JP3337766B2 - Linear amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

(Contents) Industrial Application Field Conventional Technology (FIGS. 8 and 9) Problems to be Solved by the Invention Means for Solving the Problems Action Embodiment (FIGS. 1 to 7) Effects of the Invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-linear amplifier for high efficiency, and more particularly to an amplifier having excellent linearity without lowering power load efficiency.

[0003]

2. Description of the Related Art Generally, an output voltage waveform of an amplifier has a harmonic distortion component. Second and third harmonic distortion components
The secondary distortion component is not negligible due to its magnitude compared to the primary component. In general, these distortion components are removed by a filter having the frequency of the input signal as a center frequency.

However, third-order distortion components, especially frequencies F1 and F1
3rd-order intermodulation distortion (3rd-Order In
Termoduration is close to the frequency of the input signal and cannot be filtered out, so its generation level must be kept low.

As a method of removing the third-order intermodulation distortion, IEEE “Transactions on Mi
crowave Theory and Technics Volume MTT-34, No.2
Pages 245-250, "A New Method of Third-
Order IntermodurationReduction in Nonlinear Microw
ave ”.

That is, the principle described in this paper is that when the input signal has two frequency components F1 and F2, the F1-F2 component is extracted from the output of the amplifier and fed back to the input side. That is, the secondary mutual distortion can be removed.

FIG. 8 is a diagram showing, in principle, an amplifier for removing the third-order intermodulation distortion described in this paper. FIG. 9 is a diagram for explaining the operation of such an amplifier. FIG.
In the input terminal IN, a signal of a plurality of frequency components,
For example, two signals having frequency components F1 and F2, respectively, are input, amplified by a non-linear amplifier element, for example, a non-linear amplifier circuit 1 composed of an FET, and guided to an output terminal OUT.

[0008] Reference numeral 50 denotes a power divider, and a part of the output from the nonlinear amplifier circuit 1 is branched and guided to the attenuator 21. The attenuator 21 applies a predetermined amount of attenuation to a signal input thereto and outputs the signal.

Reference numeral 22 denotes a bandpass filter, which is a second-order distortion component of the output of the non-linear amplifier circuit 1 among the signals from the attenuator 21, that is, a difference component (F1) between the frequency components F1 and F2.
-F2) is selectively filtered and output. An adder 23 adds the output of the bandpass filter 22 to the bias power supply Vgs and supplies the result to the nonlinear amplifier circuit 1.

That is, the output from the adder 23 is supplied as a gate bias power to a gate of a nonlinear amplifying element, for example, an FET constituting the nonlinear amplifying circuit 1. Therefore, the output from the adder 23 is included in the band-pass filter 22.
Is added to the input signal from the input terminal IN.

Next, based on FIG. 9, the above-mentioned conventional amplifier feeds back and injects a second-order distortion component extracted from the output of the nonlinear amplifier circuit 1 into the input signal from the input terminal IN, thereby injecting the signal into the input side. Next, the principle of compensating the intermodulation distortion component will be described.

In FIG. 9, (1) is a spectrum of two signals of frequency components F1 and F2, respectively. FIG. 9B shows the frequency components F1 and F2 of these two signals.
Of the difference (F1−F2), and is a secondary distortion component extracted from the output of the nonlinear amplifier circuit 1 and fed back to the input side.

The two frequency components F1 and F2 are input to the non-linear amplifier circuit 1, and at the same time, a difference component (F1-F2) between the two frequency components F1 and F2 is injected from the adder 23 as a second-order distortion component.

FIG. 9C shows two frequency components F1 and F2.
Reference numeral 2 denotes a spectrum component after being amplified and output by the non-linear amplifier circuit 1, and generates fundamental wave components F1 and F2 and third-order intermodulation distortion components 2F1-F2 and 2F2-F1. FIG.
(4) is a spectrum component generated by the second-order distortion injection.

