JP2010154459A - High-frequency amplifying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-frequency amplifying device capable of aiming at a higher efficiency by improving the gain of the high-frequency amplifying device that is a Doherty amplifier, combined with a general distortion compensation method and by bringing the distortion compensation amount to that of an AB class amplifier. <P>SOLUTION: The high-frequency amplifying device includes a freuqnecy-doubling wave injection Doherty amplifier 10, having a frequency-doubling wave generating section; an adaptive bias control circuit 116, and a distortion compensating section by pre-distortion, wherein the gain when the input level is low is improved by injecting a second-order harmonics generated in the double-frequency wave generating section and the phase and amplitude of which are adjusted into a carrier amplifier of a Doherty amplifying section and at the same time; and the adaptive bias control circuit 116 appropriately controls the gate voltage of a peak amplifier, according to the input level to improve the gain in the vicinity of saturation and improve the distortion compensation amount. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a high-frequency amplifier that amplifies a high-frequency signal, and in particular, can improve distortion compensation characteristics when combining a Doherty amplifier and general distortion compensation, and can further improve power conversion efficiency. The present invention relates to a high frequency amplification device.

[Description of Prior Art]
In order to realize high-speed data communication, OFDM (Orthogonal Frequency Division Multiplexing) using a plurality of carriers orthogonal to each other is employed in fields such as wireless LAN and terrestrial digital broadcasting. However, since modulation by OFDM uses a large number of carriers, there is a drawback that the peak power to average power ratio (PAPR) of the signal waveform becomes high.
Therefore, in order to amplify such a microwave signal, it is necessary to operate the backoff given as a difference between the average power and the saturation power during actual operation of the amplifier in a sufficiently large state.
However, in general amplifiers, there is a trade-off relationship in which the efficiency is significantly reduced in a large backoff state, and high efficiency cannot be obtained until the output of the amplifier approaches the maximum output power.

[Doherty amplifier]
A Doherty amplifier is known as an amplifier having a high output level and high efficiency.
The Doherty amplifier uses a carrier amplifier biased to class AB and a peak amplifier biased to class C in parallel. Normally, the carrier amplifier operates, but an instantaneous large peak component activates the peak amplifier and synthesizes it with the carrier amplifier at the output end. Normally, only the carrier amplifier operates with a small back-off, so that high efficiency can be obtained as compared with class AB single-unit operation.
The configuration and operation of the Doherty amplifier are described in, for example, Japanese Patent Laid-Open No. 2008-125044 (Patent Document 1).

[Distortion compensation]
As general distortion compensation methods for compensating for nonlinear distortion of an amplifier, there are feedforward distortion compensation, feedback distortion compensation, and predistortion distortion compensation.
[Predistortion method: Fig. 9]
Here, an example of a conventional distortion compensation method will be described with reference to FIG. FIG. 9 is a schematic configuration block diagram of an amplifying apparatus having a general predistortion distortion compensation function.
Predistortion is a method of reducing intermodulation distortion by providing an inverse characteristic of a power amplifier in the previous stage, and this inverse characteristic is adaptively controlled in accordance with temperature changes and individual differences.

  As shown in FIG. 9, a conventional amplifying apparatus having a predistortion distortion compensation function includes a predistorter 101, a D / A converter 102, a quadrature modulator 103, an oscillator 104, a power amplifier 105, A directional coupler 106, a mixer 107, an oscillator 108, an A / D converter 109, a distortion detector 112, and a controller 118 are included. The distortion detection unit 112 further includes an FFT calculation unit (FFT in the figure) 110 and an IM calculation unit 111.

The predistorter 101 performs distortion compensation for adding an inverse characteristic of nonlinear distortion to the input signal in accordance with an instruction from the control unit 118.
The D / A converter 102 converts the distortion-compensated digital input signal into an analog signal.
The oscillator 104 oscillates the RF frequency.
The quadrature modulator 103 performs quadrature modulation on the input analog signal and up-converts it with the frequency of the oscillator 104.
The power amplifier 105 amplifies the input RF signal with a predetermined amplification factor and outputs it.

The directional coupler 106 branches the output signal from the power amplifier 105 and feeds it back.
The mixer 107 synthesizes the signal from the oscillator 108 and the signal branched from the directional coupler 106 and down-converts them to the IF frequency.
The A / D converter 109 performs A / D conversion on the down-converted signal with the clock 2 (CLK2) and samples the signal.

