JP2007267328A - Predistortion compensation circuit for amplifier for amplifying modulation signal having amplitude modulated component - Google Patents

Predistortion compensation circuit for amplifier for amplifying modulation signal having amplitude modulated component Download PDF

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JP2007267328A
JP2007267328A JP2006093212A JP2006093212A JP2007267328A JP 2007267328 A JP2007267328 A JP 2007267328A JP 2006093212 A JP2006093212 A JP 2006093212A JP 2006093212 A JP2006093212 A JP 2006093212A JP 2007267328 A JP2007267328 A JP 2007267328A
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signal
amplitude
predistortion
modulation
modulation signal
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Takayoshi Sasaki
孝義 佐々木
Norihisa Kawazumi
典久 河住
Keijiro Ito
恵二郎 伊藤
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Japan Radio Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To give more appropriate predistortions to a modulation signal that has an amplitude modulated component. <P>SOLUTION: A predistortion compensation circuit 50a includes an LUT 53a that is a memory for storing the input/output distortion characteristics of an amplifier which amplifies the modulation signal that has amplitude modulated components; and an amplitude detection section 51a for detecting the amplitude of the inputted modulation signal having the amplitude modulation component. The predistortion compensation circuit 50a gives predistortions, read from the LUT 53a based on the detected values of the amplitude detection section 51a, to the modulated signal having the amplitude modulated component on a pre-stage of the amplifier 70. Thus, the predistortions are given to the modulated signal, having amplitude modulated components, while keeping its radio frequency band, and the signal is supplied to the amplifier 70 so that more appropriate distortion compensations can be performed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、増幅器への入力信号に前置歪を予め与える前置歪補償回路に関する。   The present invention relates to a predistortion circuit that preliminarily applies predistortion to an input signal to an amplifier.

前置歪補償回路は、増幅器から歪補償されて増幅された出力信号を得るための回路である(特許文献1)。この前置歪補償回路は、増幅器への入力信号に、増幅器の入出力歪特性(非線形性)により出力信号に発生する歪成分を打ち消すための前置歪を予め与える。   The predistortion circuit is a circuit for obtaining an output signal that is amplified by distortion compensation from an amplifier (Patent Document 1). This predistortion compensation circuit applies in advance a predistortion for canceling a distortion component generated in an output signal due to input / output distortion characteristics (nonlinearity) of the amplifier to an input signal to the amplifier.

従来の前置歪補償回路について、図3を用いて、以下に説明する。図3は、従来の前置歪補償回路を示す図である。前置歪補償回路50bは、ベースバンド周波数帯の入力信号(IQ信号)に対して増幅器70の入出力歪特性(非線形性)により出力信号に発生する歪成分を打ち消すような前置歪を与える回路である。   A conventional predistortion compensation circuit will be described below with reference to FIG. FIG. 3 is a diagram showing a conventional predistortion circuit. The predistortion compensation circuit 50b applies a predistortion that cancels a distortion component generated in the output signal to the input signal (IQ signal) in the baseband frequency band due to the input / output distortion characteristics (nonlinearity) of the amplifier 70. Circuit.

この前置歪補償回路50bは、IQ信号の振幅値を検出する振幅検出部51bと、検出された振幅値に対応する前置歪を発生させるルックアップテーブル(LUT)53bと、IQ信号に前置歪を与える加算部55bと、を備えている。なお、LUT53bには、IQ信号の振幅値と、IQ信号に与える前置歪と、が対応付けられたテーブルが記憶されている。   The predistortion compensation circuit 50b includes an amplitude detector 51b that detects the amplitude value of the IQ signal, a look-up table (LUT) 53b that generates a predistortion corresponding to the detected amplitude value, and an IQ signal. And an adder 55b for giving a distortion. The LUT 53b stores a table in which the amplitude value of the IQ signal is associated with the predistortion applied to the IQ signal.

