JPH05183349A - Feed forward amplifier - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a feedforward amplifier in which nonlinear distortion generated in an amplifier circuit is compensated for, and only one combiner is inserted at the output side of the main amplifier to make the nonlinearity. By compensating for the distortion, the purpose is to reduce the insertion loss in the combiner on the output side of the main amplifier. A main amplifier 21 for amplifying an input signal, a distributor / combiner 22 for distributing and combining a passing signal between a primary side and a secondary side when an output signal from the main amplifier 21 is input to the primary side, and a main amplifier 21. A part of the input signal to the divider / combiner 22 and the output signal from the secondary side of the divider / combiner 22 are equal in amplitude.
A distortion extraction circuit 23 for synthesizing in a reverse phase to extract a distortion component and an auxiliary amplifier 24 for amplifying the distortion component extracted by the distortion extraction circuit 23 are provided, and the extracted / amplified distortion component is distributed to the distributor / combiner 2.
In No. 2, the output signal from the main amplifier is injected with the same amplitude and opposite phase as the distortion component contained in the output signal.

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 compensates for non-linear distortion generated in an amplifier circuit.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional feedforward amplifier. In the figure, 1 is a directional coupler for distributing a part of the input signal E _IN input to the primary line to the secondary line side, 2
Is a main amplifier for amplifying the output signal from the primary line of the directional coupler 1, 11 is the phase of the distribution signal distributed to the secondary line side of the directional coupler 1 and the phase opposite to the output signal from the main amplifier 2 Is a phase shifter that shifts the phase so that

Reference numeral 12 is a directional coupler in which the output signal from the main amplifier is input to the primary line and the distribution signal from the phase shifter 11 is input to the secondary line, and these are combined to generate a distortion component. To extract. Reference numeral 14 is a phase shifter for changing the phase of the distortion component extracted by the directional coupler 12, and 15 is a phase shifter 1.
4 is an auxiliary amplifier that linearly amplifies the extracted distortion component from 4.

Reference numeral 13 is a directional coupler in which the output signal from the primary line of the directional coupler 12 is input to the primary line and the extracted distortion component from the auxiliary amplifier 15 side is input to the secondary line. In the line, the extracted distortion component from the auxiliary amplifier 15 side is injected into the output signal from the main amplifier 2 side with the same amplitude and opposite phase as the distortion component, thereby canceling the distortion component of the output signal from the main amplifier 2 side. It is a thing.

This conventional feedforward amplifier is
By distributing a part of the input signal E _IN by the directional coupler 1 so as to bypass the main amplifier 2 and synthesizing it with the output signal from the main amplifier 2 in the directional coupler 12 in equal amplitude and opposite phase, The distortion component generated in the output signal is extracted by the main amplifier 2, the extracted distortion component is further adjusted in amplitude and phase, and the directional coupler 13 has the same amplitude as the distortion component included in the output signal of the main amplifier 2. The injection in the opposite phase cancels the distortion component in the output signal of the main amplifier 2.

[0006]

Thus, in the conventional feedforward amplifier, the two combiners (that is, the directional couplers 12 and 13) are connected in series on the output side of the main amplifier, and therefore the combiner is used. If there is an insertion loss in, the conventional circuit will have an insertion loss of two on the output side of the main amplifier. Generally, since the output power of the main amplifier is large, even if the insertion loss of the combiner is small, the power amount of the loss is large and the heat generation amount is also large. Therefore, it is necessary to reduce the number of combiners inserted on the output side of the main amplifier as much as possible.

The present invention has been made in view of the above circumstances, and an object thereof is to perform distortion compensation for non-linear distortion by using only one combiner inserted on the output side of the main amplifier. ..

[0008]

FIG. 1 is an explanatory view of the principle of the present invention. The feedforward amplifier of the present invention is
A main amplifier 21 for amplifying an input signal, a distributor / combiner 22 for distributing and combining a passing signal between the primary side and the secondary side when an output signal from the main amplifier 21 is input to the primary side, and a main amplifier 21.
A distortion extraction circuit 23 that distributes a part of the input signal to the input signal to the input side and outputs the output signal from the secondary side of the distribution combiner 22 with equal amplitude and opposite phase to extract a distortion component; Extraction circuit 2
And an auxiliary amplifier 24 that amplifies the distortion component extracted in step 3, and the extracted / amplified distortion component has the same amplitude as the distortion component included in the output signal from the main amplifier in the distributor / combiner 22. It is configured to be injected in reverse phase.

The distribution combiner 22 described above can be formed by a directional coupler. The distribution combiner 22 described above can be configured by a hybrid combiner. Further, a directional coupler can be used as a means for distributing a part of the input signal to the main amplifier in the distortion extraction circuit 23 described above.
A hybrid coupler can be used as a means for distributing a part of the input signal to the main amplifier in the distortion extraction circuit 23 described above. A directional coupler can be used as a means for combining the two signals in the distortion extraction circuit 23 described above.