The distortion detection unit 112 detects distortion included in the input sampling signal and outputs it to the control unit 118 as a distortion value.
The FFT calculation unit 110 of the distortion detection unit 112 obtains a spectrum of the input signal by FFT (Fast Fourier Transform).
The IM calculation unit 111 calculates the frequency of intermodulation distortion from the number of carriers of the modulation signal and the detuning frequency, and outputs the power value at the frequency to the control unit 118 as a distortion value based on the spectrum.
Then, the control unit 118 adaptively controls the predistorter 101 so that the input distortion value becomes small.

The operation of the amplification device having the above configuration will be described.
The IF signal input in the digital I / Q format is compensated for nonlinear distortion by the predistorter 101, converted to an analog signal by the D / A converter 102, and orthogonally modulated by the orthogonal modulator 103. And up-converted to an RF frequency, amplified by the power amplifier 105 with a predetermined amplification factor, and output.

On the other hand, a part of the output of the power amplifier 105 is taken out by the directional coupler 106, down-converted to an IF frequency by the mixer 107, converted into a digital signal by the A / D converter 109, and The spectrum is detected by the FFT calculation unit 110, the power value in the intermodulation distortion (IM3, IM5) calculated by the IM calculation unit 111 is calculated, and the distortion value is output to the control unit 118.
The control unit 118 adaptively controls the predistorter 101 so as to reduce the distortion value.

Since the nonlinear characteristic of the amplifying device appears as intermodulation distortion is odd-order distortion, the processing in the predistorter that adds the nonlinear inverse characteristic of the amplifying apparatus can be approximated by equation (1).
y = x + α · | x | ² · x + β · | x | ⁴ · x + γ · | x | ⁶ · x Equation (1)
Here, x and y are an input signal and an output signal of the predistorter 101, and are complex numbers. The control unit 118 controls the values of α, β, and γ using a perturbation method so that the strain value obtained by the strain detection unit 112 becomes small.

[Configuration of predistorter: FIG. 10]
Here, a schematic configuration of the predistorter 101 will be described with reference to FIG. FIG. 10 is a block diagram showing a schematic configuration of the predistorter 101.
As shown in FIG. 10, the predistorter 101 includes a plurality of multipliers and adders, calculates the third, fifth, and seventh power components from the input signal (x), and has coefficients α and β respectively. , Γ is multiplied to obtain an output signal (y) based on equation (1).

α, β, and γ are complex numbers.
α = A3 · exp (j * Φ3)
β = A5 · exp (j * Φ5)
γ = A7 · exp (j * Φ7) Equation (2)
It is expressed.
Therefore, the control unit 118 cyclically controls these coefficients by the perturbation method in the order of Φ3 → A3 → Φ5 → A5 → Φ7 → A7 → Φ3.

[Control in control: FIG. 11]
Control using the perturbation method in the control unit 118 will be described with reference to FIG. FIG. 11 is a flowchart showing the control using the perturbation method in the control unit 118.
As shown in FIG. 11, when the processing is started, the control unit 118 first sets an update target coefficient (K, here, first Φ3) as an initial setting, reads the number of times of setting, and reads the previous distortion value (200). ).

When the current distortion value calculated by the distortion detection unit 112 is input, the control unit 118 compares the current distortion value with the previous distortion value (201), and determines the current distortion value. Is smaller (in the case of Yes), the coefficient is further updated in the same direction (K = K + Step) (203).
Further, if the distortion value is large in the process 101 (in the case of No), the control unit 118 reverses the update direction (Step = Step * (− 1)) (202), and proceeds to the process 203. Update the coefficients.

Next, the control unit 118 counts how many times the same coefficient (here, Φ3) has been continuously updated (204), and stores the distortion value detected as the “current distortion value” in the process 201 (205). ). The distortion value stored here is used as the “previous distortion value” in the next processing 201.
Then, the control unit 118 compares the stored number of updates with the set number set in the initial setting of the process 200 (206), and if the update number is equal to or less than the set number (if No), the process Returning to 201, the coefficient update of Φ3 is repeated.

In the process 206, when the number of updates exceeds the set number (in the case of Yes), the control unit 118 changes the update target coefficient (207). Here, the update target coefficient is changed from Φ3 to A3. Then, the control unit 118 clears the stored number of updates (208).
The control unit 118 controls the coefficient of the predistorter 101 so that the distortion value becomes small by the control using such a perturbation method. In this way, the non-linear inverse characteristic in the amplifying apparatus can be approximated by a predistorter using a power series, and distortion compensation is possible.

[Doherty amplifier with distortion compensation]
An amplifying apparatus has been devised that combines a general Doherty amplifier and a general distortion compensation method to suppress nonlinearity in the Doherty amplifier and further improve efficiency.

