JP4500671B2 - Distortion generator and low distortion amplifier - Google Patents

Description

  The present invention relates to a distortion generator that generates a distortion component in order to compensate for distortion of an amplifier having nonlinear characteristics, and a low distortion amplifier that compensates for the distortion component using the distortion generator.

  Conventionally, an amplifier has a linear characteristic between input power and output power when the input power level is small, but has a nonlinear characteristic when the input power level increases. It is known that third-order, fifth-order... Distortion components are generated due to the above.

  As an amplifier that compensates for this distortion component, the feedforward method shown in FIG. 7 is known. The feedforward type amplifier shown in FIG. 7 will be described. To simplify the description, consider a case where a two-frequency signal 110 having two frequencies f1 and f2 as main components is input to an amplifier. The two-frequency signal 110 is distributed by the loop I distributor 120 into a signal input to the main amplifier 121 and a signal input to the delay line 124. The signal input to the main amplifier 121 is amplified and output as a signal 111 including distortion components 111a and 111b. The frequency of the third-order distortion component 111a is 2f1-f2 on the lower side, 2f2-f1 on the upper side, and the frequency of the fifth-order distortion component 111b is 3f1-2f2 on the lower side and 3f2-2f1 on the upper side. The distortion component is generated up to a high order at a frequency interval of (f2-f1), but here, only the third-order distortion component 111a and the fifth-order distortion component 111b are displayed.

  Next, the output signal 111 of the main amplifier 121 is distributed by the distributor 122 into a signal input to the loop II circuit and a signal input to the attenuator 123. The signal input to the attenuator 123 is attenuated to a desired level and becomes a signal 113.

  On the other hand, the signal branched by the distributor 120 and inputted to the delay line 124 becomes a signal 112 delayed by a desired time by the delay line 124. Since the signal 112 does not pass through the nonlinear element, it has almost the same waveform as the input signal 110 and has no distortion component.

  These two signals 113 and 112 are synthesized by a synthesizer 125. The signal 113 is given an appropriate attenuation by an attenuator 123, and an appropriate delay is given to the signal 112 by a delay line 124. The main signal of f2 is attenuated, and the distortion components 114a and 114b are output as the signal 114 that is not attenuated. Signal 114 is amplified by error amplifier 126 to become signal 115.

  On the other hand, the signal branched by the distributor 122 and inputted to the circuit of the loop II becomes a signal 116 delayed by a desired time by the delay line 127.

  Then, these two signals 115 and 116 are synthesized by a synthesizer 128 so as to cancel out distortion components, whereby an amplified signal 117 in which distortion is compensated is obtained.

  In this amplifier, a loop I circuit having a function for obtaining the signal 114 corresponds to a distortion generator.

  However, in the amplifier based on the feedforward method described above, it is necessary to increase the length of the delay lines 124 and 127 in order to correspond to the delay time due to the main amplifier 121 or the error amplifier 126 (for example, a cable of 1 m or more is required) However, there is a problem that the number of circuits increases and the loss due to such a long delay line cannot be ignored. Further, in order to generate distortion in a wide temperature range, it is necessary to compensate for the temperature characteristics of the main amplifier 121 and the error amplifier 126. However, since the temperature characteristics are different from each other, the compensation is difficult. There are challenges.

  As an amplifier that compensates for distortion components other than the feedforward method described above, the amplifier described in Patent Document 1 is known.

  An amplifier described as a prior art in Patent Document 1 is shown in FIG. For the sake of explanation, in the same way as in FIG. 7, considering the case where a two-frequency signal 210 having two frequencies f 1 and f 2 is input to the amplifier, the two-frequency signal 210 is distributed into two signals by the distribution circuit 221. One signal is linearly amplified by the power amplifier 223 via the vector adjustment circuit 222 and input to the synthesis circuit 229. The other output from the distribution circuit 221 is input to the distribution circuit 224 and further divided into two signals. One output of the distribution circuit 224 is linearly amplified by the power amplifier 226 via the vector adjustment circuit 225 and input to the synthesis circuit 228. The other output from the distribution circuit 224 becomes a signal including a distortion component by the power amplifier 227 and is input to the synthesis circuit 228.

