JPH08321725A - Feedforward amplifier - Google Patents

Abstract

PURPOSE: To provide a feedforward amplifier in which a stable amplified signal is easily obtained with less distortion. CONSTITUTION: A 2-distributer 19 distributing an input signal, a delay line 20, a synthesizer 23, a distributer 24, a broad band detector (DET) 25, and a control circuit 72 are added in addition to a conventional configuration. The output of the synthesizer 23 is distributed into two by the distributer 24, the one is fed to a narrow band detector (DET) 18 and the other is given to a broad band detector 25. The output of the broad band detector 25 is given to the control circuit 27 and the control circuit 27 adjusts the attenuation of the variable attenuator 21 and the phase shift of the variable phase shifter 22 so that a detection level of the broad band detector 25 is minimized. The output signal of the narrow band detector 18 is given to a control circuit 26, which adjusts the attenuation of the variable attenuator 15 and the phase shift of the variable phase shifter 16 so that the detection level of the narrow band detector 18 is minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedforward amplifier which detects distortion in an output signal amplified by a feedforward loop and outputs a signal in which the distortion is suppressed.

[0002]

2. Description of the Related Art Conventionally, as a linear amplifier used for high-frequency multi-frequency simultaneous amplification and the like, for example, Japanese Patent Laid-Open No. 1-19
A feedforward amplifier disclosed in Japanese Patent No. 8809 is known.

FIG. 3 shows the basic configuration of this feedforward amplifier. This feedforward amplifier is configured to have a distortion detection loop L1 as distortion detection means and a distortion removal loop L2 as distortion removal means, and is mainly used for input multi-frequency multiplexed signals in the high frequency band input from the input terminal 1. The amplifier 7 is designed to perform collective amplification. Here, the distortion detecting means cancels the input signal component to detect the non-linear distortion component generated during the amplification, and the distortion removing means amplifies the distortion component detected by the distortion detecting means using the auxiliary amplifier 17. After that, the distortion component is canceled by injecting it again into the output of the main amplifier 7.

That is, the distortion detection loop L1 includes a two-way divider 2, a variable attenuator (T) 3, a variable phase shifter (φ) 4, a main amplifier 7 and a delay line 13, and a distortion elimination loop L.
It has a configuration including a distributor 8 and a combiner 14 which are shared with 2. The variable attenuator 3 and the variable phase shifter 4 here are adjusted so that the power applied to the auxiliary amplifier 17 is minimized.

On the other hand, the distortion elimination loop L2 has a pilot signal oscillator 6, a combiner 5, a delay line 9, a combiner 10, and a variable attenuator in addition to the distributor 8 and the combiner 14 which are shared with the above-mentioned distortion detecting loop L1. (T) 15, variable phase shifter (φ) 1
6 and the auxiliary amplifier 17 are included.

The variable attenuator 15 of the distortion eliminating loop L2 is also provided.
Also, the control circuit 26 connected to the variable phase shifter 16 detects the pilot signal in the output circuit of the feedforward circuit via the distributor 11 and the narrow band detector (DET) 18, and the detection level of the pilot signal is minimum. The variable attenuator 15 and the variable phase shifter 16 are adjusted so that

The operation of the feedforward amplifier (linear amplifier) having such a configuration will be described. The high frequency band multi-frequency multiplexed signal (input signal) input to the input terminal 1 is divided into two by the two-way divider 2, and one signal is passed through the variable attenuator 3 and the variable phase shifter 4 and transferred to the attenuation amount. After the phase amount is adjusted, it is multiplexed with the pilot signal from the pilot signal oscillator 6 in the combiner 5 and supplied to the main amplifier 7. After being amplified by the main amplifier 7, the distributor 8 is further added.
And is input to the combiner 10 via the delay line 9. The input signal of the synthesizer 10 is the main amplified signal, and includes the distortion component generated when the main amplifier 7 is amplified.

The other signal distributed by the two-way divider 2 is given a delay time equivalent to the signal delay time for the variable attenuator 3, the variable phase shifter 4, and the main amplifier 7 by the delay line 13, and then, The variable attenuator 15, the variable phase shifter 16, and the auxiliary amplifier 17 are provided after a part of the main amplified signals branched by the distributor 8 are combined in the reverse phase by the combiner 14.
Is input to. At this time, the variable attenuator 3 and the variable phase shifter 4 are adjusted so that the signal level applied to the auxiliary amplifier 17 is minimized. Here, since the delay line 13 is the only constituent element from the output end of the bi-distributor 2 to the combiner 14, the generated distortion can be ignored. Therefore, if the operation of the distortion detection loop L1 is proper, a part of the input signal amplified by passing through the variable attenuator 3, the variable phase shifter 4, and the main amplifier 7 is in the opposite phase in the combiner 14. Only the distortion components generated or mixed in the main amplifier 7 due to the combination are output from the combiner 14.