変調処理部10bは、後述する発振部30bから出力された無線周波数信号を、IQ信号で直交変調及び周波数変換などの処理を施して変調信号を生成しこれを出力する。また、発振部30bは、搬送波である無線周波数信号を生成しこれを変調処理部10bに供給する。さらに、増幅器70は、変調処理部10bからの変調信号を増幅して出力する。   The modulation processing unit 10b performs a process such as quadrature modulation and frequency conversion on the radio frequency signal output from the oscillation unit 30b, which will be described later, with an IQ signal to generate a modulation signal and outputs it. The oscillation unit 30b generates a radio frequency signal that is a carrier wave and supplies it to the modulation processing unit 10b. Further, the amplifier 70 amplifies and outputs the modulation signal from the modulation processing unit 10b.

以下、図3に示す前置歪生成回路50bの動作について説明する。(図示しない)ベースバンド信号発生回路は、IQ信号を生成し、前置歪補償回路50bに出力する。前置歪補償回路50bにおいて、入力されたIQ信号は、振幅検出部51bと加算部55bに送られる。振幅検出部51bは、入力されたIQ信号の振幅値を検出しこれをLUT53bに出力する。LUT53bは、入力された振幅値に対応する前置歪を発生しこれを加算部55bに出力する。前述したように、加算部55bには、IQ信号が入力されている。このため、加算部55bは、IQ信号に前置歪を与え、これを変調処理部10bに出力する。   Hereinafter, the operation of the predistortion generation circuit 50b shown in FIG. 3 will be described. A baseband signal generation circuit (not shown) generates an IQ signal and outputs it to the predistortion compensation circuit 50b. In the predistortion compensation circuit 50b, the input IQ signal is sent to the amplitude detector 51b and the adder 55b. The amplitude detector 51b detects the amplitude value of the input IQ signal and outputs it to the LUT 53b. The LUT 53b generates a predistortion corresponding to the input amplitude value, and outputs this to the adder 55b. As described above, the IQ signal is input to the adder 55b. For this reason, the adding unit 55b applies predistortion to the IQ signal, and outputs this to the modulation processing unit 10b.

変調処理部10bは、前置歪が与えられたIQ信号で、発振部30bで生成された無線周波数信号に直交変調(及び周波数変換)を施し、生成された変調信号を増幅器70に出力する。そして、増幅器70は、前置歪が与えられた変調信号を増幅して出力する。前述したように変調信号には、予め前置歪が与えられているため、増幅器70からは、歪補償された増幅信号が出力される。   The modulation processing unit 10 b performs quadrature modulation (and frequency conversion) on the radio frequency signal generated by the oscillation unit 30 b with the IQ signal to which the predistortion is applied, and outputs the generated modulation signal to the amplifier 70. The amplifier 70 amplifies and outputs the modulation signal to which the predistortion is given. As described above, since the predistortion is given to the modulation signal in advance, the amplifier 70 outputs an amplified signal with distortion compensation.

特開平11−154880号公報Japanese Patent Laid-Open No. 11-154880

従来(例えば特許文献1)の前置歪補償回路では、ベースバンド周波数帯のIQ信号に対して前置歪が与えられる。しかしながら、増幅器に入力される信号は、図4に示すように(IQ信号に応じた)包絡線に沿って振幅変移をする変調信号(振幅変調成分を有する変調信号)である。このため、変調信号に対しては、与えられる前置歪が必ずしも好適な値であるとは限らない。本発明の目的は、振幅変調成分を有する変調信号に対してより好適な前置歪を与える前置歪補償回路を実現することにある。   In a conventional predistortion compensation circuit (for example, Patent Document 1), predistortion is applied to an IQ signal in a baseband frequency band. However, as shown in FIG. 4, the signal input to the amplifier is a modulation signal (a modulation signal having an amplitude modulation component) that undergoes amplitude shift along an envelope (corresponding to the IQ signal). For this reason, the applied predistortion is not necessarily a suitable value for the modulation signal. An object of the present invention is to realize a predistortion circuit that gives a more suitable predistortion to a modulation signal having an amplitude modulation component.

