, the distortion component included in the amplified signal) from the second output terminal to the directional coupler 2
3 to the pilot receiver 24 and the variable attenuator 25.

The pilot receiver 24 detects a voltage proportional to the reception level of the pilot signal p ₁ generated by the pilot oscillator 3 and outputs it to the control circuit 32. The above is the operation of the distortion detection loop A.

The output of the directional coupler 23 is applied to the auxiliary amplifier 27 via the variable attenuator 25 and the variable phase shifter 26 controlled by the control circuit 32, where the distortion component (see FIG. 6).
(E)) is amplified to a specified value and input to the backward directional coupler 28. On the other hand, the amplified signal input to the delay line 22 is provided with the same delay amount as the delay amount of the path from the second output terminal of the power combiner 21 to the output terminal of the auxiliary amplifier 27, and then the directivity is changed. It is supplied to the combiner 28.

The directional coupler 28 synthesizes these input signals in anti-phase and outputs an amplified signal in which the distortion component is canceled, as shown in FIG. 6 (F). This output signal is output to the output terminal 31 via the directional coupler 29 and also to the pilot receiver 30. Pilot receiver 30
Is the pilot signal p ₂ generated by the pilot oscillator 15.
Detection circuit outputs a voltage proportional to the reception level of the control circuit 3
2 is applied. The above is the operation of the distortion removal loop.

The control circuit 32 performs the following control operation to maintain the operation of the feedforward amplifier in the best condition.

First, the pilot signal oscillator 3 is first operated to apply the pilot signal p ₁ to the directional coupler 2. Next, the control circuit 32 converts the detection output from the pilot receiver 24, which receives the pilot signal p ₁ combined by the directional coupler 23, by an internal A / D converter or the like, and based on this, the pilot receiver 24 The control amounts of the variable attenuator 19 and the variable phase shifter 20 are set so that the detection output signal level of 1 is minimized. At this time, the input signal of the directional coupler 23 is erased with the pilot signal p ₁ together with the carrier signal as shown by the broken line in FIG. 6 (E).

Next, the control circuit 32 controls the pilot oscillator 3
And the pilot signal p ₂ is applied from the pilot oscillator 15 to the directional coupler 14. This allows
The output amplified signal of the main amplifier 16 is as shown in FIG. The output signal of the variable phase shifter 20 is shown in FIG.
It is assumed that the frequency spectrum in p ₁ of the omission, the input signal of the directional coupler 23, becomes a pilot signal p ₂ is shown by the solid line to the position of the broken line in the frequency spectrum of FIG. 6 (E). Therefore, at this time, the directional coupler 28
6F, the pilot signal p ₂ is shown as a solid line at the position of the broken line in the frequency spectrum of FIG. 6F, and appears as an output.

The output signal of the directional coupler 28 is supplied to the pilot receiver 30 through the directional coupler 29, and the pilot signal p ₂ is received and detected. The control circuit 32 outputs the detection output from the pilot receiver 30 to the internal A
The value is converted by the / D converter or the like, and the control amounts of the variable attenuator 25 and the variable phase shifter 26 are set so that the detection output signal level of the pilot receiver 30 is minimized based on the conversion.

As a result, the output signal of the directional coupler 28 is erased as shown by the broken line in the pilot signal p ₂ as shown in FIG. 6 (F), and at the same time, the distortion component in the amplified signal is also erased. The amplified multi-frequency input signal without distortion is output to the output terminal 31.

Therefore, the phase and amplitude characteristics of each component in the loop represented by the main amplifier 16 and the auxiliary amplifier 27 are as follows.
The characteristics of the feedforward amplifier can be optimally maintained by periodically performing the above control by the control circuit 32 even if the characteristics change with temperature or aging.

FIG. 5 shows a block diagram of an example of an input system of this conventional feedforward amplifier. Here, a multi-frequency signal of 8 waves is synthesized, and the feedforward amplifier 50
Shows the input system to be input to. The signal generators 33 to 40 generate signals having different frequencies. The signals generated by the signal generators 33 and 34 are respectively generated by the power combiner 41.
And then applied to the power combiner 45. Also,
The signals generated from the signal generators 35 and 36 are combined by the power combiner 42 and then applied to the power combiner 45.

