JP2005020379A - Predistortor and predistortion linearixer system using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a predistortor capable of controlling an ACLR at the time of multi-carrier by controlling an IMD3 (the third order distortion) and an IMD5 (the fifth order distortion) independently, and to provide a predistortion linearizer system using the predistortor. <P>SOLUTION: A main route attenuator is divided into an AttM1 (11) and an AttM2 (13) and arranged before and behind a distortion generating amplifier 12. When the attenuation amount of an AttS14 of a sub route is set to a [dB] and the attenuation amount of the AttM1 and the AttM2 is respectively set to c [dB] and d [dB], it becomes a=c+d in order to make them equivalent routes. Consequently, if the attenuation amount at the predistortor is set to a certain value x [dB], what is necessary is just to satisfy a conditional expression of c+d+b=x. There is a degree of freedom for two parameters of c and d. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a predistorter that generates an input signal including a distortion component having an antiphase with a distortion component generated by a nonlinear characteristic of a main amplifier, and a predistortion linearizer system using the predistorter.
[0002]
[Prior art]
FIG. 4 is a circuit diagram showing a configuration of an equal path predistortion linearizer system in the prior art. The circuit shown in FIG. 4 includes a branch line (90 ° hybrid) 40, a distortion generation amplifier 41, an attenuator (attenuator) AttM42, an attenuator AttS43, a distortion generation amplifier 44, a distributor 45, a distributor 46, a branch line 47, and a branch line. 48, a branch line 49, and an attenuator AttE 50, and the output is input to the main amplifier 51.
[0003]
The branch line 40 branches the input signal (RF signal) from the main route (distortion line) to the sub route (linear line) by 90 ° phase shift. The main route signal is amplified by the distortion generating amplifier 41 with a predetermined gain. The amplified signal includes a distortion component. This signal is attenuated by the attenuation amount a by the attenuator AttM42 and is output to the branch line 47 via the distributor 45.
[0004]
On the other hand, the signal of the sub route is attenuated by the attenuation amount a by the attenuator AttS43. Here, the attenuation amounts attenuated by the attenuator AttM42 and the attenuator AttS43 are equal. The output signal of the attenuator AttS 43 is amplified by the distortion generation amplifier 44 with the same gain as that of the distortion generation amplifier 41. Thus, the distortion signal of the main route is amplified by the distortion generation amplifier 41 and then attenuated by the attenuator AttM42, so that the attenuation amount is small, and the signal of the sub route is amplified by the distortion generation amplifier 44 after being attenuated by the attenuator AttS43. Therefore, the amount of attenuation is large. The circuit shown in FIG. 4 is a circuit that extracts only the distortion component using the difference in attenuation. The signal amplified by the distortion generating amplifier 44 is distributed to the branch line 47 and the branch line 48 by the distributor 46.
[0005]
The branch line 47 phase-shifts the signal input from the sub route by 90 ° and combines it with the signal input from the main route. Since the signal input from the main route and the signal input from the sub route are synthesized with the opposite phase in the equal route, the carrier signal is canceled and the signal includes only the distortion component. This signal is output to the branch line 49.
[0006]
On the other hand, the branch line 48 outputs a signal input from the sub route to the branch line 49. The branch line 49 synthesizes the signal input from the main route and the signal input from the sub route, and outputs a phase shift of 90 °. The output signal of the branch line 49 is attenuated by the attenuation amount b by the attenuator AttE50. Thereby, an input signal including a distortion component having a phase opposite to that of the distortion component generated in the main amplifier 51 is generated.
