JP2000261253A - Feed forward distortion compensation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To disuse a pilot signal conventionally used for adjustment of a distortion elimination loop. SOLUTION: A residual distortion extraction loop L3 is provided which extracts a residual distortion component included in an output signal. The extracted residual distortion component is subjected to orthogonal detection to obtain a signal for optimization of the distortion elimination loop L2. A feedback loop reaching a modulator MOD3 from a detector DEM3 is provided in the residual distortion extraction loop L3 in order to suppress carrier leakage from a hybrid HYB4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedforward distortion compensation circuit for removing or compensating for a distortion component in the output of a main amplifier using a feedforward, and further relates to an amplifier circuit and a distortion compensation method using the same.

[0002]

2. Description of the Related Art When a signal is spread in a relatively wide frequency band, it is necessary to use an amplifier having good linearity as an amplifier for amplifying the signal. For example, digital terrestrial television broadcasting scheduled to be implemented in Japan uses an orthogonal frequency division multiplexing (OFDM) system. In this method, since information is transmitted by a multicarrier signal in which a large number of carriers are arranged at predetermined frequency intervals, it is necessary to use a power amplifier capable of amplifying the multicarrier signal without distortion in a broadcaster or a repeater. . In particular, among various types of distortion generated in the power amplifier, distortion appearing at the same or close frequency as the carrier, for example, intermodulation distortion or intermodulation distortion, is difficult to remove by a filter after amplification.
Therefore, there is a demand for a power amplifier that does not generate intermodulation distortion or the like or that has a function of compensating for such distortion. Similar requirements exist for amplifiers for various mobile communication systems.

FIG. 5 shows a configuration of a circuit that can be used as a power amplifier or the like in a digital terrestrial television broadcasting system or a mobile communication system. The circuit shown in the figure includes a distortion extraction loop L1 for extracting distortion generated due to the nonlinearity of the main amplifier MAIN, and a distortion removal loop L2 for eliminating distortion in the output of the main amplifier MAIN using the extracted distortion.
And two types of feedforward loops. Such a circuit that compensates for distortion using a feedforward loop is called a feedforward distortion compensation circuit (see Japanese Patent Laid-Open No. 4-70203).

More specifically, a signal from a preceding circuit (not shown) is supplied to a main amplifier MAIN via a hybrid HYB1, an attenuator ATT1, and a phase shifter PS1.
And is amplified. The amplified signal is output via the hybrid HYB2, the delay line DL2, and the hybrid HYB3 to a circuit (not shown) in a subsequent stage, for example, an antenna or an output filter in the preceding stage. The above-described signal path from the input terminal at the left end in the drawing to the output terminal at the right end in the drawing via the main amplifier MAIN and the delay line DL2 is called a main line in comparison with two types of feedforward paths described later. In the following description, for simplicity of description,
A signal on the main line may be referred to as a main line signal.

[0005] The hybrid HYB1 branches a part of the input signal from the preceding circuit and supplies it to the hybrid HYB2 via the delay line DL1. Hybrid HYB2
Divides a part of the signal to be output from the main amplifier MAIN via the delay line DL2, combines it with the signal supplied via the delay line DL1, and outputs the resultant signal to the auxiliary amplifier SUB. Carriers in the signal to be combined have the same timing,
With the same amplitude and opposite phase, a signal indicating a distortion component generated in the main amplifier MAIN can be obtained by this signal coupling. Thus, the signal path from the hybrid HYB1 to the output terminal of the hybrid HYB2 via the delay line DL1 can be called a feedforward loop for extracting distortion. Therefore, in the present application, this is called a distortion extraction loop L1.

[0006] From the hybrid HYB2 to the auxiliary amplifier SU
The signal output to the B side is input to the auxiliary amplifier SUB via the attenuator ATT2 and the phase shifter PS2, and is amplified. The hybrid HYB3 combines the signal amplified by the auxiliary amplifier SUB with the main line signal via the delay line DL2, and outputs the combined signal to a subsequent circuit (not shown). Therefore, if the distortion components in the two types of signals to be coupled in the hybrid HYB3 have the same timing, the same amplitude, and the opposite phase, the distortion component generated in the main amplifier MAIN by the signal coupling in the hybrid HYB3 is converted to the main line. It can be removed from the signal. Thus, the hybrid HYB2
A signal path extending from the signal through the auxiliary amplifier SUB to the output terminal of the hybrid HYB3 can be called a feedforward loop for removing distortion. Therefore, in the present application, this is referred to as a distortion removal loop L2.

In order to realize distortion extraction and elimination according to the above-described principle, the carriers in the signals coupled by the hybrid HYB2 must have the same timing, the same amplitude and the opposite phase, and the signals must be coupled by the hybrid HYB3. It is necessary that the distortion components in a given signal have the same timing, the same amplitude, and the opposite phase. The delay lines DL1 and DL2 are means for adjusting the timing, and include an attenuator ATT1, a phase shifter PS1 and a main amplifier MAIN or an attenuator ATT2, a phase shifter PS2 and an auxiliary amplifier SUB, respectively.
The amount of the delay is set so as to compensate for the processing delay. The attenuators ATT1 and ATT2 adjust the amplitude, and the phase shifters PS1 and PS2 adjust the phase. The attenuation and phase shift in these are controlled by the control unit CTL.

The control unit CTL generates two types of pilot signals for controlling the attenuation and the phase shift in the attenuators ATT1 and ATT2 and the phase shifters PS1 and PS2.

