KR100312403B1 - Predistorter for the Linear Output Character of a Power Amplifier - Google Patents

Abstract

The present invention relates to a shear amplifier for a power amplifier, and more particularly, a power amplifier capable of totally canceling not only the third-order intermodulation components generated in the amplification process of the power amplifier but also the third-order intermodulation components other than the third order. Its purpose is to provide a shearing strainer for the linearization of.

The present invention provides a shear amplifier for a power amplifier comprising: a main divider (10) for splitting and outputting an input signal into first and second signals (S1) and (S2); Non-linear, which is connected to the second signal output terminal of the main divider 10 and has an active element of the same type as the last stage active element of the power amplifier, and the second signal S2 passes through the same active element. Distortion signal generating means (30) for extracting and outputting only the distortion signal (SN1); A phase shifter connected to the first signal output terminal of the main dividing unit 10 and shifting the phase of the first signal S1 so that the nonlinear distortion signal SN1 and the first signal S1 have mutually opposite phases. Means 20; The main signal receiving the first signal S1 output from the phase shifting means 20 and the nonlinear distortion signal SN1 output from the distortion signal generating means 30, synthesizes the input signals, and outputs the main signal. Mixing section 40; Characterized in having a.

Description

Shear Distortor for Linearizing Power Amplifiers {Predistorter for the Linear Output Character of a Power Amplifier}

The present invention relates to a shear amplifier for a power amplifier, and more particularly, a signal of a nonlinear distortion component generated in an output signal of a power amplifier by using an active device of the same type as the active device used in the final stage of the power amplifier. By inputting the nonlinear distortion signal to the power amplifier together with the signal to be amplified, it is possible to collectively cancel not only the third-order intermodulation components generated during the amplification process of the power amplifier but also the third-order intermodulation components other than the third order. The present invention relates to a shear strainer for linearization of a power amplifier.

In general, in case of transmitting signals such as high frequency, radio frequency, and microwave, the transmitted signal attenuates inversely with the square of the communication distance, so that a large amount of power is required to transmit the signal over a long distance. Signal must be output through the antenna.

In addition, in order to transmit a signal having a large power through an antenna, a power amplifier with a large output is required, and the power amplifier increases the nonlinear distortion component in the output signal as the amplification rate increases. The component not only reduces the reliability of the signal, but also makes it impossible to transmit the signal in some cases.

Therefore, in order to satisfy the requirements of the nonlinear distortion components required by the communication system, a power amplifier that generates an output significantly larger than that required by the system must be applied. That is, the output generated by amplifying most of the actual power amplifiers is configured to generate a significantly smaller output than the maximum output that the power amplifier can output. The operation of the power amplifier such that the output is smaller than the maximum possible output is said to operate by powering off the power amplifier (Power Back 0ff). The greater the level of such power back-off, the higher the reliability of the transmitted signal, the larger the size and power consumption of the power amplifier of the transmission system, and the more complicated the structure of the device to dissipate generated heat. The cost for the construction of the system is increased.

Therefore, in the transmission system, it is required to manufacture a power amplifier having a low nonlinear distortion component even when the power back off level is small, that is, a power amplifier having linearized output characteristics.

The linearization method of the power amplifier includes a method of applying an active element having a high linearity to the power amplifier, a circuit design to minimize nonlinear distortion components, and a feed forward method.

However, since active elements with high linearity are not only expensive but also have a limit in power allowance of active elements, there is a need for a circuit capable of minimizing nonlinear distortion components and minimizing nonlinear distortion components. Circuit design has a problem in that the circuit configuration is complicated and difficult to manufacture. The feed forward method is configured to cancel the mutual distortion at the output side of the power amplifier by generating the same distortion components as the nonlinear distortion components generated at the output of the power amplifier, and separately configured an amplifier for generating the same distortion signal as the power amplifier. In addition, the circuit structure was complicated and the circuit adjustment was difficult, which made it difficult to use.

Therefore, in the recent power amplifier, a method for canceling the nonlinear distortion component generated in the power amplifier is mainly applied by inputting a distortion signal generated by using a shearing predistorter to the power amplifier together with the input signal. have.

In other words, a conventional shearing distortion generator generates a third-order intermodulation signal by using a diode or a dual gate MOSFET, and inputs the third-order intermodulation signal to a power amplifier together with an input signal to be amplified. It was configured to cancel the third order intermodulation signal generated. This is because the third-order intermodulation component among the nonlinear distortion components of the power amplifier is the closest to the frequency band of the input signal, which is difficult to remove, and its size is larger than that of other intermodulation components, thereby degrading the reliability of the amplified signal. Because it acts as an element.

