JP2003198273A - Amplifier circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a distortion compensation type amplifier circuit that maintains a fixed amount of phase delay and gain, independently of the signal frequency. <P>SOLUTION: In an input signal, one portion is extracted as an input comparison signal by a directional coupler 12, phase delay and attenuation corresponding to a phase control signal 183 and an amplitude control signal 184 each are given by a variable phase-shifter 13 and a variable attenuator 14, and amplification output is made by an amplification section 100, including a distortion compensation circuit and a power amplifier to be compensated. A directional coupler 16 extracts its one portion as an output comparison signal and outputs the remainder as an output signal. A compensation circuit 17 detects the phase difference between the input and output comparison signals and amplitude ratio. An adjustment circuit 18 changes a phase control signal 183 and an amplitude control signals 184 so that a fixed amount of phase difference and amplitude ratio is maintained. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a predistortion compensation type amplifier circuit for compensating for non-linear distortion, and more particularly to a frequency characteristic improving technique and a noise reducing technique for such an amplifying circuit.

[0002]

2. Description of the Related Art Conventionally, a power amplifier is used in a general wireless communication apparatus to amplify a transmission signal to a transmission level. In any amplifier including the power amplifier, when the input signal is amplified in the characteristic region (so-called nonlinear region) where the level of the output signal is saturated, nonlinear distortion occurs.

When this non-linear distortion occurs in a signal modulated by using a linear modulation method, the amplitude component and the phase component of the signal are distorted, so that the modulation accuracy is deteriorated and the spectrum is expanded. The deterioration of the modulation accuracy increases the bit error rate, and the expansion of the spectrum increases the leakage power to the adjacent channel, which deteriorates the communication quality.

Further, when non-linear distortion occurs in a multi-carrier signal obtained by multiplexing a plurality of carrier signals of different frequencies, the distortion components of the carrier signals interfere with each other, and as a result, the carrier signals themselves. Intermodulation distortion occurs in the frequency band of. This intermodulation distortion that occurs in the frequency band of the carrier signal itself due to the non-linear distortion cannot be removed using a filter or the like, and is extremely harmful in maintaining proper communication quality.

Nonlinear distortion can be suppressed, for example, by using a power amplifier having an excessive saturated output in a characteristic region having a good linearity by taking a large backoff.
In this method, it is necessary to use an excessively expensive power amplifier and the power efficiency is also poor, which is not preferable in reducing the manufacturing cost and operating cost of the wireless communication device. Therefore, conventionally, a predistortion circuit (also referred to as a predistortion compensation circuit) is used as a method of using a power amplifier even in a non-linear region and suppressing non-linear distortion.

The predistortion circuit is a circuit for generating a distortion signal by adding a compensation signal obtained by applying a predetermined phase and level fluctuation to the harmonics of the input signal with respect to the input signal, And the level variation are provided so as to compensate the non-linear characteristic of the compensated power amplifier. When the generated distortion signal is amplified by the power amplifier to be compensated, the non-linear distortion component in the amplified output signal is reduced as compared with the case where the input signal itself is amplified.

For the principle of action in which the non-linear distortion component is reduced, see, for example, the document "HIGH-LINEARITY RF AMPLIFIER.
DESIGN ”by PETER B. KENINGTON, Artech House Publishe
Since it is described in detail in the rs publication, its explanation is omitted here. Fig. 9 shows an amplifier circuit equipped with a predistortion circuit as shown in the paper "Proposal of High-Power Amplifier Distortion Reduction by EVEN-ORDER PRE-DISTORTION" by Koji Horikawa et al., 1996 IEICE Communications Society Conference B-230. 800
Indicates. Hereinafter, this type of amplifier circuit is referred to as a predistortion compensation type amplifier circuit, or simply an amplifier circuit.

The amplifier circuit 800 includes a main signal path including a distributor 802, an amplitude modulator 806, and a low pass filter 807, an even product multiplication unit 803, and a high pass filter 80.
4 and a compensation signal generation path including a phase shifter / variable attenuator 805, and a compensated power amplifier 808. The distributor 802 distributes the input signal applied to the input terminal 801 to the main signal path and the compensation signal generation path.

The even product multiplication unit 803 generates an even product signal of the input signal from the signal distributed to the compensation signal generation path. The high-pass filter 804 blocks the frequency band of the input signal and extracts even harmonics of the input signal from the output signal of the even product multiplication unit 803. The phaser / variable attenuator 805 adjusts the phase and amplitude of the even harmonics and outputs them.

The amplitude modulator 806 is realized by, for example, a dual gate FET, and amplitude-modulates the signal distributed to the main signal path by the output signal from the phase shifter / variable attenuator 805. The low-pass filter 807 blocks a frequency band equal to or higher than the third harmonic of the target signal, extracts a target signal and a distortion signal including only the second harmonic of the target signal from the amplitude-modulated signal, and outputs the distortion signal.

The distorted signal is a compensated power amplifier 80.
Amplified by 8. By adjusting the phase / amplitude of the second harmonic wave according to the non-linear characteristic of the compensated power amplifier 808, the distortion component generated in the output signal from the compensated power amplifier is reduced.

[0012]

However, the above-mentioned conventional amplifier circuit has the first problem that the frequency characteristic of the compensated power amplifier is not improved. More specifically, the phase delay amount and the gain between the input and output signals in a general amplifier including the compensated power amplifier differ depending on the signal frequency, but the amplifier circuit has such characteristics of the compensated power amplifier. Does not improve.

Therefore, in the adaptive array apparatus which forms the antenna directivity in the desired mobile station direction by changing the phase and amplitude of the transmission / reception signal for each of a plurality of antennas by an appropriate amount, the amplification circuit of the prior art is used. When the transmission / reception signal is amplified, different group delays and gains are added to the transmission / reception signals of different frequencies in the communication band, which makes it difficult to form the antenna directivity with high accuracy in the entire communication band.

