JP5010542B2 - High frequency power amplifier and amplification method - Google Patents

Description

  The present invention relates to a high-frequency power amplifier and an amplification method with high efficiency and wide dynamic range.

  In recent years, broadcasting and mobile communication have been performed using a wireless signal that has been subjected to multi-value modulation in a wide band such as CDMA and OFDM. The transmission of these wideband multi-level modulation signals requires power amplification with low linearity and good linearity while minimizing distortion from low output levels to high output levels. is necessary.

  As a method for performing low distortion power amplification, methods such as negative feedback (NFB) amplification and feedforward compensation are adopted. As a result, the power efficiency of the power amplifier (hereinafter abbreviated as PA) is lowered at the time of low output.

FIG. 6 is a functional block diagram for explaining the operation of a conventional power amplifier (hereinafter abbreviated as PA) using feedforward compensation (hereinafter abbreviated as FF), and FIG. 7 is an operational characteristic for explaining the operation of PA. FIG.
In the conventional PA using the FF in FIG. 6, the input RF signal is branched by the hybrid H <b> 1 for the purpose of low distortion amplification, one of which is fed to the main amplifier 10 and the other is fed via the delay line d <b> 2. Supplied to one of the inputs of H2. As for the output of the main amplifier 10, one of the branch outputs of the divider c2 is supplied to the other input of the hybrid H2.

  The output of the sub-amplifier 20 is input to the coupler c1, and the output from the divider c2 of the main amplifier 10 is further combined with the signal supplied to the other input of the coupler c1 via the delay line d1 and output. The delay lines d1 and d2 align the delays in both amplifiers. The conventional PA has a relationship in which the output of the sub-amplifier 20 cancels the distortion component of the main amplifier 10 and has a gain characteristic that compensates for the saturation of the gain characteristic of the main amplifier 10.

  FIG. 7A shows the gain characteristic with respect to the input level of the main amplifier 10. The main amplifier 10 is required to operate with good linearity such as class A operation. However, as the input becomes larger, the output becomes saturated rather than linear with respect to the input, and the gain characteristic shown by the dotted line in FIG.

  Therefore, when the input to the PA increases and the output of the main amplifier 10 reaches the output saturation point, it seems to compensate for the gain reduction, that is, when the PA is viewed from the outside, it has the output characteristics shown in FIG. As shown in FIG. 7B, the output of the sub-amplifier increases with respect to the input level of the sub-amplifier 20, the power ratio between the peak level and the average level increases, and the sub-amplifier also operates. High power operation is required.

  In order to improve efficiency, there is an example in which the main amplifier and the sub-amplifier are provided with power supplies independently to improve efficiency (for example, Patent Document 1). However, since the main amplifier 10 needs to have a large back-off even at a small output, there is a problem that the operation becomes low efficiency and the efficiency of the PA as a whole deteriorates.

On the other hand, switching amplifiers called class D, class E, and class F are known as efficient amplifiers. However, although these switching amplifiers have high efficiency, they have a drawback that cannot be dealt with when the dynamic range, that is, the fluctuation of the input level of the amplifier is wide.
JP 2007-124103 A (page 5, FIG. 1)

  Conventional low-distortion high-frequency power amplifiers cannot achieve high efficiency, while high-efficiency switching amplifiers cannot cope with wide input level fluctuations, and there is a problem that high efficiency and wide dynamic range cannot be achieved at the same time. .

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a high-frequency power amplifier and an amplification method that have high efficiency and a wide dynamic range.

In order to achieve the above object, a high-frequency power amplifier according to the present invention is a high-frequency power amplifier that amplifies a high-frequency input signal by a main amplifier and a sub-amplifier, adds the amplified signals of the main amplifier and the sub-amplifier, and outputs the result. A first hybrid that branches and outputs a high-frequency input signal from the first output terminal toward the main amplifier, and a branch output from the second output terminal toward the sub-amplifier, and a second output of the first hybrid The branched signal is input from the terminal, becomes inactive when it is below a predetermined average input level of the input signal, and outputs an amplified signal that is amplified when it is higher than the predetermined level. When the sub-amplifier and the signal branched from the first output terminal of the first hybrid are input to its own first input terminal, Part of the amplified signal output from the sub-amplifier is input to the second input terminal of the sub-amplifier, and the amplified signal input from the sub-amplifier and the signal input from the first hybrid are in reverse phase. When the level of the input signal exceeds the predetermined level by adding, the level of the output signal output from the output terminal to the main amplifier is suppressed from the second hybrid and the second hybrid. A main amplifier that outputs an amplified signal obtained by switching and amplifying the output signal, and outputs a combined signal obtained by adding the amplified signal output from the main amplifier and the amplified signal output from the sub-amplifier in phase. It is characterized by.