Similarly, the signals from the signal generators 37 and 38 are combined by the power combiner 43, and the signals from the signal generators 39 and 40 are combined by the power combiner 44. It is applied to the combiner 46. The four-wave signal combined by the power combiner 45 and the four-wave signal combined by the power combiner 46 are respectively supplied to the power combiner 49 and further combined to form an eight-wave combined signal. , Feedforward amplifier 50. The feedforward amplifier 50 has the structure shown in FIG. 4, and amplifies the frequency-multiplexed signal of 8 waves by the above-described operation and outputs the amplified signal to the output terminal 48.

[0023]

The above-mentioned conventional feedforward amplifier does not output a distortion component to the output terminal 31 as long as it performs an ideal operation according to the principle of the feedforward method. Further, even if the characteristics in the loop change due to temperature or the like, the characteristics are corrected by the control operation of the control circuit 32, so that it looks like an ideal state.

Here, when it is attempted to secure a signal distortion amount of -60 dB or more with respect to the input signal amplitude, the distortion amount generated in the main amplifier 16 is -30 dB or more.
If the amount of compensation by feedforward is set to -30 dB or more, the two output paths of the power distributor 4, that is, the first path in which the directional coupler 14 and the main amplifier 16 are arranged, the delay line 18, the variable attenuator 19 are provided. And variable phase shifter 20
It is necessary to keep the amplitude deviation within ± 0.3 dB and the phase deviation within ± 2 ° with respect to the second path in which is arranged.

However, in the above-mentioned conventional feedforward amplifier, since the pilot signal is one wave in the multi-frequency input signal band, if the pilot signal is set to the center frequency of the desired band and the amplitude and phase are controlled. If the amplitude / phase characteristic of the main amplifier 16 is not adjusted within ± 0.3 dB and within ± 2 ° in the desired band, for example, 10 MHz, the compensation amount becomes -30 dB only at the point frequency where the pilot signal is arranged, If deviated from this frequency, it is not possible to secure a compensation amount of -30 dB by feedforward.

For example, assuming that the amplitude-frequency characteristic of the main amplifier 16 is such that the amplitude decreases above the number of turns of the pilot signal p ₁ as shown in FIG. 7 (G), it is input to the input terminal 1. The multi-frequency input signal composed of the frequencies f ₁ and f _{2 of} equal amplitude shown in FIG. 7A is combined with the pilot signal p ₁ by the directional coupler 2 to form the signal shown in FIG. 7B. When supplied to the amplifier 16 and amplified, the frequency spectrum of the output amplified signal of the main amplifier 16 has a frequency f ₂ lower than f ₁ as shown in FIG.
Even when the pilot signal p ₂ is input through the directional coupler 14, the frequency f ₂ is changed to f ₁ as shown in FIG. 7D.
Lower.

Therefore, the input frequency f ₂ remains in the signal output from the power combiner 21 to the directional coupler 23, as shown in FIG. 7 (E). Therefore, as shown in FIG. 7F, the output signal of the directional coupler 29 is a signal in which the amplitudes of the frequencies f ₁ and f ₂ are not equal, and the distortion remains unerased.

The present invention has been made in view of the above points,
A feedforward amplifier that solves the above problems is provided by providing a plurality of input terminals of the feedforward amplifier and sequentially inputting different pilot signals to the distortion detection loop from each input terminal to adjust the components of the distortion detection loop sequentially. The purpose is to do.

[0029]

In order to solve the above problems, the present invention provides n (n is an integer of 2 or more) input terminals to which two or more input signals of one or different frequencies are input. And a first pilot signal generating means for generating a plurality of pilot signals of different frequencies, and n power distributors provided corresponding to the input terminals, respectively for distributing at least n input signals from the input terminals. And a first adjusting means for performing relative amplitude and phase shift adjustment for each one of the divided output signals of the n power dividers, and each signal adjusted by the first adjusting means. A first power combiner; second pilot signal generating means for generating a pilot signal to be multiplexed with the output signal of the first power combiner; and an output signal of the first power combiner or a second output signal of the output signal. Main amplifier for amplifying a signal in which pilot signals from the pilot signal generating means are multiplexed, amplitude and phase shift adjustment relative to other distribution output signals of the n power dividers, and the main amplifier It comprises a second adjusting means for performing a delay process for time adjustment with respect to an input signal, a second power combiner, a distortion removing loop and a controlling means.