[Prior art documents]
As a prior art related to an amplifier that achieves high efficiency, there is JP-A-2005-204208 (Patent Document 2).
Patent Document 2 generates an odd-order harmonic signal for a fundamental wave signal to be amplified, generates a rectangular wave signal by combining the odd-order harmonic signal with the fundamental wave signal to be amplified, When the rectangular wave signal is amplified by an active element and the load side is viewed from the output end of the active element, the impedance value for the odd-order harmonic signal is infinite, and the impedance for the even-order harmonic signal is An amplifier that can achieve high efficiency by setting the value to zero is described.

JP 2008-125044 A JP-A-2005-204208

  However, in a conventional high-frequency amplifier that combines a general Doherty amplifier and a general distortion compensation method, the gain of the Doherty amplifier is reduced near saturation and at a low input, so that the distortion compensation amount is the same as the conventional one. There is a problem that the amount of distortion compensation becomes lower than that of the class AB amplifier, and the efficiency cannot be brought out to the limit due to degradation of intermodulation distortion.

  In addition, although the said patent document 1 describes injecting odd-order harmonics into the amplifier input, it does not describe injecting even-order high-frequency waves.

  The present invention has been made in view of the above circumstances, and improves the gain of a high-frequency amplifier that combines a Doherty amplifier and a general distortion compensation method so that the distortion compensation amount approaches that of a class AB amplifier. Another object of the present invention is to provide a high-frequency amplifier that can achieve higher efficiency.

  The present invention for solving the problems of the above conventional example has a carrier amplifier operating in class AB and a peak amplifier path operating in class B or class C, and combines the outputs of the carrier amplifier and the peak amplifier. A high frequency amplification device including a Doherty amplifier that outputs a second harmonic from an input fundamental frequency signal, adjusts the phase and amplitude of the second harmonic, and a carrier amplifier of the Doherty amplifier, Or a second harmonic generation circuit that outputs to both the carrier amplifier and the peak amplifier, and an adaptive bias control circuit that controls the gate voltage of the peak amplifier of the Doherty amplifier according to the input level to the Doherty amplifier. It is characterized by.

  Further, the present invention is characterized in that the above-described high-frequency amplifier device includes a distortion compensation circuit that compensates for nonlinear distortion generated in the Doherty amplifier.

  According to the present invention, a high frequency amplifying apparatus including a Doherty amplifier generates a second harmonic from an input fundamental frequency signal, adjusts the phase and amplitude of the second harmonic, A carrier amplifier, or a second harmonic generation circuit that outputs to both the carrier amplifier and the peak amplifier, and an adaptive bias control circuit that controls the gate voltage of the peak amplifier of the Doherty amplifier according to the input level to the Doherty amplifier. Because it is a high-frequency amplification device, the gain at the low input level is improved by injecting the second harmonic into the amplifier, and the gain near saturation is controlled by controlling the gate voltage of the peak amplifier according to the input level. There is an effect that it is possible to improve the efficiency.

  In addition, according to the present invention, the above-described high-frequency amplification device is provided with a distortion compensation circuit that compensates for nonlinear distortion generated in the Doherty amplifier. Therefore, even if a combination of Doherty amplifier and general distortion compensation is used, a class AB amplifier A sufficient amount of distortion compensation close to the above can be realized, and further efficiency can be improved.

[Summary of Invention]
Embodiments of the present invention will be described with reference to the drawings.
A high-frequency amplifier according to an embodiment of the present invention is an amplifier having a configuration in which a Doherty amplifier and predistortion distortion compensation are combined, and an adaptive bias that controls a bias voltage of a peak amplifier of the Doherty amplifier according to an input level. A control circuit is provided to improve the gain in the vicinity of saturation and a second harmonic generation unit that injects a second harmonic whose phase and amplitude are adjusted to the input of the carrier amplifier. Thus, it is possible to improve the overall efficiency of the amplifier by improving the distortion compensation characteristics by suppressing the deterioration of the distortion compensation due to the gain reduction near saturation and at the time of low input.

  In addition to the above configuration, the high-frequency amplifier according to the embodiment of the present invention can further improve efficiency by injecting the second harmonic into the peak amplifier.