本発明は、振幅変調成分を有する変調信号を増幅する増幅器の入出力歪特性を記憶するメモリと、入力された振幅変調成分を有する変調信号の振幅を検出する振幅検出部と、を有し、振幅検出部の検出値と前記メモリに記憶されている入出力歪み特性に基づいて決定された前置歪を増幅器の前段で振幅変調成分を有する変調信号に与える前置歪補償回路において、振幅変調成分を有する変調信号を無線周波数帯のまま増幅器に供給し、前置歪を無線周波数帯の振幅変調成分を有する変調信号に与えることを特徴とする。   The present invention includes a memory that stores input / output distortion characteristics of an amplifier that amplifies a modulation signal having an amplitude modulation component, and an amplitude detection unit that detects the amplitude of the modulation signal having an input amplitude modulation component, In a predistortion compensation circuit that applies a predistortion determined based on a detection value of an amplitude detector and an input / output distortion characteristic stored in the memory to a modulated signal having an amplitude modulation component in the front stage of the amplifier, amplitude modulation A modulation signal having a component is supplied to an amplifier in a radio frequency band, and predistortion is applied to the modulation signal having an amplitude modulation component in the radio frequency band.

本発明によれば、振幅変調成分を有する変調信号に対してより好適な前置歪を与える前置歪補償回路を実現することができる。   According to the present invention, it is possible to realize a predistortion compensation circuit that gives a more suitable predistortion to a modulation signal having an amplitude modulation component.

以下、本発明を実施するための形態について図面を用いて説明する。なお、従来の構成と同一若しくは同様の構成には同一の符号を付すものとする。図1は、本実施形態に係る前置歪補償回路を示す図である。   Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In addition, the same code | symbol shall be attached | subjected to the same or similar structure as the conventional structure. FIG. 1 is a diagram illustrating a predistortion circuit according to the present embodiment.

なお、本実施形態では、ベースバンド信号発生装置(図示せず)からIQ信号を発生させる構成(例えば無線基地局等)を用いて説明するが、すでに生成された変調信号を前置歪補償回路50aに与える構成(例えば無線中継局等)であっても構わない。   In this embodiment, a configuration (for example, a radio base station) that generates an IQ signal from a baseband signal generator (not shown) will be described. However, a modulation signal that has already been generated is converted into a predistortion circuit. The configuration given to 50a (for example, a radio relay station) may be used.

まず、図1に示す前置歪補償回路などの構成について説明する。変調処理部10aは、入力されたベースバンド周波数信号であるIQ信号で後述する無線周波数信号を直交変調する。また、発振部30aは、搬送波となる無線周波数信号(数百MHz以上の信号)を発生しこれを変調処理部10aに供給する。   First, the configuration of the predistortion circuit shown in FIG. 1 will be described. The modulation processing unit 10a orthogonally modulates a radio frequency signal described later with an IQ signal that is an input baseband frequency signal. The oscillation unit 30a generates a radio frequency signal (a signal of several hundred MHz or more) as a carrier wave and supplies it to the modulation processing unit 10a.

前置歪補償回路50aは、増幅器70へ入力される信号(前述した変調信号)に対して増幅器70の入出力歪特性(非線形性)により出力信号に発生する歪成分を打ち消すような前置歪を与える回路である。   The predistortion compensation circuit 50a cancels the distortion component generated in the output signal due to the input / output distortion characteristics (nonlinearity) of the amplifier 70 with respect to the signal (modulated signal) input to the amplifier 70. Is a circuit that gives

この前置歪補償回路50aは、変調信号(振幅変調成分を有する変調信号)の振幅値を検出する振幅検出部51aと、検出された振幅値に応じて変調信号(振幅変調成分を有する変調信号)に与える前置歪を発生させるLUT53aと、変調信号(振幅変調成分を有する変調信号)に前置歪を与える加算部55aと、を備えている。   The predistortion compensation circuit 50a includes an amplitude detector 51a that detects an amplitude value of a modulation signal (a modulation signal having an amplitude modulation component), and a modulation signal (a modulation signal having an amplitude modulation component) according to the detected amplitude value. LUT 53a that generates a predistortion to be applied to (), and an adder 55a that applies the predistortion to a modulation signal (a modulation signal having an amplitude modulation component).