The second power combiner outputs the output amplified signal of the main amplifier as it is from the first output terminal, and outputs a reverse phase combined signal of the output amplified signal and the output signal of the second adjusting means. Output from the second output terminal. The distortion removal loop is based on both output signals of the first and second output terminals of the second power combiner, and is an amplified signal in which distortion is removed and input signals of the n input terminals are multiplexed. Is output.

Then, the control means sequentially multiplexes the pilot signals from the first pilot signal generating means with the corresponding input signals of the n input terminals, and the second signal of the second power combiner. The pilot signal is received and detected from the output signal of the output terminal, and the adjustment amount by the first or second adjusting means is controlled so that the pilot signal level is minimized, and then the second pilot signal generating means outputs the pilot signal. The pilot signal is multiplexed with the output signal of the first power combiner, the pilot signal is received and detected from the output amplified signal of the distortion removal loop, and the transfer function of the distortion removal loop is minimized so that the pilot signal level is minimized. Variably controlled.

[0032]

In the present invention, the control means first multiplexes the pilot signal from the first pilot signal generating means with the input signal of the first input terminal of the corresponding n input terminals, and this multiplex signal is multiplexed. Inputting a signal to the main amplifier through the first adjusting means and the first power combiner,
Further, it is input to the second power combiner. Then, the control means receives and detects the pilot signal from the output signal of the second output terminal of the second power combiner, and controls the adjustment amount by the first adjusting means so that the pilot signal level is minimized. . As a result, the amplitude-frequency characteristic of the main amplifier seen from the first input terminal can be a predetermined characteristic near the pilot signal frequency.

Similarly, the control means sequentially multiplexes the corresponding pilot signals with respect to the input signals of the other input terminals of the n input terminals, and outputs the output of the second output terminal of the second power combiner. A pilot signal is received and detected from the signal, and the adjustment amount by the first or second adjusting means is controlled so that the pilot signal level is minimized. As a result, the amplitude-frequency characteristics of the main amplifier seen from the other input terminals can be made to have predetermined characteristics near the pilot signal frequency. Therefore, according to the present invention, the amplitude-frequency characteristic of the main amplifier can be corrected.

[0034]

1 is a block diagram of an embodiment of a feedforward amplifier according to the present invention. In the figure, parts that are the same as the parts shown in FIG. 4 are given the same reference numerals, and descriptions thereof will be omitted. In the embodiment shown in FIG. 1, the configuration of the distortion removal loop B is the same as the conventional one, but the configuration of the distortion detection loop C is different from the conventional one. 1 and 7 are the input terminals of the feedforward amplifier,
It is connected to the power distributors 4 and 10 via the directional couplers 2 and 8. The pilot signal is input to the directional coupler 8 from the pilot oscillator 9. The output pilot signal of the pilot oscillator 9 is the first pilot signal from the pilot oscillator 3.
The pilot signal p _a a second pilot signal p _b of different frequencies. However, these pilot signals p _a and p _b are set to a level near the distortion component (−60 dB) at frequencies near the multi-frequency input signal.

The power distributor 4 divides the input signal into two parts, a first output path and a second output path, and a fixed attenuator 5 and a fixed phase shifter 6 are arranged in the first output path to form a power combiner. The power combiner 17, the delay line 18, the variable attenuator 19 and the variable phase shifter 20 are arranged in the second output path and are connected to the power combiner 21. On the other hand, the power distributor 10 divides the input signal into two parts, a third output path and a fourth output path, and a variable attenuator 11 and a variable phase shifter 12 are arranged in the third output path, and the power combiner 13 is provided. The fourth output path is the same as the second output path, and the power combiner 17, delay line 18, variable attenuator 19 and variable phase shifter 20 are arranged and connected to the power combiner 21. Has been done.

The power combiner 13 is connected to the power combiner 21 via the directional coupler 14 and the main amplifier 16.
The above is the configuration of the distortion detection loop C. The control circuit 55, like the conventional control circuit 32, includes the variable attenuator 19, the variable phase shifter 20, the variable attenuator 25, and the variable phase shifter 26.
And the operation of the pilot oscillators 3 and 15 are controlled, and in the present embodiment, the variable attenuator 11 and the variable phase shifter 12 are also controlled, and the operation of the pilot oscillator 9 is controlled. The pilot oscillators 3, 9 and 1
In the operation control of 5, the oscillation operation itself may be controlled, or the oscillation output may be controlled by passing or blocking the oscillation output.