First, the first pilot signal PILOT1
Is inserted into the input signal to the hybrid HYB1 by the coupler C7. Therefore, the first pilot signal PI
LOT1 is included in the amplified output of the main amplifier MAIN and also in the signal input to the hybrid HYB2 via the delay line DL1. The control unit CTL is a hybrid H
Using a coupler C9 provided on a signal path from the output terminal of YB2 to the input terminal of the hybrid HYB3 via the auxiliary amplifier SUB, the first pilot signal PILOT1 is used.
Check if can be detected. That is, when the first pilot signal PILOT1 can be detected by the coupler C9, the attenuator ATT1 and the phase shifter PS1 are not in the optimal adjustment state, and as a result, carriers leak from the hybrid HYB2 to the auxiliary amplifier SUB. Yes,
Therefore, the control unit CTL controls the attenuator ATT1 and the phase shifter PS1 to suppress the carrier leak.
The amount of attenuation and the amount of phase shift are changed. Also, coupler C
9, the first pilot signal PILOT having a significant level
When 1 cannot be detected, it can be considered that the attenuator ATT1 and the phase shifter PS1 are in an almost optimal adjustment state and no carrier leak from the hybrid HYB2 to the auxiliary amplifier SUB side occurs.
The attenuation amount and the phase shift amount in the attenuator ATT1 and the phase shifter PS1 are held.

Next, the second pilot signal PILOT2
Is connected to the hybrid HYB2 from the main line by the coupler C8.
Inserted into the input signal to Therefore, the second pilot signal PILOT2 is included in the amplified output of the auxiliary amplifier SUB and also in the signal input to the hybrid HYB3 via the delay line DL2. The control unit CTL includes a coupler C1 provided on the output side of the hybrid HYB3.
Using 0, it is checked whether the second pilot signal PILOT2 can be detected. That is, if the second pilot signal PILOT2 can be detected by the coupler C10, the attenuator ATT2 and the phase shifter PS2 are not in the optimum adjustment state, and as a result, distortion remains in the output of the hybrid HYB3. To be considered, the control unit CTL
In order to suppress this residual distortion, the amount of attenuation and the amount of phase shift in the attenuator ATT2 and the phase shifter PS2 are changed. When the significant level of the second pilot signal PILOT2 cannot be detected by the coupler C10, the attenuator ATT2 and the phase shifter PS2 are in an almost optimum adjustment state, and no significant residual distortion is generated in the output of the hybrid HYB3. Therefore, the control unit CTL holds the attenuation amount and the phase shift amount in the attenuator ATT2 and the phase shifter PS2.

Note that R in the figure is the terminating resistance of each hybrid. G1 and G2 are signals for controlling the amount of attenuation (gain), and φ1 and φ2 are signals for controlling the amount of phase shift. Further, in the present application, from the related art to the embodiments, a configuration in which a signal is branched or combined using a hybrid is shown, but another type of directional coupler may be used instead of the hybrid.

[0012]

In the circuit described above, 2
Pilot signals PILOT1 and PILOT2 are used. Therefore, the necessity of providing an oscillator for generating a pilot signal is an obstacle in reducing the circuit scale. Further, since the frequency range in which distortion can be preferably extracted and removed is limited to the frequency of the pilot signal and its vicinity, it is not possible to easily cope with a change in the desired signal frequency. Are born. Further, the control by the control unit CTL is
It is performed exclusively by software, and control delays associated with execution of software processing have been a problem.

In view of these problems, the applicant of the present application has made the first pilot signal PILOT in accordance with the idea of detecting carrier leak from hybrid HYB2 using a reference signal generated using an automatic level control circuit.
No. 1 is proposed (Japanese Patent Application No. Hei 10-300)
No. 667). FIG. 6 shows an example configuration of a circuit according to the prior proposal. In the circuit shown in FIG.
What is provided to control the amount of attenuation and the amount of phase shift instead of L is a circuit realized by hardware using synchronous detectors DEM1 and DEM2.

First, couplers C10 and C11 are provided on the output end side of the hybrid HYB3. The output of the coupler C11 is transmitted through a delay line DL5 for compensating a time difference with respect to an input to the main amplifier MAIN.
The signal is input to the automatic level control circuit ALC1. The automatic level control circuit ALC1 removes the level fluctuation from the signal from the coupler C11, thereby making the synchronous detector DEM1
Generates the reference signal REF. On the other hand, a coupler C9 is provided on a signal path from the output terminal of the hybrid HYB2 to the input terminal of the hybrid HYB3 via the auxiliary amplifier SUB. The output of the coupler C9 is input as an error signal ERR to the synchronous detector DEM1 via a delay line DL4 for compensating a time difference with respect to an input to the main amplifier MAIN. The synchronous detector DEM1 is
The error signal ERR is synchronously detected based on the reference signal REF. As a result, the hybrid HYB2
Output from the synchronous detector DEM1 to the attenuator ATT1
And the control of the amount of attenuation and the amount of phase shift by the phase shifter PS1.

Next, as in the conventional circuit shown in FIG.
In the circuit of the above, couplers C8 and C10 are also provided. Second pilot signal PILOT generated by oscillator OSC
2 is in-phase distributed to the coupler C8 and the synchronous detector DEM2 by the in-phase distributor BR2, and the signal branched by the coupler C10 is input to the synchronous detector DEM2 via the band-pass filter BPF. Synchronous detector DEM2
Is the second pilot signal PILOT2 that has undergone in-phase distribution.
Is used as a reference signal REF and a signal from the coupler C10 is used as an error signal ERR to perform synchronous detection, thereby generating a control signal for an attenuation amount and a phase shift amount to be given to the attenuator ATT2 and the phase shifter PS2.

Since the synchronous detectors DEM1 and DEM2 and the automatic gain control circuit ALC1 and the like can be configured in hardware, according to the previously proposed circuit whose example is shown in FIG. 6, the control in the conventional circuit shown in FIG. A portion corresponding to the unit CTL can be implemented by hardware. Further, since the first pilot signal PILOT1 can be eliminated, an oscillator for generating the first pilot signal PILOT1 can be eliminated. However, the second pilot signal P
Since control using ILOT2 is continuously employed, it is necessary to provide an oscillator OSC for generating the control, and there remains a problem that a frequency band in which distortion can be compensated is narrow. Further, the second pilot signal PILOT
2 remains in the output signal.

