JP2003051722A - Feedforward system distortion compensation amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a feedforward system amplifier that can reduce the power consumption. SOLUTION: In the feedforward system distortion compensation amplifier for outputting signals by canceling distortion in a distortion detection loop consisting of a first phase shifter, a first amplitude unit and a main amplifier, distortion in a distortion compensation loop consisting of a second phase shifter, a second amplitude unit and an error amplifier, and distortion in a distortion detection loop by distortion of the distortion compensation loop with an inverted phase, bias control is applied to the main amplifier and the error amplifier according to the level of the outputted signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a common amplifier, and more particularly to automatic distortion control in a feedforward system.

[0002]

2. Description of the Related Art In a base station / relay station for mobile communication, a multi-carrier signal having a predetermined frequency interval and containing a large number of appropriately modulated carriers is amplified at a high frequency and then wirelessly transmitted. If the linearity of the amplifier used for high frequency amplification is not sufficiently good, distortion such as intermodulation distortion will occur. This distortion hinders realization of normal and high-quality communication. Therefore, the amplifier used for amplifying the multicarrier signal is required to have good linearity over the entire frequency band to which the multicarrier signal belongs.

As one of the methods for realizing it, there is a feedforward distortion compensation method. First, the signal path from the signal input terminal to the signal output terminal via the main amplifier, that is, the signal path for transmitting the signal to be amplified and the amplified signal will be referred to as a main line. In the feed-forward method, a distortion detection loop is provided to combine a signal branched from a point on the main line after the main amplifier and a signal branched from a point on the main line before the main amplifier. If the electrical lengths of the signal paths through which both signals pass are equal to each other, and if both signals have the same amplitude and opposite phase, the carrier component is canceled by the above-mentioned signal combining operation, and it occurs in the main amplifier and its peripheral circuits. The signal corresponding to the distortion can be extracted.

In the feedforward method, a distortion compensation loop is further provided, and the signal extracted by the distortion detection loop, that is, the signal corresponding to the distortion is recombined with the signal on the main line. The signal delay in the distortion compensation loop is compensated on the main line, and the distortion component included in the signal on the main line and the signal obtained from the distortion compensation loop have the same amplitude and opposite phase to each other. By adjusting the amplitude and the phase appropriately, the distortion generated in the main amplifier can be compensated by the signal recombining operation described above.

A specific operation of the feed-forward distortion compensation will be described with reference to FIG. In FIG. 11, a distortion detection loop including a directional coupler 1, a phase shifter 2, an amplitude shifter 3, a pilot signal output device 4, a coupler 5 and a main amplifier 6, a coupler 8, a wave detector 9, a phase shifter 10, Amplifier 1
1, a distortion compensation loop composed of an error amplifier 12 is divided into two blocks. Further, the feedforward system amplifier is configured by the distributor 7, the distributor 13, the distortion terminator 14, the coupler 15, and the control unit 18 that controls various configurations.

In the distortion detection loop, there are a distortion-free route via a->c->e-> g and a distortion route of a->b->d-> f. At point g, the sign of each transfer function is inverted and only the distortion component is extracted. At that time, the phase shifter 2 and the amplitude shifter 3 are controlled, and the detector 9 of the distortion compensation loop automatically controls so that the signal level is minimized.

[0007]

Recently, the demand for mobile phones has been increasing remarkably, and the demand for base stations is increasing accordingly. As a result, basic maintenance costs are increasing. In contrast, base station manufacturers are trying to reduce costs in various ways.

As one of cost reductions, there is a method of "suppressing power consumption". For example, in a CDMA mobile communication system, electric power transmitted from a mobile station at a short distance or from a mobile station at a long distance is controlled. Such power control is performed in order to overcome the perspective effect, that is, a phenomenon in which a strong signal from a mobile station at a short distance overwhelms a weak signal from a mobile station at a distant place. The output power level of the mobile station is adjusted by the combination of the received signal width in the mobile station and the fine adjustment message received from the base station.

A CDMA system uses multiple coded channels as control channels, including pilot channels, synchronization channels, paging channels, connection channels, and the like. The active mobile station sends out a registration message and then monitors the pilot, paging and synchronization channels to form a communication link with the base station.