このLUT53aには、予め定められた後述する増幅器70の入出力歪み特性である、入力された変調信号の振幅値と、変調信号に与える前置歪とが対応付けられたテーブルが記憶されている。なお、このLUT53aは、予め対応テーブルが記憶された構成であってもよいが、増幅器70から出力された信号に基づいて対応テーブルの内容を更新する構成であっても良い。すなわち、特定の入力信号に対する出力特性を調べることで、増幅器70のそのときの入出力歪み特性を調べ、その結果によって内容を更新しても良い。   The LUT 53a stores a table in which the amplitude value of the input modulation signal, which is a predetermined input / output distortion characteristic of the amplifier 70 described later, is associated with the predistortion to be given to the modulation signal. . The LUT 53a may have a configuration in which a correspondence table is stored in advance, or may have a configuration in which the contents of the correspondence table are updated based on a signal output from the amplifier 70. That is, by examining the output characteristics with respect to a specific input signal, the input / output distortion characteristics at that time of the amplifier 70 may be examined, and the contents may be updated according to the results.

なお、振幅検出部51aは、搬送波となる無線周波数信号(数百MHz以上の信号)の振幅値を検出するために、無線周波数よりも高速(例えば2倍以上)で検出する構成であることが望ましい(例えば、無線周波数が400MHzである場合は、800MHz以上で検出する構成であることが望ましい)。これにより、変調信号(振幅変調成分を有する変調信号)の振幅値を変調信号の包絡線よりもより分解能の高い値で検出することができる。   The amplitude detector 51a may be configured to detect the amplitude value of a radio frequency signal (a signal of several hundred MHz or more) serving as a carrier wave at a higher speed (for example, twice or more) than the radio frequency. Desirable (for example, when the radio frequency is 400 MHz, it is desirable that the detection is performed at 800 MHz or more). Thereby, the amplitude value of the modulation signal (a modulation signal having an amplitude modulation component) can be detected with a value having a higher resolution than the envelope of the modulation signal.

本実施形態に係る前置歪補償回路の動作について、図1及び2を用いて、以下に説明する。(図示しない)ベースバンド信号発生回路は、IQ信号を生成しこれを変調処理部10aに出力する。また、発振部30aは、搬送波となる無線周波数信号を生成しこれを変調処理部10aに出力する。   The operation of the predistortion circuit according to this embodiment will be described below with reference to FIGS. A baseband signal generation circuit (not shown) generates an IQ signal and outputs it to the modulation processing unit 10a. The oscillation unit 30a generates a radio frequency signal serving as a carrier wave and outputs it to the modulation processing unit 10a.

変調処理部10aは、入力された無線周波数信号をIQ信号により直交変調し、これにより生成された変調信号を出力する。このように生成された変調信号は、振幅変調成分を有する変調信号となる。変調処理部10aから出力された変調信号(振幅変調成分を有する変調信号)は、前置歪補償回路30aに出力される。   The modulation processing unit 10a orthogonally modulates the input radio frequency signal with the IQ signal, and outputs a modulation signal generated thereby. The modulation signal thus generated becomes a modulation signal having an amplitude modulation component. The modulation signal (a modulation signal having an amplitude modulation component) output from the modulation processing unit 10a is output to the predistortion circuit 30a.

前置歪補償回路30aは、入力された変調信号(振幅変調成分を有する変調信号)を、振幅検出部51aと加算部55aに送る。なお、加算部55aに送られる変調信号は、無線周波数帯のまま加算部55aに送られる。さらに、加算部55aに送られる変調信号は、後述する前置歪の生成処理に係る時間分だけ(図示しない遅延回路により)遅延される。   The predistortion compensation circuit 30a sends the input modulation signal (a modulation signal having an amplitude modulation component) to the amplitude detection unit 51a and the addition unit 55a. Note that the modulation signal sent to the adding unit 55a is sent to the adding unit 55a in the radio frequency band. Further, the modulation signal sent to the adding unit 55a is delayed (by a delay circuit not shown) by a time related to a predistortion generation process described later.