[0010]

A part of the output signal from the main amplifier 21 is taken out by the distributor / combiner 22, the distortion extracting circuit 23 is used to extract the distortion component contained in the output signal of the main amplifier 21, and the extracted distortion is extracted. The component is amplified by the auxiliary amplifier 24, and is again injected into the output signal from the main amplifier 21 by the divider / combiner 22 to cancel the distortion component.

The operation of this feedforward amplifier is
Description will be made using the equivalent circuit model of FIG. 2, which is a simplified view of the feedforward amplifier of FIG. It is assumed here that the distortion extraction circuit 22 is composed of an attenuator 221, a phase shifter 222, and an adder 223. Here the main amplifier 21
Is A, the gain of the auxiliary amplifier 24 is B, the coupling coefficient of the divider / combiner 22 is γ, and the attenuation coefficient of the attenuator 221 is β.

The relationship between the input signal E _IN and the output signal E _OUT is E _OUT = AE _IN + {(1 + βγA) / (1 + βB)} BE _IN , and the right side is required to determine the overall output regardless of the auxiliary amplifier 21. The second term of is set to 0, and therefore A = −1 / βγ. Further, the gain of the main amplifier 21 is from A to A + δ.
When the gain becomes A, if the gain B of the auxiliary amplifier 24 is B = −1 / β (1 + γ), the output is always E _OUT = AE _IN , and the distortion generated in the main amplifier 21 can be removed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 shows a feedforward amplifier as an embodiment of the present invention. In FIG. 3, the input signal E _IN
Is input to the main amplifier 2 via the primary line of the directional coupler 1, and is further output as an output signal E _OUT from the main amplifier 2 via the primary line of the directional coupler 3. The directional coupler 1 distributes a part of the output signal of the main amplifier 2 to the secondary line side and outputs it. The directional coupler 3 is a 2-input 2-output type in which signals pass through both the primary line and the secondary line, and the passing signals are mutually distributed / combined between the primary line and the secondary line.

The output signal from the secondary line side of the directional coupler 3 is input to the secondary line of the directional coupler 6 via the attenuator 4 and the phase shifter 5. The distribution signal from the secondary line of the directional coupler 1 is input to the primary line of the directional coupler 6, and the distortion components in the output signal of the main amplifier 2 are extracted by combining these two signals. And output. This extracted distortion component is input to the secondary line of the directional coupler 3 via the phase shifter 7 and the auxiliary amplifier 8.

The operation of this embodiment will be described below. The input signal E _IN is divided into two through the directional coupler 1. Most of the input signal E _IN output from the primary side of the directional coupler 1 enters the main amplifier 2 and is amplified there. A part of the amplified output signal is further distributed by the directional coupler 3. The distributed output signal is input to the directional coupler 6 through the attenuator 4 and the phase shifter 5. One of the input signals distributed by the directional coupler 1 is input to this directional coupler 6, and the directional coupler 6 and the attenuator 4 are moved so that these input signals are added and synthesized with equal amplitude and opposite phase. The phaser 5 adjusts the amplitude and phase of the signal distributed by the directional coupler 3. As a result, only the distortion component is extracted from the signals distributed by the directional coupler 3.

The distortion component extracted by the directional coupler 6 is further phase-adjusted by the phase shifter 7, linearly amplified by the auxiliary amplifier 8, and input to the directional coupler 3. The directional coupler 3 outputs an output signal from the main amplifier 2 passing through its primary side by injecting an extracted distortion component from the auxiliary amplifier 8 side into the output signal from the auxiliary amplifier 8 in the same amplitude and opposite phase to the distortion component included in the output signal. Cancels distortion components in the signal. The respective constants of the phase shifter 7 and the auxiliary amplifier 8 are determined so that the distortion components in the output signal of the main amplifier 2 can be canceled in this way.

FIG. 4 shows a simplified equivalent circuit model of the feedforward amplifier of this embodiment. Here, the gain of the main amplifier 2 is A, the gain of the auxiliary amplifier 8 is B, the coupling coefficient of the directional coupler 3 is γ, the attenuation coefficient of the attenuator 4 is β, and the coupling coefficient of the directional coupler 1 is ε. .. According to this equivalent circuit model, the overall input / output relationship is E _OUT = AE _IN + {(ε + Aβγ) / (1 + Bβ)} BE _IN . In order to determine the total output E _OUT independently of the auxiliary amplifier 7, A = −ε / βγ may be set. The gain B of the auxiliary amplifier 8 required for distortion compensation is B = γA / ε (γ + 1).

That is, since the overall input / output relationship is E _OUT = AE _IN + {(ε + Aβγ) / (1 + Bβ)} / BE _IN , consider the case where the gain of the main amplifier 2 changes from A to A + δA. _OUT = (A + δA) E _IN + [{ε + (A + δA) βγ} / (1 + Bβ)}] / BE _IN + {(ε + Aβγ) / (1 + Bβ)} / BE _IN Here, considering the condition of ε + Aβγ = 0, With A = −ε / βγ, E _OUT = AE _IN + δA {Bβγ / (1 + Bβ) +1} E _IN . Therefore, if Bβγ / (1 + Bβ) = − 1, the second term on the right side is eliminated and the distortion can be removed from the output signal E _OUT . Solving this with respect to B, the gain B of the auxiliary amplifier 8 becomes B = γA / ε (γ + 1).