In addition, the fact that different group delays and gains are given to transmission / reception signals of different frequencies within the communication band means that a wideband, high-speed transmission system using the multilevel digital modulation such as the recent 16QAM (Quadrature Amplitude Modulation). When applied to, it causes a significant deterioration in modulation accuracy, and has a large adverse effect on communication quality. Further, when a multi-carrier signal is amplified using the amplifier circuit, it is difficult to maintain constant communication quality for all carrier signals because the transmission power is not constant between carrier signals of different frequencies.

In addition to this, in the conventional amplifier circuit, since the noise component in the input signal is also amplified by the amplitude modulator 806 provided on the main signal path and realized by the active element, the power amplifier to be compensated is compensated. There is also a second problem that it is difficult to reduce the overall noise of the amplifier circuit, because the input noise figure is adversely affected. In addition, in an amplification system that obtains a desired output power by connecting amplifiers in multiple stages, which is represented by a wireless transmission device, when considering application to a large power stage, the amplitude modulator 806 has a signal power from the previous stage. However, when the amplitude modulator 806 is realized by an active element, it is necessary to use expensive parts corresponding to the electric power to be passed, which is disadvantageous in terms of cost.

In view of these problems, it is a first object of the present invention to provide a predistortion compensation type amplifier circuit which can maintain the amount of phase delay and the gain at a constant amount regardless of the signal frequency. Also,
INDUSTRIAL APPLICABILITY The present invention reduces the adverse effect on the input noise figure for the power amplifier to be compensated, thereby realizing the overall noise reduction of the amplifier circuit, and predistortion compensation applicable to a large power stage at low cost. A second object is to provide a type amplifier circuit.

[0017]

(1) In order to solve the above problems, an amplifier circuit according to the present invention includes a first amplitude control signal and a phase delay of an amount indicated by a first phase control signal with respect to an input signal. And a first adjuster for generating an adjustment signal by providing a ratio attenuation represented by: and to reduce a non-linear distortion component generated when the adjustment signal is generated by the first adjuster. A distortion compensation circuit that generates a distortion signal by adding a predetermined compensation signal, a compensated amplifier that amplifies the distortion signal and outputs an amplified output signal, and compares the input signal with the amplified output signal. A comparison circuit for detecting a phase difference and an amplitude ratio between the two;
The phase control signal and the first amplitude control signal are changed so that the detected phase difference and amplitude ratio are maintained at predetermined values, respectively, and output to the first adjuster. (2) In the amplification circuit, the distortion compensation circuit includes a first distribution / combiner that distributes the adjustment signal into a main signal and a sub signal, a signal waveform compression circuit that compresses the sub signal, and the compression circuit. A second adjuster for changing the phase and amplitude of the generated signal, an amplifier for amplifying the signal with the changed phase and amplitude to generate a compensation signal, and adding the compensation signal to the main signal. A second divider / combiner for generating the distortion signal, wherein the first divider / combiner and the second divider / combiner are both passive elements, and the generated compensation signal is not fed back. The feedback input may be blocked by a directional element such as a directional coupler or an isolator. (3) Further, in the amplifier circuit, the distortion compensation circuit further includes a third distribution combiner for extracting a part of the output signal from the compensated amplifier as a feedback signal, and the first signal included in the feedback signal. A bandpass filter that passes only the harmonic component of the signal and outputs it as a compensation error signal, and a control circuit that generates a second phase control signal and a second amplitude control signal according to the magnitude of the compensation error signal are provided. ,
The second adjuster includes the second phase control signal and the second phase control signal.
Change the phase and amplitude respectively according to the amplitude control signal,
The control circuit may change the second phase control signal and the second amplitude control signal so as to reduce the compensation error signal.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Predistortion-compensated amplifier circuits according to embodiments of the present invention will be described in detail with reference to the drawings. <First Embodiment> The amplifier circuit according to the first embodiment is a kind of amplifier circuit including a predistortion circuit, and maintains the phase delay amount and the gain at constant amounts as a whole of the amplifier circuit, and It is configured to reduce the noise of the output signal and to be applicable to a large power stage at low cost. <Overall Configuration> FIG. 1 is a block diagram showing the overall configuration of the amplifier circuit 10 according to the first embodiment. Amplifier circuit 1
0 is a directional coupler 12, a variable phase shifter 13, a variable attenuator 14, an amplifier 100, a directional coupler 16, and a comparison circuit 1.
7 and the adjusting circuit 18.

The directional coupler 12 extracts a part of the input signal as an input comparison signal and outputs the rest to the variable phase shifter 13. The variable phase shifter 13 is a variable phase shifter capable of voltage control. When the voltage of the phase control signal 183 is lower than a predetermined reference value, the variable phase shifter 13 changes the phase of the signal input in proportion to the difference from the reference value. If it is delayed, on the contrary, if it is high, the phase of the input signal is advanced in proportion to the difference from the reference value and output to the variable attenuator 14.

The variable attenuator 14 is a variable attenuator capable of voltage control. When the voltage of the amplitude control signal 184 has a predetermined reference value, the input signal is output without being attenuated and the predetermined reference value is output. If it is lower than the reference value, it is attenuated at a ratio proportional to the difference from the reference value and is output to the amplification unit 100. The amplification unit 100 includes a predistortion circuit and a power amplifier to be compensated, and a distortion signal generated by adding a predetermined compensation signal to the input signal by the predistortion circuit is amplified by the power amplifier to be compensated. Output. Details of the amplification unit 100 will be described later.

The directional coupler 16 extracts a part of the amplified output signal from the amplifier 100 as an output comparison signal and outputs the rest as an output signal. The comparator circuit 17 detects the phase difference and the amplitude ratio between the input comparison signal and the output comparison signal by comparing them, and determines the voltage signal proportional to the phase difference between the output comparison signal and the input comparison signal. The phase difference signal 173 and the amplitude ratio signal 174, which is also a voltage signal proportional to the amplitude ratio, are output to the adjustment circuit 18.