The distortion component output from the combiner 14 is adjusted in attenuation amount and phase shift amount by the variable attenuator 15 and the variable phase shifter 16, and then supplied to the auxiliary amplifier 17 to be amplified. The distortion component amplified here is combined with the main amplified signal delayed by the propagation delay time of the variable attenuator 15, the variable phase shifter 16, and the auxiliary amplifier 17 by the delay line 9 to the combiner 1
It is synthesized in reverse phase via 0. This composite signal is distributed to the distributor 1.
1 is supplied to the narrow band detector 1
8 is input. The narrow band detector 18 detects the pilot signal in the input signal by performing simultaneous detection, for example, and controls the control circuit 2.
Output to 6. The control circuit 26 controls the attenuation amount of the variable attenuator 15 and the phase shift amount of the variable phase shifter 16 so that the output level of the narrowband detector 18 is minimized. As a result, the pilot signal from the synthesizer 10 is minimum, that is,
The main amplified signal with the minimum distortion component is output to the output terminal 12.

Incidentally, FIG. 4 shows the spectra in each part of this feedforward amplifier in comparison with each other. The input spectrum of the input terminal 1 is the output spectrum of the main amplifier 7 as shown in FIG. As shown in FIG. 2B, the output spectrum of the output terminal 12 is as shown in FIG. 3C, and the output spectrum of the auxiliary amplifier 17 is as shown in FIG.

As another feedforward amplifier, for example, the one disclosed in Japanese Patent Laid-Open No. 3-335841 can be cited.

[0012]

In the case of the above-mentioned feedforward amplifier, a pilot signal is injected into the main amplifier in order to perform stable distortion removal, and the pilot signal is removed to simultaneously remove the distortion signal. However, the level of the pilot signal to be injected can be set arbitrarily, but if leaked from the output terminal, it is considered as an unnecessary radio wave, so it is usually necessary to suppress it to an extremely small value. Therefore,
Since the narrow band detector needs to reliably capture the strength of the pilot signal, which is extremely smaller than that of the carrier, it is required to have a high capability of removing an interfering signal.

The present invention has been made in order to solve such a problem, and its technical problem is to provide a feedforward amplifier which can easily obtain a stable amplified signal with little distortion.

[0014]

According to the present invention, a distortion detecting means and a distortion removing means coupled to the distortion detecting means are included, and an input signal is divided into two, one of which is the distortion detecting means and the other is the first distortion detecting means. In a feedforward amplifier including a first bisector that respectively transmits to a delay line, an input signal is bisected in a stage before the first bisector, one of the first bisector and the other of the second bisector A second two divider for transmitting to the delay line,
A variable attenuation / phase shift unit for adjusting the amount of attenuation and amount of phase shift in the second delay line, and a first distributor for distributing a part of the output of the first combiner provided on the output side of the distortion removing means. Of the output signal of the second divider and the second combiner for dividing the output signal of the second combiner, and the output signal of the second combiner Narrow band detector that measures the strength of a specific frequency component, wide band detector that measures the strength of the entire output signal of the second divider, and variable attenuation and shift to minimize the output level of the wide band detector. A feedforward amplifier with a first control circuit for adjusting the phase part is obtained.

According to the present invention, in the above feedforward amplifier, the distortion detecting means and the distortion removing means share the third distributor and the fourth combiner connected to each other, and further, the distortion detecting means A first variable divider and a first delay line together with a first variable attenuator that adjusts the amplitude of the input signal, a first variable phase shifter that adjusts the amount of phase shift of the input signal, The distortion removing means, together with the first combiner, generates an oscillation signal having a predetermined frequency, and includes a main amplifier that amplifies an input signal whose amplitude and phase shift amount are adjusted and outputs an amplified signal. A signal oscillator, a third combiner that superimposes the oscillation signal on the amplified signal and outputs the superimposed signal, a third delay line that connects the third distributor and the first combiner, and The second possibility of adjusting the amplitude of the distortion signal synthesized and output from the synthesizer of 4 An attenuator, a second variable phase shifter that adjusts the phase shift amount of the distortion signal, and an auxiliary amplifier circuit that amplifies the amplitude and phase shift amount of the distortion signal and outputs an amplified distortion signal. A feed-forward amplifier including is obtained.

Further, according to the present invention, in the feedforward amplifier, the second variable attenuator and the second variable phase shifter are adjusted so that the output level of the narrow band detector is minimized. A feedforward amplifier with a control circuit is obtained.

[0017]

The feedforward amplifier of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a basic configuration of a feedforward amplifier according to an embodiment of the present invention. However, since this feedforward amplifier also has the same components as those of the conventional device shown in FIG. 3, the same components are designated by the same reference numerals to simplify the description, and different components will be mainly described.

