Power amplifier having predistortion linearizer

• US 6,522,198 B2
• Filed: 12/14/2000
• Issued: 02/18/2003
• Est. Priority Date: 12/15/1999
• Status: Expired due to Fees

• Current Assignee: LG Nortel Company Limited
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Ahn, Kwang Eun
• Primary Examiner(s): NGUYEN, PATRICIA T
• Application Number:
  US09/735,530
• Publication Number:
  US 20010052816A1
• Time in Patent Office: 796 Days
• Field of Search: 330/149, 330/151
• US Class Current: 330/149
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence

Abstract

A power amplifier having a predistortion linearizer for improving the non-linear property of the power amplifier is disclosed. The powers amplifier includes a predistorter for outputting a distortion compensating signal to the high power amplifier, a delay line for delaying an input signal for a prescribed period of time and outputting a reference signal, a distortion component detection circuit for detecting a distortion component by comparing the output signal of the power amplifier with the reference signal of the delay line, and an adaptive controller for controlling the properties of the predistorter in order to minimize the detected distortion component.

Claims

1. A power amplifier, comprising:

a predistorter configured to receive an input signal and output a distortion compensating signal;

a power amplifier coupled to receive the distortion compensating signal and generate an output signal;

a delay line coupled to receive the input signal and generate a reference signal;

a distortion component detection circuit coupled to receive the output signal from the power amplifier and the reference signal from the delay line, and detect a distortion component of the output signal to generate a distortion level output signal; and

an adaptive controller coupled to receive the distortion level output signal and generate a control signal to control the predistorter.

2. The power amplifier of claim 1, wherein the distortion component detection circuit detects a distortion component by adjusting the output signal so that the output signal and the reference signal have the same amplitude and a phase difference of 180 degrees.

3. The power amplifier of claim 1, wherein the reference signal is formed by inverting the phase of the input signal by 180 degrees.

4. The power amplifier of claim 1, wherein the distortion component detection circuit comprises:

a vector modulator coupled to receive the output voltage and a feedback signal to control at least one of the gain and phase of the output signal; and

a distortion component detection unit coupled to receive an output of the vector modulator and the reference signal, detect the distortion component of the output signal by comparing the output signal with the reference signal, and output the feedback signal corresponding to a difference in gain and phase to the vector modulator.

5. The power amplifier of claim 4, wherein the feedback signal is a voltage control signal.

6. The power amplifier of claim 4, wherein the distortion component detection unit comprises:

a branch line coupler to add vector components of the output signal and reference signal;

a 2-way combiner to combine outputs of the branch line coupler and output the distortion component; and

a control signal generator coupled to receive the output signal of the vector modulator, the reference signal, the output signal of the branch line coupler, and a power signal of the distortion component to produce the feedback signal proportional to a difference in the outputted gain and phase of the reference signal and the output signal.

7. The power amplifier of claim 6, wherein the distortion component detection unit further comprises a power detector configured to detect and output a power of the distortion component.

8. The power amplifier of claim 1, wherein the delay line delays the input signal for a prescribed period of time to generate the reference signal.

9. The power amplifier of claim 1, wherein the distortion component detection circuit compares the output signal to the reference signal to generate the distortion level output signal.

10. A distortion component detection circuit for a power amplifier, comprising:

a delay line coupled to delay an input signal for a prescribed period of time to generate a reference signal;

a vector modulator coupled to receive an output signal of a power amplifier and a control voltage feedback signal to control a gain and phase of the output signal; and

a distortion component detection unit coupled to receive an output of the vector modulator and detect a distortion component of the output signal by computing vector components of the output signal and the reference signal, and outputting the control voltage feedback signal corresponding to a difference in gain and phase between the reference signal and the output signal to the vector modulator.

11. The circuit of claim 10, wherein the reference signal is formed by inverting the phase of the input signal.

12. The circuit of claim 10, wherein the distortion component detection unit comprises:

a branch line coupler configured to add vector components of the output signal and reference signal;

a 2-way combiner configured to add vector outputs of the branch line coupler and output the distortion component; and

a control signal generator coupled to receive the output signal, the reference signal, the output of the branch line coupler, and a power signal of the distortion component, to output the control voltage feedback signal.