An object of the present invention is to solve such a problem. The second pilot signal and an oscillator for generating the second pilot signal are abolished, and the circuit is smaller in size than the previous proposal. It is an object of the present invention to realize a circuit capable of removing distortion over a wide band, easily coping with a frequency change, and having no pilot signal remaining in an output signal.

[0018]

In order to achieve the above object, in the present invention, a new residual distortion extraction loop is provided in addition to the distortion extraction loop and the distortion removal loop. Modifications were made. Therefore, the feedforward distortion compensation circuit according to the present invention can be grasped and expressed as a circuit including three types of loops, that is, a distortion extraction loop, a distortion removal loop, and a residual distortion extraction loop.

(1) Roles and Functions of Each Loop The distortion extraction loop utilizes a part of an input signal supplied to the main amplifier from a preceding circuit and a part of an amplified signal output from the main amplifier. An extracted distortion signal representing a distortion component generated in the main amplifier is generated. That is, since the input signal does not include a distortion component caused by the non-linearity of the main amplifier, the amplified signal does include the distortion component. Therefore, by using these signals, an extracted distortion component representing the distortion component is obtained. Can be generated. Next, the distortion removal loop generates an output signal to a subsequent circuit by combining the extracted distortion signal with the amplified signal. Since the extracted distortion signal is a signal representing a distortion component included in the amplified signal, by combining this with the amplified signal, an output signal that does not include the distortion component included in the amplified signal is generated. Is possible.

The residual distortion extraction loop according to the first aspect of the present invention utilizes a part of an input signal and a part of an output signal,
An extracted residual distortion signal is generated which represents a residual distortion component generated in the main amplifier and remaining in the output signal. That is, since the input signal is a signal that does not include a distortion component caused by the main amplifier,
By utilizing this, it is possible to detect a residual distortion component in the output signal and generate an extracted residual distortion signal representing the detected residual distortion component. A second feature of the present invention is that the distortion removal loop is modified to use the extracted residual distortion signal generated in this manner. In the distortion removal loop, the amplitude and / or phase are adjusted based on the extracted residual distortion signal so as to suppress the residual distortion component, and then the extracted distortion signal is combined with the amplified signal.

Therefore, according to the present invention, it is not necessary to use the second pilot signal when adjusting the amplitude and / or phase of the extracted distortion signal in the distortion removal loop, and therefore, an oscillator for generating this is provided. No need. As a result, the circuit becomes smaller. In addition, the residual distortion component contained in the output signal is extracted in the form of an extracted residual distortion signal, and the distortion is removed based on the extracted residual distortion signal. Can be realized. That is, the frequency range in which distortion can be suitably compensated for is wider than the comparatively narrow range (frequency of the pilot signal and its vicinity) in the related art and the prior art example, and the reliability of distortion compensation is improved. Since no pilot signal is used, the pilot signal does not remain in the output signal. Further, an output filter used for removing harmonics, a pilot signal, and the like from the output signal becomes unnecessary, thereby producing an effect such as a reduction in circuit scale. In addition, even when the frequency of the input signal (the frequency of each carrier when the input signal is a multi-carrier signal) is changed,
Since it is not necessary to take measures such as changing the frequency of the pilot signal, it is possible to immediately respond to the situation.

(2) More Detailed Circuit Configuration The configuration of the feedforward distortion compensation circuit according to the present invention is as follows.
A directional coupler, an amplitude and / or phase adjustment member,
In addition, it can be defined and expressed by the connection relation and signal transmission / reception relation of the adjustment amount determining member for determining the adjustment amount.

First, the first directional coupler is arranged before the main amplifier, and the second and third directional couplers are arranged sequentially after the main amplifier. The first directional coupler supplies an input signal to the main amplifier, the second directional coupler supplies an amplified signal output from the main amplifier to a third directional coupler, and the third directional coupler is The amplified signal is received, and an output signal to a subsequent circuit is generated. This path, that is, the path from the input terminal of the first directional coupler to the output terminal of the third directional coupler via the main amplifier (but not through the auxiliary amplifier) corresponds to the main line described above. .

The first directional coupler supplies a part of the input signal to the second directional coupler. The second directional coupler extracts a part of the amplified signal and combines the extracted signal with the input signal supplied from the first directional coupler to generate an extracted distortion signal and supply it to the auxiliary amplifier. This path, that is, the signal path from the signal input to the first directional coupler to the generation of the extracted distortion signal forms a main part of the distortion extraction loop described above. Next, the third directional coupler couples the amplified signal supplied from the second directional coupler with the extracted distortion signal supplied via the auxiliary amplifier, thereby outputting the signal to the subsequent circuit. Generate a signal. This path, that is, the signal path from the output of the extracted distortion signal from the second directional coupler to the generation of the output signal forms a main part of the distortion removal loop described above.

In order to realize preferable distortion extraction and distortion removal,
A predetermined relationship must be established between the signals to be combined in the second and third directional couplers. First, the second
As for the directional coupler, a plurality of carriers included in the input signal supplied from the first directional coupler and arranged densely and a plurality of carriers included in the amplified signal combined with the input signal are included. The carrier must be of the same amplitude and opposite phase at the output of the second directional coupler. Therefore, a first adjusting member is provided on a signal path from the first directional coupler to the second directional coupler via the main amplifier to adjust the amplitude and / or phase of the signal. Next, regarding the third directional coupler, the distortion component included in the amplified signal supplied from the second directional coupler and the extracted distortion signal combined with the amplified signal are the third component. At the output of the directional coupler, they must be of the same amplitude and opposite phase. Therefore, a second adjustment member is provided on the signal path from the second directional coupler to the third directional coupler via the auxiliary amplifier to adjust the amplitude and / or phase of the signal.