Therefore, the components output from the nonlinear amplifier circuit 1 are eventually canceled by the third-order intermodulation distortion components, and only the fundamental wave components F1 and F2 are output as shown in FIG. 9 (5). As described above, the third-order intermodulation distortion component can be reduced by the conventional configuration of FIG.

[0016]

In the conventional amplifier of FIG. 8, the attenuation level of the attenuator 21 or the signal phase of the input and output is set as an initial design value so as to reduce the third-order intermodulation distortion component to a predetermined level. Is set to a predetermined value.

However, in the case where a deviation from a predetermined value occurs due to aging or temperature fluctuation, the expected decrease in the third-order intermodulation distortion component cannot be expected. Accordingly, it is an object of the present invention to provide a configuration of an amplifier capable of reducing a third-order intermodulation distortion component to a predetermined level even in such a case.

[0018]

SUMMARY OF THE INVENTION A linear amplifier according to the present invention includes a nonlinear amplifier to which a signal having a plurality of frequency components is input, and a second-order distortion component extracted from an output of the nonlinear amplifier. And a feedback circuit for injecting the signal having the plurality of frequency components into the signal having a plurality of frequency components. The feedback circuit further includes a high-frequency blocking coil, a voltage-controlled variable attenuator, a low-pass filter, and an adder. The adder is intended for a conventional linear amplifier configured to add the output of the low-pass filter and the input bias power supply (Vgs) and to inject the input into the input side of the nonlinear amplification element.

In such a linear amplifier, a detector which is connected to the input side of the non-linear amplification element, detects an input level of a signal having a plurality of frequency components, and outputs a control signal corresponding to the detected level; A control circuit is provided for controlling the amount of attenuation of the voltage-controlled variable attenuator according to the control signal.

Further, first and second power dividers provided on the input side and the output side of the nonlinear amplification element, a voltage-controlled variable phase shifter provided on the input side or the output side of the nonlinear amplification element, and Input and output signals branched from the first and second power dividers are input, the phase difference between these input and output signals is detected, and the voltage-controlled variable phase shifter is controlled so that the phase difference becomes a predetermined value. A phase shift control circuit for controlling the amount of phase shift is provided.

In another aspect, a first and a second power divider provided on an input side and an output side of the nonlinear amplifying element, a voltage controlled variable phase shifter provided in the feedback circuit, 1. The input and output signals branched from the second power divider are input, the phase difference between these input and output signals is detected, and the voltage-controlled variable phase shifter is shifted so that the phase difference becomes a predetermined value. A phase shift control circuit for controlling the phase amount is provided.

Further, as one embodiment, the nonlinear amplification element is constituted by an FET. The voltage-controlled variable attenuator is controlled such that when the level of the signal detected by the detector is high, the amount of attenuation is small.

[0023]

In the amplifier of the present invention, the secondary distortion component is extracted in the feedback circuit. Then, the extracted second-order distortion component is fed back to the input side and injected into the input signal. As a result, the third-order intermodulation distortion is reduced as described in the conventional example.

The amplifier of the present invention further has a detector on the input side, and detects the level of the input signal. The feedback circuit is provided with a voltage-controlled variable attenuator, and the amount of attenuation is controlled according to the level of the input signal detected by the detector. Therefore, even when the level of the input signal fluctuates, it is possible to inject a second-order distortion component corresponding to the level of the input signal into the input signal.

Further, the amplifier of the present invention comprises a power divider placed on an input side and an output side, a phase shift control circuit for detecting a phase difference between input and output signals branched from the power divider, and an input side and an output. It has a voltage-controlled variable phase shifter provided on the side or in the feedback circuit.

The phase shift control circuit controls the amount of phase shift of the voltage-controlled variable phase shifter so that the detected phase difference between the input and output signals becomes a predetermined value. Thus, even if the phase difference between the input and output signals deviates from a predetermined value due to aging and temperature fluctuation, control can be performed so as to return the phase difference to the predetermined value.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. Prior to the description, a third-order intermodulation distortion in the above-described conventional amplifier to which the present invention is applied for a more accurate understanding of the present invention. Will be described using mathematical formulas.