Next, the operation of this embodiment will be described with reference to the characteristic diagram of FIG. 3 (A) to 3 (F) are frequency spectra of the signals of the respective parts in FIG. 1, and FIG. 3 (G) is the main amplifier 16.
The amplitude-frequency characteristic of FIG. 3 (H) shows the input signal spectrum of the main amplifier 16 after adjusting the variable attenuator 11 and the variable phase shifter 12.

In FIG. 1, the input signal of the frequency f ₁ indicated by a1 in FIG. 3A input to the input terminal 1 is the same as the first pilot signal p _a multiplexed by the directional coupler 2. The power distributor 4 after the multiple signal shown by b1 in FIG.
Is supplied to. Multiplexed signal b divided by the power divider 4
One of the two is attenuated by a fixed value by a fixed attenuator 5 and further phase-shifted by a fixed value by a fixed phase shifter 6, and then the power combiner 1
3, and is supplied to the main amplifier 16 through the directional coupler 14 and amplified.

The other side of the multiplex signal b1 divided into two by the power distributor 4 is output from the output terminal of the power combiner 4 by the power combiner 17, the delay line 18, the variable attenuator 19 and the variable phase shifter 20. A delay amount of the same time as the signal delay time until reaching the input terminal of the main amplifier 16 is added, and the amplitude and phase are further controlled and then input to the power combiner 21.

On the other hand, FIG. 3A input to the input terminal 7
The input signal of the frequency f ₂ indicated by a2 in FIG.
The second pilot signal p _b is multiplexed at
Then, it is supplied to the power distributor 10 after being converted into a multiplexed signal indicated by b2. One of the multiplex signals b2 divided into two by the power distributor 10 is attenuated by the variable attenuator 11, further phase-shifted by the variable phase shifter 12, and then is mainly passed through the power combiner 13 and the directional coupler 14. It is supplied to the amplifier 16 and amplified.

As a result, the main amplifier 16 causes the signal b
The frequency-multiplexed signals 1 and b2 are simultaneously amplified, and the amplified signal having the frequency spectrum shown by c in FIG. 3C or the frequency spectrum shown by d in FIG. 3D is output. However, the frequency spectrum c does not show the pilot signal, and the frequency spectrum d shows the frequency spectrum when the pilot signal p from the directional coupler 15 is input. In any case, the third-order, fifth-order, or other intermodulation distortion occurs due to the amplification of the multi-frequency signal.

On the other hand, the other of the multiplexed signal b2 divided into two by the power divider 10 is composed of the power combiner 17, the delay line 18, the variable attenuator 19 and the variable phase shifter 20, and the power combiner 1
The delay amount of the same time as the signal delay time from the output terminal of 0 to the input terminal of the main amplifier 16 is added, and the amplitude and the phase are further controlled and then input to the power combiner 21.

As described with reference to FIG. 4, the power combiner 21 provides the output amplified signal of the main amplifier 16 with a certain amount of passing attenuation and supplies it from the first output terminal to the delay line 22. A signal obtained by synthesizing the output amplified signal of 1 and the output signal of the variable phase shifter 20 in anti-phase is supplied to the directional coupler 23 from the second output terminal. Thereafter, the amplified signal is output to the output terminal 31 through the operation of the distortion removal loop B similar to the conventional one.

Next, the control operation by the control circuit 55 will be described. First, first, the pilot signal oscillator 3 is operated to apply the pilot signal p _a to the directional coupler 2. Next, the control circuit 55 converts the detection output from the pilot receiver 24, which receives the pilot signal p _a combined by the directional coupler 23, by an internal A / D converter or the like, and based on this, the pilot receiver 24 The control amounts of the variable attenuator 19 and the variable phase shifter 20 are set so that the detection output signal level of 1 is minimized. At this time, the input signal of the directional coupler 23 is erased with the pilot signal p _a together with the carrier signal as shown in FIG. In addition,
At this time, p _b and p do not exist in FIG.