With respect to the amplitude and / or phase adjustment amount of the first adjustment member among the first and second adjustment members, the carrier in the extracted distortion signal is detected using the input signal, and based on the result, May be determined. As a member for that purpose, a first adjustment amount determining member is provided. The first adjustment amount determining member is formed by a method previously proposed by the present applicant,
It is feasible. On the other hand, the method of determining the amplitude and / or phase adjustment amount in the second adjustment member is a novel method, and can be said to be one of the great features of the present invention. Second
In order to determine the amplitude and / or phase adjustment amount in the adjustment member, the present invention uses, for example, a circuit having the following configuration and operation.

First, a fourth directional coupler is provided.
The directional coupler inputs and couples a part of the output signal and a part of the input signal. The resulting signal is
Since a component corresponding to the residual distortion component included in the output signal is included, it is referred to as an extracted residual distortion signal here. However, this signal may include a carrier leak through the fourth directional coupler in addition to the component corresponding to the residual distortion component. In other words, both the input signal and the output signal contain carriers, and the extracted residual distortion signal obtained by combining these with the fourth directional coupler has signals to be combined with exactly the same amplitude and opposite phase. When there is no carrier, the carrier remains without being removed.

The extracted residual distortion signal output from the fourth directional coupler is supplied to a second adjustment amount determining member and a third adjustment amount determining member. The second adjustment amount determining member detects a residual distortion component in the extracted residual distortion signal using the extracted distortion signal, and determines an amplitude and / or phase adjustment amount in the second adjustment member based on the detection result. In order to suppress the residual carrier in the extracted residual distortion signal, the third adjustment amount determining member detects the carrier in the extracted residual distortion signal using the input signal,
Based on the result, the amplitude and / or phase adjustment amount in the third adjustment member is determined. The third adjustment member supplies an input signal on a signal path from the third directional coupler to the fourth directional coupler or to the fourth directional coupler to adjust the amplitude and / or phase of the signal. It is a member provided on the route. Therefore, the operation of the third adjusting member and the third adjusting amount determining member causes feedback in the direction of suppressing the carrier in the extracted residual distortion signal supplied to the second adjusting amount determining member.
The amount of amplitude and / or phase adjustment in the second adjustment member can be suitably determined.

As described above, in the present invention, the leakage of the carrier into the extracted distortion signal via the second directional coupler is reduced to the first level.
Suppressed by amplitude and / or phase adjustment in the adjustment member,
Further, the residual distortion component, which is a distortion component generated by the non-linearity of the main amplifier and remaining in the output signal, is canceled by the amplitude and / or phase adjustment in the second adjusting member, and the extracted residual distortion is output through the fourth directional coupler. Carrier leakage to the signal is suppressed by amplitude and / or phase adjustment in the third adjustment member. In particular, if the fourth directional coupler is cascade-connected in a plurality of stages (a plurality of third adjusting members and third adjusting amount determining members are provided along with this), and the carrier suppression amount is shared in each stage, The accuracy of the adjustment by the third adjusting member can be low for each third adjusting member, and the circuit can be easily realized.

(3) Others In practicing the present invention, the first to third adjusting members are realized by a combination of an attenuator or an amplifier and a phase shifter according to the prior art and the prior proposal. The amount of attenuation or gain and the amount of phase shift may be determined by the three adjustment amount determining member. Further, instead of the method of directly adjusting the amplitude and the phase, quadrature modulation may be used. That is,
By adjusting the in-phase (I) and quadrature (Q) components of the signal, the amplitude and phase of the signal can be adjusted substantially, so that attenuators (amplifiers) and phase shifters can be replaced by quadrature modulators. .

Each of the first to third adjustment amount determining members can be realized by a combination of a quadrature detector and an automatic level control circuit. The automatic level control circuit is a circuit that generates a reference signal to be given to a corresponding quadrature detector by suppressing a level fluctuation in a given signal. First
Each of the automatic level control circuits constituting the third to third adjustment amount determining members generates a reference signal from a part of the input signal, a part of the extracted distortion signal, or another part of the input signal. The quadrature detectors constituting the first to third adjustment amount determining members respectively receive a part of the extracted distortion signal, a part of the residual extracted distortion signal, or another part of the residual extracted distortion signal as an error signal, Based on the reference signal from the corresponding automatic level control circuit, the corresponding error signal is subjected to quadrature detection. Each of the first to third adjustment members, for example, the quadrature modulator, quadrature modulates a signal to be subjected to amplitude and / or phase adjustment according to the detection output of the corresponding quadrature detector.

The present invention can be further understood as an invention relating to an amplifier circuit. That is, an amplifier circuit according to the present invention includes the main amplifier and the feedforward distortion compensation circuit according to the present invention. According to this amplifier circuit, low distortion or distortion-free characteristics can be provided in a wider frequency band than before. The circuit scale is relatively small,
No pilot signal leakage, no output filter required,
Can respond immediately to frequency changes.

The present invention can be further understood as a distortion compensation method. That is, the distortion compensation method according to the present invention uses the part of the input signal provided to the main amplifier from the circuit in the preceding stage and the part of the amplified signal output from the main amplifier to generate the distortion in the main amplifier. When generating an output distortion signal representing a distortion component and generating an output signal to a subsequent circuit by combining the extraction distortion signal with the amplified signal, a part of the input signal and a part of the output signal are combined. Utilizing this, an extracted residual distortion signal representing the residual distortion component generated in the main amplifier and remaining in the output signal is generated, and the amplitude and // Alternatively, after the phase adjustment, the extracted distortion signal is combined with the amplified signal.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. The same or corresponding components as those of the circuit of the related art shown in FIG. 5 or the previously proposed circuit shown in FIG. 6 are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 1 shows a circuit configuration according to an embodiment of the present invention. The circuit shown in this figure is an amplification circuit that can be used as a power amplifier in a broadcaster for digital terrestrial television broadcasting, for example.