However, in order to make a distortion signal symmetrical with the third-order intermodulation signal output from the power amplifier, the conventional shearing distorter has to include a function of adjusting the magnitude and phase of the output distortion signal. The adjustment was complicated and difficult.

In addition, in signal modulation schemes such as digital communication, which are rapidly emerging in recent years, higher order intermodulation distortion signals other than the third order have emerged as a new problem in spectral regrowth of amplified signals. Particularly, in the four-phase shift keying (QPSK) method such as code division multiple access, the spectral reproduction of the power amplifier includes not only third-order intermodulation but also high-order intermodulation distortion components other than third-order. Therefore, in order to linearize the power amplifier for amplifying such a digital signal, it is necessary to collectively cancel not only the third-order intermodulation component but also other higher-order intermodulation distortion components among the nonlinear distortion components.

Accordingly, the present invention has been made to solve the above problems, by using an active element of the same type as the active element used in the final stage of the power amplifier, the signal of the nonlinear distortion component generated in the output signal of the power amplifier By inputting the nonlinear distortion signal to the power amplifier together with the signal to be amplified, it is possible to collectively cancel not only the third-order intermodulation components generated during the amplification process of the power amplifier but also the third-order intermodulation components other than the third order. Accordingly, the linear output characteristics of the power amplifier can be maintained even if the power back off level is set to a low value using a small power amplifier, and the reliability of the digital signal can be improved. The purpose is to provide a shear distortion device for the linearization of power amplifiers.

Another object of the present invention is to simplify the adjustment of the shear strainer that can collectively cancel not only the third-order intermodulation components generated in the amplification process of the power amplifier but also the third-order intermodulation components other than the third, and at the same time, such shear distortion It is to provide a shear distortion device for the linearization of power amplifiers, which makes it easy to manufacture a low cost device.

1 is a circuit diagram of a shear strainer according to an embodiment of the present invention;

2 is a configuration diagram showing a schematic configuration of a power amplifier.

<Description of the reference numerals for the main parts of the drawings>

10: main division unit, 20: phase conversion unit, 21: main attenuation unit, 22: second time delay unit, 23: phase conversion unit, 30: distortion signal generating unit, 31: sub division unit, 32: signal distortion unit 33: phase adjuster, 34: first sub attenuator, 35: second sub attenuator, 36: first time delay, 37: sub mix, 40: main mix, R1, R2, R3, R4: Termination resistors, PA: power amplifiers, PD: shear strainers.

In order to achieve the above object, the present invention is a shear distortion device provided in front of the power amplifier to cancel the non-linear distortion component of the power amplifier including a plurality of active elements: the input signal to the first signal and the second signal A main divider for dividing the output into; A non-linear distortion signal, connected to a second signal output terminal of the main divider, having an active element that is the same as the last active element of the power amplifier, and allowing the second signal to pass through the homogeneous active element; Distortion signal generating means for extracting and outputting only the nonlinear distortion signal; Phase conversion means connected to a first signal output terminal of the main divider and converting a phase of the first signal such that the non-linear distortion signal and the first signal output from the distortion signal generating means have an inverse phase with each other; A main mixing unit configured to receive the first signal output from the phase shifting unit and the nonlinear distortion signal output from the distortion signal generating unit, and synthesize the input signals; Characterized in having a.

Hereinafter, with reference to the accompanying drawings, a preferred embodiment of a shear distortion device for linearization of the power amplifier according to the present invention will be described in detail.

1 is a circuit configuration diagram of a shear distortion device for linearization of a power amplifier according to an embodiment of the present invention, as shown in the present invention, a shear distortion device (PD) installed in the front of the power amplifier, the main component The installment unit 10, the phase conversion unit 20, the distortion signal generating unit 30, and the main mixing unit 40 are configured to be included. In the figure, R1 to R4 represent resistors connected to the termination without signal input and output.

The main coupler 10 generates the first and second signals S1 and S2 by dividing the power of the radio frequency signal input to the input terminal, and generates the generated first and second signals ( It is configured to output S1) S2 through two output terminals, respectively. In this case, the first and second signals S1 and S2 have the same frequency and a phase of 90 ° with the radio frequency signal input to the input terminal.

The distortion signal generating means 30 is connected to a second signal output terminal to receive the second signal S2 output from the main dividing unit 10, and is the same type as the last active element of the power amplifier PA. And an active element, the second signal S2 passes through the same active element to generate a nonlinear distortion signal SN1, and then extracts and outputs only the nonlinear distortion signal SN1.