The comparison circuit 17 compares the input comparison signal and the output comparison signal logarithmically converted by a built-in log amplifier (not shown) so as to perform comparison in the case where the dynamic range of the signal is wide. Also produces stable output. Such a comparison circuit 17 is a one-chip I
It has already been realized as C, and as an example, a product such as AD8302 manufactured by Analog Devices, Inc. can be used.

The adjusting circuit 18 adjusts the phase difference signal 1 when the output signal causes a desired phase delay amount with respect to the input signal.
A first variable resistor (not shown) that generates a first reference voltage that is a voltage indicated by 73 is provided, and a voltage obtained by subtracting the voltage of the phase difference signal 173 from the first reference voltage is used as the phase control signal 183.
And output to the variable phase shifter 13. here,
The first variable resistor generates the first reference voltage by dividing a predetermined reference voltage. As the desired phase delay amount, for example, an average value of the phase delay amounts of the amplification unit 100 may be used.

When the amount of phase delay generated by the amplifier 100 exceeds the desired amount of phase delay, the phase of the output comparison signal is delayed and the voltage of the phase difference signal 173 drops, so that the voltage of the phase control signal 183 changes. Then, the variable phase shifter 13 advances and advances the phase of the input signal, so that the phase difference between the input signal and the output signal is maintained at the desired phase delay amount. When the amount of phase delay generated by the amplification unit 100 is less than the desired amount of phase delay, the opposite action maintains the desired phase delay amount of the phase difference between the input signal and the output signal.

The adjusting circuit 18 outputs the amplitude ratio signal 174 when the output signal produces a desired amplitude ratio with respect to the input signal.
Is provided with a second variable resistor (not shown) that generates a second reference voltage, and a voltage obtained by subtracting the voltage of the amplitude ratio signal 174 from the second reference voltage is generated as the amplitude control signal 184 and is changed. Output to the attenuator 14. Here, the second variable resistor generates the second reference voltage by dividing a predetermined reference voltage. For the desired amplitude ratio, for example, the average gain of the amplifier 100 may be used.

When the gain generated by the amplifier 100 exceeds the average gain, the amplitude of the output comparison signal increases,
Since the voltage of the amplitude ratio signal 174 increases, the voltage of the amplitude control signal 184 decreases, and the variable attenuator 14 increases the attenuation amount of the input signal. Therefore, the amplitude ratio of the input signal and the output signal is the desired amplitude ratio. Kept in. When the gain generated by the amplification unit 100 is lower than the average gain, the reverse action maintains the amplitude ratio between the input signal and the output signal at the desired amplitude ratio.

Similar control operations are performed by the conventional automatic level adjuster (ALC circuit: Automatic Level Control circuit) and phase locked loop circuit (PLL circuit: Phase Locked Loo).
p circuit), but especially the amplifier circuit 1
At 0, since the control operation described above is performed by comparing the input comparison signal and the output comparison signal, the phase difference and the amplitude ratio between the input and output signals are the same when the phase delay amount and the gain of the amplification unit 100 change. Even if they exist, they are kept at the values when they are in desired phase delay amounts and desired gains.

By this control, the amount of phase delay and the gain provided between the input and output signals by the amplifier circuit 10 are maintained at constant values independently of the signal frequency. The amplifier circuit 10 has a constant delay and gain with respect to a transmission / reception signal of any frequency in the communication band. Therefore, when applied to the adaptive array device, the antenna directivity is formed with high accuracy in the entire communication band. can do. In addition, when applied to a wide-band, high-speed transmission system using multi-valued digital modulation, deterioration of modulation accuracy is prevented and deterioration of communication quality is mitigated.

Further, when the amplifier circuit 10 amplifies a multi-carrier signal, carrier signals of any frequencies included in the multi-carrier signal are amplified and output to the same level, so that uniform communication is carried out over all carrier signals. Quality is obtained. <Structure of Amplifier Unit 100> FIG. 2 is a block diagram showing the structure of the amplifier unit 100 according to the first embodiment. The amplifying unit 100 is an amplifying circuit including a predistortion circuit, and is configured so as to reduce noise and be applicable to a large power stage at low cost as compared with a conventional amplifying circuit of the same type.

The amplification section 100 includes a directional coupler 101, a signal transmission line 102, a low pass filter 103, and an amplifier 10.
4, low-pass filter 105, signal waveform compression circuit 10
6, variable phase shifter 114, variable attenuator 115, amplifier 11
2. Directional coupler 116 and compensated power amplifier 11
It consists of 7. The signal waveform compression circuit 106 includes a resistor 107 and a diode 108.

Here, among the constituent elements of the amplifier 100,
A signal path including the directional coupler 101, the signal transmission path 102, and the directional coupler 116 is called a main signal path, and a signal path including the low-pass filter 103 to the amplifier 112 is called a compensation signal generation path. A circuit portion including the main signal path and the compensation signal generation path is called a distortion compensation circuit.

In particular, in the main signal path, the signal transmission line 102 is directly connected to the directional coupler 101, and the directional coupler 116 is directly connected to the signal transmission line 102. That is, the main signal paths are the directional coupler 101 and the signal transmission path 1.
02, and the components other than the directional coupler 116 are not included. The directional coupler 101 distributes the input signal to the main signal path and the compensation signal generation path at a predetermined ratio. The input signal corresponds to the adjustment signal in the claims, and the signals distributed to the main signal path and the compensation signal generating path correspond to the main signal and the sub-signals, respectively.

The compensation signal generating path is a directional coupler 1.
From the sub-signal distributed by 01, a compensation signal including a harmonic of the sub-signal is generated. Low-pass filter 103,
The amplifier 104 and the low-pass filter 105 amplify the distributed signal and supply only the signal component included in the frequency band of the input signal to the signal waveform compression circuit 106. Resistor 10 in signal waveform compression circuit 106
Diode 1 biased in the non-linear operating region by 7.
08 compresses the waveform of the input signal and outputs a distorted signal including harmonics of the input signal. The variable phase shifter 114 and the variable attenuator 115 adjust the phase and amplitude by giving a predetermined phase delay amount and attenuation ratio to the distorted signal, and the amplifier 11
2 amplifies the distortion signal after adjusting the phase and amplitude,
Output as a compensation signal.

