Distortion compensation apparatus and method

A technology of distortion compensation and series, which is applied in amplitude adaptive pre-distortion, components of amplification devices, look-up table adaptive pre-distortion, etc., which can solve problems such as inability to maintain sufficient performance of distortion compensation and increase of out-of-band radiation power

Inactive Publication Date: 2010-06-23
FUJITSU LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

In the above-mentioned distortion compensation method using the conventional power series, there is a problem that unless the optimal distortion compensation coefficient is used immediately after the power fluctuation of the transmitted signal, the out-of-band radiation power temporarily increases
As a result, both the correction curves 1403 and 1404 deviate from the ideal correction curve 1402 before the coefficient update, so there is a problem that sufficient performance of distortion compensation may not be maintained

Method used

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  • Distortion compensation apparatus and method
  • Distortion compensation apparatus and method

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Experimental program
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no. 1 approach

[0045] figure 1 is a configuration diagram of the first embodiment of the distortion compensation device.

[0046] The predistortion unit 101 performs a power series operation consisting of odd-order power terms, and is composed of a power calculation unit 101-1, a coefficient multiplier 101-2, and an accumulator 101-3. The predistortion unit 101 therefore performs distortion compensation of the transmit amplifier 105 .

[0047] The output of the pre-distortion unit 101 is converted into an analog signal by the D / A converter 102, and further quadrature modulated by the quadrature modulator 103 based on the signal oscillated by the local oscillator 104 according to the transmitting base station.

[0048] The transmission amplifier 105 amplifies the power of the modulated transmission analog signal, and its output is provided to the transmission antenna 107 via the coupler 106, and then transmitted therefrom.

[0049] In addition, feedback of the output of the transmission am...

no. 2 approach

[0055] figure 2 is a configuration diagram of a second embodiment of the distortion compensation device. The second embodiment and figure 1 The difference from the first embodiment in is in the structure related to the distortion compensation coefficients stored in the initial coefficient memory 113 . exist figure 2 , append the same number as the figure 1 The units in the same unit.

[0056] In this embodiment, if figure 2 As shown, the initial coefficient memory 113 stores a corresponding set of power series operation coefficients for each power level of the transmitted signal. exist figure 2 In the embodiment of , corresponding coefficients A, B, C and D are stored for four power levels (peak power levels are Pa, Pb, Pc and Pd). Each coefficient is a power series operation coefficient group. figure 2 An embodiment is illustrated in which the peak power of the transmitted signal fluctuates from Pc to Pb. A coefficient (coefficient A or coefficient B) correspo...

no. 3 approach

[0059] image 3 is a configuration diagram of a third embodiment of the distortion compensation device. The third embodiment and figure 1 The difference from the first embodiment in is in the structure related to the distortion compensation coefficients stored in the initial coefficient memory 113 . exist image 3 , append the same number as the figure 1 The units in the same unit.

[0060] exist image 3 , only coefficients corresponding to the maximum output power of the transmit amplifier 105 are held in the initial coefficient memory 113 . Then, when power fluctuation occurs, regardless of the power value after fluctuation, the coefficient corresponding to the maximum output power is read from the initial coefficient memory 113 and input to the coefficient updating unit 111 .

[0061] In the present embodiment, since only one set of coefficients is held in the initial coefficient memory 113, the increase of the out-of-band radiation power is greater than in the sec...

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Abstract

A distortion compensation apparatus includes a distortion compensation unit that performs distortion compensation processing on a transmission signal by a series operation, a coefficient update unit that updates a group of series operation coefficients used for the series operation based on a feedback signal of transmission signal output that is output after power amplification processing is performed on output of the distortion compensation unit and the transmission signal, an initial coefficient memory that stores the groups of series operation coefficients that become initial values for coefficient update processing by the coefficient update unit, and a power fluctuation detection unit that detects a power fluctuation of the transmission, signal and, when the power fluctuation is detected, reads the groups of series operation coefficients from the initial coefficient memory and provides the groups of series operation coefficients to the coefficient update unit.

Description

technical field [0001] Embodiments of the present invention relate to a predistortion type distortion compensation technique for suppressing nonlinear distortion of a transmission amplifier output by performing distortion compensation processing on an input signal entering a transmission amplifier in advance in radio communication. Background technique [0002] Generally, high-efficiency transmit amplifiers used in radio transmission devices such as mobile base stations have strong nonlinear characteristics. Therefore, when transmitting a modulated signal for high-speed radio communication, this nonlinear distortion in the transmit amplifier results in out-of-band radiated power in the transmitted modulated signal, affecting adjacent transmit channels. [0003] As a method of suppressing out-of-band radiation by a transmission amplifier, there is known a predistortion method in which a distortion signal having a characteristic opposite to the nonlinear distortion characteris...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03F1/32
CPCH03F3/24H03F2200/207H03F2200/105H03F1/3247H03F2201/3233H03F1/3258H04L27/368H03F2201/3227H03F1/32H04B1/02
Inventor 宇都宫裕一滨田一石川广吉札场伸和长谷和男
Owner FUJITSU LTD
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