Predistortion linearizer using cascaded lower-order linearizers

• US 7,348,843 B1
• Filed: 04/21/2006
• Issued: 03/25/2008
• Est. Priority Date: 04/21/2005
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Qiu, Joe X, Abe, David K
• Primary Examiner(s): NGUYEN, PATRICIA T
• Application Number:
  US11/416,512
• Time in Patent Office: 704 Days
• Field of Search: 330/149, 330/151, 455/63.1
• US Class Current: 330/149
• CPC Class Codes: H03F 1/3241 using predistortion circuits H03F1/3211, H03F1/3217 take precedence

Abstract

A predistortion linearizer for predistorting a radiofrequency (RF) signal includes a first third-order predistortion linearizer having an input for receiving the RF signal, and a second third-order predistortion linearizer connected in cascade with the first linearizer, whereby fifth order nonlinearities are introduced into a cascaded, predistorted RF output signal. Cascading additional third-order linearizers similarly provides higher-order linearizers.

Claims

1. A predistortion linearizer for predistorting a radiofrequency (RF) signal, comprising:

a first third-order predistortion linearizer having an input for receiving the RF signal; and

a second third-order predistortion linearizer connected in cascade with the first third-order predistortion linearizer, whereby fifth-order nonlinearities are introduced into a cascaded, predistorted RF output signal.

2. A predistortion linearizer as in claim 1, wherein the input-output relationship is defined by

{tilde over (v)}_o={tilde over (v)}_i+(ã

₃₁+ã

₃₂)|{tilde over (v)}_i|²{tilde over (v)}_i+ã

₃₂(2ã

₃₁+ã

₃₁*)|{tilde over (v)}_i|⁴{tilde over (v)}_i+higher order terms

where {tilde over (v)}_i and {tilde over (v)}_o are complex input and output voltages, respectively, and ã

₃₁ and ã

₃₂ are the respective complex nonlinear coefficients.

3. A predistortion linearizer as in claim 2, wherein amplitudes and phases of the third- and fifth-order components can be obtained by simultaneously adjusting ã

₃₁ and ã

₃₂.

4. A predistortion linearizer as in claim 1, wherein each predistortion linearizer comprises two anti-parallel diodes, a FET channel, or a low-power solid-state amplifier driven into compression.

5. A predistortion linearizer as in claim 1, further comprising a third predistortion linearizer connected in cascade with the second predistortion linearizer.

6. A method for predistorting a radiofrequency (RF) signal, comprising:

receiving an RF signal;

inputting the RF signal to a first third-order predistortion linearizer to generate a first RF output signal having third-order nonlinearities;

inputting the first RF output signal to a second third-order predistortion linearizer connected in cascade with the first third-order predistortion linearizer to generate a second RF output signal having fifth-order nonlinearities; and

applying the second RF output signal to a power amplifier in a communication device.

7. A method as in claim 6, wherein the power amplifier is a microwave power amplifier in a microwave communications system.

8. A method as in claim 6, wherein an input-output relationship is defined by

{tilde over (v)}_o={tilde over (v)}_i+(ã

₃₁+ã

₃₂)|{tilde over (v)}_i|²{tilde over (v)}_i+ã

₃₂(2ã

₃₁+ã

₃₁*)|{tilde over (v)}_i|⁴{tilde over (v)}_i+higher order terms

where {tilde over (v)}_i and {tilde over (v)}_o are complex input and output voltages, respectively, and ã

₃₁ and ã

₃₂ are the respective complex nonlinear coefficients.

9. A method as in claim 7, wherein amplitudes and phases of the third- and fifth-order components can be obtained by simultaneously adjusting ã

₃₁ and ã

₃₂.

10. A method as in claim 6, wherein each predistortion linearizer comprises two anti-parallel diodes, a FET channel, or a low-power solid-state amplifier driven into compression.

11. A method for predistorting a radiofrequency (RF) signal, comprising:

receiving an RF signal;

inputting the RF signal to a first third-order predistortion linearizer to generate a first RF output signal having third-order nonlinearities;

inputting the first RF output signal to a second third-order predistortion linearizer connected in cascade with the first third-order predistortion linearizer to generate a second RF output signal having fifth-order nonlinearities;

inputting the second RF output signal into a third third-order predistortion linearizer connected in cascade with the second third-order predistortion linearizer to generate a third RF output signal; and

applying the third RF output signal to a power amplifier in a communication device.

12. A method as in claim 11, wherein the power amplifier is a microwave power amplifier in a microwave communications system.

13. A method as in claim 11, wherein an input-output relationship is defined by

{tilde over (v)}_o={tilde over (v)}_i+(ã

₃₁+ã

₃₂)|{tilde over (v)}_i|²{tilde over (v)}_i+ã

₃₂(2ã

₃₁+ã

₃₁*)|{tilde over (v)}_i|⁴{tilde over (v)}_i+higher order terms

where {tilde over (v)}_i and {tilde over (v)}_o are complex input and output voltages, respectively, and ã

₃₁ and ã

₃₂ are the respective complex nonlinear coefficients.

14. A method as in claim 13, wherein amplitudes and phases of the third- and fifth-order components can be obtained by simultaneously adjusting ã

₃₁ and ã

₃₂.

15. A method as in claim 11, wherein each predistortion linearizer comprises two anti-parallel diodes, a FET channel, or a low-power solid-state amplifier driven into compression.