The pilot signal is transmitted by the base station with constant power. Upon start-up, the mobile station handles stronger or weaker pilot signals depending on its position relative to the base station. The mobile station attempts to connect to the base station at the initially selected transmission signal level. However, if this connection fails, the mobile station will try to reconnect at a higher transmission signal level. This process is continued until the mobile station temporarily stops operation or connects to the base station.

When the mobile station is connected to the base station, the mobile station starts transmitting voice and / or data signals at the transmission signals of the normal power level realized by the base station. Then, the base station transmits a signal including an up / down bit to the mobile station, and when the up / down bit is set, the power of the mobile station is increased (up) by a small amount and the up / down bit is set. If not, the power of the mobile station is reduced (down) by a small amount. In this way, the separated up / down control signals transmitted from the base station to each mobile station reduce the power of the mobile station in the short distance and increase the power of the mobile station in the distant place. This process is repeated in a number of message frames until the above two signals are transmitted to the base station at almost the same power level.

The CDMA system also provides power control for RF (radio frequency) signals transmitted by the base station. This type of power control is done to minimize transmission interference in adjacent cells. To that end, for several mobile stations, the base station automatically reduces the RF output power level in the speech channel by a predetermined decrement Δ1. This decrement △ 1
Is set to a sufficiently low level so that the output power level of the RF signal transmitted by the base station gradually decreases for many message frames. Then, when the mobile station detects, for example, five consecutive bad frames, the mobile station determines that the signal from the base station is weak enough to be unreceivable. A power control signal is transmitted to the base station so as to increase the power level only.

The base station transmitter power amplifier consumes a significant amount of constant power regardless of the relative strength of the transmitted output signals. For example, at normal daytime speech load, the RF output power level is about 10 watts and the primary DC power consumed by the transmitter power amplifier is about 80-100 watts (ie, 8-10 dB higher). However, at night when the call load is low, the transmitter RF output power level is reduced by about 1 watt due to the power control on the RF output signal as described above. Nevertheless, in the prior art, the operating bias point of the power amplifier is fixed, so that about 80-100 watts of primary DC power is consumed by the transmitter, similar to daytime. Thus, in the conventional system, the power consumption D of the transmitter power amplifier is increased.
Although C power reduction has been attempted, nothing is noted about the output RF power level being held constant.

Therefore, in the CDMA mobile communication system,
What is needed is a technique for implementing power control within the power amplifier of a base station transmitter. Such a system reduces the DC power level required to generate the RF output signal, but at the same time requires monitoring and maintaining the level of the amplifier's RF output signal.

An object of the present invention is to suppress an increase in power consumption even when the output level is low, which is the above problem.

[0016]

In order to solve the above problems, according to the present invention, a distortion detection loop including a first phase shifter, a first amplitude shifter, and a main amplifier, a second phase shifter, and a second phase shifter are provided. In a feed-forward distortion amplifier that cancels the distortion of the distortion compensation loop including the two amplitude units and the error amplifier by the inverse distortion of the distortion compensation loop, and outputs a signal, the main amplifier according to the level of the output signal A feedforward distortion amplifier characterized by performing bias control on an error amplifier.

Further, in order to solve the above problems, the first
The distortion detection loop consisting of the phase shifter, the first amplitude unit and the main amplifier, the distortion compensation loop consisting of the second phase shifter, the second amplitude unit and the error amplifier, and the distortion detection loop In a feedforward distortion amplifier that cancels each other and outputs a signal, a first bias control unit that biases the main amplifier according to the level of the output signal, and a bias control to the error amplifier according to the level of the output signal. There is provided a distortion compensation amplifier characterized in that a second bias control section for performing the above is provided.

Further, in order to solve the above-mentioned problem, in the feedforward distortion amplifier according to claim 1 or 2, the output signal is divided into a plurality of levels, and bias control according to the level is performed. And a feedforward distortion amplifier.