On the other hand, the main signal distributed to the main signal path by the directional coupler 101 is transmitted to the directional coupler 116 by the signal transmission line 102, and the directional coupler 116 and the transmitted signal are combined with each other. The compensating signal and the compensating signal are mixed together and output as an output signal. The output signal corresponds to the distortion signal in the claims. Next, the amplification unit 1
The operation of 00 will be described.

FIGS. 3A, 3B and 3C are diagrams for explaining the operation principle of the signal waveform compression circuit 106. FIG. 7A is a graph showing the input voltage Vin vs. output voltage Vout characteristic of the signal waveform compression circuit 106. The output voltage proportional to the input voltage up to a predetermined level is shown according to the nonlinear characteristic of the diode 108. Although obtained, the output voltage becomes less than the proportional value for the input voltage exceeding the level. Due to this characteristic, an output signal obtained by compressing the signal waveform of the input signal can be obtained.

FIG. 1B shows an example of the voltage vs. time waveform of the input / output signal in the case of assuming a multi-carrier signal in which carrier signals of two kinds of frequencies are superimposed on the input signal.
The input signal is represented by a thin line, the output signal is represented by a thick line, and each envelope is represented by a broken line. FIG. 6C is a graph for explaining the deformation of the output signal waveform with respect to the input signal waveform in the frequency domain, and represents the frequency component of the output signal. The output signal contains, in addition to the fundamental wave components f ₁ and f ₂ contained in the input signal, the harmonic components 2f ₁ , 2f ₂ ... Due to the distortion of the waveform, and the mutual components due to the interference between the fundamental wave and the harmonic components. Modulation distortion (2f ₁ −f ₂ ) and (2f ₂
-F ₁ ) component is included.

FIG. 4 is a graph showing the magnitude of the frequency component of the signal in each part of the amplification section 100 when the multicarrier signal is assumed as the input signal. The signal (A) represents the input signal to the amplifier 100,
The fundamental wave components f ₁ and f ₂ are included. The signal (B) and the signal (D) represent the main signal and the sub signal distributed by the directional coupler 101, respectively, and include the fundamental wave components f ₁ and f ₂ . As described above, the signal waveform compression circuit 106 applies the intermodulation distortion (2f ₁ − to the signal (D).
The signal (E) to which the f ₂ ) and (2f ₂ −f ₁ ) components are added is output. The signal (F) shows the signal after adjusting the phase and the amplitude with respect to the signal (E), and particularly shows that the phase is different from the signal (E) using a graph in the opposite direction.

The directional coupler 116 receives the signal (B) and the signal.
No. (E) is added and output. Signal (F) and signal
In (G), the signal (B) and the signal (E) are compensated respectively.
Indicates the signal component amplified and output by the power amplifier 117
is doing. For the signal (F), the compensated power amplifier 117
Intermodulation distortion (2f₁-F₂) And (2
f ₂-F₁) Components are mixed. This intermodulation distortion component is
Intermodulation distortion included in amplified output signal (G) of signal (E)
Only (2f₁-F₂) And (2f₂-F₁) Ingredients and cancellation
As shown in FIG.
By adjusting the damping ratio of the attenuator 115,
Fundamental wave f₁And f₂Obtain an amplified output signal consisting of only components
be able to. Note that the harmonic component remains in the amplified output signal.
When staying, the detuning from the fundamental wave is large, so filter
Can be easily removed with.

Regarding the adjustment of the phase delay amount of the variable phase shifter 114 and the attenuation ratio of the variable attenuator 115, the amplified output signal (F) + (from the compensated power amplifier 117 is changed in advance while changing both. G) and the input signal (A), the difference (that is, the distortion component included in the amplified signal) is measured, the optimum phase delay amount and the optimum attenuation ratio that minimize the difference are found, and the phase is calculated. The delay amount and the attenuation ratio are fixed to the optimum phase delay amount and the optimum attenuation ratio, respectively.

In the above-mentioned structure, the signal transmission line 102 is simply a conductor or a waveguide, and specifically, any one of a strip line, a microstrip line, a coaxial cable, and a waveguide, or It is configured by combining a plurality of these. Further, as the directional coupler 116, one having a frequency characteristic that responds up to the frequency band of the second harmonic of the input signal may be used.

According to the configuration described above, the amplifying section 100 performs the mixing process of the input signal and the compensation signal by the directional coupler 116, so that noise is not amplified in the mixing process. Therefore, compared to the conventional example in which the mixing process is performed using an active element such as an amplitude modulator, the noise component in the output signal can be suppressed to be small, and the noise component should be passed when applied to a large power stage. There is no need to use expensive parts corresponding to electric power, which is advantageous in terms of cost.

Further, the loss in the main signal path can be reduced as compared with the case where the mixing process is performed using a reactance element such as a transformer. Further, by using a passive element having a small loss and a low noise figure such as a strip line, a micro strip line, a coaxial cable, or a waveguide in the signal transmission line 102, the loss and the noise figure in the main signal path can be suppressed to be small. .

Since this main signal path is particularly preceded in series with the power amplifier to be compensated, the power amplifier to be compensated for is included by reducing the loss and noise figure of the main signal path itself. It greatly contributes to the reduction of the noise figure in the entire amplifier circuit. In this way, the amplification unit 100 achieves low noise of the main signal path, low noise of the entire amplification unit 100 including the main signal path, and low cost when applied to a large power stage.

The signal waveform compression circuit 106 is only required to generate harmonics by compressing the signal waveform of the input signal, and the present invention is also applicable to the case where the following signal waveform compression circuit is used. included. In FIG. 5 (A) and (B),
Other signal waveform compression circuit 156 and signal waveform compression circuit 2
A configuration example of 06 is shown.

