Method of and circuit for generating parameters for a predistortion circuit in an integrated circuit

• US 7,741,906 B1
• Filed: 08/29/2008
• Issued: 06/22/2010
• Est. Priority Date: 08/29/2008
• Status: Active Grant

• Current Assignee: Xilinx, Inc. (Advanced Micro Devices, Inc.)
• Original Assignee: Xilinx, Inc. (Advanced Micro Devices, Inc.)
• Inventors: Summerfield, Stephen
• Primary Examiner(s): Nguyen; Khanh V
• Application Number:
  US12/201,642
• Time in Patent Office: 662 Days
• Field of Search: 330/149, 375/296, 375/297, 455/114.3
• 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 2201/3233 Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion

Abstract

A method of generating parameters for a predistortion circuit in an integrated circuit is disclosed. The method comprises receiving, at the predistortion circuit, an input signal to be amplified by a power amplifier; receiving an output of the power amplifier at an input of the integrated circuit; comparing an output of the predistortion circuit with the output of the power amplifier; conforming the output of the power amplifier with the output of the predistortion circuit; and generating parameters to be applied to the predistortion circuit based upon the conformed output of the power amplifier and the predistortion circuit. An integrated circuit having a circuit for generating parameters for a predistortion circuit of the integrated circuit is also disclosed.

Claims

1. A method of generating parameters for a predistortion circuit in an integrated circuit, the method comprising:

receiving, at the predistortion circuit, an input signal to be amplified by a power amplifier;

receiving an output of the power amplifier at an input of the integrated circuit;

comparing an output of the predistortion circuit with the output of the power amplifier;

conforming the output of the power amplifier with the output of the predistortion circuit; and

generating parameters to be applied to the predistortion circuit based upon the conformed outputs of the power amplifier and the predistortion circuit;

wherein conforming the output of the power amplifier with the output of the predistortion circuit comprises eliminating a frequency offset between the output of the predistortion circuit and the output of the power amplifier by determining a phase difference between the output of the predistortion circuit and the output of the power amplifier and generating an approximation of the phase difference, the approximation of the phase difference being generated by converting a trigonometric representation of the phase difference to an algebraic representation of the phase difference.

2. The method of claim 1 wherein conforming the output of the power amplifier with the output of the predistortion circuit comprises adjusting the amplitude of the input signal received at the predistortion circuit or the output of the power amplifier to make the amplitude of the output of the predistortion circuit and the output of the power amplifier equal.

3. The method of claim 1 wherein conforming the output of the power amplifier with the output of the predistortion circuit comprises eliminating any delay between the output of the predistortion circuit and the output of the power amplifier.

4. The method of claim 1 wherein conforming the output of the predistortion circuit with the output of the power amplifier comprises modifying the output of the power amplifier.

5. A method of generating parameters for a predistortion circuit in an integrated circuit, the method comprising:

receiving, at the predistortion circuit, an input signal to be amplified by a power amplifier;

receiving an output of the power amplifier at an input of the integrated circuit;

comparing an output of the predistortion circuit with the output of the power amplifier;

determining a phase difference between the output of the predistortion circuit and the output of the power amplifier;

generating an approximation of the phase difference;

conforming the output of the power amplifier with the output of the predistortion circuit based upon the approximation of the phase difference by providing delay alignment between the output of the predistortion circuit and the output of the power amplifier, wherein providing delay alignment comprises comparing an edge of the output of the predistortion circuit to an edge of the output of the power amplifier; and

generating parameters to be applied to the predistortion circuit based upon conformed outputs of the power amplifier and the predistortion circuit.

6. The method of claim 5 wherein conforming the output of the power amplifier with the output of the predistortion circuit comprises modifying the amplitude of the output of the power amplifier.

7. The method of claim 5 further comprising selecting a delay of a delay circuit in response to the comparison of the edge of the output of the predistortion circuit with the edge of the output of the power amplifier.

8. The method of claim 5 further comprising storing the parameters to be applied to the predistortion circuit in a look-up memory.

9. The method of claim 8 further comprising selecting a parameter set to be applied to the predistortion circuit based upon a power measurement of the input signal.

10. An integrated circuit having a circuit for generating parameters for a predistortion circuit of the integrated circuit, the circuit for generating parameters comprising:

a predistortion circuit coupled to receive an input signal to be amplified by a power amplifier coupled to the integrated circuit;

a signal correction circuit comprising an amplitude alignment circuit coupled to receive an output of the predistortion circuit and an output of the power amplifier, the signal correction circuit conforming the output of the power amplifier with the output of the predistortion circuit; and

an estimation circuit coupled to receive the output of the signal correction circuit, the estimation circuit generating parameters for the predistortion circuit based upon the conformed outputs of the power amplifier and the predistortion circuit.

11. The integrated circuit of claim 10 wherein the signal correction circuit comprises a delay alignment circuit.

12. The integrated circuit of claim 10 wherein the signal correction circuit comprises frequency offset correction circuit.

13. The integrated circuit of claim 12 wherein the frequency offset correction circuit determines a trigonometric representation of a phase difference between the input signal received at the predistortion circuit and the output of the power amplifier and generates an approximation comprising an algebraic representation of the phase difference.

14. The circuit for generating parameters of claim 13 wherein the frequency correction circuit comprises processor of a programmable logic device.