The circuit shown in FIG. 3 includes a distortion extraction loop L1,
It has a distortion removal loop L2 and a residual distortion extraction loop L3. Among these, the distortion extraction loop L1 is connected to the main amplifier MAI.
A hybrid HYB1 as a first directional coupler before N
At the subsequent stage, a hybrid HYB2 as a second directional coupler.
Are further arranged, and a quadrature modulator MOD1 is provided on a main path among signal paths from the hybrid HYB1 to the hybrid HYB2. The hybrid HYB1 supplies a signal, for example, a multicarrier signal, supplied from a circuit at the preceding stage via an input terminal on the left end in the drawing to the main amplifier MAIN. Main amplifier MAIN
Amplifies this input signal and supplies it to the hybrid HYB2 as an amplified signal. In addition, hybrid HYB1
Divides a part of the input signal to the main amplifier MAIN and supplies it to the hybrid HYB2 via the delay line DL1. The hybrid HYB2 supplies the amplified signal from the main amplifier MAIN to the hybrid HYB3 via the delay line DL2, extracts a part of the amplified signal, and combines the amplified signal with the input signal supplied via the delay line DL1. Let it. The hybrid HYB2 supplies the resulting signal, that is, the extracted distortion signal, to the auxiliary amplifier SUB.

The main function of the distortion extraction loop L1 is to detect a distortion component generated due to the non-linearity of the main amplifier MAIN in the form of an extracted distortion signal. In order for the extracted distortion signal to be a signal containing only a distortion component and no carrier, that is, to eliminate the leakage of the carrier from the hybrid HYB2 to the auxiliary amplifier SUB side, the coupling target in the hybrid HYB2 is Must have the same timing, the same amplitude, and the opposite phase. The delay line DL1 is connected to the quadrature modulator M to eliminate the time difference between the signals.
Compensates for delays in OD1 and main amplifier MAIN. The quadrature modulator MOD1, which is a first adjusting member, is provided on a signal path from the output terminal of the hybrid HYB1 to the input terminal of the hybrid HYB2 via the main amplifier MAIN, and the first adjusting amount determining member is connected via the amplifier AMP1. According to the signal supplied from the detector DEM1, the signal propagating on the signal path is quadrature-modulated. Detector DEM1
Is a signal detected by the coupler C2 as an error signal,
The output of the automatic level control circuit ALC1 is input as a reference signal, and the error signal is subjected to quadrature detection based on the reference signal. The coupler C2 is a hybrid HYB2
From the output terminal of the hybrid HY via the auxiliary amplifier SUB
The extracted distortion signal is provided on the signal path leading to the input terminal of B3, and is input as an error signal to the detector DEM1. The signal detected by the coupler C1 is input to the automatic level control circuit ALC1, and the coupler C1 is connected to the hybrid H from the leftmost input terminal in the figure.
The reference signal obtained by the automatic level control circuit ALC1 is a signal obtained by making the level of the input signal to the main amplifier MAIN constant since the signal is provided on the signal path extending to the input terminal of the hybrid HYB2 via the YB1 and the delay line DL1. is there. Therefore, as a result of quadrature detection in the detector DEM1,
The carrier component in the extracted distortion signal is detected, and by controlling the modulator MOD1 using the result of the detection, it is possible to suppress the leakage of the carrier into the extracted distortion signal.

The distortion removing loop L2 includes a hybrid HYB3 as a third directional coupler and a modulator MO as a second adjusting member.
D2 and a detector DEM2 as a second adjustment amount determining member. The hybrid HYB3 couples the amplified signal supplied from the hybrid HYB2 via the delay line DL2 and the extracted distortion signal amplified by the auxiliary amplifier SUB to a subsequent circuit (not shown) from the right output terminal in the figure. To generate an output signal to be output. Modulator MOD
2 is an auxiliary amplifier SU from the output terminal of the hybrid HYB2.
B is provided on the signal path extending to the input terminal of the hybrid HYB3 via the B, and the detector DE via the amplifier AMP2.
The extracted distortion signal is quadrature-modulated according to the signal supplied from M2. The detector DEM2 inputs the extracted residual distortion signal supplied from the residual distortion extraction loop L3 as an error signal and the signal supplied from the automatic level control circuit ALC2 as a reference signal, and converts the error signal based on the reference signal. Perform quadrature detection. The automatic level control circuit ALC2 has a coupler C
3 is a circuit for converting the signal detected by 3 into a constant level.
The coupler C3 is provided on a signal path from the output terminal of the hybrid HYB2 to the input terminal of the hybrid HYB3 via the auxiliary amplifier SUB. Therefore, the detector DEM2
Is supplied as a reference signal, the extracted residual distortion signal supplied to the detector DEM2 from the residual distortion extraction loop L3 to the detector DEM2 is exclusively a residual distortion component. If the signal includes the main amplifier MAIN, the quadrature modulation operation in the modulator MOD2 is controlled by the detection output of the detector DEM2.
Can be suppressed or compensated for a residual distortion component which is a distortion component generated in the output signal from the hybrid HYB3.

The residual distortion extraction loop L3 includes a hybrid HYB4 serving as a fourth directional coupler, a modulator MOD3 serving as a third adjusting member, and a detector DEM3 serving as a third adjusting amount determining member. First, the hybrid HYB4 has an output signal detected by the coupler C6 provided at the output end of the hybrid HYB3 and a coupler C4 provided on a signal path from the input end of the hybrid HYB1 to the input end of the hybrid HYB2. And the signal detected by the above are input. The signal detected by the coupler C4 is passing through the delay line DL3. The delay line DL3 is connected to the hybrid HYB3 from the place where the coupler C4 is provided.
Is a delay line for compensating for a processing delay on a signal path leading to an output terminal of the first embodiment. The hybrid HYB4 generates an extracted residual distortion signal by combining the two types of signals thus input. The in-phase distributor BR1 distributes in-phase the extracted residual distortion signal generated by the hybrid HYB4 to the detector DEM2 and the detector DEM3.