The signal waveform compression circuit 156 shown in FIG. 9A is a general full-wave rectification circuit, and outputs the second harmonic of the input signal. In the signal waveform compression circuit 206 of FIG. 7B, the 90 ° hybrid 207 divides the input signal into two. One of the distributed signals passes through a diode 209 biased in a non-linear operation region by a resistor 208, so that mainly even harmonics are mixed. The other is grounded via the resistor 210 and the diode 211, so that mainly odd-order harmonics are mixed. 9
The 0 ° hybrid 212 outputs a signal including both even harmonics and odd harmonics of the input signal by mixing the both signals. When this circuit is used, the directional coupler 116 having a frequency characteristic that responds up to the frequency band of the third harmonic of the input signal is used.

Further, by inserting an isolator in series in the signal transmission path 102, the feedback input of the compensation signal to the compensation signal generation path may be blocked. The amplifier circuit having this configuration is also included in the present invention. The isolator has, for example, 0. By using the one having a low forward loss of about several dB, it is possible to improve the adjustability of the circuit while maintaining a certain effect in reducing the loss and the noise figure in the main signal path. Second Embodiment The amplifier circuit according to the second embodiment is different from the amplifier circuit 10 according to the first embodiment in that
Further, the strain reducing effect is improved. Amplifier circuit 1
A circuit having the same overall configuration as 0, but for changing the phase delay amount and the attenuation ratio given to the compensation signal at any time in the amplification unit according to the residual distortion level included in the amplified output signal of the power amplifier to be compensated. It is different in that it is equipped with.

FIG. 6 is a block diagram showing the configuration of an amplifying section 300 used in place of the amplifying section 100 of the first embodiment in the amplifying circuit of the second embodiment. Less than,
The same components as those of the amplification unit 100 according to the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. Different components will be mainly described. The amplification section 300 further includes a compensated power amplifier 318, a directional coupler 319, a bandpass filter 320, and a control circuit 321 in addition to the amplification section 100 of the first embodiment, and the amplification section 300 of the first embodiment is different from that of the first embodiment. Instead of the variable phase shifter 114 and the variable attenuator 115, respectively, a variable phase shifter 314 and a variable attenuator 315 are used.
Equipped with.

Among the components of the amplification section 300, the directional coupler 101, the signal transmission line 102, and the directional coupler 11
The signal path including 6 is referred to as a main signal path, and the signal path including the low-pass filter 103 to the amplifier 112 is referred to as a compensation signal generation path, and the main signal path is the directional coupler 1.
01, the signal transmission path 102, and the directional coupler 116 are the same as the first embodiment in that the components other than those are not included.

The variable phase shifter 314 outputs a phase delay amount within a predetermined range including at least the optimum phase delay amount described in the first embodiment from the amplifier 112 according to the phase control signal 324 given from the control circuit 321. Is a variable phase shifter which is applied to the output signal of. The variable attenuator 315 provides the amplitude control signal 3 supplied from the control circuit 321 with an attenuation ratio within a predetermined range including at least the optimum attenuation ratio described in the first embodiment.
25 is a variable attenuator that provides the output signal according to 25.

The compensated power amplifier 318 amplifies and outputs the output signal output from the directional coupler 116.
The directional coupler 319 extracts a part of the signal output from the compensated power amplifier 318 and extracts the bandpass filter 3 from the signal.
20 and outputs the rest as an amplified signal. The bandpass filter 320 passes only the harmonic component of the input signal included in the supplied signal and outputs it to the control circuit 321. In the state where the distortion is completely compensated, the signal output from the power amplifier 318 to be compensated includes only the harmonic component originally possessed because the input signal is a modulation signal, but the compensation error increases. As a result, harmonic components due to distortion increase. The bandpass filter 320 outputs the harmonic component resulting from both of them to the control circuit 321 as a compensation error signal.

As in the first embodiment, in advance,
While changing the phase control signal and the amplitude control signal, by measuring the difference between the amplified signal and the input signal,
It is assumed that the optimum phase control signal and the optimum amplitude control signal that minimize the difference between the two have been discovered in advance. For example, if both signals are voltage signals, it is assumed that the voltage values corresponding to both are known.

Further, the control circuit 321 outputs the optimum phase control signal and the optimum amplitude control signal to the variable phase shifter 314, respectively.
Also, it is assumed that the average magnitude of the compensation error signal obtained when the variable attenuator 315 is given and controlled is also known and measured in advance. The control circuit 321 stores a first reference value, a second reference value, and a third reference value indicating the magnitudes of the optimum phase control signal, the optimum amplitude control signal, and the average compensation error signal, respectively. The optimum phase control signal and the optimum amplitude control signal are output as initial values.

In the previous measurement, the compensation error signal was minimized by the phase control signal and the amplitude control signal respectively indicated by the first reference value and the second reference value. The phase control signal and the amplitude control signal to be changed fluctuate due to temperature changes, changes over time, and the like. Therefore, the control circuit 321 controls the bandpass filter 32.
When the magnitude of the compensation error signal output from 0 exceeds the third reference value, compensation is performed by changing the phase control signal and the amplitude control signal from the first reference value and the second reference value, respectively. The variable phase shifter 314 and the variable attenuator 315 are controlled so that the error signal becomes small.

More specifically, the control circuit 321 controls the DSP (D
digital signal processor), and the DS
The control described above may be performed by executing a program included in P. FIG. 7 shows a flowchart showing the program. The program includes the following steps. (Step S01) The phase control signal indicated by the first reference value is output to the variable phase shifter 314, and the amplitude control signal indicated by the second reference value is output to the variable attenuator 315. (Step S02) It is determined whether or not the magnitude of the compensation error signal exceeds the third reference value, and if it exceeds, the step S02.
Execute 03 or later. (Step S03) The phase control signal is increased by a predetermined minute amount. (Step S04) It is determined whether or not the compensation error signal has decreased. If it has decreased, step S05 is executed, and if it has increased, step S06 is executed. (Step S05) The phase control signal is the third compensation error signal.
The value is increased within a predetermined range until it falls below the reference value. (Step S06) The phase control signal compensates for the third error signal.
Decrease within a predetermined range until it falls below the reference value. (Step S07) The amplitude control signal is increased by a predetermined minute amount. (Step S08) It is determined whether or not the compensation error signal has decreased. If it has decreased, step S09 is executed, and if it has increased, step S10 is executed. (Step S09) The amplitude control signal is the third compensation error signal.
The value is increased within a predetermined range until it falls below the reference value. (Step S10) The amplitude control signal is the third compensation error signal.
Decrease within a predetermined range until it falls below the reference value. (Step S11) Step S02 and subsequent steps are repeated.

