Predistorter

• US 20050195030A1
• Filed: 01/26/2005
• Published: 09/08/2005
• Est. Priority Date: 01/29/2004
• Status: Active Grant

• Current Assignee: Hitachi Kokusai Electric Incorporated (Hitachi, Ltd.)
• Original Assignee: Hitachi Kokusai Electric Incorporated (Hitachi, Ltd.)
• Inventors: Okazaki, Takashi, Hongo, Naoki
• Granted Patent: US 7,190,222 B2
• Time in Patent Office: Days
• US Class Current: 330/149
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 2201/3224 Predistortion being done for compensating memory effects
• CPC Class Codes: H04B 1/62 for providing a predistortion of the signal in the transmitter and corresponding correction in the receiver, e.g. for improving the signal/noise ratio

Abstract

A predistortion distortion signal generating unit uses a signal to be amplified to generate a predistortion distortion signal including odd-order signal components of the signal. A delay time difference adjusting unit adjusts a delay time difference between a signal to be amplified and a distortion signal for predistortion such that an influence by the memory effect occurring in the amplifier can be reduced. A predistortion distortion signal giving unit gives a predistortion distortion signal to a signal to be amplified in a form that the delay time difference is adjusted.

Claims

1. A predistorter in a distortion-compensated amplifier using predistortion technique provided before the amplifier for compensating for distortion occurring in the amplifier in amplifying a signal to be amplified by the amplifier by using a predistortion technique, the predistorter comprising:

means outputting a signal for predistortion based on a signal to be amplified;

means adjusting a delay time difference between a signal to be amplified and a signal for predistortion such that an influence by a memory effect occurring in the amplifier can be reduced; and

means performing processing based on a signal for predistortion on a signal to be amplified in a form that the delay time difference is adjusted.

2. A predistorter according to claim 1,

wherein the means adjusting a delay time difference adjusts the delay time difference in a smaller time than the time unit equivalent to about the double of a band width of the signal for predistortion.

3. A predistorter according to claim 1,

wherein the means adjusting the delay time difference:

adjusts a delay time difference by defining an update value for updating the delay time difference, adding an update value defined for the current delay time difference thereto and updating the delay time difference,

when the update of the delay time difference decreases an amount of distortion remaining after distortion compensation at that time, leaves the plus/minus sign of the update value as it is, and

when the update of the delay time difference increases an amount of distortion remaining after distortion compensation, sets a new update value having a sign inverted from that of the update value.

4. A predistorter according to claim 1, comprising:

predistortion distortion signal generating means using a signal to be amplified to generate and output a predistortion distortion signal including an odd-order signal component of the signal;

delay time difference adjusting means adjusting a delay time difference between a signal to be amplified and a predistortion distortion signal generated by the predistortion distortion signal generating means such that distortion due to the memory effect occurring in the amplifier can be reduced; and

predistortion distortion signal giving means giving a predistortion distortion signal generated by the predistortion distortion signal generating means to a signal to be amplified in a form that the delay time difference is adjusted by the delay time difference adjusting means.

5. A predistorter according to claim 4, comprising:

a signal path including a detector that detects an even-power-raised value of an input signal, a multiplier that multiplies a detection result by the detector by the input signal and a complex-multiplier that complex-multiplies a multiplication result by the multiplier and a distortion compensation coefficient;

a delay circuit delaying the input signal; and

an adder adding a signal output from the signal path and a signal output from the delay circuit,

wherein the predistortion distortion signal generating means is provided by the function of the signal path, the delay time difference adjusting means is provided by the function of the delay circuit, and the predistortion distortion signal giving means is provided by the function of the adder.

6. A predistorter according to claim 4, comprising:

a signal path including a detector that detects an even-power raised absolute value of an input signal, a multiplier that multiplies a detection result by the detector by the input signal and a complex-multiplier that complex-multiplies a multiplication result by the multiplier and a distortion compensation coefficient;

a delay circuit delaying a signal output from the signal path; and

an adder adding a signal output from the delay circuit and the input signal,

wherein the predistortion distortion signal generating means is provided by the function of the signal path, the delay time difference adjusting means is provided by the function of the delay circuit, and the predistortion distortion signal giving means is provided by the function of the adder.

7. A predistorter according to claim 6, comprising a first signal path and a second signal path are provided as the signal path,

wherein the first signal path includes a square-law detector that detects a square absolute value of an input signal, a first multiplier that multiplies a detection result by the square-law detector by the input signal, and a first complex-multiplier that complex-multiplies a multiplication result by the first multiplier by a first distortion compensation coefficient,

the second signal path includes a fourth-power-law detector that detects a fourth-power-raised absolute value of an input signal, a second multiplier that multiplies a detection result by the fourth-power-law detector by the input signal, and a second complex-multiplier that complex-multiplies a multiplication result by the second multiplier by a second distortion compensation coefficient,

the delay circuit delays a signal output from the first signal path and a signal output from the second signal path, and

the adder adds two signals delayed by the delay circuits and the input signal.

