Scalar cost function based predistortion linearizing device, method, phone and basestation

• US 6,240,278 B1
• Filed: 07/30/1998
• Issued: 05/29/2001
• Est. Priority Date: 07/30/1998
• Status: Expired due to Term

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Midya, Pallab, Grosspietsch, John
• Primary Examiner(s): LE, THANH C
• Application Number:
  US09/126,573
• Time in Patent Office: 1,034 Days
• Field of Search: 455/550, 455/575, 455/93, 455/114, 455/115, 455/116, 455/126, 455/127, 375/295, 375/296, 330/129, 330/149
• US Class Current: 455/126
• CPC Class Codes: H03F 1/3241 using predistortion circuits H03F1/3211, H03F1/3217 take precedence
• 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 2200/336 A I/Q, i.e. phase quadrature, modulator or demodulator being used in an amplifying circuit
• 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 1/00 Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
• CPC Class Codes: H04B 1/04 Circuits
• CPC Class Codes: H04B 2001/0425 with linearisation using predistortion

Abstract

A device (400), method (1200), phone (400) and basestation (400) for providing scalar measurement-based predistortion for linearization in a radio frequency RF power amplifier, includes: a polynomial predistortion unit (406), coupled to receive an input baseband signal and polynomial coefficient weights, for predistorting the baseband signal to provide a predistorted baseband signal in accordance with the polynomial coefficient weights; an RF modulator (402), coupled to the polynomial predistortion unit (406) and to an RF generator (403), for modulating the predistorted baseband signal to provide an RF signal; an RF power amplifier (401), coupled to the RF modulator (402) and to a power supply (408), for amplifying the RF signal to provide an amplified RF signal, a scalar cost function generator (405), coupled to receive the amplified RF signal, for computing a scalar cost function; and a coefficient update unit (407), coupled to receive the scalar out-of-band-energy cost function, for tuning the polynomial coefficients in accordance with minimizing the scalar cost function to provide a linear amplified RF signal.

Claims

1. A device for providing scalar measurement-based predistortion for linearization in a radio frequency RF power amplifier, comprising:

A) a polynomial predistortion unit, coupled to receive an input baseband signal and polynomial coefficient weights, for predistorting the baseband signal to provide a predistorted baseband signal in accordance with the polynomial coefficient weights;

B) an RF modulator, coupled to the polynomial predistortion unit and to an RF generator, for modulating the predistorted baseband signal to provide an RF signal;

C) an RF power amplifier, coupled to the RF modulator and to a power supply, for amplifying the RF signal to provide an amplified RF signal;

D) a scalar cost function generator, coupled to receive the amplified RF signal, for computing a scalar cost function; and

E) a coefficient update unit, coupled to receive the scalar out-of-band-energy cost function, for tuning the polynomial coefficients in accordance with minimizing the scalar cost function to provide a linear amplified RF signal.

2. The device of claim 1 wherein voltage of the power supply is a function of the baseband signal.

3. The device of claim 1 wherein the coefficient update unit uses orthogonal polynomial basis functions.

4. The device of claim 1 wherein the scalar cost function generator comprises:

A) an RF demodulator, coupled to receive the amplified RF signal, for demodulating the amplified RF signal to provide a demodulated signal;

B) a bandpass filter, coupled to receive the demodulated signal, for providing an out-of-band signal;

C) a squared envelope calculator, coupled to receive the out-of-band signal, for providing a squared envelope signal;

D) a low pass filter, coupled to receive the squared envelope signal, for providing the scalar cost function.

5. The device of claim 1 wherein the coefficient update unit includes a memory having stored thereon instructions and data which, when loaded into a processor causes the processor to perform the steps of a predetermined gradient algorithm that computes a set of polynomial coefficient weights that minimize the scalar cost function.

6. The device of claim 1 wherein the polynomial predistortion unit comprises:

A) a power envelope generator, coupled to receive the input baseband signal, for computing an instantaneous power envelope;

B) an orthogonal basis function generator, coupled to the power envelope generator, for computing orthogonal basis functions;

C) a plurality of multipliers, each coupled to receive one of the orthogonal basis functions and one of the polynomial coefficient weights, for multiplying the orthogonal basis function with the polynomial coefficient weight;

D) a summer, coupled to the plurality of multipliers and to receive the input baseband signal, for computing the predistorted baseband signal.

7. A method for providing scalar measurement-based predistortion for linearization in a radio frequency RF power amplifier, comprising the steps of:

A) using a polynomial predistortion unit for predistorting the baseband signal to provide a predistorted baseband signal in accordance with the polynomial coefficient weights;

B) using an RF modulator for modulating the predistorted baseband signal to provide an RF signal;

C) using an RF power amplifier, coupled to the RF modulator and to a power supply, for amplifying the RF signal to provide an amplified RF signal;

D) using a scalar cost function generator for computing a scalar cost function; and

E) using a coefficient update unit for tuning the polynomial coefficients in accordance with minimizing the scalar cost function to provide a linear amplified RF signal.

8. The method of claim 7 wherein voltage of the power supply is a function of the baseband signal.

9. The method of claim 7 wherein using the coefficient update unit includes using orthogonal polynomial basis functions.

10. The method of claim 7 wherein using the scalar cost function generator includes the steps of:

A) using an RF demodulator, coupled to receive the amplified RF signal, for demodulating the amplified RF signal to provide a demodulated signal;

B) using a bandpass filter, coupled to receive the demodulated signal, for providing an out-of-band signal;

C) using a squared envelope calculator, coupled to receive the out-of-band signal, for providing a squared envelope signal; and

D) using a low pass filter, coupled to receive the squared envelope signal, for providing the scalar cost function.