According to the above-mentioned configuration, the amplifying section 300 is
Even if the compensation error due to the phase control signal and the amplitude control signal that are actually output increases due to temperature change, temporal change, etc., the phase control signal and the amplitude control signal are adaptively controlled so as to reduce the compensation error. As a result, the amplification unit 300 is
Maintains high compensation accuracy regardless of temperature changes and changes over time,
The distortion reduction effect is maintained.

Further, the amplification section 300 has a main signal path equivalent to that of the amplification section 100, and by the action equivalent to that of the amplification section 100, noise reduction of the distortion compensation circuit itself and the entire amplification circuit including the distortion compensation circuit. To achieve low noise and low cost when applied to a high power stage. In the amplification unit 300 as well, the signal waveform compression circuit is not limited to the signal waveform compression circuit 106 as in the amplification unit 100. For example, the signal waveform compression circuit 156 or the signal waveform compression circuit 206 may be used. Further, an isolator may be inserted in series with the signal transmission path 102.

Further, since the amplifying section 300 can be applied at a lower cost than before when compensating a large power amplifier, the amplifying circuit of the present invention can be applied to all stages including a large power stage in a multistage amplifying system in terms of cost. Can be incorporated advantageously. <Third Embodiment> In the amplification system according to the third embodiment, some of the plurality of amplification circuits shown in the first or second embodiment are connected in parallel and some are connected in cascade. It is an amplification system.

FIG. 8 is a structural example of such an amplification system 500. In the amplification system 500, the amplification circuit 510 includes a distortion compensation circuit 501 and a power amplifier 5 to be compensated.
And 09. As described above, the distortion compensation circuit 501 is a circuit portion including a main signal path and a compensation signal generation path, and includes a directional coupler 502, a signal waveform compression circuit 503, a variable phase shifter 504, a variable attenuator 505, It includes an amplifier 506, a signal transmission line 507, and a directional coupler 508.

Each of amplifier circuits 520 to 580 is constructed similarly to amplifier circuit 510. The distributor / combiner 591 is
The output from the amplifier circuit 520 is supplied to the amplifier circuits 530 and 540.
And the distributor / combiner 592 distributes to the amplifier circuits 530 and 5
The output from 40 is combined. The distributor / combiner 593 distributes the signals combined by the distributor / combiner 592 to the amplifier circuits 550 to 580, and the distributor / combiner 594 distributes the signals to the amplifier circuit 55.
The outputs from 0 through 580 are combined.

The amplification system 500 has four amplification stages connected in series, the first stage amplifies the signal by the amplification circuit 510, and the second stage amplifies the signal by the amplification circuit 520.
The third stage amplifies the signal by the amplifier circuits 530 and 540 connected in parallel, and the final stage amplifies the amplifier circuit 55 connected in parallel.
The signal is amplified by 0 to 580. Amplification system 50
For example, 0 amplifies an input signal of 0 dBm to +10 dBm in the first stage, +17 dBm in the second stage, +27 dBm in the third stage, and +37 dBm in the final stage.

The distortion compensation circuit at each stage in the amplification system 500 injects a compensation signal to the signal from the previous stage. Therefore, for example, in another distortion compensation circuit that inserts a nonlinear element (for example, a diode) in series in the main signal path to generate a compensation signal component, the stages that can be adapted are limited according to the maximum rated power of the nonlinear element. It In contrast to this circuit configuration, the distortion compensating circuit of the present invention generates a compensation signal in the compensation signal generating path and mixes it with the main signal by the directional coupler. Since it does not have a non-linear element, it has excellent compatibility with high power stages.

Further, in another circuit configuration for comprehensively compensating for the linear amplification distortion generated from a plurality of power amplifiers to be compensated arranged in the predetermined intermediate stage to the final stage, the linear amplification to be compensated is performed. Since the distortion is a complicated function including a multi-order term, it is difficult to compensate the distortion with high accuracy and stability. In contrast to this circuit configuration, the amplification system of the present invention is configured such that a distortion compensation circuit having excellent compatibility with a large power stage is placed in front of each compensated power amplifier including the large power stage, Since the variable phase shifter and the variable attenuator included in each distortion compensation circuit are properly adjusted to accurately remove the linear amplification distortion of each power amplifier to be compensated, the compensation accuracy and stability are excellent.

Of course, each amplifier circuit can be applied to a high power stage at low cost, and the loss and noise figure can be suppressed to be small in all the amplifier stages.
This is as described in the first and second embodiments.

[0064]

The amplifier circuit of the present invention has a phase delay of the amount indicated by the first phase control signal with respect to the input signal and a first phase control signal.
A first adjuster that generates an adjustment signal by giving a ratio attenuation indicated by the amplitude control signal, and a nonlinear distortion component that occurs when the adjustment signal generated by the first adjuster is amplified. A distortion compensation circuit that generates a distortion signal by adding a predetermined compensation signal for reduction, a compensated amplifier that amplifies the distortion signal and outputs an amplified output signal, and the input signal and the amplified output signal. A comparison circuit for comparing and detecting the phase difference and the amplitude ratio of the both,
And an adjusting circuit that changes the first phase control signal and the first amplitude control signal so that the detected phase difference and amplitude ratio are maintained at predetermined values, and outputs the first phase control signal and the first amplitude control signal to the first adjuster. .

