Predistortion type-linearized power amplification system using digital if technology
First Claim
1. A linearized power amplification system, comprising:
- a preprocessing unit for processing I- and Q-phase digital input signals in a digital domain;
a D/A converter for converting I′ and
Q′
signals output from the preprocessing unit into an analog signal;
an up-mixer for up-converting the analog signal by multiplying the analog signal with a local oscillation frequency;
a high power amplifier (HPA) for amplifying and transmitting a high frequency signal output from the up-mixer into the air;
a feedback circuit which extracts an output signal from the HPA and converts the output signal into a digital signal for input into the preprocessing unit; and
a digital signal processor (DSP) which generates a coefficient for controlling the preprocessing unit using the I- and Q-phase digital input signals and the output signal of the HPA, which is processed in the digital domain by the preprocessing unit.
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Abstract
A power amplification system uses digital intermediate frequency (IF) processing to increase the linearity of a high-pass amplifier which may be used, for example, in a variety of communications applications. The system includes a preprocessing unit which digitally processes I- and Q-phase digital input signals, a digital-to-analog converter which converts the preprocessed signals into an analog signal, and a mixer for up-converting the analog signal based on an intermediate frequency. The resulting signal is amplified by the amplifier. The preprocessing unit includes a predistortion unit having a characteristic which is inverse to the nonlinear distortion characteristic of the amplifier. The inverse characteristic is defined based on information output from another digital processor located in a feedback loop connecting the digital IF processor to the predistortion unit. By performing digital IF processing before analog conversion, the system improves the linearization of the amplifier by removing imbalances and other adverse affects that occur in conventional amplifier control circuits.
58 Citations
24 Claims
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1. A linearized power amplification system, comprising:
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a preprocessing unit for processing I- and Q-phase digital input signals in a digital domain;
a D/A converter for converting I′ and
Q′
signals output from the preprocessing unit into an analog signal;
an up-mixer for up-converting the analog signal by multiplying the analog signal with a local oscillation frequency;
a high power amplifier (HPA) for amplifying and transmitting a high frequency signal output from the up-mixer into the air;
a feedback circuit which extracts an output signal from the HPA and converts the output signal into a digital signal for input into the preprocessing unit; and
a digital signal processor (DSP) which generates a coefficient for controlling the preprocessing unit using the I- and Q-phase digital input signals and the output signal of the HPA, which is processed in the digital domain by the preprocessing unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 17, 18)
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11. A linearized power amplification system, comprising:
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a predistorter for distorting the I- and Q-phase digital input signals so as to have a characteristic which is inverse to the nonlinearized characteristic of the output signal of the HPA, using the coefficient from the DSP;
a digital IF processing unit for modulating the I′ and
Q′
signals pre-distorted by the predistorter, for sending the modulated signals to the D/A converter, and for demodulating the signal from the feedback circuit and inputting the demodulated signal to the DSP;
a D/A converter for converting I′ and
Q′
signals output from the preprocessing unit into analog signals;
an up-mixer for up-converting the analog signals by multiplying the analog signal with the local oscillation frequency;
a high power amplifier (HPA) for amplifying and transmitting a high frequency signal output from the up-mixer into the air;
a feedback circuit for extracting an output signal from the HPA and converting the output signal into a digital signal so as to provide the digital signal to the preprocessing unit; and
a digital signal processor (DSP) for generating a coefficient for controlling the preprocessing unit using the I- and Q-phase digital input signals and the output signal of the HPA, which is processed in the digital domain by the preprocessing unit. - View Dependent Claims (12, 13, 14, 15, 16, 19)
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20. A method for processing amplifier signals, comprising:
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determining a nonlinear distortion characteristic of an amplifier;
digitally processing an input signal based on a transfer function which is inverse to said nonlinear distortion characteristic of the amplifier, said digital processing step including digitally modulating the input signal based on a predetermined intermediate frequency;
converting the digitally processed input signal into an analog signal; and
inputting the analog signal into the processor. - View Dependent Claims (21, 22, 24)
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23. The method of claim 23, wherein said predistorting step includes:
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measuring a power level of the input signal; and
distorting the input signal based on a predistortion work function based on the measured power level and coefficients derived from said digital processing step.
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Specification