That is, this feedforward amplifier also includes a distortion detecting loop L1 as a distortion detecting means and a distortion removing loop L2 as a distortion removing means coupled to the distortion detecting loop L1, and also divides an input signal into two and outputs one of them. Distortion detection loop L1, the first transmitting the other to the first delay line 13 respectively
It includes a second distributor 2.

Further, in the case of this feedforward amplifier, the input signal is divided into two in the preceding stage of the first two-way divider 2 and one is transmitted to the first two-way divider 2 and the other to the second delay line 20. A variable attenuation / phase shift unit for adjusting the amount of attenuation and the amount of phase shift in the second second divider 19 and the second delay line 20 [third variable attenuator (T) 21, third variable phase shifter (Φ) 22]
And a first distributor 1 for distributing a part of the output of the first combiner 10 provided on the output side of the distortion removal loop L2.
The second combiner 23 for combining the output of 1 and the outputs of the third variable attenuator 21 and the third variable phase shifter 22, and the second distributor for distributing the output signal of the second combiner 23 24,
A wideband detector (DET) 25 for measuring the intensity of the entire output signal of the second distributor 24, and a third variable attenuator 21 and a third variable attenuator 21 and a third detector so as to minimize the output level of the wideband detector 25.
And a first control circuit 27 for adjusting the variable phase shifter 22 of the second divider 2 and the narrow band detector (DET) 18 are provided.
It is configured such that the intensity of a specific frequency component is measured from the output signal of No. 4.

By the way, since each part here is described by the order number, the structure of the other part described in FIG. 3 will be briefly described as a reference. The distortion detection loop L1 and the distortion removal loop L2 are connected to each other. The third distributor 8 and the fourth combiner 14 will be shared.

Further, the distortion detection loop L1, together with the first divider / divider 2 and the first delay line 13, has a first variable attenuator (T) 3 for adjusting the amplitude of the input signal and a shift of the input signal. It includes a first variable phase shifter (φ) 4 for adjusting the phase amount, and a main amplifier 7 for amplifying the input signal whose amplitude and phase shift amount are adjusted and outputting the amplified signal.

Further, the distortion elimination loop L2, together with the first synthesizer 10, a signal oscillator 6 for generating an oscillation signal having a predetermined frequency, and a third signal for superimposing the oscillation signal on the amplified signal and outputting the superimposed signal. Of the distortion signal combined and output from the third combiner 5, the third distributor 8 and the first combiner 10, and the third combiner 8 and the fourth combiner 14. A second variable attenuator (T) 15, a second variable phase shifter (φ) 16 for adjusting the phase shift amount of the distortion signal, and an amplifier for which the amplitude and phase shift amount of the distortion signal are adjusted are amplified. And an auxiliary amplification circuit 17 that outputs an amplified distortion signal.

In addition, a second control circuit 26 for adjusting the second variable attenuator 15 and the second variable phase shifter 16 so that the output level of the narrow band detector 18 is minimized is provided. Become.

Therefore, the operation of this feedforward amplifier will be briefly described below by omitting the order number of each part.

In this feedforward amplifier,
The input signal input to the input terminal 1 is divided into two by the two divider 19. One of the distributed input signals is input to the dual distributor 2. In the two-way divider 2, the input signal is divided into a path amplified by the main amplifier 7 and a path delayed by the delay line 13, and the combiner 14 extracts only the distortion component. Main amplifier 7
After being delayed by the delay line 9, the output of 1 is combined with the distortion component previously extracted by the combiner 10 in anti-phase.

The output of the combiner 10 passes through the distributor 11 and is then transmitted to the output terminal 12 as a distortion-free output signal. A part of the signal branched by the distributor 11 is combined with the signal branched by the two distributor 19 in the combiner 23. The signal input from the two-way divider 19 to the combiner 23 is the delay line 20,
The variable attenuator 21 and the variable phase shifter 22 adjust the amplitude and phase so that the signal output from the distributor 11 to the combiner 23 has the same amplitude and opposite phase. Therefore, the synthesizer 23
The input signal component is canceled from the output signal of.

The output of the combiner 23 is divided into two by a divider 24, one of which is a narrow band detector 18 and the other of which is a wide band detector 2.
Input to 5. The output of the wideband detector 25 is the control circuit 2
7, and the control circuit 27 adjusts the amount of attenuation of the variable attenuator 21 and the amount of phase shift of the variable phase shifter 22 so that the detection level of the wideband detector 25 is minimized. Narrow band detector 18
Is input to the control circuit 26, and the control circuit 26 adjusts the amount of attenuation of the variable attenuator 15 and the amount of phase shift of the variable phase shifter 16 so that the detection level of the narrow band detector 18 is minimized. .