11. The method of claim 7 wherein using the coefficient update unit includes using a memory having stored thereon instructions and data which, when loaded into a processor causes the processor to perform the steps of a predetermined gradient algorithm that computes a set of polynomial coefficient weights that minimize the scalar cost function.

12. The method of claim 7 wherein using the polynomial predistortion unit includes using the input baseband signal to compute an instantaneous power envelope, using an orthogonal basis function generator to compute orthogonal basis functions, using a plurality of multipliers, each coupled to receive one of the orthogonal basis functions and one of the polynomial coefficient weights, to multiply the orthogonal basis function with the polynomial coefficient weight, and using a summer, coupled to the plurality of multipliers and to receive the input baseband signal, for computing the predistorted baseband signal.

13. A phone having a device for providing scalar measurement-based predistortion for linearization in a radio frequency RF power amplifier, the device comprising:

A) a polynomial predistortion unit, coupled to receive an input baseband signal and polynomial coefficient weights, for predistorting the baseband signal to provide a predistorted baseband signal in accordance with the polynomial coefficient weights;

B) an RF modulator, coupled to the polynomial predistortion unit and to an RF generator, for modulating the predistorted baseband signal to provide an RF signal;

C) an RF power amplifier, coupled to the RF modulator and to a power supply, for amplifying the RF signal to provide an amplified RF signal;

D) a scalar cost function generator, coupled to receive the amplified RF signal, for computing a scalar cost function; and

E) a coefficient update unit, coupled to receive the scalar out-of-band-energy cost function, for tuning the polynomial coefficients in accordance with minimizing the scalar cost function to provide a linear amplified RF signal.

14. The phone of claim 13 wherein voltage of the power supply is a function of the baseband signal.

15. The phone of claim 13 wherein the coefficient update unit uses orthogonal polynomial basis functions.

16. The phone of claim 13 wherein the scalar cost function generator comprises:

A) an RF demodulator, coupled to receive the amplified RF signal, for demodulating the amplified RF signal to provide a demodulated signal;

B) a bandpass filter, coupled to receive the demodulated signal, for providing an out-of-band signal;

C) a squared envelope calculator, coupled to receive the out-of-band signal, for providing a squared envelope signal;

D) a low pass filter, coupled to receive the squared envelope signal, for providing the scalar cost function.

17. The phone of claim 13 wherein the coefficient update unit includes a memory having stored thereon instructions and data which, when loaded into a processor causes the processor to perform the steps of a predetermined gradient algorithm that computes a set of polynomial coefficient weights that minimize the scalar cost function.

18. The phone of claim 13 wherein the polynomial predistortion unit comprises:

A) a power envelope generator, coupled to receive the input baseband signal, for computing an instantaneous power envelope;

B) an orthogonal basis function generator, coupled to the power envelope generator, for computing orthogonal basis functions;

C) a plurality of multipliers, each coupled to receive one of the orthogonal basis functions and one of the polynomial coefficient weights, for multiplying the orthogonal basis function with the polynomial coefficient weight;

D) a summer, coupled to the plurality of multipliers and to receive the input baseband signal, for computing the predistorted baseband signal.

19. A basestation having a device for providing scalar measurement-based predistortion for linearization in a radio frequency RF power amplifier, the device comprising:

A) a polynomial predistortion unit, coupled to receive an input baseband signal and polynomial coefficient weights, for predistorting the baseband signal to provide a predistorted baseband signal in accordance with the polynomial coefficient weights;

B) an RF modulator, coupled to the polynomial predistortion unit and to an RF generator, for modulating the predistorted baseband signal to provide an RF signal;

C) an RF power amplifier, coupled to the RF modulator and to a power supply, for amplifying the RF signal to provide an amplified RF signal;

D) a scalar cost function generator, coupled to receive the amplified RF signal, for computing a scalar cost function; and

E) a coefficient update unit, coupled to receive the scalar out-of-band-energy cost function, for tuning the polynomial coefficients in accordance with minimizing the scalar cost function to provide a linear amplified RF signal.

20. The basestation of claim 19 wherein voltage of the power supply is a function of the baseband signal.

21. The basestation of claim 19 wherein the coefficient update unit uses orthogonal polynomial basis functions.

22. The basestation of claim 19 wherein the scalar cost function generator comprises:

A) an RF demodulator, coupled to receive the amplified RF signal, for demodulating the amplified RF signal to provide a demodulated signal;

B) a bandpass filter, coupled to receive the demodulated signal, for providing an out-of-band signal;

C) a squared envelope calculator, coupled to receive the out-of-band signal, for providing a squared envelope signal;

D) a low pass filter, coupled to receive the squared envelope signal, for providing the scalar cost function.

23. The basestation of claim 19 wherein the coefficient update unit includes a memory having stored thereon instructions and data which, when loaded into a processor causes the processor to perform the steps of a predetermined gradient algorithm that computes a set of polynomial coefficient weights that minimize the scalar cost function.

24. The basestation of claim 19 wherein the polynomial predistortion unit comprises:

A) a power envelope generator, coupled to receive the input baseband signal, for computing an instantaneous power envelope;

B) an orthogonal basis function generator, coupled to the power envelope generator, for computing orthogonal basis functions;

C) a plurality of multipliers, each coupled to receive one of the orthogonal basis functions and one of the polynomial coefficient weights, for multiplying the orthogonal basis function with the polynomial coefficient weight;

D) a summer, coupled to the plurality of multipliers and to receive the input baseband signal, for computing the predistorted baseband signal.