Baseband-derived RF digital predistortion

• US 8,213,884 B2
• Filed: 12/08/2008
• Issued: 07/03/2012
• 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:
  US12/330,451
• Publication Number:
  US 20090146736A1
• Time in Patent Office: 1,303 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 comprising:

a baseband input for receiving a baseband signal,

an RF output for providing a signal to an RF power amplifier,

logic for deriving a predistortion function from the baseband signal and generating a predistortion signal, wherein the logic comprises a polynomial calculation, and

a vector modulator responsive to the predistortion function and connected to the RF output for applying the predistortion signal to the RF output.

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

3. The wideband predistortion system of claim 1 wherein the baseband signal is at an Intermediate Frequency.

4. The wideband predistortion system of claim 1 wherein the baseband signal is output using a digital to analog converter for a quadrature component and for an in-phase component.

5. The wideband predistortion system of claim 1 wherein the baseband signal is frequency translated to a RF frequency using a quadrature modulator.

6. The wideband predistortion system of claim 1 further comprising a digital delay block.

7. The wideband predistortion system of claim 6 wherein the digital delay block comprises an equalizer.

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

a baseband input for receiving a baseband signal, wherein the baseband signal is frequency translated to an RF frequency using a quadrature modulator;

an RF output for providing a signal to an RF power amplifier;

logic for deriving a predistortion function from the baseband signal and generating a predistortion signal, wherein the logic comprises a lookup table; and

a vector modulator responsive to the predistortion function and connected to the RF output for applying the predistortion signal to the RF output.

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

10. The wideband predistortion system of claim 8 wherein the baseband signal is at an Intermediate Frequency.

11. The wideband predistortion system of claim 8 wherein the baseband signal is output using a digital to analog converter for a quadrature component and for an in-phase component.

12. The wideband predistortion system of claim 8 further comprising a digital delay block.

13. The wideband predistortion system of claim 12 wherein the digital delay block comprises an equalizer.