[First Embodiment: FIG. 1]
A high-frequency amplifier according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of a high-frequency amplification device (first amplification device) according to the first embodiment of the present invention.
As shown in FIG. 1, the first amplifying device includes a predistorter 101, a D / A converter 102, a quadrature modulator 103, an oscillator 104, a second harmonic injection Doherty amplifier 10, and a directional coupling. 106, mixer 107, oscillator 108, A / D converter 109, distortion detection unit 112, control unit 118, adaptive bias control circuit 116, delay correction circuit 115, and directional coupler 119 It has. The distortion detection unit 112 further includes an FFT calculation unit 110 and an IM calculation unit 111.

  Among the above components, the predistorter 101, the D / A converter 102, the quadrature modulator 103, the oscillator 104, the directional coupler 106, the mixer 107, the oscillator 108, and the A / D converter. 109, the distortion detection unit 112, and the control unit 118 are portions for performing distortion compensation by predistortion (distortion compensation unit), and each component and configuration in the conventional amplifying apparatus having the predistortion function shown in FIG. Since the operation is the same, the description is omitted here.

The characteristic part in the first amplifying device will be described.
The directional coupler 119 branches the signal output from the quadrature modulator 103.
The delay correction circuit 115 includes a transmission line, a filter, and the like, and delays the input signal in accordance with the signal branched to the adaptive bias circuit 116.
The adaptive bias circuit 116 controls the bias voltage of the peak amplifier of the second harmonic injection Doherty amplifier 10 according to the input level. The configuration of the adaptive bias circuit 116 will be described later.
The second harmonic injection Doherty amplifier 10 is provided with a second harmonic generation unit that injects a second harmonic into the input of the carrier amplifier in addition to the configuration of a general Doherty amplifier. The configuration of the second harmonic generation unit will be described later.

[Adaptive Bias Control Circuit 116: FIG. 2]
Next, the configuration of the adaptive bias control circuit 116 will be described with reference to FIG. FIG. 2 is a circuit diagram showing a configuration example of the adaptive bias control circuit 116.
As shown in FIG. 2, the adaptive bias control circuit 116 includes an input terminal, a level adjustment circuit for adjusting the level of the input signal, a matching resistor for matching the input signal, and the slope of the gate voltage. A slope adjusting resistor to adjust, a detection Schottky diode for detecting an input signal, an offset power source for flowing an idle current at the time of no input signal, an LPF for removing unnecessary waves after detection, and detection A limit Schottky diode for limiting the voltage, a limit power source, and an output terminal are provided.
An output terminal of the adaptive bias control circuit 116 is connected to a gate terminal 12 of a second harmonic injection Doherty amplifier 10 described later, and supplies a gate voltage to the peak amplifier.

[Operation of Adaptive Bias Control Circuit 116: FIG. 2, FIG. 6 (a)]
Next, the control of the gate voltage of the peak amplifier by the adaptive bias control circuit 116 will be described with reference to FIG. 2 and FIG. FIG. 6A is an explanatory diagram showing an example of controlling the gate voltage of the peak amplifier by the adaptive bias control circuit 116.
In the adaptive bias circuit 116 shown in FIG. 2, the gate voltage in the A region (the peak amplifier performs the C class operation) in FIG. 6A is controlled by the offset power supply.

In addition, the gate voltage in the B region (the peak amplifier performs the AB class operation from C to C) in FIG. 6A is controlled by the inclination adjusting resistor.
Then, the gate voltage in the region C (the peak amplifier performs the AB class operation) in FIG. 6A is controlled by the limit Schottky diode and the limit power source.
As a result, the idle current of the peak amplifier can be changed according to the input level.

  In the first amplifying apparatus, by providing the adaptive bias control circuit 116, the bias voltage of the peak amplifier can be controlled in accordance with the input level to compensate for the decrease in gain near saturation, which is equivalent to the class AB amplifier. Therefore, it is possible to ensure non-linearity that enables distortion compensation.

[Double Harmonic Injection Doherty Amplifier 10: FIGS. 3 and 4]
Next, the second harmonic injection Doherty amplifier 10 of the first amplifying device will be described.
The second harmonic injection Doherty amplifier 10 of the first amplifying device includes a Doherty amplification unit having a configuration substantially similar to that of a general Doherty amplifier, and a second harmonic generation unit that generates second harmonics. Yes.

[Double harmonic generator: Fig. 3]
First, the second harmonic generation unit of the second harmonic injection Doherty amplifier 10 of the first amplifying device will be described with reference to FIG. FIG. 3 is a configuration block diagram of the second harmonic generation unit of the second harmonic injection Doherty amplifier 10 of the first amplification device.
As shown in FIG. 3, the second harmonic generation unit of the second harmonic injection Doherty amplifier 10 includes an input terminal 21, a divider 22, a fundamental wave adjustment circuit 31, a second harmonic generation circuit 30, and an output terminal A. And an output terminal B.