  The synthesis circuit 228 adjusts the vector adjustment circuit 225 so that the components of the frequencies f1 and f2 from the two input signals have the same amplitude and opposite phase, so that the output from the synthesis circuit 228 includes only the distortion component. Signal. This signal is input to the synthesis circuit 229.

  The synthesis circuit 229 adjusts the vector adjustment circuit 222 so that the distortion component output from the synthesis circuit 229 has the same amplitude and opposite phase as the distortion component generated in the power amplifier 230. By inputting a signal including such distortion to the power amplifier 230, distortion components generated in the power amplifier 230 are suppressed.

  However, in this amplifier, the vector adjustment circuits 222 and 225 have to adjust the phase, which makes it difficult to adjust and increases the number of circuits.

  In the cited document 1, in order to further solve such a problem, the signal distributed by the distribution circuit is distributed to the linear amplifier and the nonlinear amplifier, and the power output ratio of the linear amplifier and the nonlinear amplifier is adjusted to 4: 1. Then, a configuration has been proposed in which these signals are synthesized with opposite phases to generate distortion having the same amplitude and opposite phase as the distortion component generated by the main power amplifier and input to the main power amplifier.

  However, in this proposed configuration, it is essential that the nonlinear amplifier has the same characteristics as the distortion characteristics of the main power amplifier, but an amplifier that has the same distortion characteristics as the main power amplifier is realized for low power. It is difficult to do so, it is difficult to put into practical use, or it is expensive. In addition, since the linear amplifier and the nonlinear amplifier have different temperature characteristics, there is a problem that it is difficult to compensate for the generation of distortion in a wide temperature range.

JP 2002-171136 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a distortion generator capable of simplifying adjustment with a simple and small circuit configuration, and a low distortion amplifier using the distortion generator. And

In order to solve the above problems, a distortion generator according to claim 1 of the present invention has an input port, an output port, a coupling port, and an isolation port, and is coupled to a signal input to the input port. A directional coupler in which there is a level difference between the signals generated in the ring port and the isolation port, and the phase difference is approximately 180 degrees;
An amplifier connected to each of the coupling port and the isolation port of the directional coupler;
A synthesizer that adjusts and synthesizes the level of the output from each amplifier;
And a distortion component generated by an amplifier connected to the coupling port with respect to a signal input to the input port is extracted from the synthesizer and output.

  The invention described in claim 2 is characterized in that the amplifiers respectively connected to the coupling port and the isolation port described in claim 1 are the same type of amplifier having the same temperature characteristics.

  The invention described in claim 3 is characterized in that a level difference between signals generated in the coupling port and the isolation port described in claim 1 or 2 is 5 to 11 dB.

  The invention according to claim 4 is characterized in that the directional coupler according to any one of claims 1 to 3 is made of a microstrip line, a strip line, or a discrete element.

A low distortion amplifier according to a fifth aspect of the present invention includes a distortion generator according to any one of the first to fourth aspects,
A main amplifier for amplifying the output from the output port of the directional coupler of the distortion generator;
And a synthesizer that synthesizes the output from the main amplifier and the output from the synthesizer of the distortion generator.

A low distortion amplifier according to a sixth aspect of the present invention includes a distortion generator according to any one of the first to fourth aspects,
A synthesizer that synthesizes the output from the synthesizer of the distortion generator and the output from the output port of the directional coupler of the distortion generator;
A main amplifier for amplifying the output synthesized by the synthesizer;
It is characterized by providing.