また、振幅検出部51aは、入力された変調信号(振幅変調成分を有する変調信号)の振幅値を検出して、検出された振幅値をLUT53aに出力する。前述したように、振幅検出部51aは、入力された変調信号の振幅を、無線周波数帯よりも速い速度(例えば2倍以上)で検出している。このため、振幅検出部51aは、変調信号(振幅変調成分を有する変調信号)の振幅値を、図4に示すように、包絡線よりもより分解能の高い値で検出する。   In addition, the amplitude detector 51a detects the amplitude value of the input modulation signal (a modulation signal having an amplitude modulation component), and outputs the detected amplitude value to the LUT 53a. As described above, the amplitude detector 51a detects the amplitude of the input modulation signal at a speed (for example, twice or more) faster than the radio frequency band. For this reason, the amplitude detector 51a detects the amplitude value of the modulation signal (a modulation signal having an amplitude modulation component) with a higher resolution than the envelope as shown in FIG.

また、前置歪補償回路50aは、検出した振幅値を(演算回路により)補間関数で補間しても良い。これにより、前置歪補償回路50aは、後述するLUT53aに対して、より分解能の高い振幅値を出力することができる(後述するように、LUT53aは、入力された振幅値に対応する前置歪を発生するため、入力される振幅値の分解能が高まると、対応する前置歪を多く出力する)。   Further, the predistortion compensation circuit 50a may interpolate the detected amplitude value with an interpolation function (by an arithmetic circuit). As a result, the predistortion compensation circuit 50a can output an amplitude value with higher resolution to the LUT 53a described later (as will be described later, the LUT 53a has a predistortion corresponding to the input amplitude value. Therefore, when the resolution of the input amplitude value is increased, a large amount of corresponding predistortion is output).

LUT53aは、入力された振幅値(すなわち、変調信号の瞬時値)に対応する前置歪を出力する。前述したように、加算部55aには、変調信号(振幅変調成分を有する変調信号)が入力されている。このため、加算部55aでは、変調信号(振幅変調成分を有する変調信号)に前置歪が与えられる。   The LUT 53a outputs a predistortion corresponding to the input amplitude value (that is, the instantaneous value of the modulation signal). As described above, a modulation signal (a modulation signal having an amplitude modulation component) is input to the adding unit 55a. For this reason, in the addition unit 55a, predistortion is given to the modulation signal (a modulation signal having an amplitude modulation component).

なお、前置歪が与えられた変調信号を生成するに際して、前述したような、変調信号に前置歪を加算する構成の他に、変調信号に対して前置歪を生成する信号を乗算する構成であってもよい(この場合、LUT53aは、前置歪ではなく前置歪生成関数を生成し、上述した乗算部に出力する)。   Note that when generating a modulation signal to which predistortion is applied, in addition to the configuration for adding predistortion to the modulation signal as described above, the modulation signal is multiplied by a signal that generates predistortion. (In this case, the LUT 53a generates a predistortion generation function instead of the predistortion and outputs it to the multiplication unit described above).

このように前置歪が与えられた変調信号(振幅変調成分を有する変調信号)は、増幅器70に出力される。また、増幅器70は、前置歪が与えられた変調信号(振幅変調成分を有する変調信号)を増幅して出力する。前述したように変調信号には、予め前置歪が与えられているため、増幅器70からは、歪補償された増幅信号が出力される。   The modulation signal (modulation signal having an amplitude modulation component) to which predistortion is applied in this way is output to the amplifier 70. The amplifier 70 amplifies and outputs a modulation signal (a modulation signal having an amplitude modulation component) to which predistortion is given. As described above, since the predistortion is given to the modulation signal in advance, the amplifier 70 outputs an amplified signal with distortion compensation.