[0007]
As described above, in order to match the levels of the two paths, the attenuation amount a [dB] of AttM42 and AttS43 must be equal, and the losses of branch lines 40, 47, 48, 49 and distributors 45, 46 and Excluding the gains of the distortion generating amplifiers 41 and 44, attenuation in a circuit (hereinafter referred to as a predistorter) that generates a signal including an antiphase distortion component input to the main amplifier 51 is a + b [dB]. When the attenuation amount in the predistorter is set to a certain value x [dB], in the above example, there is a degree of freedom in how to take a in the relationship of a + b = x. Further, since IMD3 (third-order distortion) / IMD5 (fifth-order distortion) moves depending on the value of a, IMD3 can be arbitrarily controlled.
[0008]
FIG. 5 is a level diagram when a signal of −20.0 dBm is input to the circuit shown in FIG. 4 by using an amplifier of Agilent Technologies MGA85563. The first and second lines from the top of the level diagram shown in FIG. 5 indicate carrier signals, the third and fourth lines indicate IMD3, and the fifth and sixth lines indicate IMD5. The details of the level diagram shown in FIG. 5 are basically the same as those of the level diagram of the present invention in FIG. As described above, Non-Patent Document 1 discloses a technique having the same concept as the techniques illustrated in FIGS. 4 and 5.
[0009]
[Non-Patent Document 1]
Suematsu Noriharu, 3 others (N. Suematsu, et al.), “App Distortion Type Equipath Linearizer Ink Band” (A Predistortion Type Equi-Path Linearizer in Ku-Band), Asia Pacific Microwave Conference Procedural APMC), Tokyo, 1990 pp. 1077-1080
[0010]
[Problems to be solved by the invention]
However, in the circuit of FIG. 4 described above, there is only one value of a for obtaining the desired level of IMD3, so the level of IMD5 is also determined as one, and there is no degree of freedom. That is, although IMD3 could be controlled, IMD5 could not be controlled, ACLR (Adjacent Channel Leakage Ratio) in the case of multi-carrier could not be reduced, and distortion compensation of IMD5 was difficult There was a problem.
[0011]
The present invention has been made in view of the above problems, and a predistorter capable of controlling ACLR during multicarrier by independently controlling IMD3 and IMD5, and a predistortion linearizer system using the predistorter The purpose is to provide.
[0012]
[Means for Solving the Problems]
In order to achieve this object, the invention according to claim 1 is characterized in that the input signal is distributed to the main route, the first distribution unit 10 that distributes the input signal to the sub route with a phase of 90 °, and the main distribution unit 10. A first attenuating means 11 for attenuating the signal branched to the route by a first predetermined amount, and a signal attenuated by the first attenuating means 11 are amplified to generate a distortion component in the signal. The first distortion generating and amplifying means 12, the second attenuating means 13 for attenuating the signal amplified by the first distortion generating and amplifying means 12 by a second predetermined amount, and the first distributing means 10 The signal branched to the sub-route has the same characteristics as the third attenuation means 14 for attenuating the signal obtained by adding the first predetermined amount and the second predetermined amount, and the first distortion generating and amplifying means 12. , By the third damping means 14 A second distortion generating and amplifying means 15 for amplifying the attenuated signal to generate a distortion component in the signal, and the main route signal attenuated by the second attenuating means 13; Based on the sub-root signal amplified by the second distortion generating and amplifying means 15, an input signal including a distortion component having a phase opposite to that of the distortion component generated by the main amplifying means 22 is generated.
[0013]
Therefore, according to the first aspect of the present invention, the first amplifying means 11 and the second attenuating means 13 are provided before and after the first distortion generating and amplifying means 12 of the main route, and the main amplifying means 22 generates the distortion. In order to generate a distortion component for canceling the distortion component, the ACLR at the time of multicarrier can be controlled by independently controlling IMD3 and IMD5. For example, the IMD 5 can be independently controlled while the IMD 3 is fixed.