8. A predistorter according to claim 1, comprising:

predistortion control signal outputting means outputting a predistortion control signal based on a level of a signal to be amplified;

delay time difference adjusting means adjusting a delay time difference between a signal to be amplified and a predistortion control signal output from the predistortion control signal outputting means such that an influence by the memory effect occurring in the amplifier can be reduced; and

predistortion control signal computing means computing a predistortion control signal output from the predistortion control signal outputting means for a signal to be amplified in a form that the delay time difference is adjusted by the delay time difference adjusting means.

9. A predistorter according to claim 8, comprising:

a detector circuit detecting an envelope value of an input signal;

a distortion compensation table outputting a distortion compensation coefficient corresponding to a value detected by the detector circuit;

a delay circuit delaying the input signal; and

a complex-multiplier complex-multiplying a distortion compensation coefficient output from the distortion compensation table by a signal output from the delay circuit,

wherein the predistortion control signal outputting means is provided by the function of the detector circuit and the function of the distortion compensation table, the delay time difference adjusting means is provided by the function of the delay circuit, and the predistortion control signal computing means is provided by the function of the complex-multiplier.

10. A predistorter according to claim 8, comprising:

a detector circuit detecting an envelope value of an input signal;

a distortion compensation table outputting a distortion compensation coefficient corresponding to a value detected by the detector circuit;

a delay circuit delaying a distortion compensation coefficient output from the distortion compensation table; and

a complex-multiplier complex-multiplying a signal output from the delay circuit by the input signal,

wherein the predistortion control signal outputting means is provided by the function of the detector circuit and the function of the distortion compensation table, the delay time difference adjusting means is provided by the function of the delay circuit, and the predistortion control signal computing means is provided by the function of the complex-multiplier.

11. A predistorter according to claim 1, comprising:

predistortion distortion generation control signal outputting means outputting a predistortion distortion generation control signal based on a level of a signal to be amplified;

delay time difference adjusting means adjusting a delay time difference between a signal to be amplified and a predistortion distortion generation control signal output from the predistortion distortion generation control signal outputting means such that an influence by the memory effect occurring in the amplifier can be reduced; and

predistortion distortion generating means generating a distortion for predistortion controlled by a predistortion distortion generation control signal output from the predistortion distortion generation control signal outputting means for a signal to be amplified in a form that the delay time difference is adjusted by the delay time difference adjusting means.

12. A predistorter according to claim 11, comprising:

a detector circuit detecting an envelope value of an input signal;

a distortion compensation table outputting an amplitude control value and a phase control value as distortion compensation coefficients corresponding to a value detected by the detector circuit;

a delay circuit delaying the input signal;

an adjustable attenuator attenuating a signal output from the delay circuit by an amount of attenuation controlled by an amplitude control value output from the distortion compensation table; and

an adjustable phase shifter shifting a phase of the signal by an amount of phase shift controlled by a phase control value output from the distortion compensation table,

wherein the predistortion distortion generation control signal outputting means is provided by the function of the detector circuit and the function of the distortion compensation table, the delay time difference adjusting means is provided by the function of the delay circuit, and the predistortion distortion generating means is provided by the function of the adjustable attenuator and the function of the adjustable phase shifter.

13. A predistorter according to claim 11, comprising:

a detector circuit detecting an envelope value of an input signal;

a distortion compensation table outputting an amplitude control value and a phase control value as distortion compensation coefficients corresponding to a value detected by the detector circuit;

a delay circuit delaying the amplitude control value and phase control value output from the distortion compensation table;

an adjustable attenuator attenuating an input signal by an amount of attenuation controlled by an amplitude control value output from the delay circuit; and

an adjustable phase shifter shifting a phase of the signal by an amount of phase shift controlled by a phase control value output from the delay circuit,

wherein the predistortion distortion generation control signal outputting means is provided by the function of the detector circuit and the function of the distortion compensation table, the delay time difference adjusting means is provided by the function of the delay circuit, and the predistortion distortion generating means is provided by the function of the adjustable attenuator and the function of the adjustable phase shifter.

14. A distortion-compensated amplifier using predistortion technique, comprising:

an amplifier; and

a predistorter provided before the amplifier for compensating for distortion occurring in the amplifier in amplifying a signal to be amplified by the amplifier by using a predistortion technique,

the predistorter having;

means outputting a signal for predistortion based on a signal to be amplified;

means adjusting a delay time difference between a signal to be amplified and a signal for predistortion such that an influence by the memory effect occurring in the amplifier can be reduced; and

means performing processing based on a signal for predistortion on a signal to be amplified in a form that the delay time difference is adjusted.