With this configuration, when the phase delay amount between the input and output signals in the compensated amplifier increases or decreases, the phase delay amount given to the input signal by the first adjuster decreases or increases, respectively. As a result, the amount of phase delay between the input and output signals in the entire amplification circuit is maintained at a constant amount. Also, when the gain between the input and output signals in the compensated amplifier increases or decreases, the attenuation ratio given to the input signal by the first adjuster is increased or decreased respectively, so that the input / output in the entire amplification circuit is increased. The gain between the signals is kept constant.

As a result, the amount of phase delay and the gain of the entire amplification circuit are maintained at a constant amount regardless of the signal frequency. As a specific example, when the amplifier circuit is applied to an adaptive array device, the accuracy of forming a directional pattern is improved,
In addition, when applied to a wide-band, high-speed transmission system using multilevel digital modulation, deterioration of modulation accuracy is suppressed and communication quality is improved.

In the amplifier circuit, the distortion compensation circuit includes a first distributor / combiner for distributing the adjustment signal into a main signal and a sub signal, a signal waveform compressor circuit for compressing the sub signal, and the compressor. A second adjuster for changing the phase and amplitude of the generated signal, an amplifier for amplifying the signal with the changed phase and amplitude to generate a compensation signal, and adding the compensation signal to the main signal. A second divider / combiner for generating the distortion signal, wherein the first divider / combiner and the second divider / combiner are both passive elements, and the generated compensation signal is fed back to the compensation signal generating circuit. It may not have been done.

According to this structure, since the present amplifying circuit performs the mixing process of the main signal and the compensation signal by the passive element, noise is not amplified in the mixing process. Therefore, the noise component in the distorted signal can be suppressed smaller than in the conventional example in which the mixing process is performed using an active element such as an amplitude modulator. Particularly when applied to a large power stage in a multi-stage amplification system, it is not necessary to use an expensive active element corresponding to the power to be passed, so that cost reduction can be achieved compared to the conventional case. Also,
It has excellent compatibility with high power stages compared to other circuit configurations that generate a compensation signal by a non-linear element inserted in series in the main signal path.

Further, the circuit loss can be reduced as compared with the case where the mixing process is performed using a reactance element such as a transformer. Further, the first distributor / combiner and the second distributor / combiner may be connected to each other by, for example, a strip line, a microstrip line, a coaxial cable, or a waveguide.
If a passive element having a small loss and a low noise figure is used for direct connection, the loss and noise figure of the amplifier circuit can be suppressed to be small.

Since this kind of distortion compensation circuit is particularly preceded in series with the compensated amplifier, the distortion compensation circuit itself and the compensated circuit are compensated by reducing the loss and noise figure of the distortion compensation circuit itself. It greatly contributes to the reduction of the noise figure in the entire amplification circuit in which the amplifier is connected in series.
In this way, the amplifier circuit achieves low noise and low cost when applied to a large power stage.

In the amplifier circuit, the first and second distribution combiners are both directional couplers, and the second distribution combiner is an input terminal of the main signal in the second distribution combiner. The first distribution / combiner may not transmit the signal added to the output end of the main signal in the first distribution / combiner to the output end of the sub-signal, without transmitting the compensation signal to.

In the amplifier circuit, the distortion compensating circuit further includes an isolator for transmitting the main signal only in one direction, and the second distribution / combining device further includes the main signal after being transmitted by the isolator. The second signal may be generated by adding the compensation signal to. With any of these configurations, the same effect as that of the amplifier circuit is realized.

In the amplifier circuit, the distortion compensating circuit further includes a third divider / combiner for extracting a part of an output signal from the compensated amplifier as a feedback signal, and the first divider / combiner included in the feedback signal. A bandpass filter that passes only the harmonic component of the signal and outputs it as a compensation error signal, and a control circuit that generates a second phase control signal and a second amplitude control signal according to the magnitude of the compensation error signal are provided. ,
The second adjuster includes the second phase control signal and the second phase control signal.
Change the phase and amplitude respectively according to the amplitude control signal,
The control circuit may change the second phase control signal and the second amplitude control signal so as to reduce the compensation error signal.

According to this configuration, in addition to achieving the noise reduction of the present amplification circuit, the present amplification circuit performs the phase control so as to reduce the compensation error signal even when the compensation error signal increases. Since the signal and the amplitude control signal are adaptively controlled, high compensation accuracy can be maintained regardless of temperature change, aging change, and the like. Further, in the amplification circuit, the second directional coupler may have a response frequency band having an upper limit of a frequency of a fundamental wave, a second harmonic wave, or a third harmonic wave of the input signal.

Further, in the amplifier circuit, the second directional coupler and the third directional coupler have the upper limit of the frequency of the fundamental wave, the second harmonic wave, or the third harmonic wave of the input signal. It may have a response frequency band. According to these configurations, in addition to achieving the noise reduction of the present amplification circuit, the present amplification circuit uses a narrow band and inexpensive passive element that responds up to the third harmonic of the input signal to distort. Since the compensation is performed, the predetermined distortion compensation accuracy and the cost reduction of the device are realized at the same time.

In the amplification system of the present invention, a plurality of any of the above-mentioned amplification circuits are cascade-connected or parallel-connected, or a part of them are connected in parallel and a part of them is connected in cascade. According to this configuration, the amplifier circuit having the above-described effect is arranged in each stage including the high power stage, and the phase and the amplitude of the input signal are appropriately adjusted for each amplifier circuit, so that the individual target signals are individually adjusted. Since the non-linear distortion of the compensation amplifier can be removed with high accuracy, an amplification system with excellent compensation accuracy and stability can be realized.

As described above, also in this configuration, each amplifier circuit can be applied to a large power stage at low cost, and loss and noise figure can be suppressed to be small in all amplifier stages.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an amplifier circuit according to a first embodiment.

FIG. 2 is a block diagram showing a configuration of an amplification unit according to the first embodiment.

FIG. 3 is a diagram for explaining the operation of the signal waveform compression circuit 106. (A) Non-linear characteristic of the diode 108. (B) is a signal waveform of an input / output signal assuming a multicarrier signal. (C) A frequency spectrum of the output signal.