In order to solve the above problems, a distortion detection loop including a first phase shifter, a first amplitude shifter, and an amplifier composed of at least one amplification section, a second phase shifter, and a second phase shifter. In a feed-forward distortion amplifier that cancels the distortion of the distortion compensation loop and the distortion detection loop formed by an amplifier configured of an amplitude device and at least one or more amplification units by the inverse distortion of the distortion compensation loop, and outputs the signal, the output is At least one first bias control circuit group for performing bias control on the amplification unit according to the level of the signal, and at least one second bias control circuit group for performing bias control on the error amplification unit according to the level of the output signal. There is provided a feedforward distortion amplifier characterized by being provided.

In order to solve the above problems, the feedforward distortion amplifier according to the fourth aspect is provided with a bias control circuit corresponding to each amplification section.

In order to solve the above problems, the feedforward distortion compensation amplifier according to claim 5, wherein one bias control circuit is provided for each of a plurality of various amplifying sections.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of the present invention, FIG. 2 is a relationship diagram between an output level of an amplification device and device power, FIG. 3 is a diagram showing wireless characteristics, FIG. 4 is a bias change flowchart, and FIG. 5 is FIG. Control value memory table for S3 of FIG. 6, FIG. 6 is a relational diagram of the bias level value and the error amplifier consumption current with respect to the output level in FIG. 5, and FIG. 7 is a relational diagram of the bias level value and the main amplifier consumption current with respect to the output level in FIG. FIG. 8 is a relational diagram of ACLR and AMP device power consumption during bias control in FIG. 5, and FIGS. 9 and 10 are amplifier bias control diagrams. Details will be described later.

The function realizing means described below may be any circuit or device as long as the function can be realized, and a part or all of the function can be realized by software. Is also possible. Further, the function realizing means may be realized by a plurality of circuits, or the plurality of function realizing means may be realized by a single circuit.

In the feedforward type amplifier, since the class AB and class B amplifying elements as shown in FIG. 2 are used depending on the trend of the amplifying elements, the power consumption tends to decrease as the output level decreases. However, an idle current must be set in the amplification element, so that the power consumption of the amplification device does not fall below the idle current of the amplification element at a low output level.

Regarding radio characteristics, for example, CDM
ACRL (Adjacent Channel Leakage power) at A signal
Ratio: Adjacent channel leakage power), etc., but it is understood that the fixed bias of the conventional main amplifier and error amplifier has a large margin as shown by the solid line at a low output level as shown in FIG. Since it is sufficient for the amplifier to satisfy the radio characteristics, the bias control of the main amplifier and the error amplifier is performed, particularly when the output level shifts to a low level. A detailed description will be given below.

The first embodiment will be described with reference to FIG.
Note that the same numbers as in FIG. 11 are the same as the conventional ones, and thus the description thereof is omitted. The main amplifier bias control circuit 16 controls the bias of the main amplifier 6. The error amplifier bias control circuit 17 controls the bias of the error amplifier 12.

The operation of the present invention is as shown in FIG. The output level of the amplifier is detected, and then the coupler 15 reports the output level to the controller 18 (S1). Control unit 1
The bias control value of each amplifier according to the output level as shown in FIG. 5 is stored in 8, and the bias control value is read according to the output level (S3). Next, the circuit 16 controls the bias of the main amplifier based on the read control value (S4). Next, the bias control circuit error 17 controls the bias of the amplifier according to the output level by the read control value (S5).

In the memory table showing the relationship between the output level and the bias control value in FIG. 5, the output level, the main amplifier bias value, and the error amplifier bias control value are divided into three stages of A, B, and C, respectively. The relationship between the output level and the bias control value will be described in detail in FIGS. 6, 7 and 8.

First, the relationship between the output level value and the main amplifier bias control value will be described with reference to FIG. The horizontal axis represents the output level, and the vertical axis represents the main amplifier bias control value (upper graph) and the current consumption value of the amplifier (lower graph). The dotted line is the case where bias control is not applied,
The solid line shows the case where bias control is applied. When the output level is high (A), the main amplifier bias control value is the same value (A ′) as when the bias control is not applied. At this time, the power consumption of the main amplifier becomes normal. When the output level is B, the bias control value (B ') is applied.
At this time, the power consumption of the main amplifier is lower than that at the output level (A). Further, when the output level is C, the bias control value (C ′) is applied to further suppress the power consumption.