  According to the present invention, there is a difference in level between signals generated at the coupling port and the isolation port, and the characteristic of the directional coupler that the phase difference is approximately 180 degrees is utilized. A signal including a distortion component can be generated by the operational characteristic of the nonlinear region by the amplifier connected to the non-linear region, and a signal including no distortion component can be generated by the amplifier connected to the isolation port. Since these two signals have a phase difference of 180 degrees, the distortion component can be mainly extracted by suppressing the main signal level by combining them with a combiner. Therefore, since a vector adjuster for phase adjustment is not required, it is possible to provide a small distortion generator that is easy to adjust and has a simple structure. Further, the same amplifier can be used as the amplifier connected to the coupling port and the isolation port.

  In other words, when the amplifiers connected to the coupling port and the isolation port are the same type of amplifier having the same temperature characteristics, the temperature characteristics are obtained by synthesizing these amplified outputs having a phase difference of 180 degrees. Since it is offset, the need for temperature compensation can be reduced.

  By setting the level difference between the signals generated at the coupling port and the isolation port to 5 to 11 dB, the phase difference between the two signals is maintained at approximately 180 degrees, and the amplifier connected to the coupling port is maintained in the nonlinear region. An amplifier connected to the isolation port can be operated in the linear region. Here, almost 180 degrees means a width of about ± 10 degrees. Even if the phase difference is not completely 180 degrees, the distortion component can be effectively extracted within this range.

  In addition, an arbitrary low distortion amplifier can be configured using the distortion generator. The output from the output port of the directional coupler of the distortion generator is amplified by the main amplifier, and the distortion component generated by the distortion generator is canceled with the distortion component generated by the main amplifier before or after the main amplifier. The distortion component can be compensated by combining with a combiner. By amplifying the output from the output port of the directional coupler of the distortion generator with the main amplifier, the loss can be suppressed without reducing the level of the main line from the output port. Also, since a large delay difference does not occur between the main line from the output port of the directional coupler of the distortion generator to the main amplifier and the distortion generation line for generating distortion, a delay element may be provided. Since the main line can be configured without including a delay line, the loss can be further suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment of strain generator)
FIG. 1 is a circuit diagram illustrating a distortion generator according to an embodiment of the present invention.

  In the figure, a distortion generator 10 includes a directional coupler 12, two amplifiers 14A and 14B connected to the directional coupler 12, and attenuators 16A and 16B connected to the amplifiers 14A and 14B. And a synthesizer 18 connected to the units 16A and 16B.

  The directional coupler 12 can be composed of either a microstrip line, a strip line, or a discrete element such as an inductance element, and has an input port 12a, an output port 12b, a coupling port 12c, and an isolation port 12d. . In general, the quarter-wavelength coupled line type shown in FIG. 2 is best known, but any other directional coupler can be used.

  A common characteristic of the directional coupler 12 is that signals coupled to the coupling port 12c and the isolation port 12d are generated with respect to the signal input to the input port 12a. There is a level difference, the level of the coupling port 12c is higher than that of the isolation port 12d, the degree of coupling to the input signal can be set as appropriate, and the position of the isolation port 12d relative to the coupling port 12c can be set within a wide coupling range. In some cases, the phase difference can be maintained at approximately 180 degrees.

  The amplifiers 14A and 14B are arranged at the same position with respect to the coupling port 12c and the isolation port 12d of the directional coupler 12, respectively, and are composed of the same type of device. Therefore, the two amplifiers 14A and 14B are amplifiers having the same temperature characteristics and the same type and the same bias condition. The amplifiers 14A and 14B can be constituted by small signal amplifiers.

  The attenuators 16A and 16B attenuate the outputs from the amplifiers 14A and 14B, respectively. The combiner 18 combines the outputs of the attenuators 16A and 16B. By appropriately adjusting the degree of attenuation in the attenuators 16A and 16B, the synthesis ratio of the synthesizer 18 can be set to 1: 1.

  The operation of the distortion generator 10 configured as described above will be described.

