DISTORTION COMPENSATION AMPLIFICATION DEVICE

• US 20110163806A1
• Filed: 08/24/2009
• Published: 07/07/2011
• Est. Priority Date: 09/09/2008
• Status: Active Grant

• Current Assignee: Hitachi Kokusai Electric Incorporated (Hitachi, Ltd.)
• Original Assignee: Hitachi Kokusai Electric Incorporated (Hitachi, Ltd.)
• Inventors: Hongo, Naoki
• Granted Patent: US 8,334,723 B2
• Time in Patent Office: Days
• US Class Current: 330/149
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 1/3258 based on polynomial terms
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2201/3209 the amplifier comprising means for compensating memory effects
• CPC Class Codes: H03F 2201/3212 Using a control circuit to adjust amplitude and phase of a signal in a signal path
• CPC Class Codes: H03F 2201/3224 Predistortion being done for compensating memory effects
• CPC Class Codes: H03F 2201/3233 Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion
• CPC Class Codes: H03F 3/189 High-frequency amplifiers, e.g. radio frequency amplifiers
• CPC Class Codes: H03F 3/24 of transmitter output stages

Abstract

It is intended to increase the efficiency of a distortion compensation amplification device having a pre-distorter 1. Level detecting means 11 detects a signal level, correspondence storage means 12 outputs a distortion compensation coefficient depending on the signal level, pre-distortion executing means 13 gives distortion with an inverse characteristic to the signal, filtering means 8 outputs a distortion component from a feedback signal output from an amplifier 4, and correspondence acquiring means 14 updates a learning coefficient constituting a function that gives the inverse characteristic so as to reduce the distortion component. The function that gives the inverse characteristic is expressed using a set of orthogonal polynomials. Each orthogonal function is the total sum of products of functions of the input signal and parameters, and the parameter values are set to cause the orthogonal functions to be orthogonal to each other when functions, which are obtained by applying a filter having the same characteristic as that of the filtering means 8 to the functions of the input signal, are replaced for the functions of the input signal constituting the orthogonal functions.

Claims

1. A distortion compensation amplification device having a pre-distorter that generates and outputs a signal with an inverse characteristic of a non-linear characteristic to an amplifier so as to compensate for distortion resulting from the non-linear characteristic of the amplifier, the distortion compensation amplification device comprising:

level detecting means for detecting a level of a signal input to the pre-distorter;

correspondence storage means for storing a correspondence between a distortion compensation coefficient for executing pre-distortion and the level of the signal input to the pre-distorter;

pre-distortion executing means for giving the inverse characteristic of the non-linear characteristic of the amplifier to the signal input to the pre-distorter in accordance with the distortion compensation coefficient for executing the pre-distortion and outputting the resultant signal to the amplifier;

filtering means for removing a frequency component of desired-waves from a feedback signal output from the amplifier and outputting a distortion component; and

correspondence acquiring means for updating a pre-distortion learning coefficient constituting a function of giving the inverse characteristic of the non-linear characteristic of the amplifier to the signal input to the pre-distorter so as to reduce the distortion component acquired by the filtering means, acquiring the correspondence between the distortion compensation coefficient for executing the pre-distortion and the level of the signal input to the pre-distorter in accordance with the updated pre-distortion learning coefficient, and outputting the acquired correspondence to the correspondence storage means,

wherein the function of giving the inverse characteristic of the non-linear characteristic of the amplifier is expressed using a set of orthogonal polynomials,

wherein each orthogonal function of the set of orthogonal polynomials is the total sum of products of one or more functions of the input signal and parameters corresponding to each of the functions of the input signal, and

wherein the parameters corresponding to the one or more functions of the input signal are set to cause the orthogonal functions to be orthogonal to each other when functions, which are acquired by applying a filter with the same filter characteristic as that of the filtering means to the functions of the input signal, are replaced for the functions of the input signal of the orthogonal functions.

2. The distortion compensation amplification device according to claim 1, further comprising function signal acquiring means for acquiring signals from the functions of the input signal of the orthogonal functions corresponding to the signal input to the pre-distorter,

wherein the correspondence acquiring means extracts signal components corresponding to the one or more orthogonal functions from the distortion component by complex-multiplying the distortion component acquired by the filtering means by the signals acquired by the function signal acquiring means respectively, and updates the pre-distortion learning coefficient so as to reduce the respective extracted signal components.

3. The distortion compensation amplification device according to claim 1, further comprising:

function signal acquiring means for acquiring signals from the functions of the input signal of the orthogonal functions corresponding to the signal input to the pre-distorter; and

function signal filtering means for acquiring signals by applying a filter having the same filter characteristic as that of the filtering means to the signals acquired by the function signal acquiring means,

wherein the correspondence acquiring means extracts signal components corresponding to the one or more orthogonal functions from the distortion component by complex-multiplying the distortion component acquired by the filtering means by the signals acquired by the function signal filtering means respectively, and updates the pre-distortion learning coefficient so as to reduce the respective extracted signal components.

4. The distortion compensation amplification device according to claim 1, wherein the correspondence acquiring means updates the pre-distortion learning coefficient so as to reduce the whole of the distortion component acquired by the filtering means.