[0014]
According to a second aspect of the present invention, in the first aspect of the present invention, the second distribution unit 17 distributes the signal amplified by the second distortion generation amplification unit 15 to the main route and the sub route. Third distribution means 16 having the same characteristics as the second distribution means 17 and distributing the signal attenuated by the second attenuation means 13 to the main route and the terminal, and the second distribution means First coupling means 18 for phase-shifting the signal distributed to the main route by 17 by 90 ° and synthesizing with the signal distributed to the main route by the third distribution means 16, and the first coupling means 18, a phase adjusting means 19 for shifting the signal distributed to the sub-route by the second distributing means 17 by 90 °, a signal synthesized by the first combining means, And a second combining unit 20 for synthesizing the signal phase-adjusted by the phase adjusting unit 19.
[0015]
Therefore, according to the second aspect of the present invention, the third distribution means 16 and the first coupling means 18 are provided in the main route, and the second distribution means 17 and the phase adjusting means 19 are provided in the sub route. The means 20 synthesizes the main route and sub-route signals, thereby ensuring an equal path and eliminating the influence of the loss of each element, while including the distortion component having the opposite phase to the distortion component generated in the main amplification means 22. A signal can be generated.
[0016]
According to a third aspect of the present invention, in the second aspect of the present invention, a fourth attenuating means 21 for adjusting the level of the signal coupled by the second coupling means 20 is further provided.
[0017]
Therefore, according to the third aspect of the present invention, by providing the fourth attenuating means 21 after the second combining means 20, the value of the distortion component included in the input signal input to the main amplifying means 22 is adjusted. can do.
[0018]
A fourth aspect of the invention includes the predistorter according to any one of the first to third aspects, and main amplification means 22 that amplifies an input signal generated by the predistorter. It is said.
[0019]
Therefore, according to the fourth aspect of the present invention, it is possible to provide a predistortion linearizer system capable of controlling the ACLR during multicarrier by independently controlling the IMD 3 and the IMD 5.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0021]
FIG. 1 is a circuit diagram showing a configuration of an equal path predistortion linearizer system according to an embodiment of the present invention. The circuit shown in FIG. 1 includes a branch line (90 ° hybrid) 10, an attenuator (attenuator) AttM1 (11), a distortion generation amplifier 12, an attenuator AttM2 (13), an attenuator AttS14, a distortion generation amplifier 15, a distributor 16, and a distribution. Device 17, branch line 18, branch line 19, branch line 20, and attenuator AttE 21, and its output is input to the main amplifier 22.
[0022]
The branch line 10 branches the input signal (RF signal) from the main route (distortion line) and the sub route (linear line) by 90 ° phase shift. The main route signal is attenuated by the attenuation amount c by the attenuator AttM1 (11) and output to the distortion generating amplifier 12. The attenuated signal is amplified with a predetermined gain by the distortion generating amplifier 12. The amplified signal includes a distortion component. This signal is attenuated by the attenuation d by the attenuator AttM2 (13), and is output to the branch line 18 via the distributor 16 for equalizing the sub route.
[0023]
On the other hand, the signal of the sub route is attenuated by the attenuation amount a by the attenuator AttS14. Here, the attenuation amount attenuated by the attenuator AttM1 (11) and the attenuator AttM2 (13) is equal to the attenuation amount attenuated by the attenuator AttS14. The output signal of the attenuator AttS 14 is amplified by the distortion generation amplifier 15 with the same gain as that of the distortion generation amplifier 12. The signal amplified by the distortion generating amplifier 15 is distributed to the branch line 18 and the branch line 19 by the distributor 17.
[0024]
The branch line 18 shifts the signal input from the sub route by 90 ° and synthesizes it with the signal input from the main route. Since the signal input from the main route and the signal input from the sub route are synthesized with the opposite phase in the equal route, the carrier signal is canceled and the signal includes only the distortion component. This signal is output to the branch line 20.
[0025]
On the other hand, the branch line 19 phase-shifts the signal input from the sub route by 90 ° and outputs it to the branch line 20. The branch line 20 combines a signal input from the main route and a signal input from the sub route. The output signal of the branch line 20 is attenuated by the attenuation amount b by the attenuator AttE21. Thereby, an input signal including a distortion component having a phase opposite to that of the distortion component generated in the main amplifier 22 is generated.