According to another aspect of the present invention, there is provided a method for amplifying a high-frequency power amplifier comprising: a main amplifier; a sub-amplifier; and first and second hybrids. The hybrid outputs the high-frequency input signal from the first output terminal to the main amplifier via the second hybrid, and outputs from the second output terminal to the sub-amplifier. The sub-amplifier to which the output signal is input from the second output terminal of the hybrid is inactivated at a level equal to or lower than a predetermined level corresponding to the average level of the input signal, and is higher than the predetermined level. And outputs a signal for addition to the output of the main amplifier, and the output from the first output terminal of the first hybrid In the second hybrid input to the first input terminal, a part of the amplified signal output from the sub-amplifier is input to its second input terminal, and the amplified signal input from the sub-amplifier and the When the level of the input signal exceeds the predetermined level by adding the signal input from the first hybrid in reverse phase, the level of the output signal is suppressed from its own output terminal to the main amplifier. The main amplifier that is output and receives the signal output from the second hybrid performs switching amplification on the input signal and outputs the amplified signal that is output from the main amplifier and the sub-amplifier that outputs the amplified signal A method of amplifying a high-frequency power amplifier, comprising: outputting a synthesized signal obtained by adding the amplified signal in phase.

  According to the present invention, it is possible to provide a high-frequency power amplifier and an amplification method that have high efficiency and a wide dynamic range.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a functional block diagram illustrating the operation of a power amplifier (hereinafter abbreviated as PA) according to an embodiment of the present invention, and FIG. 2 is an operation characteristic diagram illustrating the operation of the PA according to the embodiment.
In FIG. 1A, in the PA of the embodiment, the arrangement of the main amplifier and the sub amplifier of the PA using the conventional FF is switched. That is, the input RF signal is branched by the hybrid H1, one of which is supplied to the sub-amplifier 2 and the other is supplied to one of the inputs of the hybrid H2 via the delay line d2.

  As for the output of the sub-amplifier 2, one of the branch outputs of the divider c2 is supplied to the other input of the hybrid H2. The output of the main amplifier 1 is input to the coupler c1, and the output of the sub amplifier 2 via the divider c2 is further combined with the signal supplied to the other input of the coupler c1 via the delay line d1 and output. The delay lines d1 and d2 align the delays in both amplifiers.

  The PA according to the embodiment has a main amplifier 1 that performs high-efficiency amplification by a switching operation in which the output does not saturate until the input level reaches the average input level, and operates only when the input level becomes high, and the output of the main amplifier 1 Amplification is performed in combination with the sub-amplifier 2 of the high-output amplifier that additionally outputs the signal.

  There are various amplifiers called Class D, Class E, and Class F that perform amplification by switching operation. Here, the region where the voltage waveform and the current waveform overlap is reduced in time. Thus, the efficiency is improved by reducing the loss generated in the final stage amplifying element.

  The sub-amplifier 2 is bias-adjusted to perform class C operation as shown in FIG. 2A. The sub-amplifier 2 is inoperative when the input level is low, and operates to increase the output of the main amplifier only when the input level is high. Therefore, power consumption can be greatly reduced.

  As described above, in the high-frequency amplifier according to the embodiment, by using a combination of the main amplifier that always performs switching operation and performs high-efficiency amplification, and the sub-amplifier that operates only when supplementing the output of the main amplifier, it is extremely efficient. A high frequency amplifier having a wide dynamic range can be realized.

  The signal inputted to the main amplifier 1 is inputted to the PA, and the difference between the signal branched by the hybrid H1 and the signal branched from the output signal of the sub-amplifier 2 by the divider c2 (in other words, both the input to the PA) The output of the amplifier is added in reverse phase.) Even if the input level becomes high, the fluctuation is controlled to be small (see FIG. 2B).

  For this reason, the main amplifier 1 performs switching operation near the output saturation start point that is equal to or higher than the average input level, that is, near saturation, and amplifies it, so that the efficiency is very high. Further, since the sub-amplifier 2 is in a non-operating state until it approaches the average input level, the power consumption is small in terms of time average. By combining these two amplifiers, a highly efficient amplification operation can be performed.

