Predistortion amplifier

• US 20030108120A1
• Filed: 12/02/2002
• Published: 06/12/2003
• Est. Priority Date: 12/05/2001
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi Communication Technologies, Ltd. (Hitachi, Ltd.)
• Inventors: Hori, Kazuyuki, Murakami, Shouhei, Nishikido, Masamitsu, Kurokawa, Toshiaki, Hara, Norie
• Granted Patent: US 7,161,990 B2
• Time in Patent Office: Days
• US Class Current: 375/297
• 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 2200/336 A I/Q, i.e. phase quadrature, modulator or demodulator being used in an amplifying circuit
• CPC Class Codes: H04L 27/368 adaptive predistortion

Abstract

Unlike a prior art digital predistortion compensation device for determining a compensation coefficient based on absolute value information about a baseband complex input signal, the present invention performs distortion compensation calculation in accordance with a complex coefficient polynomial using real and imaginary parts of the baseband complex input signal as its variables.

Claims

1. A predistortion amplifier comprising:

a 2-variable polynomial calculating unit for calculating a polynomial using real and imaginary parts of a baseband complex input signal as its two variables and having a complex coefficient;

an orthogonal modulator for performing orthogonal modulation using two carriers perpendicular to the real and imaginary parts of an output signal of the polynomial calculating unit;

a distributor for distributing the output of the orthogonal modulator to a power amplifier for power amplification and to part of an output of the power amplifier;

an orthogonal demodulator for performing orthogonal demodulation over an output signal of the distributor and generating a baseband complex demodulation signal; and

a coefficient updating section for sequentially updating a complex coefficient of the polynomial calculating unit on the basis of said baseband complex input signal and said baseband complex demodulation signal.

2. A predistortion amplifier wherein a peak factor reducing device for attenuating an amplitude exceeding a predetermined value down to the predetermined value on the basis of a momentary amplitude of the baseband complex input signal is provided at a preceding stage of the predistortion amplifier set forth in claim 1.

3. A predistortion amplifier wherein a multicarrier combiner for modulating a plurality of baseband complex input signals with a complex carrier determined depending on a carrier spacing, adding modulated signals together into a single complex signal, and outputting the single complex signal therefrom is provided at a preceding stage of the predistortion amplifier set forth in claim 1.

4. The predistortion amplifier wherein a multicarrier combiner for modulating a plurality of baseband complex input signals with a complex carrier determined depending on a carrier spacing, adding modulated signals together into a single complex signal, and outputting the single complex signal therefrom is provided at a preceding stage of the predistortion amplifier set forth in claim 2.