Next, the relationship between the output level value and the error amplifier bias control value will be described with reference to FIG. The horizontal axis represents the output level, and the vertical axis represents the main amplifier bias control value (upper graph) and the current consumption value of the amplifier (lower graph). The dotted line shows the case where the bias control is not applied, and the solid line shows the case where the bias control is applied. When the output level of the main amplifier bias control value is high (A),
The value is the same as that when the bias control is not applied (A ″). At this time, the power consumption of the main amplifier is normal. When the output level is (B), the bias control value (B ″) is applied. . At this time, the power consumption of the main amplifier is lower than that at the output level (A). Further, when the output level is (C), the bias control value (C ″) is applied to further suppress the power consumption.

FIG. 5 shows the relationship between the ACLR value during bias control and the power consumption of the amplifier. Next, the horizontal axis indicates the output level, and the vertical axis indicates the ACLR (upper graph) and the power consumption value of the amplifier (lower graph). The dotted line shows the case where the bias control is not applied, and the solid line shows the case where the bias control is applied. As you can see from Figure 5,
By applying bias control according to the output level,
It can be seen that the power consumption of the entire amplification device can be suppressed while satisfying the wireless characteristics.

As shown in FIGS. 6 and 7, by controlling the bias according to the output level, the overall power consumption can be suppressed. Here, the output levels are (A), (B),
Although it is divided into three stages of (C), it is not limited to this,
It is possible to set more finely according to the time zone and the like. In this case, for example, it becomes similar to the dotted line graphs of FIGS.

Next, the amplifier bias control circuit will be described with reference to FIGS. This corresponds to the dotted line frame portion in FIG. 1, that is, the bias control circuit and the control unit of the main amplifier 6 or the error amplifier 12, respectively.
The amplifiers described here are main amplifiers or error amplifiers in multiple configurations.

In FIG. 9, the amplifier is controlled by one bias control circuit. The amplifier includes a small power amplifier 91, a medium power amplifier 92, and a large power amplifier 93. In this case, the bias corresponding to the output can be simultaneously performed by one circuit.

Further, in FIG. 10, each amplifier and the bias control circuit correspond to each other. The amplifier includes a small power amplifier 91, a medium power amplifier 92, and a large power amplifier 93. In this case, since the bias control of the amplification elements can be performed individually, it is possible to perform the bias control separately for the amplification elements required for the bias control and the amplification elements not required for the bias control. Since the power consumption of the large power amplification unit and the medium power amplification unit influences the power consumption of the amplification device, the bias of the main power amplification unit is mainly fixed and the bias of the medium power amplification unit 92 and the large power amplification unit 93 is fixed. Take control. As a result, efficient power consumption can be achieved.

Here, the amplifier section and the bias control circuit have a plural-to-one relationship or a one-to-one relationship, but the present invention is not limited to this, and they may be combined to perform the bias control of the amplifier.

The description above has focused on CDMA.
The present invention is not limited to this, and may be any system that uses a base station that consumes normal power such as TDMA.

[0038]

According to the first aspect of the invention, in the feedforward amplifier, there is an effect that the power of the entire amplifying device is suppressed while satisfying the radio characteristic.

According to the second aspect of the invention, since the bias of the main amplifier and the error amplifier is controlled according to the output level, there is an effect that finer power control can be performed while satisfying the radio characteristics.

According to the third aspect of the present invention, since the output level can be divided into a plurality of levels for control, the main amplifier and the error amplifier can support power control at a plurality of levels. This is possible and has the effect of simplifying the soft control.

According to the invention of claim 4, at least 1
In the entire amplifying device having the amplifier including the two amplifying sections, the power of the entire amplifying device can be suppressed, and the soft control can be simplified.

According to the fifth aspect of the invention, since the bias control circuit corresponding to the amplifying unit is provided, the power can be controlled in the unit of the amplifying unit, and finer power control can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram of this embodiment.

FIG. 2 is a diagram showing the relationship between the amplifier output level and the device power of this embodiment.

FIG. 3 is a wireless characteristic diagram of the present embodiment.

FIG. 4 is a flowchart of bias change according to the present embodiment.