  Here, the input terminal 21 is connected to the output terminal of the delay correction circuit 115 shown in FIG. The output terminal A is connected to the input terminal 1 (A) of the Doherty amplifier shown in FIG. 4, and the output terminal B is connected to the second harmonic input terminal 13 (B) of the Doherty amplifier shown in FIG. It is connected.

The fundamental wave adjustment circuit 31 adjusts the fundamental frequency input signal input to the Doherty amplification unit of the double wave injection Doherty amplifier 10, and includes a delay correction circuit 23, a variable attenuator 24, and an amplifier 25. It is configured.
The delay correction circuit 23 adjusts the phase by delaying the input signal so as to match the phase with the signal passing through the second harmonic generation circuit 30.
The variable attenuator 24 and the amplifier 25 adjust the amplitude of the signal so that the input level to the later-described Doherty amplifier becomes an appropriate input level.

The second harmonic generation circuit 30 generates and adjusts the second harmonic from the input fundamental frequency signal. The harmonic generator 26, the amplifier 27, the variable phase shifter 28, the variable attenuation, and the like. And a container 29.
The harmonic generation circuit 26 generates a second harmonic from an input fundamental frequency signal, and has, for example, a configuration in which an input matching circuit, a diode, and an output matching circuit are connected in series.
The amplifier 27 amplifies the second harmonic, the variable phase shifter 28 adjusts the phase of the second harmonic, and the variable attenuator 29 adjusts the amplitude of the second harmonic so as to obtain an appropriate injection level. Make adjustments.
The fundamental wave adjusting circuit 31 and the second harmonic wave generating circuit 30 adjust so that the relationship between the fundamental frequency signal to be output and the phase and amplitude of the second harmonic is optimized.

[Operation of second harmonic generation unit: Fig. 3]
In the second harmonic generation unit of the second harmonic injection Doherty amplifier 10, the fundamental frequency signal input from the input terminal 21 is distributed by the distributor 22, and one of the signals is input to the fundamental wave adjustment circuit 31, and the delay correction circuit. 23, the level is adjusted by the variable attenuator 24 and the amplifier 25, is output from the output terminal A, and is input to the input terminal 1 of the Doherty amplifier described later.

  The other fundamental frequency signal distributed by the distributor 22 is input to the second harmonic generation circuit 30, a second harmonic is generated by the harmonic generator 26, and the second harmonic is amplified by the amplifier 27. Then, the phase is adjusted by the variable phase shifter 28, the level is adjusted by the variable attenuator 29, and is input from the output terminal B to the input matching circuit 41 of the carrier amplifier 4 from the second harmonic input terminal 13 of the Doherty amplifier.

[Doherty amplifier: Fig. 4]
Next, the Doherty amplification unit of the second harmonic injection Doherty amplifier 10 will be described with reference to FIG. FIG. 4 is a configuration block diagram of the Doherty amplification unit of the second harmonic injection Doherty amplifier 10 of the first amplification device.
As shown in FIG. 4, the Doherty amplification unit includes an input terminal 1 (A), an output terminal 8, a distributor 2, a phase shifter 3, a carrier amplifier 4, a peak amplifier 5, and a Doherty combining unit 6. And a λ / 4 transformer 7 and an output terminal 8.

Further, the carrier amplifier 4 includes an input matching circuit 41, an amplification element 42, and an output matching circuit 43. The peak amplifier 5 includes an input matching circuit 51, an amplification element 52, and an output matching circuit 53. Has been.
The Doherty combining unit 6 includes a λ / 4 transformer 61 and a combining point 62.

As a characteristic part of the first amplifying device, a second harmonic input terminal 13 (injecting a second harmonic input from the second harmonic generator into the input matching circuit 41 of the carrier amplifier 4 is input to the Doherty amplifier. B) is provided, and a gate terminal 12 for controlling the gate voltage of the amplifying element 52 of the peak amplifier 5 is provided.
3 and 4, the terminals indicated by “A” are connected to each other, and the terminals indicated by “B” are connected to each other to constitute the double wave injection Doherty amplifier 10.

  From the second harmonic input terminal 13, a second harmonic whose phase and amplitude are appropriately adjusted is input from the B terminal of the second harmonic generation unit described above. Thus, the efficiency of the carrier amplifier 4 operating at a low input level is reduced by reducing the overlap of the voltage / current waveforms. The effect of the second harmonic injection is particularly remarkable at a low input level, and improves the gain of the Doherty amplifier at the low input level.