The detector DEM3 inputs the extracted residual distortion signal distributed from the in-phase distributor BR1 as an error signal, and inputs the signal from the automatic level control circuit ALC3 as a reference signal. The automatic level control circuit ALC3 is a circuit for converting the signal detected by the coupler C5 to a constant level. The coupler C5 is provided on a signal path from the input terminal of the hybrid HYB1 to the input terminal of the hybrid HYB2 via the delay line DL1. I have. Therefore, the detector DEM
3 is a signal obtained by converting the input signal to a constant level. Therefore, the detector DEM3 performs quadrature detection of the extracted residual distortion signal, which is an error signal, by using the reference signal, thereby passing through the hybrid HYB4. Carrier leakage can be detected.

The detector DEM3 supplies the detection output to the modulator MOD3 via the amplifier AMP3. Modulator M
The OD3 is provided between the coupler C6 and the hybrid HYB4, and orthogonally modulates an input signal to the hybrid HYB4 based on a signal from the detector DEM3. With this quadrature modulation operation, feedback is applied to the extracted residual distortion signal output from the hybrid HYB4 in a direction to suppress carrier leakage via the hybrid HYB4. That is, the detector DEM2 is transmitted through the in-phase distributor BR1.
The carrier in the extracted residual distortion signal supplied to is suppressed,
It is a signal that exclusively represents the residual distortion component in the output signal.

As described above, according to the present embodiment, the residual distortion extraction loop L3 is provided, and the residual distortion component in the output signal is detected by the residual distortion extraction loop L3 to perform quadrature modulation (specifically, the extraction distortion signal) of the extracted distortion signal. Since the I component and the Q component are adjusted (and the amplitude and the phase are adjusted), it is not necessary to use the second pilot signal PILOT2 used in the related art and the prior proposal. Therefore, when the frequency of the input signal is changed, it is possible to respond to the change, and the pilot signal does not leak out in the output signal. Furthermore, since the residual distortion component in the output signal is extracted by detection and the extracted distortion signal is adjusted, the frequency band in which distortion can be appropriately removed as in the related art and the prior proposal is the frequency and frequency of the pilot signal. Without being limited to that vicinity,
It is possible to perform highly reliable distortion removal over a wide frequency band as compared with the related art and the previous proposal. Along with this, it is no longer necessary to provide an output filter that was conventionally provided as a subsequent circuit. As a result, the circuit scale when including the peripheral circuits is smaller than that of the related art or the prior proposal.

Further, various modifications can be made to the circuit shown in FIG. For example, in this embodiment, the quadrature modulation is performed by the modulators MOD1 to MOD3. However, instead of the quadrature modulation, the attenuation (or gain) and the phase shift are adjusted as in the related art and the previous proposal. May be performed. The quadrature detection in the detectors DEM1 to DEM3 may be performed after frequency conversion according to the heterodyne method. Further, in order to supply a reference signal to the detectors DEM1 to DEM3, automatic level control circuits ALC1 to ALC are used.
Although 3 is provided, these can be omitted if there is no problem in circuit operation. For example, in the automatic level control circuit ALC1, since the signal detected by the coupler C1 is an input signal, omitting the signal does not cause any trouble. Further, the modulators MOD1 to MOD3 and the detector DE
As the circuit configurations of M1 to DEM3, conventionally known configurations can be appropriately applied. In addition, each coupler C1
About C6, the arrangement | positioning place can be changed suitably. For example, the couplers C1, C4, and C5 may be moved to another location as long as an input signal containing no distortion component is obtained. Couplers C2 and C3
May be moved to another location where the extracted distortion signal can be detected.

Further, the couplers C4 and C5 in FIG. 1 may be replaced with a coupler C4a and an in-phase distributor BR3 as shown in FIG. The coupler C4a is a hybrid HY
A part of the input signal is branched from the path from B1 to the hybrid HYB2 via the delay line DL1 to form the in-phase distributor B.
Supply to R3. In-phase distributor BR3 distributes this signal in-phase to automatic level control circuit ALC3 and hybrid HYB3. Also, in the circuit shown in FIG.
OD3 is not placed on the signal path from the coupler C6 to the hybrid HYB4, but on the delay line DL from the in-phase distributor BR3.
3 on the signal path to hybrid HYB4,
Provided. Even in this case, the same effect as the circuit shown in FIG. 1 can be obtained.

FIG. 3 shows another modification of the residual distortion extraction loop L3. In the example shown in this figure, two cascade-connected hybrids HYB4a and HYB4b are provided instead of the hybrid HYB4 in the first embodiment shown in FIG. 1 and the second embodiment shown in FIG.
Further, the modulator 3a corresponding to the hybrid HYB 4a,
Detector 3a, automatic level control circuit ALC3a, amplifier 3
a and the in-phase distributor BR1a are hybrid HYB4b
The modulator 3b, the detector 3b, the automatic level control circuit ALC3b, the amplifier 3b, and the in-phase distributor BR1b correspond to
Each is provided. Further, following the second embodiment shown in FIG. 2, one coupler C4a is provided on the signal path from the hybrid HYB1 to the hybrid HYB2 via the delay line DL1, and the branch is extracted by the coupler C4a. The signals are divided into three in-phase distributors BR3a and BR3a.
In-phase 4 distribution is performed by R3b and BR3c. The distribution destinations are the automatic level control circuits ALC3a and ALC3b and the hybrid HYB4a and HYB4b. Further, similarly to the second embodiment, the modulators MOD3a and MOD3b are provided on a signal path from the in-phase distributors BR3b and BR3c to the hybrid HYB4a or HYB4b.

