JPS60171813A - Distortion generating device - Google Patents

Abstract

PURPOSE:To compensate the distortion characteristic by forming synthesizingly only a distortion compensation signal from a signal simulating a distortion component with a signal branching an input signal and applying said distortion compensating signal to a power amplifer of milti-stage constitution. CONSTITUTION:The input signal at a terminal 21 is branched by a directional coupler 22, fed to a control circuit 41, branched into two by a distributor 23 of the next stage and fed to a distortion generator 27 via an attenuator 24 and a variable attenuator 28. The distortion generator 27 consists of a distributor 29, amplifiers 30-32, attenuators 33-35, a delay circuit 36, a phase shifter 37 and a synthesizer 38. The signal from the variable attenuator 28 is branched by the distributor 29 and fed to the amplifier 30 and the delay circuit 36. The delay time of the amplifiers 30-32 is compensated by the delay circuit 36 so as to make input signal components fed to the synthesizer 38 opposite to each other, allowing to output the distortion compensatig signal only from the synthesizer 38. The compensating signal is fed to the syntehsizer 26 via a variable attenuator 39 and a variable phase shifter 40, the distortion compensating signal is added to the input signal and the result is inputted to a power amplifier 42.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a distortion generation device for compensating for distortion in a microwave power amplifier using a predistortion method.

Prior Art and Problems A predistortion method is known in which a distortion compensation component is added to an input signal and input to a power amplifier to cancel out the distortion component of the power amplifier. FIG. 1 is a diagram showing an example of the configuration of such a predistortion method. The input signal from the input terminal 1 is split into two by the divider 2, one is sent to the delay circuit 3, and the other is used to generate distortion. A distortion compensation signal is outputted from the distortion generator 4 and applied to the synthesizer 5, and the delay circuit 3 is for compensating the delay time in the distortion generator 4. A distortion compensation signal from the distortion generator 4 is added to the human input signal via the delay circuit 3, and the resulting signal is input to the power amplifier 6. This distortion compensation signal is
Since it is inputted in an opposite phase relation to the distortion component of the power amplifier 6, an amplified output signal whose distortion has been compensated appears at the output terminal 7.

FIG. 2 shows a block diagram of an example of the distortion generator 4, and the input terminal 8 is connected to the distributor 2 shown in FIG. Branched into two, one connected to the phase shifter IO and the other connected to the distortion generating amplifier 11.
are added to each. The distortion generating amplifier 11 outputs a signal containing a distortion compensation signal that simulates the distortion characteristics of the power amplifier 6. The output signal of the distortion generating amplifier 11 is level-adjusted by an attenuator 12 and sent to a combiner 13. The input signal that has been input and whose phase has been adjusted by the phase shifter 10 is input to the synthesizer 13 . In this case, the signal component from the distortion generating amplifier 11 and the signal phase-adjusted by the phase shifter 10 are made to have opposite phases, so that only the distortion compensation signal is output from the combiner 13. The first output is output from the output terminal 14.
It is added to the synthesizer 5 shown in the figure.

Further, FIG. 3 shows a block diagram of a conventional example in which a diode 15 is used as a distortion generating section, and the same reference numerals as in FIG. 2 indicate the same parts. In this case, since the diode 15 has no gain, an attenuator 12 is provided on the phase shifter 10 side, and the phase-adjusted input signal level is adjusted by the attenuator 12.
This is to match the human input signal level via 5.

Microwave power amplifiers have traditionally been constructed using traveling wave tubes, but with recent advances in semiconductor technology, microwave field effect transistors have been developed, and power amplifiers are now constructed using such transistors. . However, since microwave field effect transistors cannot perform large power amplification in one stage, they are generally configured in a multi-stage parallel configuration. In such a multi-stage power amplifier, a signal containing distortion generated in the previous stage is input to the next stage, and further distortion occurs in the next stage, resulting in complex distortion characteristics as a whole. Become. Therefore, as shown in FIG. 2 or 3, in the distortion compensation signal from the distortion generator,
This means that the distortion components of the power amplifier cannot be sufficiently compensated for.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a distortion generating device that can compensate for distortion in a multi-stage power amplifier.