The outputs of the main amplifier 1 and the sub-amplifier 2 are combined by the coupler c1, and the back-off and saturation characteristics of the main amplifier 1 and the input / output characteristics of the sub-amplifier 8 (operating conditions) so that the combined output becomes linear with respect to the input to the PA. ) Is adjusted.

  FIG. 1B is a circuit configuration example in which FIG. 1A is simplified and the number of parts is reduced. In the main amplifier 1, when the input from the hybrid 1 becomes a large input that is equal to or greater than a predetermined input, the output level of the sub-amplifier 2 is combined with the input in the reverse phase in the hybrid H2, so that the input level becomes constant. It can be suppressed. Further, since the output of the main amplifier 1 and the output of the sub-amplifier 2 are coupled so as to be in phase, the output of the sub-amplifier 2 that starts operation when the input is large is added to the combined output of both amplifiers, which is efficient. Amplification operation becomes possible.

  FIG. 1B shows a simplified configuration in which the coupler c1 and the divider c2 are omitted from the circuit configuration shown in FIG. 1A, but either the coupler c1 or the divider c2 is simplified. Needless to say, the above configuration may be used.

  Hereinafter, an example of setting operating conditions for each amplifier will be described with reference to FIG. The coupling degree of the coupler c1 on the output side of both amplifiers is 6 dB, and the saturation level of the sub-amplifier 2 is twice the saturation level of the main amplifier 1. In addition, the class C bias point of the sub-amplifier 2 is adjusted so that the sub-amplifier 2 rises when the input is 6 dB backoff. Here, the loss of the output side coupler at the 6 dB back-off point is 1.25 dB.

  This value is an example of the total value of the divider, delay line, and coupler on the output side of the main amplifier 1 used in the feedforward circuit in the GHz band. It can be seen that the output level of the main amplifier at the 6 dB back-off point is only about 1.5 dB lower than the maximum output level point, and operates near the saturated output at the back-off 6 dB point. Also, the sub-amplifier is prevented from operating at the 6 dB back-off point. In this way, the efficiency can be increased at a level where 6 dB back-off is taken for a signal having a large difference between the average power and the peak power.

  An example of the resulting operation is shown in FIG. The input and output of the sub-amplifier rises from the point indicated by the small J-shaped curve. Also, the output of the main amplifier is indicated by a large dotted arc curve, and the combined output corresponding to the output of the coupler c1 in FIG. 1 is a solid straight line.

  Here, the coupling degree of the output side coupler is 6 dB, the saturation power difference between the main amplifier and the sub-amplifier is 3 dB, and the level at which the sub-amplifier 2 is turned on (operation) is 6 dB back-off. Needless to say, the output may be adjusted to be linear.

FIG. 3 is a functional block diagram showing the functional configuration of the PA according to the first modification of the present embodiment.
In FIG. 3, compensation circuits 31 and 32 are inserted into the inputs of both the main amplifier 1 and the sub-amplifier 2 of the PA. The compensation circuit is an attenuator and phase shifter for correcting in detail the phase and amplitude of each amplifier, and further improves the input / output characteristics.

  Further, a predistortion circuit may be inserted into the input of the main amplifier 1 in FIG. For example, it is possible to construct a high output, extremely low distortion high frequency power amplifier by accurately correcting the distortion of the high-efficiency PA described above by a predistortion circuit using an FPGA (Field Programmable Gate Array). (In this case, it goes without saying that even if the compensation circuits 31 and 32 in FIG. 3 are deleted, the compensation may be performed by the predistortion circuit).

FIG. 4 is a functional block diagram showing the functional configuration of the PA of the second modification example of the present embodiment.
In FIG. 4, a detector 6 for measuring the input level of the sub-amplifier is provided to accurately set the input-to-output characteristic of the sub-amplifier 2. Then, by performing bias control of the class C operation of the sub-amplifier 2 at the output level of the detector 6, it becomes possible to perform output control with high accuracy in a wider output range. Normally, the rising point due to this bias is set to an input level corresponding to the output saturation start point of the main amplifier.

  As described above, according to the embodiment of the present invention, an efficient high frequency power amplifier can be provided. In addition, the configuration and processing procedure of the above embodiment may be changed or combined without departing from the spirit of the invention.