  For the sake of simplicity, consider a case where a two-frequency signal 20 having two frequencies f1 and f2 as main components is input. The two-frequency signal is coupled to the coupling port 12c and the isolation port 12d by the directional coupler 12. At this time, a large level signal appears at the coupling port 12c, and a small level signal appears at the isolation port 12d, and the phase difference between these signals is about 180 degrees.

  These two signals are amplified by the amplifiers 14A and 14B, respectively, and the amplifier 14A amplifies a large level signal, so that it operates in a non-linear region, and its output is a signal 21 including distortion components 21a and 21b. Here, the distortion component 21a represents a third-order distortion component, and the distortion component 21b represents a fifth-order distortion component. On the other hand, the amplifier 14B operates in the linear characteristic region of the amplifier to amplify a small level signal, and its output is a signal 23 having almost no distortion component.

  These signals 21 and 23 become signals 24 and 25 whose levels are adjusted by the attenuators 16A and 16B so that the levels of the principal component signals f1 and f2 are equal. When these signals 24 and 25 are synthesized by the synthesizer 18, the level of the main signal is canceled and suppressed by the phase difference of 180 degrees between the two signals, and the levels of the distortion components 26 a and 26 b are not suppressed and are mainly distorted. A signal 26 having components 26a and 26b is obtained.

  If the phase difference is 180 degrees, the main signal is almost completely canceled, but if the phase difference is in the range of 180 degrees ± 10 degrees, the level difference from the distortion component is compressed even if the main signal remains. can do.

  FIG. 3 is a waveform diagram showing experimental results comparing the output on the coupling port side before being synthesized by the synthesizer 18 and the output after being synthesized by the synthesizer 18. 5th and higher order distortion components are omitted. It can be seen that the main component is compressed by about 40 dB before and after the synthesis, whereas the distortion component is hardly compressed. If the level difference can be compressed to such a degree, it can be sufficiently put into practical use.

  FIG. 4 is a graph showing the relationship between the level difference and the phase difference of each signal generated at the coupling port and the isolation port of the ¼ wavelength coupled line type directional coupler shown in FIG. It can be seen from the graph that the phase difference can be maintained within 180 ° ± 10 ° over a wide range of level differences. The difference in level between two signals required for operating the amplifier 14A connected to the coupling port side in the nonlinear region and operating the amplifier 14B connected to the isolation port side in the linear region is possible if it is 5 dB or more. It is. Therefore, it can be seen from the graph that the level difference between the coupling port and the isolation port should be 5 to 11 dB in order to maintain the phase difference of 180 ° ± 10 ° and provide the necessary level difference. This level difference depends on the degree of coupling, and the degree of coupling is a function of the distance (g in FIG. 2) between the main line and the coupled line of the directional coupler as is well known. By setting to, a desired level difference can be provided.

  As described above, the distortion generator 10 uses the characteristics of the level difference between the coupling port and the isolation port of the directional coupler and the phase difference of about 180 degrees, so that the phase adjustment is unnecessary, and Since the delay line can be eliminated, the circuit configuration is simple and downsized, and the adjustment is also simplified. Further, the two amplifiers 14A and 14B are composed of the same device and have the same temperature characteristics, and the temperature characteristics are canceled out, so that there is no need for temperature compensation. Even if there is a difference, the value is small.

(Embodiment of low distortion amplifier)
FIG. 5 is a circuit diagram showing an embodiment of a low distortion high output amplifier 30 configured using the distortion generator 10.

  The low distortion high output amplifier 30 includes a distortion generator 10, an amplifier 32 connected to the output port 12b of the directional coupler 12 of the distortion generator 10, a main amplifier 34 connected to the amplifier 32, and distortion generation. The delay line 36 is connected to the combiner 18 of the combiner 10, the amplifier 38 is connected to the delay line 36, and the combiner 40 combines the outputs from the main amplifier 34 and the amplifier 38.

  The operation of the low distortion high output amplifier 30 will be described using the same dual frequency signal 20 as before. By the directional coupler 12 of the distortion generator 10, the input two-frequency signal 20 is coupled to the main line continuing from the output port 12b, and to the coupling port 12c and the isolation port 12d for distortion generation. Divided into tracks.