Next, the control circuit 55 controls the pilot oscillator 3
Is cut off, and the pilot signal p _b is applied from the pilot oscillator 9 to the directional coupler 8. The control circuit 55 then controls the pilot signal p _b combined by the directional coupler 23.
The detection output from the pilot receiver 24 for receiving the signal is converted by an internal A / D converter or the like, and based on this, the variable attenuator 11 and the variable shifter 11 are arranged so that the detection output signal level of the pilot receiver 24 is minimized. The control amount of the phase shifter 12 is set.
At this time, the input signal of the directional coupler 23 is erased as well as the pilot signal p _b as shown by the broken line together with the carrier signal as shown in FIG. At this time, Fig. 3
In (E), p _a and p do not exist.

By the above control, as shown in FIG. 3G, the frequency spectrum of the input signal of the main amplifier 16 showing the frequency characteristic that the frequency f ₂ has a smaller amplitude by Δ than the frequency f ₁ is shown in FIG. As shown in (H), the frequency f ₂ becomes larger than the frequency f ₁ by Δ.

Next, the control circuit 55 controls the pilot oscillator 3
The outputs of 9 and 9 are turned off, and the pilot signal p is applied from the pilot oscillator 15 to the directional coupler 14. As a result, the output signal of the variable phase shifter 20 is p _a,
p _b disappears, and the input signal of the directional coupler 23 has the pilot signal p indicated by the solid line at the position of the broken line in the frequency spectrum e of FIG. 3 (E) and appears as the output (at this time, p _a , p _b does not exist). Therefore, at this time, the output signal of the directional coupler 28 has the pilot signal p indicated by the solid line at the position of the broken line in the frequency spectrum f of FIG. 3 (F) and appears as the output (at this time, p _a , p _b
Does not exist).

The output signal of the directional coupler 28 is supplied to the pilot receiver 30 through the directional coupler 29, and the pilot signal p is received and detected. Control circuit 5
5 indicates the detection output from the pilot receiver 30 as an internal A /
It is converted by a D converter or the like, and based on this, the pilot receiver 3
The control amounts of the variable attenuator 25 and the variable phase shifter 26 are set so that the detection output signal level of 0 becomes the minimum.

As a result, the output signal of the directional coupler 28 is erased as shown in FIG. 3 (F) by eliminating the pilot signal p as indicated by the broken line, and at the same time, the distortion component in the amplified signal is also erased. The amplified multi-frequency input signal with no noise is output to the output terminal 31.

Therefore, the phase and amplitude characteristics of each component in the loop represented by the main amplifier 16 and the auxiliary amplifier 27 are as follows.
The characteristics of the feedforward amplifier can be optimally maintained by periodically performing the above control by the control circuit 32 even if the characteristics change with temperature or aging.

Moreover, according to this embodiment, the main amplifier 16
Has a frequency f as shown in FIG.
Even if it is a high-frequency attenuation characteristic that attenuates at a frequency f ₂ higher than ₁ ,
The input signal spectrum of the main amplifier 16 can have a higher frequency f ₂ than the frequency f _{1 as} shown in FIG. 3 (H). Therefore, the amplitude-frequency characteristics of the main amplifier 16 are equivalent to the frequency f ₁ Can be corrected to a characteristic exhibiting substantially equal amplitude at frequency f ₂ .

FIG. 2 shows a block diagram of an input system of an embodiment of the feedforward amplifier of the present invention. 8 here
An input system for synthesizing multi-frequency signals of waves and inputting them to the feedforward amplifier 47 having the configuration shown in FIG. 1 is shown. Figure 5
Similarly, the signals generated from the signal generators 33 and 34 are combined in the power combiner 41 and then applied to the power combiner 45, and the signals generated from the signal generators 35 and 36 are , Which are respectively combined by the power combiner 42 and then applied to the power combiner 45.

Similarly, the signals from the signal generators 37 and 38 are combined by the power combiner 43, and the signals from the signal generators 39 and 40 are combined by the power combiner 44. It is applied to the combiner 46. The four-wave signal combined by the power combiner 45 and the four-wave signal combined by the power combiner 46 are separately provided to the first input terminal and the second input terminal of the feedforward amplifier 47, respectively. Is entered. The feedforward amplifier 47 amplifies the eight-wave frequency-multiplexed signal by the operation described with reference to FIGS. 1 and 3 and outputs it to the output terminal 48.

