System and method for digital memorized predistortion for wireless communication

• US 9,374,196 B2
• Filed: 04/13/2015
• Issued: 06/21/2016
• Est. Priority Date: 05/01/2002
• Status: Expired due to Term

• Current Assignee: Dali Wireless Inc. (Dali Systems Co., Ltd.)
• Original Assignee: Dali Systems Co., Ltd.
• Inventors: Yang, Dali, Yang, Jia
• Primary Examiner(s): AKINYEMI, AJIBOLA A
• Application Number:
  US14/684,678
• Publication Number:
  US 20150326349A1
• Time in Patent Office: 435 Days
• Field of Search: 455/297
• US Class Current: 1/1
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• 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 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2201/3224 Predistortion being done for compensating memory effects
• CPC Class Codes: H03F 2201/3227 Adaptive predistortion based on amplitude, envelope or power level feedback from the output of the main amplifier
• CPC Class Codes: H03F 2201/3233 Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion
• CPC Class Codes: H03F 3/189 High-frequency amplifiers, e.g. radio frequency amplifiers
• CPC Class Codes: H03F 3/19 with semiconductor devices only
• CPC Class Codes: H03F 3/195 in integrated circuits
• CPC Class Codes: H03F 3/20 Power amplifiers, e.g. Class B amplifiers, Class C amplifiers H03F3/26 - H03F3/30 take precedence
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04L 1/0043 Realisations of complexity reduction techniques, e.g. use of look-up tables
• CPC Class Codes: H04L 1/0044 specially adapted for power saving
• CPC Class Codes: H04L 27/367 using predistortion
• CPC Class Codes: H04L 27/368 adaptive predistortion
• CPC Class Codes: H04W 52/52 using AGC [Automatic Gain Control] circuits or amplifiers

Abstract

A power amplifier system includes an input operable to receive an original value that reflects information to be communicated and an address data former operable to generate a digital lookup table key. The power amplifier system also includes a predistortion lookup table coupled to the address data former and a power amplifier having an output and coupled to the predistortion lookup table. The power amplifier system further includes a feedback loop providing a signal associated with the output of the power amplifier to the predistortion lookup table and a switch disposed in the feedback loop and operable to disconnect the predistortion lookup table from the output of the power amplifier.

Claims

1. A power amplifier system comprising:

an input operable to receive a signal that reflects information to be communicated;

an address data former operable to generate a digital lookup table key;

a predistortion lookup table coupled to the address data former;

a power amplifier having an output and an input, wherein the input to the power amplifier is coupled to the predistortion lookup table;

a feedback signal representing the output of the power amplifier; and

a switch coupled to the feedback signal and the predistortion lookup table, wherein the switch is configured to disconnect the feedback signal from the predistortion lookup table.

2. The power amplifier system of claim 1, wherein the power amplifier system is a component of a mobile device.

3. The power amplifier system of claim 1, wherein the power amplifier system is a component of a base station.

4. The power amplifier system of claim 1, wherein the switch couples the feedback signal and the predistortion lookup table during a training phase, and wherein the switch decouples the feedback signal and the predistortion lookup table during an operating phase.

5. A predistorter, comprising:

an address data former;

a linearity and time-delay lookup table coupled to the address data former;

a predistortion lookup table coupled to the address data former;

a vector multiplier coupled to an output of the predistortion lookup table;

an error comparator coupled to an output of the linearity and time-delay lookup table and an input of the predistortion lookup table;

a status switch; and

an on/off switch.

6. The predistorter of claim 5, wherein the address data former is configured to accept coded in-phase and quadrature symbols, wherein the coded in-phase and quadrature symbols represent information that is to be communicated.

7. The predistorter of claim 5, wherein the address data former is configured to provide an address to both the linearity and time-delay lookup table and the predistortion lookup table.

8. The predistorter of claim 5, wherein the linearity and time-delay lookup table is used to store linearity characteristics of a power amplifier and time-delay characteristics of a channel from an output of the power amplifier to the error comparator.

9. The predistorter of claim 5, wherein the predistortion lookup table is used to store predistortion signals to linearize a power amplifier.

10. The predistorter of claim 9, wherein the predistortion signals are obtained by comparing signals from the linearity and time-delay lookup table and feedback signals representing the output of the power amplifier.

11. The predistorter of claim 5, wherein the on/off switch couples the error comparator and the predistortion lookup table during a training phase.

12. The predistorter of claim 5, wherein the status switch enables the linearity and time-delay lookup table and the predistortion lookup table to be adaptively updated during a training phase.

13. A method for operating a power amplifier, the method comprising:

initializing the power amplifier, wherein initializing includes setting a switch to connect an output of the power amplifier to a training circuit; and

executing a training procedure, wherein the training procedure includes;

determining a pre-computed distortion contribution associated with a feedback signal representative of an output of the power amplifier, wherein the feedback signal includes a nonlinear distortion component; and

storing the pre-computed distortion contribution in a lookup table.

14. The method of claim 13, further comprising:

executing an operating phase, wherein the operating phase includes;

setting the switch to disconnect the output of the power amplifier from the training circuit;

accepting an original value that reflects information to be communicated;

generating a digital lookup table key using the original value;

retrieving, using the digital lookup table key, a pre-computed distortion contribution from the lookup table, wherein the pre-computed distortion contribution corresponds to the original value;

distorting the original value using the pre-computed distortion contribution to obtain a distorted value;

wherein distorting the original value pre-compensates for nonlinear characteristics of the power amplifier;

generating a pre-distorted signal using the original value and the distorted value; and

wirelessly transmitting a pre-distorted signal.

15. The method of claim 14, wherein the power amplifier is a component of a mobile device.

16. The method of claim 15, wherein the operating phase lasts for at least one entire telephone conversation.

17. The method of claim 14, wherein the power amplifier is a component of a base station.

18. The method of claim 13, wherein determining a pre-computed distortion contribution includes:

determining reference information, wherein the reference information is determined by training, wherein the training uses reference training feedback signals, wherein the reference training feedback signals are representative of the output of the power amplifier; and

storing the reference information in a reference table.

19. The method of claim 18, wherein determining a pre-computed distortion contribution includes:

squaring an in-phase component of the feedback signal to produce a squared in-phase output value;

squaring a quadrature component of the feedback signal to produce a squared quadrature output value;

squaring an in-phase component of a reference signal to produce a squared in-phase reference value, wherein the reference signal is derived from the reference information;

squaring a quadrature component of the reference signal to produce a squared quadrature reference value;

determining an in-phase difference between the squared in-phase reference value and the squared in-phase output value;

determining a quadrature difference between the squared quadrature reference value and the squared quadrature output value; and

determining the pre-computed distortion contribution based on the in-phase difference and the quadrature difference.

20. The method of claim 18, wherein the reference information represents linearity characteristics of the power amplifier and time-delay parameters of the feedback signals.