FIG. 5 is a functional block diagram and operation characteristic diagram for explaining the operation of the PA of the third modification of the present embodiment.
FIG. 5A is a functional block diagram of the PA of the third modification example. The input signal level of the main amplifier 1 is measured by the detector 6 and the gain of the sub-amplifier 2 is adjusted based on the measurement level.

  FIG. 5B shows the gain (gate) of the sub-amplifier so that the detection voltage becomes constant when the input level of the main amplifier 1 of the PA of the third modification increases and the detection voltage becomes a certain value or more. Voltage). The input level corresponding to the rising point is a level corresponding to the saturation start point of the output of the main amplifier.

  In this case, even if the input from the hybrid H1 increases, the output of the sub-amplifier 2 is input to the hybrid H2 via the divider c2 with the reverse polarity that cancels the input. Although the input is kept constant in the main amplifier 1, even if the main amplifier is saturated, the RF signal amplified by the sub-amplifier 2 is added, so that a large output can be obtained efficiently.

The functional block diagram explaining operation | movement of the high frequency power amplifier using FF concerning the Example of this invention. The operation characteristic figure explaining operation of the high frequency power amplifier concerning an example. The functional block diagram which shows the function structure of the high frequency power amplifier by the 1st modification of a present Example. The functional block diagram which shows the function structure of the high frequency power amplifier by the 2nd modification of a present Example. The functional block diagram which shows the function structure of the high frequency power amplifier by the 3rd modification of a present Example. The functional block diagram explaining operation | movement of the power amplifier using the conventional feedforward compensation. The operation characteristic figure explaining operation of the conventional high frequency power amplifier.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main amplifier 2 Sub amplifier 31, 32 Compensation circuit 6 Detector H1, H2 Hybrid c1 Coupler c2 Dividers d1, d2 Delay line

Claims (3)

  In a high-frequency power amplifier that amplifies a high-frequency input signal by a main amplifier and a sub-amplifier, and adds and outputs the amplified signals of the main amplifier and the sub-amplifier,
  A first hybrid for branching and outputting the high-frequency input signal from the first output terminal to the main amplifier, and branching and outputting from the second output terminal to the sub-amplifier;
  When the branched output signal is input from the second output terminal of the first hybrid, and when the input signal is below a predetermined average input level of the input signal, it becomes inactive and becomes higher than the predetermined level. A sub-amplifier that operates and outputs an amplified signal;
  The branched output signal from the first output terminal of the first hybrid is input to the first input terminal of the first hybrid, and a part of the amplified signal output from the sub-amplifier is input to the second input terminal of the first hybrid. When the level of the input signal exceeds the predetermined level by adding the amplified signal input to the input terminal and the signal input from the sub-amplifier and the signal input from the first hybrid in reverse phase, A second hybrid in which the level of the output signal output from the output terminal to the main amplifier is suppressed;
A main amplifier that inputs an output signal from the second hybrid and outputs an amplified signal obtained by switching amplification;
A combined signal obtained by adding the amplified signal output from the main amplifier and the amplified signal output from the sub-amplifier in the same phase is output.
A high frequency power amplifier characterized by that. The high frequency power amplifier according to claim 1, wherein the sub-amplifier performs a class C operation. A main amplifier, a sub-amplifier, and first and second hybrids;
In an amplification method of a high frequency power amplifier that amplifies power of a high frequency input signal,
  The first hybrid is:
The high-frequency input signal is output from the first output terminal to the main amplifier via the second hybrid, and is output from the second output terminal to the sub-amplifier.
  The subamplifier to which the output signal is input from the second output terminal of the first hybrid is,
It becomes inactive below a predetermined level corresponding to the average level of the input signal, and outputs an amplified signal that is operated and amplified when it becomes higher than the predetermined level,
  The second hybrid in which the output from the first output terminal of the first hybrid is input to the first input terminal of the first hybrid,
Part of the amplified signal output from the sub-amplifier is input to its own second input terminal, and the amplified signal input from the sub-amplifier and the signal input from the first hybrid are added in reverse phase. When the level of the input signal exceeds the predetermined level, the output signal level is suppressed and output from the output terminal to the main amplifier,
  The main amplifier to which the signal output from the second hybrid is input, switches and amplifies the input signal to output an amplified signal,
  A combined signal obtained by adding the amplified signal output from the main amplifier and the amplified signal output from the sub-amplifier in the same phase is output.
A method for amplifying a high-frequency power amplifier.

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