For the sake of simplicity, consider the case where the signal input from the input terminal IN is two waves. The input signal ei at this time is as follows. ei = A Cos (at + θa) + B Cos (bt + θb) (1)

In general, the output voltage waveform of an amplifier contains harmonic components and can be expressed as a function of the input voltage waveform as in the following equation. _{e 0 = k 1 ei + k} 2 ei 2 + k 3 ei 3 + k 4 ei 4 + ··· (2) From this (2) in equation (1) is substituted for expression. However, consider up to the third order.

The results of the substitution are summarized as follows. The primary component _{(k 1 ei) k 1 A} Cos (at + θa) + k 1 B Cos (bt + θb) (3)

The secondary component ^{_{(k 1 ei 2) k 2}} {A 2/2 + B 2/2} (4) k 2 AB Cos {(a + b) t + (θa + θb)} (5) k 2 AB Cos ｛(A−b) t + (θa −θb)｝ (6) 1/2 k ₂ A ² Cos2 (at + θa) + 1/2 k ₂ B ² Cos (bt + θb) (7)

Third-order component (k ₃ ei ³ ) 1/4 k ₃ A ³ Cos (3 at +3 θa) +1/4 k ₃ B ³ Cos (3 bt +3 θb) (8) 3/4 k ₃ [A ^{2 BCos {(2a + b)} t + (2θa + θb) + AB 2 Cos {(2b + a) t + (2θb + θa)}] (9) 3 / 4k 3 [A 2 BCos {(2a -b) t + (2θa - θb)｝ + AB ² Cos ｛(2b−a) t + (2θb−θa)｝] (10) 3/4 k ₃ A ³ B Cos (at + θa) + B ³ Cos (bt + θb)｝ (11) 3/2 k ₃ [A ² B Cos (bt + θb) + AB ² Cos (at + θa)] (12)

From the above results, the actually output waveform is as follows. _{e 0 = (k 1 A +} 3/4 k 2 A 3 + 3/2 k 3 AB 2) Cos (at + θa) + (k 1 B + 3/4 k 3 B 3 + 3/2 k 3 A 2 B) Cos (bt + θb) + 3/4 k 3 [A 2 B Cos {(2a-b) t + (2θa -θb)} + AB 2 Cos {(2b- a) t + (2θb -θa)}]

Here, if A = B = 1, k ₁ >> k ₃ , the above equation is as follows. _{e 0 = k 1 (Cos (} at + θa) + Cos (bt + θb)) + 3/4 k 3 [Cos {(2a - b) t + (2θa -θb)} + Cos {(2b- a) t + ( 2θb −θa)｝]

If the phase components θa and θb are set to 0, the following is obtained. e ₀ = k ₁ (Cos at + Cos bt) + 3 / 4k ₃ ｛Cos (2a−b) t + Cos (2b−a) t｝ (13) (13) Equation (13) is spectrally similar to FIG. It becomes the same as 3).

Here, the problem of the amplifier distortion is as follows.
The spectrum becomes (2a-b) and (2b-a) which are intermodulation distortion components. Although only the third order is considered here, when considering all the orders, the above-mentioned spectrum spreads right and left. This spectrum (2a−b,
2b-a) is alleviated by the amplifier of the present invention.

For this reason, among the output components of the amplifier,
The third-order intermodulation distortion (IM3) component can be reduced by adding the second-order component of equation (6) to the input side of the amplifier by feedback as described in the configuration of FIG.

This is proved as follows. The input signal of the amplifier is set as follows. The ei = Cos at + Cos bt + 2 Cos (a-b) t (14) the above equation (2) is substituted into equation obtaining the e _0.

Primary component k ₁ eik ₁ Cos at + k ₁ Cos bt + k ₁ 2Cos (ab) tk ₁ Cos at + k ₁ Cos bt + k ₁ 2Cos (b -a) t Ingredients are not considered.