  A signal 27 (see FIG. 1) passing through the main line output to the output port 12b is amplified by the amplifier 32 and the main amplifier 34, and becomes a signal 42 including distortion components 42a and 42b. The amplifier 32 is for adjusting the delay amounts caused by the amplifiers of the main line and the distortion generation line to be approximately the same, but may be omitted.

  On the other hand, in the distortion generation line, the signal 26 from which distortion components are mainly extracted by the distortion generator 10 passes through the delay line 36 and the amplifier 38 to become a signal 44. The amplifier 38 is set to an amplification degree such that the distortion components 42a and 42b of the signal 42 from the main line and the distortion components 44a and 44b of the signal 44 are at the same level, and the delay line 36 is The signal 42 and the signal 44 from the line are set to have the same amount of delay, and the phase difference between the distortion components of both is set to 180 degrees.

  In the synthesizer 40, the signals 42 and 44 are synthesized. However, since the phase difference between the distortion components 42a and 42b and the distortion components 44a and 44b is 180 degrees, they are offset and the distortion components are suppressed. A final output signal 46 is output.

  The synthesizer 40 may be a synthesizer having a structure that does not cause a loss in the main line signal, such as a directional coupler. In this case, the isolation port is terminated.

  The delay line 36 and the amplifier 38 may be fixed and need not be adjusted once set. However, in order to compensate the temperature characteristic of the main amplifier 34 in a wide temperature range, the delay amount and the amplification degree are set. Can be made variable and adjustable. The output signal 46 may be monitored and appropriately adjusted so that the distortion component appearing in the output signal 46 is reduced. Even in such a case, since the distortion generator 10 is stable with respect to the temperature characteristics, the adjustment for compensating the temperature characteristics by the main amplifier 34 can be easily performed.

  Thus, the low distortion high output amplifier 30 using the distortion generator 10 outputs a high output signal in which the distortion signal is reduced and the main signal is amplified.

(Other embodiment of low distortion amplifier)
FIG. 6 is a circuit diagram showing another embodiment of the low distortion high output amplifier 50 configured using the distortion generator 10.

  The low distortion high output amplifier 50 includes a distortion generator 10, an amplifier 52 connected to the output port 12 b of the directional coupler 12 of the distortion generator 10, and a delay connected to the combiner 18 of the distortion generator 10. It comprises a line 56, an amplifier 58 connected to the delay line 56, a combiner 54 for combining the outputs from the amplifier 52 and the amplifier 58, and a main amplifier 60 connected to the combiner 54.

  The operation of this low distortion high output amplifier 50 will be described using the same dual frequency signal 20 as before. By the directional coupler 12 of the distortion generator 10, the input two-frequency signal 20 is coupled to the main line continuing from the output port 12b, and to the coupling port 12c and the isolation port 12d for distortion generation. Divided into tracks.

  A signal 27 (see FIG. 1) passing through the main line output to the output port 12b is amplified by the amplifier 52 to become a signal 62 including distortion components 62a and 62b. The amplifier 52 is for adjusting the delay amounts caused by the amplifiers of the main line and the distortion generation line to be approximately the same, but may be omitted.

  On the other hand, in the distortion generation line, the signal 26 from which distortion components are mainly extracted by the distortion generator 10 passes through the delay line 56 and the amplifier 58 to become a signal 64.

  The synthesizer 54 synthesizes the signals 62 and 64 and outputs a signal 66. Here, the distortion components 64a and 64b of the signal 64 interfere with the distortion components 62a and 62b of the signal 62, and new distortion is generated. The delay amount of the delay line 56 and the amplification degree of the amplifier 58 are set so that the components 66a and 66b are generated.

  The signal 66 is amplified by the main amplifier 60. Since the distortion components 66a and 66b of the signal 66 are at a level and phase that cancel out the distortion components newly generated by the main amplifier 60, the main amplifier 60 The output from 60 is the final output signal 68 with suppressed distortion components.