The power amplifier PA coupled to the rear end of the shear strainer PD includes a plurality of active elements P1 to P5, as shown in FIG. 2. Most of the nonlinear distortion signals included in the signal amplified by the power amplifier PA are generated by the last stage active element P5 having a significantly larger output value than the other active elements P1 to P4. do. Accordingly, the distortion signal generating means 30 includes an active element that is the same type as the last stage active element P5 of the power amplifier PA, and the input radio frequency signal passes through the same active element. The nonlinear distortion signal SN1 having the same magnitude as that of the nonlinear distortion signal SN2 generated by the power amplifier PA may be generated.

The distortion signal generating means 30 includes a sub dividing unit 31, a signal distorting unit 32, a phase adjusting unit 33, a first sub attenuating unit 34, a first time delay unit 36, and a sub-mixing unit. It may be configured with a portion 37.

The sub dividing unit 31 is a hybrid coupler provided to divide the second signal S2 output from the main dividing unit 10 into third and fourth signals S3 and S4. ), An input terminal is connected to the second signal output terminal of the main division unit 10 to receive the second signal S2, and divides the power of the input second signal S2 to generate the third and fourth signals. And generate the third and fourth signals S3 and S4 through two output stages, respectively.

The signal distortion unit 32 includes active elements that are the same type as the last stage active element P5 of the power amplifier PA, and receives the third signal S3 output from the sub dividing unit 31. An input terminal is connected to the third signal output terminal of the sub dividing unit 31. Accordingly, the third signal S3 that is amplified while passing through the signal distortion unit 32 is a nonlinear distortion signal (similar to the nonlinear distortion signal SN2 generated by the power amplifier PA to be installed later). It is outputted with SN1) included.

The signal distortion unit 32 may be configured in various ways according to the last stage active device P5 of the power amplifier PA. That is, when the FET is applied as an active device of the last stage of the power amplifier PA, the signal distortion unit 32 is replaced by a similar low FET or a monolithic microwave integrated circuit (MMIC) using the FET. In addition, when the BJT is applied as the last stage active element of the power amplifier PA, the signal distortion unit is similar to the low-output BJT or the monolithic microwave integrated circuit (MMIC) using BJT. The non-linear distortion signal SN1 similar to the non-linear distortion signal SN2 generated by the power amplifier PA may be generated through the signal distortion unit 32.

The phase adjustment unit 33 is connected to an output terminal of the signal distortion unit 32 and phases of the third signal S3 such that the third signal S3 and the fourth signal S4 have mutually out of phase. Serves to adjust the The first sub attenuator 34 is connected to an output terminal of the phase adjuster 33, and the third signal S3 and the fourth signal S4 have the same amplitude as each other. It acts to attenuate the amplitude of (S3).

On the other hand, a first time delay unit 36 is connected to the fourth signal output terminal of the sub dividing unit 31. The third signal passing through the first sub attenuator 34 and the fourth signal via the first time delay unit 36 are respectively input to two input terminals of the sub mixing unit 37. do. In this case, the fourth signal S4 is delayed for a predetermined time by the first time delay unit 36, so that the third signal S3 and the fourth signal S4 output from the sub dividing unit 31 are delayed. ) Is input to the input terminal of the sub mixing section 37 at the same time.

In the sub mixing unit 37, the third signal S3 and the fourth signal S4 distorted by the signal distorting unit 32 are simultaneously input, and the input third signal S3 and the fourth are input. When the signal S4 is mixed, the original third and fourth signals S3 and S4 outputted from the sub dividing unit 31 cancel each other and are generated by the signal distortion unit 32. After the extracted nonlinear distortion signal SN1 is extracted, it is configured to be output through the output terminal of the sub mixing section 37.

On the other hand, when it is difficult to match the amplitude of the third signal S3 and the fourth signal S4 with only the first sub attenuator 34, the fourth signal output terminal of the sub dividing unit 31 and the first A second sub attenuator 35 may be additionally installed between the time delay units 36. That is, by the second sub attenuator 35, the amplitude of the fourth signal S4 may be adjusted, so that the third signal S3 and the fourth signal input to the sub mixer 37 may be adjusted. The amplitude of S4) can be matched more easily and accurately.

The phase shifting means 20 is connected to a first signal output terminal of the main division part 10, and the nonlinear distortion signal SN1 is output from the distortion signal generating means 30 by the first signal S1. As a means for converting the phase of the first signal (S1) so as to have an out of phase (), including a main attenuator 21, a second time delay unit 22 and a phase shifter 23 It is composed.