Third-order component k ₃ ei ³ Here, only the third-order intermodulation distortion (IM3) component is considered. 3/4 k ₃ Cos (2a − b) t 3/4 k ₃ α Cos (a− b) t 3/4 k ₃ Cos (2b − a) t 3/4 k ₃ α Cos (b− a) t ^{_{3/4 k 3 α 2 Cos (a}} - 2b) t 3/4 k 3 α 2 Cos (b - 2a) t

When α = 1 is set and these IM3 components are added, the following contents are obtained. 3/4 k ₃ {Cos (ab) t + Cos (ba)} From the above results, there is no IM3 component and the output is only the following basic components. e ₀ = k ₁ Cos at + k ₁ Cos bt

That is, for two input signals of frequencies a and b,
By adding a second-order distortion component having a frequency (ab) component, it is possible to remove third-order intermodulation distortion (IM3).

FIG. 1 is a block diagram showing a first embodiment of the present invention. In the following description of the embodiments of the present invention, the same or similar components are denoted by the same numerals and symbols.

In the drawing, reference numeral 1 denotes F as a non-linear amplification element.
ET is used. Vds is a bias power supply,
Reference numerals 10 and 11 denote DC blocking capacitors. 20,
Reference numerals 21, 22, and 23 are a coil, a voltage-controlled variable attenuator, a band-pass filter including a DC component rejection function, and an adder, respectively, provided in the feedback circuit.

An input signal having a plurality of frequency components passes through the DC blocking capacitor 10 and is input to the FET 1 which operates as an efficient class B or class C nonlinear amplifier circuit. The output is output to the output terminal OUT through the DC blocking capacitor 11.

A coil 20 is connected in front of the DC blocking capacitor 11 to extract a secondary distortion component. The extracted second-order distortion component passes through a voltage-controlled variable attenuator 21, a bandpass filter 22 having a DC blocking function, and an adder 23 composed of an operational amplifier or the like for further appropriate level adjustment. I will

In the adder 23, the band-pass filter 2
2 is combined with the bias voltage Vgs, and FE
It is applied to the gate of T1 and injected into the input signal. Thereby, the IM3 characteristic, which is the third-order intermodulation distortion component, is improved based on the principle described above.

On the other hand, the detector 30 connected to the input side detects the level of the input signal input from the input terminal IN, and outputs a signal corresponding to the detected level. This signal is input to the control circuit 31. The control circuit 31 controls the voltage-controlled variable attenuator 21 based on the input detection signal from the detector 30 so that the attenuation becomes an appropriate value with respect to the level of the input signal.

As a result, when the level of the input signal is increased, the attenuation of the voltage-controlled variable attenuator 21 is reduced, and when the level of the input signal is reduced, the attenuation is increased. Controlled.

Therefore, it is possible to inject a second-order distortion component of an appropriate level into the input signal in response to the fluctuation of the input signal level, and the IM3 characteristic as the third-order intermodulation distortion component is accurately improved. .

FIG. 2 is a block diagram showing a second embodiment of the present invention, in which a voltage-controlled variable phase shifter 14 is provided on the output side of a nonlinear amplification element 1 so as to detect the phase difference between input and output signals. Correspondingly, the amount of phase shift of the output signal of the nonlinear amplification element 1 is controlled. Thus, the phase difference between the input and output signals is always set to a predetermined value so that the third-order intermodulation distortion is accurately reduced.

To this end, as a specific configuration, power distributors 12 and 13 are provided on the input side and the output side, and a phase shift control circuit 40 is further provided. The input and output signals are branched from each of the power dividers 12 and 13, and the phase shift control circuit 40 detects the phase difference.

Here, the phase shift control circuit 40 comprises, for example, a mixer (not shown), a low-pass filter, and a loop gain amplifier. The phase shift control circuit 40 sends a control signal corresponding to the detected phase difference to the voltage-controlled variable phase shifter 14,
The voltage-controlled variable phase shifter 14 shifts the output phase of the nonlinear amplification element 1 so that the phase difference between the input and output signals becomes a predetermined value.

