Distortion control device and method
View Patent ↗This invention includes a waveform analyzing means ( 13 ) for calculating an estimated value of a back-off value required by a power amplifier ( 2 ), which amplifies a high-frequency signal generated from a baseband signal (I, Q) to a predetermined transmission power, by analyzing the waveform of the baseband signal (I, Q), and a control means ( 14 ) for controlling at least one of the amplitude of high-frequency power input to the power amplifier ( 2 ) and the supply power of the power amplifier ( 2 ) on the basis of the estimated value. The invention calculates the estimated value of a back-off value by analyzing the waveform of a baseband in this manner, and hence need not generate a table in advance by calculating a back-off value for each combination of code channels. The invention can therefore be applied to even a case in which the number of code channels greatly increases, and can effectively prevent an increase in adjacent channel leakage power due to a signal obtained by multiplexing these code channels.
1. A distortion control device comprising:
a variable gain amplifier which amplifies a high-frequency signal generated from a baseband signal that is output from a digital baseband unit according to a control signal and outputs the amplified signal to a power amplifier which amplifies the amplified signal output from the variable gain amplifier to a predetermined transmission power;
a waveform analyzing unit which calculates an estimated value of a back-off value by analyzing a waveform of the baseband signal that is output from the digital baseband unit; and
a control unit which generates the control signal by subtracting based on the estimated value calculated by the waveform analyzing unit from at least a maximum value of a gain control signal that is output from the digital baseband unit and outputs the control signal to the variable gain amplifier.
2. A distortion control device according to claim 1 , wherein said waveform analyzing unit calculates the estimated value by using a CM (Cubic Metric) method.
3. A distortion control device according to claim 1 , wherein said waveform analyzing unit obtains a variable associated with an amplitude probability density function from amplitude data of the baseband signal, and calculates and outputs the estimated value of the back-off value from the variable.
4. A distortion control device according to claim 3 , wherein said waveform analyzing unit obtains, as the variable, a first value which is obtained by dividing a sextic moment of the amplitude probability density function by a cube of a quadrature moment of the amplitude probability density function and is represented by a dB value of power, and outputs, as the estimated value, a second value obtained by dividing, by a predetermined constant, a third value obtained by subtracting a predetermined offset value from the first value of the variable.
5. A distortion control device according to claim 1 , wherein the estimated value of the back-off value is calculated from a combination of weighting relative values of a plurality of code channels constituting the baseband signal.
6. A distortion control device according to claim 1 , wherein said device is used in a transmitter which amplifies the high-frequency signal generated from the baseband signal to the predetermined transmission power by using the power amplifier and transmits the power amplified signal.
7. A transmitter comprising:
a high-frequency converter which generates a high-frequency signal by converting a baseband signal that is output from a digital baseband unit;
a variable gain amplifier which amplifies the high-frequency signal output from said high-frequency frequency converter, according to a control signal, and which outputs the amplified signal;
a power amplifier which amplifies the amplified signal output from said variable gain amplifier to a predetermined transmission power;
an antenna which transmits the power amplified signal output from said power amplifier; and
a distortion control device which controls distortion of transmission power of said power amplifier,
said distortion control device comprising:
a waveform analyzing unit which calculates an estimated value of a back-off value by analyzing a waveform of said baseband signal that is output from the digital baseband unit, and
a control unit which generates the control signal by subtracting the estimated value calculated by the waveform analyzing unit from at least a maximum value of a gain control signal that is output from the digital baseband unit and outputs the control signal to the variable gain amplifier.
8. A distortion control method comprising the steps of:
amplifying a high-frequency signal generated from a baseband signal that is output from a digital baseband unit according to a control signal, by a variable gain amplifier;
outputting the amplified signal to a power amplifier, by the variable gain amplifier;
amplifying the amplified signal output from the variable gain amplifier to a predetermined transmission power, by the power amplifier;
calculating an estimated value of a back-off value by analyzing a waveform of the baseband signal that is output from the digital baseband unit; and
generating the control signal by subtracting the estimated value from at least a maximum value of a gain control signal that is output from the digital baseband unit and outputting the control signal to the variable gain amplifier.
9. A distortion control method according to claim 8 , wherein the calculating step comprises the step of calculating the estimated value by using a CM (Cubic Metric) method.
10. A distortion control method according to claim 8 , wherein the calculating step comprises the steps of
obtaining a variable associated with an amplitude probability density function from amplitude data of the baseband signal, and
calculating and outputting the estimated value of the back-off value from the obtained variable.
11. A distortion control method according to claim 10 , wherein
the obtaining step comprises the step of obtaining, as the variable, a first value which is obtained by dividing a sextic moment of the amplitude probability density function by a cube of a quadrature moment of the amplitude probability density function and is represented by a dB value of power, and
the outputting step comprises the step of outputting, as the estimated value, a second value obtained by dividing, by a predetermined constant, a third value obtained by subtracting a predetermined offset value from the first value of the variable.
12. A distortion control method according to claim 8 , further comprising the step of calculating the estimated value of the back-off value from a combination of weighting relative values of a plurality of code channels constituting the baseband signal.
13. A distortion control device comprising:
first means for amplifying a high-frequency signal generated from a baseband signal that is output from a digital baseband unit according to a control signal and for outputting an amplified signal;
second means for amplifying the amplified signal that has been output to a predetermined transmission power;
means for calculating an estimated value of a back-off value by analyzing a waveform of the baseband signal that is output from the digital baseband unit; and
means for generating the control signal by subtracting the estimated value from at least a maximum value of a gain control signal that is output from the digital baseband unit and outputting the control signal to the first means for amplifying the high-frequency signal.
14. A transmitter comprising:
a high-frequency converter which generates a high-frequency signal by converting a baseband signal that is output from a digital baseband unit;
a variable gain amplifier which amplifies the high-frequency signal output from said high-frequency converter, according to a control signal, to output the amplified signal;
a power amplifier which amplifies the amplified signal output from said variable gain amplifier to a predetermined transmission power;
an antenna which transmits the power amplified signal output from said power amplifier; and
a distortion control device which controls distortion of transmission power of said power amplifier,
said distortion control device comprising
means for calculating an estimated value of a back-off value by analyzing a waveform of the baseband signal that is output from the digital baseband unit, and
means for generating the control signal by subtracting the estimated value calculated from at least a maximum value of a gain control signal that is output from the digital baseband unit and for outputting the control signal to the variable gain amplifier.