In the third embodiment shown in FIG. 3, the coupler C6
Is output by the hybrid HYB
4a is combined with the input signal to form a hybrid HYB 4a
Is output from the detector DEM3a by the in-phase distributor BR1a.
And the hybrid HYB4b. Hybrid HYB4b out of the output of hybrid HYB4a
Are combined with the input signal at the hybrid HYB 4b, and the output of the hybrid HYB 4b is output to the detector DEM3b and the detector DE by the in-phase distributor BR1b.
In-phase distribution with M2. Detector DEM3a and DEM
3b are automatic level control circuits ALC3a and ALC3b
Of the in-phase distributors BR1a and BR1b, the signal obtained from the corresponding one of the in-phase distributors BR1a and BR1b is subjected to quadrature detection, and the resulting signal is amplified by the amplifier AMP3a and the amplifier AMP3a. AMP3
The signal is supplied to a corresponding one of the modulators MOD3a and MOD3b through a corresponding one of the modulators b.

As described above, the residual distortion extraction loop L3 is
By adopting a stage cascade connection configuration, the embodiment of the present invention becomes easy. First, in order for the residual distortion suppression according to the principle of the present invention to function properly, the residual carrier in the extracted residual distortion signal supplied to the detector DEM2 must be sufficiently small. That is, the hybrid HYB4 or HYB
Carrier leak through the 4a and the HYB 4b must be sufficiently suppressed. In the circuit according to the first embodiment shown in FIG. 1, the operation of the hybrid HYB4 and the modulator MOD3 provided before the hybrid HYB4 causes the hybrid HYB4 to operate.
Since the carrier leak via the B4 is suppressed, in order to suppress the carrier leak via the hybrid HYB4 to a sufficient amount, the adjustment accuracy of the I and Q component values (amplitude and phase) in the modulator MOD3 is extremely high. Must be higher. On the other hand, in the circuit according to the third embodiment shown in FIG. 3, for example, the hybrid HYB 4a suppresses 30 dB and the hybrid HYB 4b suppresses 30 dB, thereby obtaining a total suppression amount of 60 dB. The adjustment accuracy required for the modulator MOD3 when achieving the suppression of each 30 dB may be a relatively low accuracy such as 0.2 dB in amplitude and 2 deg in phase. Although this increases the circuit scale, it is easy to realize because the operation accuracy of the circuit is low. Conversely, it is possible to realize high-accuracy, high-stability, and high-reliability control over a wide frequency band. Means In addition, the required operation accuracy is reduced, so that the circuit is resistant to noise, and the time required for leading to a stable state or the time required for adjusting the circuit can be reduced.

In the third embodiment, the signal distribution from the coupler C4a to the residual distortion extraction loop L3 and the modulator MOD3a
Although the arrangement of the MOD 3b and the MOD 3b follow the second embodiment, the circuit configuration may follow the first embodiment.
Further, the delay lines DL3a and DL3b can be appropriately moved to another place in combination with the invention of the distribution form. Furthermore, 2
Not limited to the stage cascade connection, a larger number of stages may be cascade-connected, or a partial parallel connection may be employed. In addition, various modifications described in the description of the first and second embodiments can be applied to the third embodiment.

Further, the document “Adaptation Behavior of a F”
eedforward Amplifier Linealizer ”, James K. Cavers,
IEEE Transactions on Vehicular Technology, vol.4
4, No. 1, February 1995, pp. 31-39, as shown in FIG. 4A, a band elimination filter BRF having a characteristic Ho (f).
Is used to remove a part of the output signal and supply it to the distortion removal loop L2. That is, according to the description format of the embodiment in the present application, a signal supplied as an error signal to the detector DEM2 is obtained by filtering the signal obtained by the coupler C6. Further, the characteristic Ho (f) shown in the above document is a band elimination characteristic for eliminating a signal belonging to the band Wm, as shown in FIG.

Therefore, the circuit described in the above document is similar to the embodiment of the present invention in that a part of the output signal is extracted and used for distortion removal. However, the distortion signal extracted from the output signal by the circuit according to the above document is only a component existing outside the band Wm, mainly distortion. In the embodiment described above, since the residual distortion component is extracted by extracting a part of the output signal and combining it with a part of the input signal, the frequency band of the residual distortion component that can be extracted is as described in the above document. There is no such band limitation. In connection with this, the present embodiment realizes an advantage that it can immediately respond to a change in the frequency of an input signal, for example, a carrier frequency. In the above document, it should be noted that it is necessary to change or change the design of the characteristic Ho (f) in order to cope with the frequency change of the input signal.

Further, the above embodiment uses the input signals detected by the couplers C4 and C5,
Hybrid HYB4 using output of detector DEM3
Also, it is essentially different from the bandpass filter BRF in the above document in that the input to the filter is fed back. That is,
In the present embodiment, the leakage of the carrier into the extracted residual distortion signal supplied as an error signal to the detector DEM2 can be described as a residual distortion extraction loop L which is a loop for extracting residual distortion.
3 is autonomously suppressed by using a feedback loop from the detector DEM3 to the modulator MOD3, which is a loop further provided in the inside of the device 3. Such an idea is not found in the above document. Rather, what is shown in the above document is the band Wm
Is a concept of suppressing a residual distortion component in an output signal by using a distortion component appearing outside the above, which is different from the idea according to the present embodiment.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a part of a residual distortion extraction loop in a circuit configuration according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a part of a residual distortion extraction loop in a circuit configuration according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a circuit when the circuit described in the prior art document is deformed according to FIG. 1, and in particular, FIG.
3 is a schematic block diagram, and FIG. 3B is a characteristic diagram of a band elimination filter.

FIG. 5 is a block diagram illustrating a configuration of a circuit according to the related art.

FIG. 6 is a block diagram showing a configuration of a circuit previously proposed by the present applicant.