FIG. 4 is a signal spectrum in each part of the distortion compensation circuit.

FIG. 5 is an example of another signal waveform compression circuit.

FIG. 6 is a block diagram showing a configuration of an amplification unit according to a second embodiment.

FIG. 7 is a flowchart showing a control method of an amplification unit according to the second embodiment.

FIG. 8 is a block diagram showing an overall configuration of an amplification system according to a third embodiment.

FIG. 9 is an example of a conventional distortion compensation amplifier circuit.

[Explanation of symbols]

10 amplifier circuit 12-way coupler 13 Variable phase shifter 14 Variable attenuator 16 directional coupler 17 Comparison circuit 18 Adjustment circuit 100 amplifier 101 Directional coupler 102 signal transmission path 103 low-pass filter 104 amplifier 105 low-pass filter 106 signal waveform compression circuit 107 resistor 108 diode 112 amplifier 114 variable phase shifter 115 Variable attenuator 116 Directional coupler 117 Compensated power amplifier 156 Signal waveform compression circuit 173 Phase difference signal 174 Amplitude ratio signal 183 Phase control signal 184 Amplitude control signal 206 signal waveform compression circuit 207 90 ° hybrid 208 resistor 209 diode 210 resistor 211 diode 212 90 ° hybrid 300 distortion compensation circuit 314 Variable phase shifter 315 Variable attenuator 318 Compensated power amplifier 319 Directional coupler 320 bandpass filter 321 control circuit 500 amplification system 501 distortion compensation circuit 502 Directional coupler 503 signal waveform compression circuit 504 Variable phase shifter 505 Variable attenuator 506 amplifier 507 signal transmission path 508 directional coupler 509 Compensated power amplifier 510-580 amplifier circuit 591-594 distribution synthesizer 800 amplifier circuit 801 input terminal 802 distributor 803 even product multiplication generator 804 High-pass filter 805 Variable attenuator 806 Amplitude modulator 807 low-pass filter 808 Compensated power amplifier

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Riichiro Obana             121-6 Yuki, Fuji City, Shizuoka Prefecture             Le and K F-term (reference) 5J090 AA01 AA41 CA21 CA41 CA61                       FA20 GN03 GN06 GN07 HA19                       HA25 HA33 KA16 KA17 KA20                       KA23 KA42 KA44 KA46 KA68                       MA08 MA11 MA20 SA14 TA01                       TA02 TA03 TA06 TA07                 5J100 JA01 LA03 LA09 QA02 SA01                 5J500 AA01 AA41 AC21 AC41 AC61                       AF20 AH19 AH25 AH33 AK16                       AK17 AK20 AK23 AK42 AK44                       AK46 AK68 AM08 AM11 AM20                       AS14 AT01 AT02 AT03 AT06                       AT07

Claims (8)

[Claims] 1. A first regulator that produces an adjustment signal by providing an amount of phase delay to the input signal indicated by the first phase control signal and attenuation of the ratio indicated by the first amplitude control signal. , With respect to the adjustment signal generated by the first adjuster,
A distortion compensation circuit that generates a distortion signal by adding a predetermined compensation signal for reducing a non-linear distortion component that occurs when amplified, a compensated amplifier that amplifies the distortion signal and outputs an amplified output signal, A comparator circuit for comparing the input signal and the amplified output signal to detect a phase difference and an amplitude ratio between the two, the first phase control signal and the first amplitude control signal, the detected phase difference and amplitude And an adjusting circuit for changing the ratio so as to be maintained at a predetermined value and outputting the changed ratio to the first adjuster. 2. The distortion compensating circuit includes a first distributor / combiner for distributing the adjustment signal into a main signal and a sub signal, a signal waveform compression circuit for compressing the sub signal, and a phase of the compressed signal. And a second adjuster for changing the amplitude, an amplifier for amplifying the signal with the changed phase and amplitude to generate a compensation signal, and generating the distortion signal by adding the compensation signal to the main signal And a second distribution / combining device for controlling the compensation signal, wherein the first distribution / combining device and the second distribution / combining device are both passive elements, and the generated compensation signal is not fed back to the compensation signal generation circuit. The amplifier circuit according to claim 1, which is characterized in that. 3. The first and second divider / combiners are both directional couplers, and the second divider / combiner applies the compensation signal to an input terminal of the main signal in the second divider / combiner. The transmission is not performed, and the first distribution / combiner does not transmit the signal added to the output end of the main signal in the first distribution / combiner to the output end of the sub-signal. Amplifier circuit. 4. The distortion compensation circuit further includes an isolator that transmits the main signal only in one direction, and the second distribution / combiner adds the compensation signal to the main signal after being transmitted by the isolator. The amplifier circuit according to claim 2, wherein the second signal is generated by adding the second signal. 5. The distortion compensating circuit further includes a third divider / combiner for extracting a part of an output signal from the compensated amplifier as a feedback signal, and a harmonic component of the first signal included in the feedback signal. And a control circuit for generating a second phase control signal and a second amplitude control signal according to the magnitude of the compensation error signal, the second adjustment And a second phase control signal and the second phase control signal.
A phase and an amplitude are respectively changed according to an amplitude control signal, and the control circuit changes the second phase control signal and the second amplitude control signal so as to reduce the compensation error signal. The amplifier circuit according to any one of claims 2 to 4. 6. The second directional coupler has a response frequency band having an upper limit of a frequency of any one of a fundamental wave, a second harmonic wave, and a third harmonic wave of the input signal.
The amplifier circuit according to claim 4. 7. The second directional coupler and the third directional coupler have a response frequency band whose upper limit is any one of the fundamental wave, second harmonic wave, and third harmonic wave of the input signal. The amplifier circuit according to claim 5, wherein: 8. A plurality of amplifying circuits according to claim 1 are connected in cascade or in parallel,
Alternatively, an amplification system in which a part is connected in parallel and a part is connected in cascade.