FIG. 5 shows a feedforward amplifier as another embodiment of the present invention. In the figure, the main amplifier 2,
The attenuator 4, phase shifter 5, directional coupler 6, phase shifter 7, and auxiliary amplifier 8 are the same as those described in the embodiment of FIG. The difference is that in this embodiment, a 3 dB hybrid coupler is used as a divider that divides the input wave E _IN into two parts, and the output signal of the main amplifier 2 and the extracted distortion component from the auxiliary amplifier 8 side are distributed and combined. That is, a 3 dB hybrid coupler is used as a combiner.

With this configuration, the power of the distributed signal by the 3 dB hybrid couplers 9 and 10 is much larger than that in the above-described embodiment, so that the magnitude of the distortion component extracted by the directional coupler 6 is increased. This makes it possible to use a small gain auxiliary amplifier 8 which requires linearity.

That is, FIG. 6 shows a simplified equivalent circuit model of the embodiment of FIG. Since 3dB hybrid circuits 9 and 10 are intended to distribute the input signal power equally each respectively, -j / 2 ^1/2 as the coupling coefficient is shown respectively, a -1 / 2 ^{1 /.} The overall input / output relationship is E _OUT = − {A + B (2 ^1/2 −jAβ) / (2 ^1/2 + jBβ)} E _IN / 2. When β is obtained under the condition of 2 ^1/2 -jAβ = 0, β = 2 ^1/2 / jA Therefore, the gain of the auxiliary amplifier 8 required for distortion compensation is B = −A / 2, and the main amplifier 2 It has the feature that the gain of half of that is enough.

Various modifications are possible in carrying out the present invention. For example, in the above embodiment, the directional coupler 3 (or the hybrid coupler 1 in the distortion extraction circuit is used.
The phase shifter 5 is placed on the side of the distribution signal from 0) and the phase adjustment is performed by the directional coupler 6 so that both input signals have opposite phases. However, the present invention is not limited to this, and the directional coupler 1 (or A phase shifter may be provided on the side of the distribution signal from the hybrid coupler 9) to adjust the phase.

[0023]

As described above, according to the present invention, a feedforward amplifier having a circuit configuration capable of compensating for distortion generated in the main amplifier by simply connecting one combiner to the latter stage of the main amplifier is provided. This can be realized, and thereby the insertion loss due to the combiner can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram showing a simplified equivalent circuit model of the device shown in FIG. 1 for explaining the operation of the present invention.

FIG. 3 is a diagram showing a feedforward amplifier as one embodiment of the present invention.

FIG. 4 is a diagram showing a simplified equivalent circuit model of the embodiment apparatus of FIG.

FIG. 5 is a diagram showing a feedforward amplifier according to another embodiment of the present invention.

6 is a diagram showing a simplified equivalent circuit model of the device of the embodiment of FIG.

FIG. 7 is a diagram showing a conventional feedforward amplifier.

[Explanation of symbols]

 1, 3, 6, 12, 13 Directional coupler 2 Main amplifier 4 Attenuator 5, 7, 11, 14 Phase shifter 8, 15 Auxiliary amplifier 9, 10 3 dB hybrid coupler

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shugaya Kobayakawa 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Kazuhiko Kobayashi 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Kyoichi Ishii 2-12-5 Iwamoto-cho, Chiyoda-ku, Tokyo Incorporated Basic Research Institute for Space Communications (72) Inventor Akio Iso 2-12-5 Iwamoto-cho, Chiyoda-ku, Tokyo Space Communication Technology Laboratory

Claims (6)

[Claims] 1. A main amplifier (21) for amplifying an input signal.
And an output signal from the main amplifier is input to the primary side, and a distributor / combiner (2) that distributes and combines the passing signal between the primary side and the secondary side.
2) and a part of the input signal to the main amplifier is distributed, and the distributed signal and the output signal from the secondary side of the distributor / combiner are combined with equal amplitude and opposite phase to extract a distortion component. A distortion extraction circuit (23) and an auxiliary amplifier (24) for amplifying the distortion component extracted by the distortion extraction circuit are provided, and the extracted and amplified distortion component is an output signal from the main amplifier in the distribution combiner. A feedforward amplifier configured to be injected with the same amplitude and opposite phase as the distortion component in the output signal. 2. The feedforward amplifier according to claim 1, wherein the distributor / combiner comprises a directional coupler. 3. The feedforward amplifier according to claim 1, wherein the distributor / combiner is a hybrid combiner. 4. The feedforward amplifier according to claim 1, wherein a directional coupler is used as a means for distributing a part of the input signal to the main amplifier in the distortion extraction circuit. 5. The feedforward amplifier according to claim 1, wherein a hybrid coupler is used as a means for distributing a part of the input signal to the main amplifier in the distortion extraction circuit. 6. A directional coupler is used as a means for combining two signals in the distortion extraction circuit.
The feedforward amplifier according to any one of 1.