[0026]
In this embodiment, the AttM 41 shown in FIG. 4 is divided and arranged as AttM1 (11) and AttM2 (13) before and after the distortion generating amplifier 12 shown in FIG. When the attenuation amount of AttS14 is a [dB] and the attenuation amounts of M1 and M2 are c [dB] and d [dB], respectively, a = c + d is obtained because the paths are equal. Therefore, if the attenuation amount in the predistorter is set to a certain value x [dB], it is sufficient to satisfy the conditional expression c + d + b = x, and the two parameters c and d have a degree of freedom. For this reason, it is possible to control the IMD 5 while keeping the IMD 3 at a certain level.
[0027]
Next, examples of the present invention will be described. FIG. 2 is a level diagram for explaining an embodiment of the present invention. The amplifier used in the present embodiment is an MGA85563 manufactured by Agilent Technologies. The present invention is not limited to application to this amplifier, but can be applied to general amplifiers in general.
[0028]
The first and second lines from the top of the level diagram shown in FIG. 2 indicate carrier signals, the third and fourth lines indicate IMD3, and the fifth and sixth lines indicate IMD5. First, the branch line 10 branches an input signal of −10.0 dBm not including IMD3 and IMD5 into a main route and a sub route at 1: 1. The signal branched to the main route is attenuated by -3.0 dB due to the loss of the branch line 10, and is input to AttM1 (11). AttM1 (11) attenuates the input signal by −7.0 dB and outputs the attenuated signal to the distortion generating amplifier 12. The specifications of the distortion generating amplifier 12 are a gain of 21.0 dB, an OIP3 of 17.0 dBm, and an OIP5 of 17.0 dBm. The signal input to the distortion generating amplifier 12 is amplified with a gain of 21.0 dB. Accordingly, the output signal of the distortion generating amplifier 12 is 1.0 dBm carrier signal, IMD3 is −31.0 dBm according to the following equation 1, and IMD5 is −63.0 dBm according to the following equation 2, and distortion components are generated.
[0029]
IMD3 = OIP3- {OIP3- (Input + Gain)} * 3 (Formula 1)
[0030]
IMD5 = OIP5- {OIP5- (Input + Gain)} * 5 (Formula 2)
[0031]
The output signal of the distortion generating amplifier 12 is input to the attenuator AttM2 (13). The attenuator AttM2 (13) attenuates the input signal by −3.0 dB and outputs the attenuated signal to the distributor 16. The distributor 16 distributes the input signal to the branch line 18 and the terminal in a 1: 1 ratio in order to make the same route as the sub route. The signal output from the distributor 16 is attenuated by −6.0 dB due to the loss of the distributor 16 and input to the branch line 18.
[0032]
On the other hand, the signal branched from the branch line 10 to the sub route is attenuated by −3.0 dB, and is input to the attenuator AttS 14 at −13.0 dB. The attenuator AttS14 attenuates the input signal by −10.0 dB and outputs the attenuated signal to the distortion generation amplifier 15. The distortion generation amplifier 15 is the same as the distortion generation amplifier 12. The signal input to the distortion generating amplifier 15 is amplified with a gain of 21.0 dB. Therefore, the output signal of the distortion generating amplifier 15 has a carrier signal of −2.0 dBm, IMD3 is −40.0 dBm from Equation 1 above, and IMD5 is −78.0 dBm from Equation 2 above, and a distortion component is generated.
[0033]
The output signal of the distortion generating amplifier 15 is output to the distributor 17. The distributor 17 distributes the input signal to the branch line 18 and the branch line 19 at a ratio of 1: 1. The signal output from the distributor 17 is attenuated by −6.0 dB due to the loss of the distributor 17 and is input to the branch line 18 and the branch line 19.
