Baseband-derived RF digital predistortion

• US 8,401,499 B2
• Filed: 05/25/2012
• Issued: 03/19/2013
• Est. Priority Date: 12/07/2007
• Status: Active Grant

• Current Assignee: Dali Systems Co., Ltd.
• Original Assignee: Dali Systems Co., Ltd.
• Inventors: Kim, Wan Jong, Stapleton, Shawn Patrick
• Primary Examiner(s): Zweizig, Jeffrey
• Application Number:
  US13/481,389
• Publication Number:
  US 20120230382A1
• Time in Patent Office: 298 Days
• Field of Search: 455/114.1, 455/114.2, 455/114.3
• US Class Current: 455/114.3
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 1/3258 based on polynomial terms
• CPC Class Codes: H03F 1/3294 Acting on the real and imaginary components of the input signal
• CPC Class Codes: H03F 2200/204 A hybrid coupler being used at the output of an amplifier circuit
• CPC Class Codes: H03F 2200/336 A I/Q, i.e. phase quadrature, modulator or demodulator being used in an amplifying circuit
• CPC Class Codes: H03F 2200/57 Separate feedback of real and complex signals being present
• CPC Class Codes: H03F 2201/3224 Predistortion being done for compensating memory effects
• CPC Class Codes: H03F 2201/3233 Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04L 2025/03356 Baseband transmission
• CPC Class Codes: H04L 2025/03477 not time-recursive
• CPC Class Codes: H04L 25/03038 with a non-recursive structure H04L25/03031 takes precedence
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end

Abstract

A baseband-derived RF predistortion system using a lookup table having coefficients extracted at baseband and then applied at RF by means of a vector modulator. The architecture combines the narrowband advantage of envelope predistortion with the accuracy of baseband predistortion, and including compensation for memory effects. A polynomial-based alternative is also described.

Claims

1. A wideband predistortion system for use with RF power amplifiers, the system comprising:

a baseband input operable to receive a baseband signal;

an RF output operable to provide a signal to an RF power amplifier;

a lookup table including a predistortion signal including predistortion components;

a vector modulator coupled to the RF output and operable to apply the predistortion signal to the RF output; and

an adaptation algorithm unit operable to optimize the predistortion components.

2. The wideband predistortion system of claim 1 wherein the predistortion signal includes predistortion coefficients based on a difference between the baseband signal and a feedback signal derived from the RF output.

3. The wideband predistortion system of claim 1 wherein the vector modulator comprises a plurality of delayed and summed vector modulators.

4. The wideband predistortion system of claim 1 wherein the lookup table is indexed by a square of a magnitude of the baseband signal.

5. The wideband predistortion system of claim 1 further comprising a quadrature modulator coupled to the baseband input and operable to receive the baseband signal and translate the baseband signal to an RF frequency.

6. The wideband predistortion system of claim 1 wherein the vector modulator comprises a variable attenuator and a variable phase shifter.

7. The wideband predistortion system of claim 1 further comprising a digital delay block coupled to the adaptation algorithm unit.

8. The wideband predistortion system of claim 7 wherein the digital delay block comprises an equalizer.

9. A wideband predistortion system for use with RF power amplifiers, the system comprising:

a baseband input operable to receive a baseband signal;

a quadrature modulator coupled to the baseband input and operable to receive the baseband signal and translate the baseband signal to an RF frequency;

an RF output operable to provide a signal to an RF power amplifier;

a vector modulator coupled to the RF output and operable to apply the predistortion signal to the RF output, the vector modulator comprising a plurality of delayed and summed vector modulators; and

a lookup table coupled to the vector modulator and including a predistortion signal including predistortion components.

10. The wideband predistortion system of claim 9 wherein the lookup table is indexed by a square of a magnitude of the baseband signal.

11. The wideband predistortion system of claim 9 wherein the predistortion coefficients are based on a difference between the baseband signal and a feedback signal derived from the RF output.

12. The wideband predistortion system of claim 9 wherein the vector modulator comprises a variable attenuator and a variable phase shifter.

13. The wideband predistortion system of claim 9 further comprising a digital delay block coupled to the quadrature modulator.

14. The wideband predistortion system of claim 13 wherein the digital delay block comprises an equalizer.