[Explanation of symbols]

ALC1 to ALC3 Automatic level control circuit, BR1 In-phase distributor, C1 to C6 coupler, DL1 to DL3 delay line, DEM1 to DEM3 detector, HYB1 to HYB4
Hybrid, L1 distortion extraction loop, L2 distortion removal loop, L3 residual distortion extraction loop, MAIN main amplifier,
MOD1 to MOD3 Modulator, SUB auxiliary amplifier.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Ryoji Ito 5-1-1 Shimorenjaku, Mitaka-shi, Tokyo Japan Radio Co., Ltd. F-term (reference) 5J090 AA04 AA41 CA21 CA27 FA08 GN03 GN05 GN07 HA25 HN08 HN16 KA15 KA45 KA53 KA55 MA14 MA20 NN16 SA14 TA01 TA03 5J091 AA04 AA41 CA21 CA27 FA08 FP04 FP09 HA25 KA15 KA45 KA53 KA55 KA68 MA14 MA20 SA14 TA01 TA03

Claims (6)

[Claims] An extracted distortion representing a distortion component generated in a main amplifier using a part of an input signal supplied to a main amplifier from a circuit in a preceding stage and a part of an amplified signal output from the main amplifier. A distortion extraction loop that generates a signal, a distortion removal loop that generates an output signal to a subsequent circuit by combining the extracted distortion signal with the amplified signal, and a part of the input signal and a part of the output signal. And a residual distortion extraction loop for generating an extracted residual distortion signal representing the residual distortion component generated in the main amplifier and remaining in the output signal, wherein the distortion removal loop comprises the residual distortion component. A feed-forward distortion compensation circuit, which performs amplitude and / or phase adjustment based on the extracted residual distortion signal so as to suppress the extracted distortion signal, and combines the extracted distortion signal with the amplified signal. 2. A first directional coupler for supplying an input signal including a plurality of closely arranged carriers to a main amplifier and supplying a part of the input signal to a second directional coupler, and an output signal from the main amplifier. The amplified signal is supplied to a third directional coupler, a part of which is extracted and combined with an input signal supplied from the first directional coupler to generate an extracted distortion signal, which is supplied to an auxiliary amplifier. A third method of generating an output signal to a subsequent circuit by combining the two-way coupler, the amplified signal supplied from the second directional coupler, and the extracted distortion signal supplied via the auxiliary amplifier A directional coupler; a first adjustment member provided on a signal path from the first directional coupler to the second directional coupler via the main amplifier to adjust the amplitude and / or phase of the signal; A second to adjust the amplitude and / or phase of the signal A second adjusting member provided on a signal path from the directional coupler to the third directional coupler via the auxiliary amplifier, to the third directional coupler. And a first adjustment amount determining member for determining the amplitude and / or phase adjustment amount in the first adjusting member based on the detection result, and a part of the output signal and a part of the input signal are input and coupled. A fourth directional coupler that generates an extracted residual distortion signal and supplies the generated signal to the second and third adjustment amount determining members; and detects and detects a residual distortion component in the extracted residual distortion signal using the extracted distortion signal. A second adjustment amount determining member for determining an amplitude and / or phase adjustment amount in the second adjustment member based on the result; and a third directional coupler to a fourth directional coupler for adjusting the amplitude and / or phase of the signal. On the signal path leading to A third terminal provided on the supply path of the input signal to the four-way coupler.
An adjustment member, and a third adjustment amount determination member that detects the carrier in the extracted residual distortion signal using the input signal and determines the amplitude and / or phase adjustment amount in the third adjustment member based on the result. Carrier leakage to the extracted distortion signal via the second directional coupler is suppressed by amplitude and / or phase adjustment in the first adjustment member, and is a distortion component generated due to nonlinearity of the main amplifier and remaining in the output signal. The residual distortion component is canceled by amplitude and / or phase adjustment in the second adjustment member, and carrier leakage to the extracted residual distortion signal via the fourth directional coupler is suppressed by amplitude and / or phase adjustment in the third adjustment member. A feed-forward distortion compensation circuit, characterized in that: 3. The feedforward distortion compensating circuit according to claim 2, wherein the fourth directional coupler generates a signal generated by combining a part of an output signal or a signal from a preceding stage with the input signal, respectively. A stage or a multi-stage directional coupler cascaded to supply to the second and third adjustment amount determination members is replaced by a third adjustment member and a third adjustment amount determination member corresponding to each of the above stages. A feedforward distortion compensation circuit, comprising a plurality of feedforward distortion compensation circuits. 4. The feedforward distortion compensation circuit according to claim 2, wherein each of the first to third adjustment amount determining members is provided with a quadrature detector that performs quadrature detection of an error signal with reference to a reference signal. An automatic level control circuit for generating a reference signal for a corresponding quadrature detector by suppressing a level fluctuation in the signal, wherein the first to third adjusting members respectively correspond to the detection output of the corresponding quadrature detector. A quadrature modulator that quadrature-modulates a signal to be subjected to amplitude and / or phase adjustment, and a quadrature detector constituting first to third adjustment amount determination members;
An automatic level control circuit, which inputs a part of the extracted distortion signal, a part of the residual extracted distortion signal, or another part of the residual extracted distortion signal as an error signal, and configures the first to third adjustment amount determination members, A feed-forward distortion compensation circuit for generating a reference signal from a part of the input signal, a part of the extracted distortion signal, or another part of the input signal, respectively. 5. An amplifier circuit comprising: the main amplifier; and the feedforward distortion compensation circuit according to claim 1. 6. An extraction distortion representing a distortion component generated in a main amplifier by utilizing a part of an input signal supplied to a main amplifier from a preceding circuit and a part of an amplified signal output from the main amplifier. In generating a signal and generating an output signal to a subsequent circuit by combining the extracted distortion signal with the amplified signal, a main amplifier is used by utilizing a part of the input signal and a part of the output signal. And generating an extracted residual distortion signal representing the residual distortion component generated in the output signal and remaining in the output signal, and performing amplitude and / or phase adjustment based on the extracted residual distortion signal so that the residual distortion component is suppressed. A distortion compensating method comprising combining an extracted distortion signal with an amplified signal.