  The gate terminal 12 is connected to the output terminal of the adaptive bias control circuit 116 described above, and the gate voltage of the amplifying element 52 of the peak amplifier 5 is changed according to the input level as shown in FIG. It comes to control. By controlling the gate voltage of the peak amplifier 5 according to the input level, the gain of the Doherty amplification unit in a region near saturation is improved.

  As a result, the first amplifying device can improve the gain at the low input level of the Doherty amplifier and near saturation, and even with a general distortion compensation method, a distortion compensation amount close to that of the class AB amplifier can be obtained. Therefore, the efficiency can be further improved.

[Operation of Doherty Amplifier: FIG. 4]
In the Doherty amplifying unit, a signal having a fundamental frequency adjusted in amplitude and phase is input from the input terminal 1, distributed by the distributor 4, one of which is input to the carrier amplifier 4, and is input from the second harmonic input terminal 13. Is amplified by the amplifying element 42 and impedance-converted by the λ / 4 transformer 61 through the output matching circuit 43.

  The other signal distributed by the distributor 4 is adjusted in phase by the phase shifter 5 in accordance with the carrier amplifier 4, and then input to the peak amplifier 5, and is amplified by the gate voltage from the adaptive bias control circuit 116. Amplified at 52, impedance-converted by the output matching circuit 53, and output.

  At the combining point 62, the output from the λ / 4 transformer 61 and the output from the peak amplifier 5 are combined, and the impedance is converted by the λ / 4 transformer 7 to match an output load (not shown), and the output terminal 8 Is output from. In this way, the operation of the Doherty amplification unit of the second harmonic injection Doherty amplifier 10 is performed.

[Drain current injected with second harmonic: FIG. 5]
Next, the drain current when the second harmonic is injected into the fundamental wave will be described with reference to FIG. FIG. 5 is an explanatory diagram showing the drain current when the second harmonic is injected into the fundamental wave.
As shown in FIG. 5, when the second harmonic is injected as compared to the drain current waveform output when only the fundamental wave is input to the transistor as the input voltage (without the second harmonic injection), The period during which the current flows is shortened, and a waveform in which the even harmonic frequency in the class F amplifier is short-circuited is obtained.
When only the fundamental wave is input, the level of the output harmonic is low and the change in the shape of the waveform is small. By injecting the second harmonic, the overlap between the drain voltage and the drain current is reduced to improve efficiency. Is.
Also, when the fundamental wave input level is low, the drain current is small and the mutual conductance is small, so the gain is low, but by injecting the second harmonic, a large amount of drain current flows, the mutual conductance increases, and the gain improves. To do.

[Example of AM-AM characteristic of first amplification device: FIG. 6B]
Next, the AM-AM characteristic of the first amplification device will be described with reference to FIG. FIG. 6B is an explanatory diagram illustrating an example of AM-AM characteristics of the first amplifying device.
In FIG. 6B, the horizontal axis indicates the input level, the vertical axis indicates the gain, (D) indicates the characteristics of the class AB amplifier, (E) indicates the characteristics of a general Doherty amplifier, and (F) indicates the Doherty amplifier. The characteristics when the gate voltage of the peak amplifier is controlled, (G) shows the characteristics of the second harmonic injection Doherty amplifier 10 in the first amplifier.

  The general Doherty amplifier shown in (E) of FIG. 6B has a lower gain at the time of low input than the class AB amplifier shown in (D), and the gain increases as the input level increases. In the vicinity of saturation, the gain decreases again.

As shown in (F), by adding a configuration such as an adaptive bias control circuit to a general Doherty amplifier and controlling the gate bias voltage in the peak amplifier according to the input level, the efficiency near the saturation of the peak amplifier is improved. Thereby, the gain of the entire amplifying apparatus is also improved. However, the efficiency at low input levels remains low compared to class AB amplifiers.
As a bias control of the peak amplifier, it is conceivable to control as shown in FIG.

  In addition, the second harmonic injection Doherty amplifier 10 in the first amplifying device controls the bias of the peak amplifier as in the amplifying device in (F), and injects the second harmonic into the carrier amplifier. As shown in FIG. 5, it can be understood that a decrease in gain near saturation can be prevented and a gain equivalent to that of a class AB amplifier can be obtained even at a low input level.