Structure of the Invention The present invention provides a splitter that splits a part of an input signal into two, and a signal that includes a distortion compensation signal that simulates the distortion component of the multi-stage power amplifier by adding one of the signals distributed by the splitter. A distortion generating amplifier consisting of a multi-stage amplifier configured to output It is equipped with a combiner that outputs only the signal, and can output a distortion compensation signal that cancels out the distortion components of the multi-stage power amplifier. Examples will be described in detail below.

Embodiment of the Invention FIG. 4 is a block diagram of an embodiment of the invention, in which 21 is an input terminal, 22 is a directional coupler that distributes a part of the input signal, 23 is a distributor that distributes the input signal, 24 is an attenuator;
25 is a delay circuit with a delay time τ2, 26 is a synthesizer, 27 is a distortion generator that outputs a distortion compensation signal, 28 is a variable attenuator,
29 is a distributor that distributes the output of the variable attenuator, 30 to 32
are amplifiers, 33 to 35 are attenuators, 36 is a delay circuit with a delay time τ1, 37 is a phase shifter, 38 is a synthesizer that outputs only a distortion compensation signal, 39 is a variable attenuator, 4o is a variable phase shifter, 4
1 is a control circuit that detects the input signal distributed by the directional coupler 22 and controls the variable attenuators 29, 39 and the variable phase shifter 40; 42 is a multistage power amplifier; and 43 is an output terminal. .

The input signal applied to the input terminal 21 is transmitted to the directional coupler 2
2, a part of it is branched and applied to the control circuit 41, and the next distributor 23 branches it into two, one of which is applied to the attenuator 24, and the other is applied to the distortion generator via the variable attenuator 28. Added to 27. The distortion generator 27 includes a divider 29, amplifiers 30 to 32, attenuators 33 to 35, a delay circuit 36, a phase shifter 37, and a combiner 38, and the input signal input via the variable attenuator 28 is , distributor 29
is branched into two, one of which is added to the amplifier 3°,
The other is applied to delay circuit 36.

The amplifiers 30 to 32 are connected in multiple stages through attenuators 33 to 35, and the level of the signal containing distortion components corresponding to the input signal is adjusted by the attenuators 33 to 35 and added to the synthesizer 38, and the delay circuit 36 compensates for the delay time of the amplifiers 30 to 32, and the phase shifter 37 adjusts the input signal components to be applied to the synthesizer 38 so that they have opposite phases to each other.
The input signal components are canceled and only the distortion compensation signals from the amplifiers 30 to 32 are output.

This distortion compensation signal is transmitted to a variable attenuator 39 and a variable phase shifter 40.
The input signal applied to the combiner 26 via the divider 23 and the attenuator 24 from the distributor 23 is compensated for the delay time caused by the distortion generator &27 etc. by the delay circuit 25, and then sent to the combiner 2.
Added to 6. Therefore, the distortion compensation signal is added to the input signal and input to the power amplifier 42. This distortion compensation signal is added to the input signal at a phase that cancels out the distortion generated by the power amplifier 42.

The power amplifier 42 is configured, for example, by connecting microwave field effect transistors in multiple stages in parallel to obtain a desired output power. In FIG. shows the case where power amplification is performed by connecting two in parallel. For example, the output distortion of the three-stage power amplifier 42 is a combination of the distortions of each stage, and the output power of each stage is sequentially changed from the first stage to P'', P', P, and the phase is set to θ3.θ.
2. If θ1, then IM (P)""' -IMl (P)""'+ I
M2 (P')"""+1M3 (P")""°"). That is, depending on the output power P, the distortion characteristics of the multi-stage power amplifier 42 change in a complicated manner. In order to generate a distortion compensation signal for a change in distortion characteristics, the distortion generation device 27 has amplifiers 30 to 32 connected in multiple stages to form a distortion generation amplifier.

The delay circuit 36 in this distortion generator 21 is an amplifier 30.
The phase shifter 37 is used to compensate for the delay time caused by the synthesizer 3B. Further, each of the amplifiers 30 to 32 has a smaller power capacity compared to the power capacity of each office amplifier constituting the power amplifier 42, and as described above, each amplifier 30
Since the distortion characteristics of .about.32 are similar to the distortion characteristics of each stage of the power amplifier 42, the output power of the power amplifier changes due to changes in the input signal level, and the distortion characteristics change in a complicated manner. Also, the multi-stage amplifier 30 of the distortion generating bag W27
Since the distortion-compensated ivi signal according to 32 undergoes complex changes in response to changes in the input signal level, by adding this distortion-compensated signal to the human input signal, it is possible to compensate for the output distortion of the power amplifier.