FIG. 5 is a control value memory table in FIG.

FIG. 6 is a bias level value and an error amplifier consumption current with respect to an output level in FIG.

FIG. 7 is a bias level value and a main amplifier current consumption with respect to an output level in FIG.

FIG. 8 is a diagram showing ACLR and amplifier consumption output relations during bias control in FIG.

FIG. 9 is an amplifier bias control diagram in this embodiment.

FIG. 10 is an amplifier bias control diagram in the present embodiment.

FIG. 11 is a conventional feedforward type distortion compensation amplifier.

[Explanation of symbols]

1, 5, 7, 8, 13, 13, 15 ... Coupler 2, 10 ... Phaser 3, 11 ... Amplifier 4 ... Pilot signal 6 ... Main amplifier 9 ... Detector 14 ... Distortion absorption terminator 12
Error amplifier 16 ... Main amplifier bias control circuit 17 ... Error amplifier bias control circuit 18 ... Control units 91, 101 ... Power saving amplifiers 92, 102 ... Medium power amplifiers 93, 103 ... Second power amplifiers 94, 104, 105, 106 ... Bias control circuit

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[Procedure amendment]

[Submission date] July 24, 2002 (2002.7.2)
4)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Title of invention

[Correction method] Change

[Correction content]

[Title of the Invention] feedforward system distortion compensation
Amplifier

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

[0003] There are a distortion compensation method by the feed-forward scheme as One way to achieve it. First, the signal path from the signal input terminal to the signal output terminal via the main amplifier, that is, the signal path for transmitting the signal to be amplified and the amplified signal will be referred to as a main line. In the feed-forward method, a distortion detection loop is provided to combine a signal branched from a point on the main line after the main amplifier and a signal branched from a point on the main line before the main amplifier. If the electrical lengths of the signal paths through which both signals pass are equal to each other, and if both signals have the same amplitude and opposite phase, the carrier component is canceled by the above-mentioned signal combining operation, and it occurs in the main amplifier and its peripheral circuits. The signal corresponding to the distortion can be extracted.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008] as one of cost reduction, a method referred to as "reducing the power consumption" there Ru. For example, it is disclosed in JP-A-11-289.
577. In a CDMA mobile communication system, electric power transmitted from a mobile station at a short distance or from a mobile station at a long distance is controlled. Such power control is performed in order to overcome the perspective effect, that is, a phenomenon in which a strong signal from a mobile station at a short distance overwhelms a weak signal from a mobile station at a distant place. The output power level of the mobile station is adjusted by the combination of the received signal width in the mobile station and the fine adjustment message received from the base station.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

[0016]

In order to solve the above problems, according to the present invention, a distortion detection loop including a first phase shifter, a first amplitude shifter, and a main amplifier, a second phase shifter, and a second phase shifter are provided. the distortion of the distortion compensation loop and the distortion detection loop consisting of two amplitude units and error amplifier offset by reverse distortion of the distortion compensation loop, the feedforward system distortion compensation amplifier which outputs a signal, of the output signal providing Fidofu <br/> Owa de type distortion compensation amplifier which is characterized in that performs bias control to the main amplifier and error amplifier according to the level.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

Further, in order to solve the above problems, the first
The distortion detection loop consisting of the phase shifter, the first amplitude unit and the main amplifier, the distortion compensation loop consisting of the second phase shifter, the second amplitude unit and the error amplifier, and the distortion detection loop offset by, and outputs a signal feedforward
In scheme distortion compensation amplifier, a second bias performing a first bias control section for biasing control the main amplifier according to the level of the output signal, a bias control to the error amplifier according to the level of the output signal providing to characterized in that a control unit feedforward side Shikiibitsu compensating amplifier.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

Furthermore, in order to solve the above problems, in claim 1 or 2, wherein the feedforward method distortion compensation amplifier, dividing the output signal into a plurality of levels,
Providing feedforward scheme distortion compensation amplifier which is characterized in that performs bias control in accordance with said level.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