The main attenuator 21 is connected to the first signal output terminal of the main divider 10 to adjust the amplitude of the first signal S1, and the second time delay unit 22 is configured to control the amplitude of the first signal S1. It is connected to the output terminal of the main attenuator 21 to adjust the propagation time of the first signal (S1), the phase shifter 23 is the second time delay to convert the phase of the first signal (S1) It is connected to the output terminal of the unit 22.

The first signal S1 phase-shifted while passing through the phase shifting means 20 and the nonlinear distortion signal SN1 generated while passing through the signal distortion part 32 are the main mixing unit ( 40 inputs to each of the two input stages. In this case, the non-linear distortion signal SN1 and the first signal S1 are simultaneously input to each input terminal of the main mixing unit 40 by the second time delay unit 22.

The main mixer 40 mixes the first signal S1 and the nonlinear distortion signal SN1 input through a pair of input terminals, wherein the last stage active element of the power amplifier PA is present. The nonlinear distortion signal SN1 similar to the nonlinear distortion signal SN2 generated by P5 is mixed in the opposite phase to the first signal S1. In other words, in the main mixing section 40, the first signal S1 and the nonlinear distortion signal SN1 are configured to output a mixed signal mixed in opposite phases, and the output synthesized signal is It is input to the power amplifier PA and amplified.

Accordingly, in the power amplifier PA, the first signal S1 and the nonlinear distortion signal SN1 are amplified together, and at this time, the nonlinear distortion signal SN2 generated when the first signal S1 is amplified. And the nonlinear distortion signal SN1 included in the first signal S1 cancel each other by having mutually opposite phases, and thus, any nonlinear distortion component is added to the output signal of the power amplifier PA. It will not be included.

Referring to the operation of the shear strainer for the linearization of the power amplifier having the above configuration as follows.

First, the radio frequency signal inputted to the main divider 10 is divided into power by the main divider 10 into a first signal S1 and a second signal S2, and then the first signal ( S1 is input to the main attenuator 21, and the second signal S2 is input to the sub dividing unit 31.

The second signal S2 input to the sub dividing unit 31 is output after the power is redivided into a third signal S3 and a fourth signal S4. The third signal S3 passes through the signal distortion unit 32, the phase adjusting unit 33, and the first sub attenuator 34, and the fourth signal S4 is the second sub attenuator 35. And the first time delay unit 36, respectively, are simultaneously input through the two input terminals of the sub mixing unit 37.

At this time, the third signal S3 is amplified by the power amplifier PA by the signal distortion unit 32 composed of active devices of the same type as the last stage active element of the power amplifier PA. The nonlinear distortion signal SN1 is similar to the nonlinear distortion signal SN2 generated when the signal is generated. In addition, the third signal S3 is adjusted to have a phase opposite to that of the fourth signal S4 by the phase adjusting unit 33 and then input to the sub mixing unit 37. In addition, the first time delay unit 36 adjusts the third signal S3 and the fourth signal S4 output from the sub dividing unit 31 to be simultaneously input to the sub mixing unit 37. In this way, the third and fourth signals S3 and S4 input to the sub mixing unit 37 are adjusted to have the same amplitude by the first and second sub attenuators 34 and 35. Will be.

Accordingly, the signal input to the sub mixing unit 37 includes a third signal S3 and a fourth signal S4 and a nonlinear distortion signal SN1 generated by the signal distortion unit 32. It becomes. In the mixing process of the sub mixing unit 37, the third and fourth signals S3 and S4 having the same amplitude and frequency while being in phase with each other are canceled with each other, thereby causing the signal distortion unit 32 to be cancelled. Only the nonlinear distortion signal SN1 generated by) is output through the output terminal of the sub mixing unit 37.

Meanwhile, the first signal S1 output through the first signal output terminal of the main division unit 10 sequentially turns the main attenuator 21, the second signal delay unit 22, and the phase shifter 23. After passing, the mixture is input to the input terminal of the main mixing unit 40 and mixed with the nonlinear distortion signal SN1 output through the sub mixing unit 37.

At this time, the non-linear distortion signal SN2 generated when the first signal S1 is amplified by the power amplifier PA of the next stage and the non-linear distortion signal SN1 output from the sub mixing unit 37 are mutually mutual. The phase of the first signal S1 is adjusted by the phase shifter 23 so as to be out of phase. In addition, the nonlinear distortion signal SN2 generated when the first signal S1 is amplified by the power amplifier PA at a later stage and the nonlinear distortion signal SN1 output from the sub mixer 37 are The amplitude of the first signal S1 is adjusted by the main attenuator 21 so as to have the same amplitude.