[0034]
The branch line 18 combines the signal input from the distributor 16 on the main route and the signal input from the distributor 17 on the sub route. The signal input from the sub route is phase-shifted by 90 ° by the branch line 10 and the branch line 18 to have an opposite phase and is combined with the signal input from the main route. Accordingly, the output signal of the branch line 18 is not canceled by the carrier signal, and the voltage of IMD3 is added by −46.0 dBm from the following formula 3, and the voltage of IMD5 is added by the following formula 4 is −74.5 dBm. Equations 3 and 4 are calculated by returning the dB value to the true value (V). Note that −3 dB is the loss of the branch line 18 having a 1: 1 connection.
[0035]
IMD3 = 20 × LOG ₁₀ {10 ⁽ main ^{IMD3 / 20)} −10 (sub ^{IMD3 / 20)} } − 3 dBm Equation 3
[0036]
IMD5 = 20 × LOG ₁₀ {10 (main ^{IMD 5/20)} −10 (sub ^{IMD 5/20)} } − 3 dBm Equation 4
[0037]
On the other hand, the signal distributed from the distributor 17 to the sub-route is phase-shifted by 90 ° at the branch line 19 and input to the branch line 20 so as to have the same route as the main route.
[0038]
The branch line 20 combines a signal input from a main route whose phase is shifted by 90 ° with respect to the input signal and a signal input from a sub route whose phase is shifted by 180 ° with respect to the input signal. , 90 ° phase shift and output. Therefore, the output signal of the branch line 20 is −14.0 dBm, the carrier signal is −14.0 dBm, IMD3 is voltage-added from Equation 3 to −56.8 dBm, and IMD5 is voltage-added from Equation 4 to −76.9 dBm. In addition, the phase of the carrier signal is 90 °, the phase of IMD3 / 5 is 270 °, and a signal including IMD3 / 5 having an opposite phase is generated. IM3 / 5 is a value obtained by subtracting the carrier from IMD3 / 5, and becomes -42.8 dBm and -62.9 dBm, respectively.
[0039]
Next, calculation results of the above-described embodiment and the conventional example shown in FIG. 4 will be described. FIG. 3 is a graph showing a calculation example when the same amplifier is used in the embodiment of the present invention and the conventional example. The above-described c + d + b (= x) is set to 10 dB. In the graph, the vertical axis represents the output level of carrier / IMD3 / IMD5 in the case of input −10 dBm, and the horizontal axis represents c. In the conventional example described above, the horizontal axis c is always 0. There are four IMD3 / IMD5 lines in the graph, which are obtained when the value of c + d is changed to 10/8/6/4 dB. Based on the condition of c + d + b (= x) = 10 dB, in these cases, b = 0/2/4/6 dB, and the carrier output level is constant.
[0040]
It is assumed that the IMD3 in the case of the input of −10 dBm is desirably −36 dBm from the condition of the amplifier for which distortion is compensated. Then, according to the graph, in the case of the conventional example (the horizontal axis c is always 0), this condition is satisfied when c + d = 4 dB. However, the value of IMD5 is also uniquely determined to be IMD5 = −47 dBm, and changing this changes IMD3.
[0041]
In contrast, in the present embodiment, the IMD 5 can be controlled while the IMD 3 is kept at the same level (IMD 3 = −36 dBm).
In the example of the graph shown in FIG.
(1) When c = 0.0 dB, d = 4.0 dB, and b = 6.0 dB (prior art)
IMD5 = −47 dBm
(2) When c = 1.0 dB, d = 5.0 dB, and b = 4.0 dB, IMD5 = −50 dBm
(3) IMD5 = -53 dBm when c = 2.0 dB, d = 6.0 dB, and b = 2.0 dB
(4) When c = 2.9 dB, d = 7.1 dB, and b = 0.0 dB, IMD5 = −56 dBm
Thus, the control range of the IMD 5 is 9 dB.