FIG. 3 is a block diagram showing a third embodiment according to the present invention. The third embodiment is different from the second embodiment in that a phase shifter 14 is provided on the input side to shift the phase of an input signal. Therefore,
The operation and the configuration of the second embodiment are substantially the same as those described with reference to FIG.

FIG. 4 is a block diagram showing a fourth embodiment of the present invention. The feature of this embodiment is that, in comparison with the second and third embodiments, a phase shifter 24 is provided in the feedback circuit of the conventional amplifier shown in FIG.

That is, a control signal for controlling the phase shift amount of the phase shifter 24 is generated by the phase shift control circuit 40 based on the input and output signals branched from the power dividers 12 and 13 provided on the input and output sides. Generated.

The meaning of the control signal generated by the phase shift control circuit 40 is the same as in the second and third embodiments described above. However, the phase shifter 24 appropriately shifts the phase of the secondary distortion component output from the bandpass filter 22 based on a control signal from the phase shift control circuit 40.

FIG. 5 is a block diagram showing a fifth embodiment of the present invention. This embodiment has a configuration in which the first embodiment shown in FIG. 1 and the second embodiment shown in FIG. 2 are combined.
According to this embodiment, even when the levels and phases of the input and output signals fluctuate, it is possible to control the input and output signals so that they become a predetermined value.

FIG. 6 is a block diagram showing a sixth embodiment of the present invention. This embodiment has a configuration in which the first embodiment shown in FIG. 1 and the third embodiment shown in FIG. 3 are combined.
Also in this embodiment, similarly to the fifth embodiment, even when the levels and phases of the input and output signals fluctuate, it is possible to control the input and output signals to be at predetermined values.

FIG. 7 is a block diagram showing a seventh embodiment of the present invention. This embodiment has a configuration in which the first embodiment shown in FIG. 1 and the fourth embodiment shown in FIG. 4 are combined.
Also in this embodiment, even when the levels and phases of the input and output signals fluctuate, it is possible to control the input and output signals to be at predetermined values.

In the above description of the embodiment, the FET is used as the non-linear amplifier 1. However, the present invention is not limited to the FET as the non-linear amplifier 1, and the same applies to the case where another element is used. The effect can be obtained.

[0062]

As described above according to the embodiments of the present invention, according to the present invention, it is possible to realize a conventional nonlinear amplifier.
Sub-intermodulation distortion can be reduced more effectively and accurately. This makes it possible to provide an amplifier having excellent linearity without lowering the power load efficiency.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram of a second embodiment of the present invention.

FIG. 3 is a block diagram of a third embodiment of the present invention.

FIG. 4 is a block diagram of a fourth embodiment of the present invention.

FIG. 5 is a block diagram of a fifth embodiment of the present invention.

FIG. 6 is a block diagram of a sixth embodiment of the present invention.

FIG. 7 is a block diagram of a seventh embodiment of the present invention.

FIG. 8 is an example of a conventional linear amplifier that reduces third-order intermodulation distortion.

FIG. 9 is an explanatory diagram of distortion compensation by second-order distortion injection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-linear amplification circuit 10, 11 DC blocking capacitor 20 Secondary distortion extraction coil 21 Fixed attenuator and voltage control type variable attenuator 22 Band-pass filter 23 Adder 30 Detector 31 Control circuit 12, 13 Power distributor 14, 24 Transfer Phaser 40 Phase shift control circuit

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Toru Umiwa 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (56) References JP-A-3-174810 (JP, A) JP-A-61-58304 (JP, A) JP-A-62-78902 (JP, A) YONGCAI et al. , A New Method of The Third-Order Intermodulation Reduction in Nonlinear Microwave Systems, IEEE TRANSACTIONS ON MICREO TECHNOLOGY. MTT-34, NO. 2,245-250 (58) Fields surveyed (Int.Cl. ⁷ , DB name) H03F 1/02 H03F 1/26 H03F 1/32

Claims (5)