As described above, even if the distortion characteristics change due to a change in the output power of the power amplifier 42 due to a change in the input signal level, the distortion generating device 27 can output a distortion compensation signal that follows the change. Therefore, the distortion of the power amplifier 42 can be compensated for and the amplified output can be performed for a wide range of input signal level changes. Also, the amplifier 30 of the distortion generator 27
32 preferably have the same number of stages as the number of amplification stages of the power amplifier 42, but it is not necessarily necessary to have the same number of stages as long as there are multiple stages.

The control circuit 41 receives a portion of the input signal branched by the directional coupler 22, detects this, identifies the input signal level, and operates the variable attenuator 28, 39 in response to the change in the input signal level. and the variable phase shifter 40, or any one of them. As described above, the distortion characteristics of the power amplifier 42 change in a complicated manner as the output power P changes, so the distortion of the power amplifier 42 may not be sufficiently compensated for only by the distortion compensation signal from the distortion generating bag M27.

Therefore, by controlling, for example, the variable attenuator 28 according to changes in the input signal level, the level of the human input signal to the distortion generator 27 is controlled, and the distortion compensation signal from the amplifiers 30 to 32 is adjusted to the distortion of the power amplifier 42. It becomes possible to set the value to a value that can be compensated. Furthermore, by controlling, for example, the variable attenuator 39 in accordance with changes in the input signal level, the level of the distortion compensation signal from the distortion generator 27 can be controlled to a value that cancels out the distortion of the power amplifier 42. Furthermore, by controlling the variable phase shifter 4°, the phase of the distortion compensation signal from the distortion generator 27 can be controlled to a phase that cancels out the distortion of the power amplifier 42. Therefore, by controlling at least one of the variable attenuators 28, 39 and the variable phase shifter 40 according to the input signal level, distortion compensation of the power amplifier 42 can be further ensured.

As described in detail, the present invention includes a divider 29 that splits a part of an input signal into two, and a distortion component of a power amplifier 42 having a multistage configuration by adding one of the signals distributed by the divider 29. A distortion generating amplifier consisting of multi-stage amplifiers 30 to 32 outputting a signal including a distortion compensation signal simulating a In addition, it is equipped with a synthesizer 38 that synthesizes the signals in opposite phases and outputs only the distortion compensation signal, and is capable of outputting a distortion compensation signal corresponding to the distortion characteristics of the power amplifier 42 having a multi-stage configuration. There is an advantage that sufficient compensation can be made for the complicated distortion characteristics of the power amplifier 42 due to changes in power.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the main parts of an amplifying device using the bridistortion method, FIGS. 2 and 3 are block diagrams of a conventional distortion generating device, and FIG. 4 is a block diagram of an embodiment of the present invention. 21 is an input terminal, 22 is a directional coupler, 23 is a distributor,
24 is an attenuator, 25 is a delay circuit with a delay time τ2, 26 is a combiner, 27 is a distortion generator, 28 is a variable attenuator, 29 is a distributor, 30 to 32 are amplifiers, 33 to 35 are attenuators, 3
6 is a delay circuit with a delay time τ1, 37 is a phase shifter, 38 is a combiner, 39 is a variable attenuator, 40 is a variable phase shifter, 41 is a control circuit, 42 is a multi-stage power amplifier, 43 is an output terminal It is. Patent Applicant: Fujitsu Ltd. Representative Patent Attorney Shoji Aitani Representative Patent Attorney Hiroshi Watanabe - Figure 1 Figure 2 0

Claims (1)

[Claims] In a distortion generator that adds a distortion compensation signal to an input signal and inputs it to a multi-stage power amplifier, and generates the distortion compensation signal for canceling the distortion component of the power amplifier, a part of the input signal is split into two. a distortion generating amplifier comprising a multistage amplifier that outputs a signal containing a distortion compensation signal that simulates a distortion component of the multistage power amplifier by adding one signal distributed by the distributor; The present invention is characterized by comprising a combiner that combines the output signal of the generation amplifier and the other signal distributed by the divider with the same level and opposite phase, and outputs only the distortion compensation signal. Strain generator.