Predistortion amplifier

• US 7,161,990 B2
• Filed: 12/02/2002
• Issued: 01/09/2007
• Est. Priority Date: 12/05/2001
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Hori, Kazuyuki, Murakami, Shouhei, Hara, Norie, Nishikido, Masamitsu, Kurokawa, Toshiaki
• Primary Examiner(s): Kumar; Pankaj
• Assistant Examiner(s): Ejaz; Naheed
• Application Number:
  US10/307,433
• Publication Number:
  US 20030108120A1
• Time in Patent Office: 1,499 Days
• Field of Search: 375/264, 375/279, 375/280, 375/286, 375/297, 375/329, 375/242, 375/244, 375/247, 375/251, 375/252, 375/259, 375/260, 375/261, 375/271, 375/295, 375/296, 375/316, 375/317, 375/318, 375/322, 330/149, 330/298, 330/250
• 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 performing predistortion of signals by 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 of the real and imaginary parts of an output signal of the polynomial calculating unit using two carriers orthogonal to each other;

a power amplifier for amplifying the output of the orthogonal modulator;

a distributor for distributing the 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 vector of the polynomial calculating unit on the basis of said baseband complex input signal and said baseband complex demodulation signal,

wherein said 2-variable polynomial calculating unit comprises;

a vectorizer for generating a 2-variable polynomial basis using said real

and imaginary parts of said baseband complex input signal, and

an inner product calculation unit for calculating an inner product of said 2-variable polynomial basis and said complex coefficient vector.

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.