Therefore, in the signal output from the main mixing section 40, the first signal S1 and the nonlinear distortion signal SN1 are mixed. In addition, the first signal S1 including the nonlinear distortion signal SN1 is amplified by the power amplifier PA. In this case, the nonlinear distortion signal included in the first signal S1 ( SN1 has a phase opposite to that of the nonlinear distortion signal SN2 generated when the first signal S1 is amplified, so that the two nonlinear distortion signals SN1 and SN2 cancel each other out. Therefore, the non-linear distortion signal is not included in the first signal S1 amplified by the power amplifier PA.

In the above, when the amplitude of the first signal S1 for canceling the nonlinear distortion signal SN1 and the nonlinear distortion signal SN2 is adjusted, the nonlinear distortion is amplified together with the first signal S1. Of course, it should be adjusted in consideration of the amplification of the signal SN1.

As can be seen by the above embodiment, the output of the power amplifier by using the active element of the same type as the active element used in the final stage of the power amplifier by the shear distortion for linearization of the power amplifier according to the present invention By generating a signal of the nonlinear distortion component generated in the signal and inputting the nonlinear distortion signal to the power amplifier together with the signal to be amplified, the third-order intermodulation component generated in the amplification process of the power amplifier, There is an effect that can be collectively canceled even higher order intermodulation components.

In addition, the linear output characteristics of the power amplifier can be maintained even when the power back off level is set to a low value by using a small capacity power amplifier. In addition, it is possible to easily produce a shearing strainer having such a function at a low cost, and to simplify the adjustment thereof.

Although the shear distortion for linearizing the power amplifier according to the preferred embodiment of the present invention has been described above, the present invention is not limited thereto, and those skilled in the art will be able to variously modify and apply the same.

Claims (3)

In shear shears installed in front of a power amplifier to cancel the nonlinear distortion component of a power amplifier comprising a plurality of active elements: A main dividing unit dividing an input signal into a first signal and a second signal and outputting the divided signal; A non-linear distortion signal, connected to a second signal output terminal of the main divider, having an active element of the same type as an active element of the last stage of the power amplifier, and allowing the second signal to pass through the same active element; Distortion signal generating means for extracting and outputting only the nonlinear distortion signal; Phase conversion means connected to a first signal output terminal of the main divider and converting a phase of the first signal such that the non-linear distortion signal and the first signal output from the distortion signal generating means have an inverse phase with each other; And, A main mixing unit configured to receive a first signal output from the phase shifting unit and a nonlinear distortion signal output from the distortion signal generating unit, and synthesize the input signals; Including; The distortion signal generating means may include: a sub dividing unit connected to a second signal output terminal of the main dividing unit and dividing an input second signal into a third signal and a fourth signal; An active element that is the same type as the last active element of the power amplifier, the amplifying and distorting the third signal output from the sub dividing unit to convert the third signal into a third signal including a nonlinear distortion signal and output the converted signal; A phase adjuster connected to an output terminal of the signal distortion part and adjusting a phase of the third signal to have an antiphase with the fourth signal; A first sub attenuator configured to adjust the amplitude of the third signal output through the phase adjuster to have the same amplitude as the fourth signal; The sub-division unit so that the fourth signal outputted from the sub-division unit can be output in a state that is consistent with the third signal output after passing through the signal distortion unit, the phase adjusting unit, and the first sub-attenuation unit; A first time delay connected to a fourth signal output terminal of the first delay unit; And, Input and mix the distorted third signal output from the first sub-attenuator and the fourth signal output from the first time delay unit, and extract only the signal of the nonlinear distortion component included in the third signal. A sub mixing unit configured to output the extracted nonlinear distortion component signal to the main mixing unit; Shear strainer for linearization of the power amplifier, characterized in that comprising a. The method of claim 1, Between the fourth signal output terminal of the sub dividing unit and the first time delay unit, a second sub attenuator for adjusting the amplitude of the fourth signal to match the amplitude of the fourth signal and the third signal is added. Shear distortion for linearization of the power amplifier, characterized in that coupled to. The method of claim 1, The phase shifting unit may include: a main attenuation unit coupled to the first signal output terminal of the main division unit and adjusting an amplitude of the first signal; A phase conversion unit connected to an output end of the main attenuation unit and converting a phase of the first signal to have a phase opposite to a nonlinear distortion signal output from the distortion signal generating unit; And, A second time delay coupled between the main attenuator and the phase shifter, such that a first signal via the phase shifter and a second signal via the distortion signal generator are simultaneously input to the main mixer; part; Shear distortion for linearizing the power amplifier, characterized in that it comprises a.