[0042]
The above-described embodiment shows an example of a preferred embodiment of the present invention, and the present invention is not limited thereto, and various modifications can be made without departing from the scope of the invention.
[0043]
【The invention's effect】
As is apparent from the above description, according to the first aspect of the present invention, an attenuator is provided before and after the distortion generating amplifier of the main route to generate a distortion component for canceling the distortion component generated in the main amplifier. By controlling IMD3 and IMD5 independently, ACLR at the time of multicarrier can be controlled. For example, the IMD 5 can be independently controlled while the IMD 3 is fixed.
[0044]
According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, a distributor and a branch line for coupling are provided in the main route, and a distributor and a branch line are also provided in the sub route, and the branch for coupling is provided. By combining the signals of the main route and sub route, the line generates an input signal that includes distortion components that are out of phase with the distortion components generated by the main amplifier, while ensuring equal paths and eliminating the effects of each element loss. can do.
[0045]
According to the invention described in claim 3, in addition to the effect of the invention described in claim 2, by providing an attenuator after the branch line for coupling, the value of the distortion component to be included in advance in the input signal input to the main amplifier Can be adjusted.
[0046]
According to invention of Claim 4, the predistortion linearizer system which can control ACLR at the time of multicarrier can be provided by controlling IMD3 and IMD5 independently.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a configuration of an equal path predistortion linearizer system in an embodiment of the present invention.
FIG. 2 is a level diagram for explaining an embodiment of the present invention.
FIG. 3 is a graph showing a calculation example when the same amplifier is used in the embodiment of the present invention and the conventional example.
FIG. 4 is a circuit diagram showing a configuration of an equal path predistortion linearizer system in the prior art.
FIG. 5 is a level diagram for explaining the prior art.
[Explanation of symbols]
10, 18, 19, 20 Branch line (90 ° hybrid)
11, 13, 14, 21 Attenuator
12, 15 Distortion generating amplifiers 16, 17 Distributor 22 Main amplifier

Claims (4)

First distribution means for distributing the input signal to the main route and to the sub route in 90 ° phase;
A first attenuating means for attenuating the signal branched to the main route by the first distributing means by a first predetermined amount;
First distortion generation amplification means for amplifying the signal attenuated by the first attenuation means to generate a distortion component in the signal;
A second attenuating means for attenuating the signal amplified by the first distortion generating amplifying means by a second predetermined amount;
A third attenuating means for attenuating the signal branched into the sub-route by the first distributing means by an amount obtained by adding the first predetermined amount and the second predetermined amount;
Second distortion generation amplification means having the same characteristics as the first distortion generation amplification means, and amplifying the signal attenuated by the third attenuation means to generate a distortion component in the signal; Have
Based on the main route signal attenuated by the second attenuating means and the sub route signal amplified by the second distortion generating amplifying means, a distortion component having a phase opposite to that of the main amplifying means is generated. The predistorter characterized by producing | generating the input signal containing. Second distribution means for distributing the signal amplified by the second distortion generation amplification means to the main route and the sub route;
Third distribution means having the same characteristics as the second distribution means and distributing the signal attenuated by the second attenuation means to the main route and the termination;
First coupling means for phase-shifting the signal distributed to the main route by the second distribution means by 90 ° and synthesizing with the signal distributed to the main route by the third distribution means;
Phase adjusting means having the same characteristics as the first combining means, and phase-shifting the signal distributed to the sub-route by the second distributing means by 90 °;
2. The predistorter according to claim 1, further comprising second combining means for combining the signal combined by the first combining means and the signal adjusted in phase by the phase adjusting means. . 3. The predistorter according to claim 2, further comprising fourth attenuation means for adjusting a level of the signal combined by the second combining means. The predistorter according to any one of claims 1 to 3,
A predistortion linearizer system, comprising: main amplification means for amplifying an input signal generated by the predistorter.

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