13. The circuit of claim 12, further comprising a power detector coupled to receive the distortion component and generate a distortion component power signal.

14. The circuit of claim 10, further comprising an adaptive controller coupled to receive an output of the distortion component detection circuit and generate a control signal to control the output signal.

25. The circuit of claim 10, wherein the output of the vector modulator and the reference signal have a same amplitude and a phase difference of 180 degrees.

15. A distortion component detection circuit for a power amplifier, comprising:

a delay line to delay an input signal for a prescribed time period and generate a reference signal;

a vector modulator coupled to receive an output signal of the power amplifier and a control voltage feedback signal to control a gain and phase of the output signal of the power amplifier;

a branch line coupler to receive an output signal of the vector modulator and the reference signal and add vector components of both signals;

a 2-way combiner to combine vector outputs of the branch line coupler and output a resultant distortion component; and

a control signal generator to calculate a difference in gain and phase of the output signal of the vector modulator and reference signal by receiving the vector modulator output signal, the reference signal, the vector output signal of the branch line coupler, and a power signal of the distortion component and outputting the control voltage feedback signal proportional to the calculated difference.

16. The circuit of claim 15, further comprising a power detector coupled to receive the distortion component and generate a distortion component power signal.

17. The circuit of claim 15, further comprising an adaptive controller coupled to receive an output of the 2-way combiner and generate a control signal to control the non-linear aspects of the power amplifier.

26. The circuit of claim 15, wherein the output signal of the vector modulator and the reference signal have a same amplitude and a phase difference of 180 degrees.

18. A method of adaptively controlling the linearity of a power amplifier, comprising:

generating a reference signal by phase shifting an input signal;

generating an amplified signal by amplifying the input signal with a power amplifier;

identifying a distortion component of the amplified signal by combining vector components of the reference signal and the amplified signal to form a resultant distortion component;

generating a control signal based on the identified level of the resultant distortion component;

controlling the non-linear effects of the power amplifier using the control signal.

19. The method of claim 18, wherein the step of identifying the distortion component comprises:

adjusting the amplified signal with a vector modulator to have a same amplitude as the reference signal, and a 180 degree phase difference;

combining vector components of the amplified signal and the reference signal to isolate a resultant distortion component;

generating gain and phase control voltages to control the vector modulator; and

outputting a control signal based on a power level of the distortion component.

20. A method of separating a distortion component from an amplified signal, comprising:

generating an output signal by amplifying an input signal;

generating a reference signal by delaying the input signal, wherein the reference signal is 180 degrees phase shifted from the input signal;

adjusting the output signal to have the same amplitude as the reference signal; and

combining vector components of the output signal with vector components of the reference signal to generate a resultant distortion component signal.

21. The method of claim 20, wherein the step of combining the output signal with the reference signal comprises adding vector components of the output signal with vector components of the reference signal.

22. The method of claim 20, wherein the step of combining the vector components of the output signal with vector components of the reference signal comprises generating a first branch line vector signal equivalent to a resultant vector of a first vector of the output signal and a first vector of the reference signal, generating a second branch line vector signal equivalent to a resultant vector of a second vector of the output signal and a second vector of the reference signal, and combining the first and second branch line vector signals to form the resultant distortion component signal equivalent to a resultant vector of the first and second branch line vector signals.

23. The method of claim 20, further comprising providing the distortion component signal to a power detector to detect an amount of distortion and generate a first control signal, and providing the first control signal to an adaptive controller to generate a second control signal, wherein the second control controls non-linear effects of a power amplifier.

24. The method of claim 23, wherein the second control signal is provided to a predistorter that preconditions the input signal, and the preconditioned input signal is amplified to generate the output signal, and wherein the non-linear effects of the amplifier are minimized in accordance with the preconditioned input signal.