Baseband-derived RF digital predistortion

• US 8,548,403 B2
• Filed: 02/25/2013
• Issued: 10/01/2013
• 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:
  US13/776,163
• Publication Number:
  US 20130214861A1
• Time in Patent Office: 218 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 radio frequency (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 plurality of polynomial blocks operable to determine a plurality of polynomial coefficients using the baseband signal;

a vector modulator coupled to the RF output and operable to apply the plurality of polynomial coefficients to the RF output; and

an adaptation algorithm unit operable to optimize predistortion components using the plurality of polynomial coefficients.

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

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

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

5. The wideband predistortion system of claim 4, wherein the digital delay block comprises an equalizer.

6. A wideband predistortion system for use with radio frequency (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 plurality of polynomial blocks operable to determine a plurality of polynomial coefficients using the baseband signal; and

a vector modulator coupled to the RF output and operable to apply the plurality of polynomial coefficients to the RF output.

7. The wideband predistortion system of claim 6, wherein the vector modulator comprises a plurality of delayed and summed vector modulators.

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

9. The wideband predistortion system of claim 6, further comprising a digital delay block coupled to the adaptation algorithm unit.

10. The wideband predistortion system of claim 9, wherein the digital delay block comprises an equalizer.

11. A method for compensating for memory effects in a wideband predistortion system, the method comprising:

receiving a baseband signal at a baseband input;

determining a plurality of polynomial coefficients at a plurality of polynomial blocks, using the baseband signal;

applying the plurality of polynomial coefficients to an RF output, using a vector modulator coupled to the RF output;

providing the RF output to an RF power amplifier; and

optimizing predistortion components at an adaptation algorithm unit coupled to the RF power amplifier, using the plurality of polynomial coefficients.

12. The method of claim 11, wherein the vector modulator comprises a plurality of delayed and summed vector modulators.

13. The method of claim 11, wherein the vector modulator comprises a variable attenuator and a variable phase shifter.