In order to solve the above problems, a distortion detection loop including a first phase shifter, a first amplitude shifter, and an amplifier composed of at least one amplification section, a second phase shifter, and a second phase shifter. amplitude unit and a distortion of the distortion compensation loop and the distortion detection loop consisting constituted amplifier of at least one or more of the amplification unit is offset by the inverse distortion of the distortion compensation loop, feedforward scheme distortion compensation amplifier which outputs a signal In at least one first bias control circuit group for bias controlling the amplifier according to the level of the output signal, and at least one second bias control circuit for bias controlling the error amplifier according to the level of the output signal. feedforward scheme Ibitsuho that characterized in that a bias control circuit group
To provide a 償増 width device.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

[0020] In order to solve the above problems, in the feedforward system distortion compensation amplifier according to claim 4, feedforward system distortion compensation, characterized in that a bias control circuit corresponding to the various amplifying section to provide the amplifier.

[Procedure Amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

[0021] In order to solve the above problems, feedforward to the feedforward system distortion compensation amplifier according to claim 5, characterized in that a single bias control circuit to various multiple amplifying section method distortion compensation amplifier.

[Procedure Amendment 11]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

[0024] In the feed-forward lateral Shikiibitsu compensator amplifier, AB class as shown in FIG. 2 by developments of the amplifying element, the tendency of the power consumption is reduced according to class B output levels from the fact that using the amplifying element of the drops is there. However, an idle current must be set in the amplification element, so that the power consumption of the amplification device does not fall below the idle current of the amplification element at a low output level.

[Procedure Amendment 12]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction content]

[0038]

Effects of the Invention According to the first aspect of the invention, in the feed <br/> forwarder de type distortion compensation amplifier, while satisfying the radio characteristics, the effect of suppressing the power of the entire amplifier.

Continued front page    F term (reference) 5J069 AA01 AA41 CA21 CA36 FA10                       KA16 KA34 KA55 KA68 KC06                       KC07 MA14 SA14 TA01 TA02                       TA07                 5J090 AA01 AA41 CA21 CA36 FA10                       GN02 GN05 GN07 KA12 KA16                       KA55 KA68 MA14 SA14 TA01                       TA07                 5J091 AA01 AA41 CA21 CA36 FA10                       KA16 KA34 KA55 KA68 MA14                       SA14 TA01 TA02 TA07                 5J092 AA01 AA41 CA21 CA36 FA10                       GR09 KA16 KA34 KA55 KA68                       MA14 SA14 TA01 TA02 TA07

Claims (5)

[Claims] 1. A distortion detection loop including a first phase shifter, a first amplitude shifter, and a main amplifier, a distortion compensation loop including a second phase shifter, a second amplitude shifter, and an error amplifier, and distortion of a distortion detection loop. In a feedforward distortion amplifier for canceling the signal by the reverse distortion of a distortion compensation loop and outputting a signal, bias control is performed on the main amplifier and the error amplifier according to the level of the output signal. 2. A distortion detecting loop including a first phase shifter, a first amplitude shifter, and a main amplifier, and a distortion compensation loop including a second phase shifter, a second amplitude shifter, and an error amplifier, and a distortion detecting loop. In a feed-forward distortion amplifier for canceling the signal by the reverse distortion of the distortion compensation loop and outputting a signal, and a first bias controller for bias-controlling the main amplifier according to the level of the output signal, and the output signal A feed-forward distortion amplifier, characterized in that a second bias control section is provided for performing bias control on the error amplifier according to the level. 3. The feedforward distortion amplifier according to claim 1, wherein the output signal is divided into a plurality of levels and bias control is performed according to the levels. 4. A distortion detecting loop comprising an amplifier composed of a first phaser, a first amplituder and at least one or more amplifiers, a second phaser and a second amplituder. In a feed-forward distortion compensation amplifier that outputs a signal by canceling the distortion of the distortion compensation loop and the distortion detection loop formed by the amplifier configured as above by the inverse distortion of the distortion compensation loop, the level of the output signal According to the above, at least one first bias control circuit group for bias controlling the amplifying section and at least one second bias control circuit group for bias controlling the error amplifying section according to the level of the output signal are provided. Feed-forward distortion amplifier featuring. 5. The feedforward distortion amplifier according to claim 4, further comprising a bias control circuit corresponding to each amplification section.