  The delay line 56 and the amplifier 58 may be fixed and need not be adjusted once set. However, in order to compensate the temperature characteristics of the main amplifier 60 in a wide temperature range, the delay amount and the amplification degree are set. Can be made variable and adjustable. The output signal 68 may be monitored and appropriately adjusted so that the distortion component appearing in the output signal 68 is reduced. Even in such a case, since the distortion generator 10 is stable with respect to the temperature characteristics, the adjustment for compensating the temperature characteristics by the main amplifier 60 can be easily performed.

  Thus, the low distortion high output amplifier 50 using the distortion generator 10 outputs a high output signal in which the distortion component is reduced and the main signal is amplified. In this embodiment, since the output of the main amplifier 60 is used as it is in the final stage, the efficiency is high.

  In each of the low-distortion high-power amplifiers 30 and 50 described above, it is not necessary to provide a delay line in the main line and it is not necessary to suppress the level in the main line, so that unnecessary loss can be prevented.

  In the above embodiment, the amplifiers 14A and 14B used in the distortion generator and the main amplifiers 34 and 60 do not have to have the same characteristics, but preferably are amplifiers having the same characteristics or the same material. It is possible to effectively suppress distortion components.

It is a circuit diagram showing embodiment of the distortion generator of this invention. It is a top view of the quarter wavelength coupling line type directional coupler which is an example of the directional coupler used with a distortion generator. It is a waveform diagram showing the experimental result which compared the coupling port side output before the synthesis | combination by the synthesizer in a distortion generator, and the output after a synthesis | combination. It is a graph showing the relationship between the level difference and phase difference of the coupling port and isolation port of a directional coupler. It is a circuit diagram showing one Embodiment of the low distortion high output amplifier comprised using the distortion generator of FIG. FIG. 6 is a circuit diagram showing another embodiment of a low distortion high output amplifier configured using the distortion generator of FIG. 1. It is a circuit diagram showing the amplifier which compensated the distortion component by the conventional feedforward system. It is a circuit diagram showing the amplifier which compensated for another conventional distortion component.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Distortion generator 12 Directional coupler 12a Input port 12b Output port 12c Coupling port 12d Isolation port 14A, 14B Amplifier 18 Synthesizer 30 Low distortion high output amplifier 34 Main amplifier 40 Synthesizer 50 Low distortion high output amplifier 54 Synthesis 60 Main amplifier

Claims (6)

It has an input port, an output port, a coupling port, and an isolation port. There is a level difference in the signal generated at the coupling port and the isolation port with respect to the signal input to the input port, and the phase difference is almost the same. A directional coupler of 180 degrees;
An amplifier connected to each of the coupling port and the isolation port of the directional coupler;
A synthesizer that adjusts and synthesizes the level of the output from each amplifier;
A distortion generator that extracts and outputs, from a combiner, a distortion component generated by an amplifier connected to the coupling port with respect to a signal input to the input port.   2. The distortion generator according to claim 1, wherein the amplifiers respectively connected to the coupling port and the isolation port are of the same type having the same temperature characteristics.   The distortion generator according to claim 1 or 2, wherein a level difference between signals generated at the coupling port and the isolation port is 5 to 11 dB.   The distortion generator according to any one of claims 1 to 3, wherein the directional coupler is made of a microstrip line, a strip line, or a discrete element. The distortion generator according to any one of claims 1 to 4,
A main amplifier for amplifying the output from the output port of the directional coupler of the distortion generator;
A low distortion amplifier comprising: a combiner that combines an output from the main amplifier and an output from the combiner of the distortion generator. The distortion generator according to any one of claims 1 to 4,
A synthesizer that synthesizes the output from the synthesizer of the distortion generator and the output from the output port of the directional coupler of the distortion generator;
A main amplifier for amplifying the output synthesized by the synthesizer;
A low distortion amplifier comprising:

Images