The present invention is not limited to the above embodiment, and the number of input terminals of the feedforward amplifier may be three or more, for example. In this case, when the input signal of each input terminal is in the high frequency band on the level attenuation side in the amplitude-frequency characteristic of the main amplifier 16, the system from the input terminal 7 to the variable phase shifter 12 is added. If not, a system from the input terminal 1 to the fixed attenuator 6 is added.

[0055]

As described above, according to the present invention,
Since the amplitude-frequency characteristics of the main amplifier can be corrected, only the distortion component mainly generated by commonly amplifying the frequency-multiplexed signal of a plurality of input signals by the main amplifier,
It can be taken out from the second output terminal of the second power combiner, and therefore, the amount of distortion cancellation of the distortion elimination loop for each of the plurality of input signals can be optimized,
It has the feature that it greatly contributes to improving the reliability of the feedforward amplifier.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of an input system according to an embodiment of the present invention.

3 is a frequency spectrum of a signal of each part of FIG. 1 and an amplitude-frequency characteristic of a main part.

FIG. 4 is a configuration diagram of a conventional example.

FIG. 5 is a block diagram of an input system of a conventional example.

6 is a diagram showing a frequency spectrum of a signal of each part in FIG.

FIG. 7 is a frequency spectrum of a signal of each part of FIG. 4 and an amplitude-frequency characteristic of a main part for explaining a conventional problem.

[Explanation of symbols]

 1 First Input Terminal 2, 8, 14, 23, 28, 29 Directional Coupler 3, 9, 15 Pilot Oscillator 4, 10 Power Divider 5 Fixed Attenuator 6 Fixed Phase Shifter 7 Second Input Terminal 11 , 19, 25 Variable attenuator 12, 20, 26 Variable phase shifter 13, 17, 21 Power combiner 16 Main amplifier 18, 22 Delay line 24, 30 Pilot receiver 27 Auxiliary amplifier 31 Output terminal 55 Control circuit

Claims (2)

[Claims] 1. n pieces (where n is an integer of 2 or more) to which two or more input signals of one or different frequencies are input
Input terminals, first pilot signal generating means for generating a plurality of pilot signals of different frequencies, and n number of input terminals are provided corresponding to the input terminals, respectively, and at least the input signals from the input terminals are distributed by n. Power divider, first adjusting means for performing relative amplitude and phase shift adjustment with respect to each one distribution output signal of the n power dividers, and the first adjusting means. A first power combiner for combining the respective signals, a second pilot signal generating means for generating a pilot signal to be multiplexed with an output signal of the first power combiner, and a first power combiner for the first power combiner The output signal or the second to the output signal
A main amplifier for amplifying a signal in which a pilot signal from the pilot signal generating means is multiplexed; an amplitude and phase shift adjustment relative to other distribution output signals of the n power distributors; Second adjusting means for performing delay processing for time adjustment with respect to the input signal, and the output amplified signal of the main amplifier is output from the first output terminal as it is, and the output amplified signal and the second adjusting means Distortion is generated based on both the second power combiner that outputs a reverse-phase combined signal with the output signal from the second output terminal and both the output signals of the first and second output terminals of the second power combiner. A distortion removal loop that outputs an amplified signal in which the input signals of the n input terminals are multiplexed, and a pilot signal from the first pilot signal generating means are associated with the n input terminals corresponding to the distortion removal loop. To the input signal of Adjustment by the first or second adjusting means so that the pilot signal is received and detected from the output signal of the second output terminal of the second power combiner by sequentially multiplexing, and the pilot signal level is minimized. After controlling the amount, the pilot signal from the second pilot signal generating means is multiplexed with the output signal of the first power combiner to receive and detect the pilot signal from the output amplified signal of the distortion elimination loop, And a control means for variably controlling the transfer function of the distortion removal loop so that the pilot signal level is minimized. 2. The input terminal comprises two input terminals, a first input terminal and a second input terminal, and the first adjusting means is provided for an input signal of the first input terminal taken out from the power distributor. Fixed amplitude and phase shift adjustments are performed, and variable amplitude and phase shift adjustments are performed by the control means with respect to the input signal of the second input terminal extracted from the power distributor, and the second adjustment means. The feedforward amplifier according to claim 1, wherein the control means performs variable amplitude and phase shift adjustments.