In the conventional device, it was necessary to capture the strength of the pilot signal, which is extremely weaker than the output signal, but in this feedforward amplifier, the output signal which is an interference wave for the narrow band detector 18 is detected by the wide band detector 25. Detected and suppressed to a minimum. Therefore, the interference signal elimination capability required for the narrow band detector 18 is greatly relaxed.

FIG. 2 shows a spectrum of each part of this feedforward amplifier in comparison with each other.
The input spectrum of the input terminal 1 is as shown in FIG. 3A, the output spectrum of the main amplifier 7 is as shown in FIG. 2B, and the output spectrum of the output terminal 12 is as shown in FIG. As shown in FIG. 6D, the output spectrum of the auxiliary amplifier 17 is as shown in FIG. 7D, and the input spectrum to the narrow band detector 18 is as shown in FIG.

[0031]

As described above, according to the present invention, a part of the input signal of the first stage in the entire amplifier is branched to the input signal of the narrow band detector used for monitoring the distortion cancellation state, and then the same amplitude is obtained. By canceling the output signal which becomes an interfering wave for the narrow band detector by synthesizing it in the opposite phase with, and greatly reducing the interference wave rejection capability required for the narrow band detector, distortion is generated in this feed forward amplifier. It becomes a high-performance product that can easily obtain a small and stable amplified signal.

[Brief description of drawings]

FIG. 1 shows a basic configuration of a feedforward amplifier according to an embodiment of the present invention.

FIG. 2 is a diagram showing the spectra of each part of the feedforward amplifier shown in FIG.
Input spectrum of input terminal, (b) Output spectrum of main amplifier, (c) Output spectrum of output terminal, (d) Output spectrum of auxiliary amplifier, (e) To narrow band detector It is about the input spectrum.

FIG. 3 shows a basic configuration of a conventional feedforward amplifier.

FIG. 4 is a diagram showing spectra of respective parts of the feedforward amplifier shown in FIG. 3 in comparison with each other.
It relates to the input spectrum of the input terminal, (b) relates to the output spectrum of the main amplifier, (c) relates to the output spectrum of the output terminal, and (d) relates to the output spectrum of the auxiliary amplifier.

[Explanation of symbols]

 1 Input Terminals 2,19 Dividers 3,15,21 Variable Attenuators (T) 4,16,22 Variable Phase Shifters (φ) 5,10,14,23 Combiner 6 Pilot Signal Oscillator 7 Main Amplifier 8, 11, 24 Distributor 9, 13, 20 Delay line 12 Output terminal 17 Auxiliary amplifier 18 Narrow band detector (DET) 25 Wide band detector (DET) 26, 27 Control circuit L1 Distortion detection loop L2 Distortion removal loop

Claims (3)

[Claims] 1. A first secondary circuit including a distortion detecting means and a distortion removing means coupled thereto, which divides an input signal into two parts, one of which is transmitted to the distortion detecting means and the other of which is transmitted to a first delay line. In a feedforward amplifier including a distributor, a second divider that divides the input signal into two in a stage before the first divider and transmits one to the first divider and the other to a second delay line. A second divider, a variable attenuation / phase shift unit for adjusting the amount of attenuation and amount of phase shift in the second delay line, and a part of the output of the first combiner provided on the output side of the distortion removing means. A second combiner for combining the output of the first distributor for distribution and the output of the variable attenuation and phase shifter; a second distributor for distributing the output signal of the second combiner; Narrow band that measures the intensity of a specific frequency component from the output signal of the second distributor A detector, a wideband detector that measures the intensity of the entire output signal of the second distributor, and the variable attenuation so that the output level of the wideband detector is minimized,
A feedforward amplifier, comprising: a first control circuit that adjusts a phase shift unit. 2. The feedforward amplifier according to claim 1, wherein the distortion detection means and the distortion removal means share a third distributor and a fourth combiner connected to each other, and further, the distortion The detection means, together with the first two-way divider and the first delay line, a first variable attenuator that adjusts the amplitude of the input signal, and a first variable attenuator that adjusts the phase shift amount of the input signal. A phase shifter and the amplitude of the input signal,
A main amplifier that amplifies a phase-shifted amount and outputs an amplified signal; and the distortion removing means, together with the first synthesizer, generate a oscillating signal having a predetermined frequency; A third combiner that superimposes the oscillation signal on the amplified signal and outputs a superimposed signal; a third delay line that connects the third distributor and the first combiner; A second variable attenuator for adjusting the amplitude of the distortion signal synthesized and output from the fourth combiner; a second variable phase shifter for adjusting the phase shift amount of the distortion signal; and an amplitude of the distortion signal, A feed-forward amplifier, comprising: an auxiliary amplifier circuit that amplifies a phase-shifted amount and outputs an amplified distortion signal. 3. The feedforward amplifier according to claim 2, wherein the second variable attenuator and the second variable phase shifter are adjusted so that the output level of the narrowband detector is minimized. A feed-forward amplifier characterized by comprising a control circuit of.