前述したように、本実施形態に係る前置歪補償回路50aは、変調信号(振幅変調成分を有する変調信号)を無線周波数よりも高速(例えば2倍以上)に検出した振幅値に基づいて、前置歪を発生させている。したがって、本実施形態に係る前置歪補償回路は、振幅変調成分を有する変調信号に対してより好適な前置歪を与えることができる。   As described above, the predistortion compensation circuit 50a according to the present embodiment is based on the amplitude value obtained by detecting the modulation signal (the modulation signal having an amplitude modulation component) at a higher speed (for example, twice or more) than the radio frequency. Predistortion is generated. Therefore, the predistortion compensation circuit according to the present embodiment can give a more suitable predistortion to the modulation signal having the amplitude modulation component.

なお、上述した実施形態では、直交変調方式の変調信号について説明したが、振幅変調成分を有する変調信号であれば、たとえばASK(Amplitude Shift Keying)等の変調信号であっても本発明が適用できることは言うまでも無い。   In the above-described embodiment, the modulation signal of the quadrature modulation method has been described. However, the present invention can be applied to a modulation signal such as ASK (Amplitude Shift Keying) as long as it is a modulation signal having an amplitude modulation component. Needless to say.

本発明の実施形態に係る前置歪補償回路を示す図である。It is a figure which shows the predistortion circuit which concerns on embodiment of this invention. 本発明の実施形態に係る前置歪補償回路における振幅検出を説明する図である。It is a figure explaining the amplitude detection in the predistortion circuit which concerns on embodiment of this invention. 従来の前置歪補償回路を示す図である。It is a figure which shows the conventional predistortion circuit. 従来の前置歪補償回路における振幅検出を説明する図である。It is a figure explaining the amplitude detection in the conventional predistortion circuit.

符号の説明Explanation of symbols

10a,10b 変調処理部、30a,30b 発振部、50a,50b 前置歪補償回路、70 増幅器。   10a, 10b modulation processing unit, 30a, 30b oscillation unit, 50a, 50b predistortion compensation circuit, 70 amplifier.

Claims (1)

振幅変調成分を有する変調信号を増幅する増幅器の入出力歪特性を記憶するメモリと、
入力された振幅変調成分を有する変調信号の振幅を検出する振幅検出部と、を有し、
振幅検出部の検出値と前記メモリに記憶されている入出力歪特性に基づいて決定された前置歪を増幅器の前段で振幅変調成分を有する変調信号に与える前置歪補償回路において、
振幅変調成分を有する変調信号を無線周波数帯のまま増幅器に供給し、
前置歪を無線周波数帯の振幅変調成分を有する変調信号に与えることを特徴とする前置歪補償回路。
A memory for storing input / output distortion characteristics of an amplifier that amplifies a modulation signal having an amplitude modulation component;
An amplitude detector that detects the amplitude of the modulated signal having the input amplitude modulation component;
In the predistortion compensation circuit that gives the predistortion determined based on the detection value of the amplitude detection unit and the input / output distortion characteristics stored in the memory to the modulation signal having the amplitude modulation component in the front stage of the amplifier,
Supply the modulation signal having the amplitude modulation component to the amplifier in the radio frequency band,
A predistortion circuit for applying predistortion to a modulation signal having an amplitude modulation component in a radio frequency band.
JP2006093212A 2006-03-30 2006-03-30 Predistortion compensation circuit for amplifier for amplifying modulation signal having amplitude modulated component Pending JP2007267328A (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003304121A (en) * 2002-04-08 2003-10-24 Hitachi Kokusai Electric Inc Adaptive predestination system amplifier
JP2005012419A (en) * 2003-06-18 2005-01-13 Hitachi Kokusai Electric Inc Amplification device
JP2005150932A (en) * 2003-11-12 2005-06-09 Hitachi Kokusai Electric Inc Predistortion device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003304121A (en) * 2002-04-08 2003-10-24 Hitachi Kokusai Electric Inc Adaptive predestination system amplifier
JP2005012419A (en) * 2003-06-18 2005-01-13 Hitachi Kokusai Electric Inc Amplification device
JP2005150932A (en) * 2003-11-12 2005-06-09 Hitachi Kokusai Electric Inc Predistortion device

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