(57) [Claims] A non-linear amplifier (1) to which a signal having a plurality of frequency components is input, and the non-linear amplifier (1)
And a feedback circuit for extracting a second-order distortion component from the output of the non-linear amplification element and feeding back the input to the input side of the nonlinear amplification element (1) to inject the signal having the plurality of frequency components into a signal having a plurality of frequency components. A coil (20) and a voltage-controlled variable attenuator (2
1), a low-pass filter (22), and an adder (23). The adder (23) includes the low-pass filter (2).
2) A linear amplifier configured to add the output of (2) and the input bias power supply (Vgs) and inject the same into the input side of the nonlinear amplifying element (1). First and second power dividers (12, 13) provided on the output side, and a voltage-controlled variable phase shifter (2
4) and the input and output signals branched from the first and second power dividers (12, 13) are input, the phase difference between the input and output signals is detected, and the phase difference becomes a predetermined value. And a phase shift control circuit (40) for controlling the amount of phase shift of the voltage-controlled variable phase shifter (24). 2. A signal having a plurality of frequency components is inputted.
Nonlinear amplifying element (1) and nonlinear amplifying element (1)
Extracts a second-order distortion component from the output of the nonlinear amplification element
It returns to the input side of (1) and has the plurality of frequency components.
A feedback circuit for injecting the signal into a signal;
A blocking coil (20) and a voltage-controlled variable attenuator (2
1), a low-pass filter (22) and an adder (23)
And the adder (23) includes the low-pass filter (2).
2) and the input bias power supply (Vgs) is added,
It is configured to be injected into the input side of the linear amplification element (1).
A linear amplifier connected to the input side of the nonlinear amplifying element (1);
The input level of a signal having a frequency component is detected, and the detection level is detected.
Detector for outputting control signal corresponding to bell (30)
And the voltage control according to a control signal from the detector (30).
A control circuit for controlling the attenuation of the control variable attenuator (21)
(31), further, first and second power dividers (12, 13) provided on the input side and the output side of the nonlinear amplifying element (1), and the input side of the nonlinear amplifying element (1) or , A voltage-controlled variable phase shifter (14) provided on the output side, and input and output signals branched from the first and second power dividers (12, 13), and the input and output signals And a phase shift control circuit (40) for controlling the amount of phase shift of the voltage-controlled variable phase shifter (14) so that the phase difference becomes a predetermined value. Linear amplifier. 3. A signal having a plurality of frequency components is input.
Nonlinear amplifying element (1) and nonlinear amplifying element (1)
Extracts a second-order distortion component from the output of the nonlinear amplification element
It returns to the input side of (1) and has the plurality of frequency components.
A feedback circuit for injecting the signal into a signal;
A blocking coil (20) and a voltage-controlled variable attenuator (2
1), a low-pass filter (22) and an adder (23)
And the adder (23) includes the low-pass filter (2).
2) and the input bias power supply (Vgs) is added,
It is configured to be injected into the input side of the linear amplification element (1).
A linear amplifier connected to the input side of the nonlinear amplifying element (1);
The input level of a signal having a frequency component is detected, and the detection level is detected.
Detector for outputting control signal corresponding to bell (30)
And the voltage control according to a control signal from the detector (30).
A control circuit for controlling the attenuation of the control variable attenuator (21)
(31), further, first and second power dividers (12, 13) provided on the input side and output side of the non-linear amplification element (1), and a voltage control type variable provided in the feedback circuit. Phase shifter (2
4) and the input and output signals branched from the first and second power dividers (12, 13) are input, the phase difference between the input and output signals is detected, and the phase difference becomes a predetermined value. And a phase shift control circuit (40) for controlling the amount of phase shift of the voltage-controlled variable phase shifter (24). 4. Oite to any one of claims 1 to 3, wherein the non-linear amplifying element (1) is a linear amplifier, characterized in that it is constituted by a FET. 5. Oite to any one of claims 1 to 3, wherein the voltage-controlled variable attenuator (21), when the level of the detection signal of the detector (30) is large, so that the attenuation amount is reduced A linear amplifier, characterized in that the linear amplifier is controlled.