  That is, in the second harmonic injection Doherty amplifier 10 of the first amplifying device, the gain voltage near saturation is reduced by controlling the gate voltage of the peak amplifier 5 as shown in FIG. 6A according to the input level. In addition, by injecting the second harmonic adjusted to an appropriate phase and amplitude into the carrier amplifier 4, the gain at the low input level can be improved, which is equivalent to the class AB amplifier as a whole. An AM-AM characteristic can be obtained.

[Example of distortion compensation characteristics in first amplifying apparatus: FIG. 7]
Next, distortion compensation characteristics of the first amplifying device will be described with reference to FIG. FIG. 7 is an explanatory diagram illustrating an example of distortion compensation characteristics of the first amplifying device.
As shown in FIG. 7, when a general Doherty amplifier and general distortion compensation are combined, sufficient distortion compensation cannot be obtained compared to the distortion compensation characteristics of the class AB amplifier, and distortion degradation is observed.

On the other hand, in the first amplifying device, the adaptive bias control circuit 116 controls the gate voltage of the peak amplifier 5 of the double wave injection Doherty amplifier 10 as shown in FIG. 6A according to the input level. At the same time, the second harmonic wave whose phase and amplitude are appropriately adjusted is injected into the carrier amplifier 4 and then distortion compensation by general predistortion is performed.
Thereby, as described above, the gain near the saturation and the low input level can be prevented, and the distortion compensation characteristic equivalent to the class AB amplifier can be obtained as shown in FIG.

[Effect of the first embodiment]
According to the high frequency amplification device according to the first embodiment, the second harmonic injection Doherty amplifier 10, the adaptive bias control circuit 116, and the distortion compensation unit by predistortion are provided. In addition, a high-frequency amplifying apparatus that performs distortion compensation after injecting a second-harmonic wave whose amplitude is adjusted and appropriately controlling the gate voltage of the peak amplifier 5 according to the input level is used. The gain can be made close to that of a class AB amplifier, and even if general distortion compensation is used, distortion compensation characteristics equivalent to those of class AB can be obtained, and the efficiency can be further improved. is there.

  In the first amplifying device, the second harmonic generation unit of the second harmonic injection Doherty amplifier 10 generates a second harmonic from the input fundamental frequency signal, adjusts the phase and amplitude, and adjusts the phase of the Doherty amplification unit. Since it is an amplifier that injects into the carrier amplifier and adjusts the phase and amplitude of the fundamental frequency and inputs them to the Doherty amplifier, the relationship between the phase and amplitude of the fundamental frequency signal and the second harmonic is optimized throughout the amplifier. There is an effect that can be adjusted so that a large gain can be obtained.

  The configuration of the second harmonic injection Doherty amplifier 10 is not limited to this. For example, the length of the transmission line of the Doherty combining unit is 0 to λ / 2, or the second harmonic injection Doherty amplifier 10 is driven before the second harmonic injection Doherty amplifier 10. An amplifier may be provided. A drive amplifier may be provided after the quadrature modulator 103 of the distortion compensation unit. Furthermore, distortion compensation is not limited to predistortion, and other methods may be used.

[Second Embodiment: FIG. 8]
Next, a high frequency amplification device (second amplification device) according to a second embodiment of the present invention will be described.
In addition to the configuration of the first amplifying device, the second amplifying device has a configuration for injecting the second harmonic into the peak amplifier of the Doherty amplification unit of the second harmonic injection Doherty amplifier.
The configuration of the second harmonic generation unit of the second harmonic injection Doherty amplifier of the second amplifying device is partially different from that of the first amplifying device, and will be described later with reference to FIG.
Further, since the Doherty amplification unit of the second amplification device is substantially the same as the first amplification device shown in FIG. 4, the illustration is omitted and will be described using the reference numerals in FIG. 4. In addition, a second harmonic input terminal for injecting a second harmonic into the input matching circuit 51 of the peak amplifier 5 is provided.

FIG. 8 is a configuration block diagram of a second harmonic generation unit of the second amplification device.
As shown in FIG. 8, the second harmonic generation unit of the second amplifying device has a configuration of the second harmonic generation unit of the first amplifying device shown in FIG. A generation circuit 37 is provided, and second harmonics are injected into the peak amplifier 5.

  The distributor 32 converts the fundamental frequency signal distributed by the distributor 22 into a second harmonic generation circuit 30 (first second harmonic generation circuit) and a second harmonic generation circuit 37 (second second harmonic generation circuit). To distribute.

The second harmonic generation circuit 37 includes a high frequency generator 33, an amplifier 34, a variable phase shifter 35, and a variable attenuator 36, and has the same configuration and operation as the second harmonic generation circuit 30. Although not described in detail, the second harmonic is generated and its phase and amplitude are optimally adjusted.
The output terminal C of the second harmonic generation circuit 37 is connected to the second harmonic input terminal (not shown) of the peak amplifier 5 of the Doherty amplification unit, and the second harmonic is input to the input matching circuit 51 of the peak amplifier 5. Inject waves.

  As a result, the gain in the vicinity of saturation of the peak amplifier 5 can be further improved, so that the gain in the second amplifying device is improved in the vicinity of saturation as compared with the first amplifying device shown in FIG. The distortion compensation amount can be made closer to the class AB amplifier as compared with the first amplifying apparatus shown in FIG.

  According to the second amplifying device, the efficiency of the peak amplifier 5 can be further improved by injecting the second harmonic whose phase and amplitude are optimally adjusted into the peak amplifier 5 in addition to the carrier amplifier 4. In addition, the gain of the entire amplifying device can be improved, and even when combined with general distortion compensation, the distortion compensation characteristic equivalent to that of the class AB amplifier can be obtained, which has the effect of further improving the efficiency.

  INDUSTRIAL APPLICABILITY The present invention is suitable for a high frequency amplifying apparatus that can improve the distortion compensation characteristic when combining Doherty amplifier and general distortion compensation, and can further improve the power conversion efficiency.

1 is a configuration block diagram of a high-frequency amplification device (first amplification device) according to a first embodiment of the present invention. 3 is a circuit diagram showing a configuration example of an adaptive bias control circuit 116. FIG. FIG. 3 is a block diagram illustrating a configuration of a second harmonic generation unit of the second harmonic injection Doherty amplifier 10 of the first amplifying device. FIG. 3 is a block diagram illustrating a configuration of a Doherty amplification unit of a second harmonic injection Doherty amplifier 10 of the first amplification device. It is explanatory drawing which shows the drain current at the time of inject | pouring a 2nd harmonic into a fundamental wave. (A) is explanatory drawing which shows the example of control of the gate voltage of the peak amplifier by the adaptive bias control circuit 116, (b) is explanatory drawing which shows the example of AM-AM characteristic of a 1st amplifier. It is explanatory drawing which shows the example of the distortion compensation characteristic of a 1st amplifier. It is a block diagram of the second harmonic generation unit of the second amplifying device. It is a schematic block diagram of an amplifying apparatus having a general predistortion distortion compensation function. 2 is a block diagram showing a schematic configuration of a predistorter 101. FIG. It is a flowchart figure which shows the control using the perturbation method in the control part 118. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,21 ... Input terminal, 10 ... Double wave injection Doherty amplifier, 2, 22, 32 ... Divider, 3 ... Phase shifter, 4 ... Carrier amplifier, 5 ... Peak amplifier, 6 ... Doherty combining part, 7, 61 ... λ / 4 transformer, 8 ... output terminal, 12 ... gate terminal, 13 ... double wave input terminal, 23 ... delay correction circuit, 24,29,36 ... variable attenuator, 25,27,34 ... amplifier, 26 , 33 ... Harmonic generator, 28, 35 ... Variable phase shifter, 30, 37 ... Double harmonic generation circuit, 31 ... Fundamental wave adjustment circuit, 41, 51 ... Input matching circuit, 42, 52 ... Amplifying element, 43, 53 ... Output matching circuit 62 ... Composite point 101 ... Predistorter 102 ... D / A converter 103 ... Quadrature modulator 104,108 ... Oscillator 105 ... Power amplifier 106,119 ... Directional coupler , DESCRIPTION OF SYMBOLS 107 ... Mixer 109 ... A / D converter 110 ... FFT operation part 111 ... IM operation part 112 ... Distortion compensation part 115 ... Delay correction circuit 116 ... Adaptive bias control circuit 118 ... Control part

Claims (2)

A high-frequency amplifier having a carrier amplifier that operates in class AB and a peak amplifier path that operates in class B or C, and a Doherty amplifier that combines and outputs the output of the carrier amplifier and the peak amplifier. And
A second harmonic is generated from the input fundamental frequency signal, and the phase and amplitude of the second harmonic are adjusted and output to the carrier amplifier of the Doherty amplifier or to both the carrier amplifier and the peak amplifier. A second harmonic generation circuit;
A high-frequency amplification device comprising: an adaptive bias control circuit that controls a gate voltage of a peak amplifier of the Doherty amplifier according to an input level to the Doherty amplifier.   2. The high frequency amplifying apparatus according to claim 1, further comprising a distortion compensation circuit for compensating for nonlinear distortion generated in the Doherty amplifier.

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