Apparatus and method for improving an output signal from a nonlinear device through dynamic signal pre-distortion based upon Lagrange interpolation

• US 6,801,582 B2
• Filed: 09/13/2002
• Issued: 10/05/2004
• Est. Priority Date: 09/13/2002
• Status: Expired due to Term

• Current Assignee: Allied Telesis Incorporated (Allied Telesis Holdings KK)
• Original Assignee: Allied Telesyn, Inc. (Allied Telesis Holdings KK)
• Inventors: Hovakimyan, Karen
• Primary Examiner(s): Fan, Chieh M.
• Application Number:
  US10/244,038
• Publication Number:
  US 20040052313A1
• Time in Patent Office: 753 Days
• Field of Search: 375/219, 375/222, 375/284, 375/285, 375/295, 375/296, 375/297, 455/63.1, 455/63.2, 455/126, 332/123, 332/124, 332/159, 332/160, 332/162
• US Class Current: 375/296
• 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: H04L 27/368 adaptive predistortion

Abstract

An apparatus for pre-distorting a signal includes input nodes to receive an in-phase input signal and a quadrature input signal. Feedback nodes receive an in-phase feedback signal and a quadrature feedback signal. Output nodes transmit an in-phase pre-distorted signal and a quadrature pre-distorted signal. A Lagrange interpolation digital pre-distortion circuit is connected to the input nodes, the feedback nodes, and the output nodes. The Lagrange interpolation digital pre-distortion circuit is configured to perform a Lagrange interpolation on the in-phase input signal, the quadrature input signal, the in-phase feedback signal, and the quadrature feedback signal to produce the in-phase pre-distorted signal and the quadrature pre-distorted signal.

Claims

1. An apparatus for pre-distorting a signal, comprising:

input nodes to receive an in-phase input signal and a quadrature input signal;

feedback nodes to receive an in-phase feedback signal and a quadrature feedback signal;

output nodes to transmit an in-phase pre-distorted signal and a quadrature pre-distorted signal; and

a Lagrange interpolation digital pre-distortion circuit connected to said input nodes, said feedback nodes, and said output nodes, said Lagrange interpolation digital pre-distortion circuit being configured to perform a Lagrange interpolation on said in-phase input signal, said quadrature input signal, said in-phase feedback signal, and said quadrature feedback signal to produce said in-phase pre-distorted signal and said quadrature pre-distorted signal

wherein said Lagrange interpolation digital pre-distortion circuit includes an error circuit to produce an error signal between said in-phase input signal and said in-phase feedback signal and between said quadrature input signal and said quadrature feedback signal;

wherein said Lagrange interpolation digital pre-distortion circuit further comprises a Lagrange interpolation circuit to receive said error signal, said in-phase input signal, and said quadrature input signal and produce a complex multiplication term therefrom; and

wherein said Lagrange interpolation digital pre-distortion circuit further comprises a complex multiplier to multiply said complex multiplication term by said in-phase input signal and said quadrature input signal to produce said in-phase pre-distorted signal and said quadrature pre-distorted signal.

2. The apparatus of claim 1 wherein said Lagrange interpolation circuit includes an input signal differencing circuit to generate input signal difference values from said in-phase input signal and said quadrature input signal.

3. The apparatus of claim 2 wherein said Lagrange interpolation circuit includes a coefficient adjustment module to process said input signal difference values and produce recursive complex multiplication terms.

4. The apparatus of claim 3 wherein said Lagrange interpolation circuit includes a quotient circuit to process said input signal difference values to produce quotient values.

5. The apparatus of claim 4 wherein said Lagrange interpolation circuit includes a complex multiplication term summing circuit to process said recursive complex multiplication terms and said quotient values to generate said complex multiplication term.

6. A method of pre-distorting a signal, comprising:

receiving an in-phase input signal, a quadrature input signal, an in-phase feedback signal, and a quadrature feedback signal;

performing a Lagrange interpolation on said in-phase input signal, said quadrature input signal, said in-phase feedback signal, and said quadrature feedback signal to produce an in-phase pre-distorted signal and a quadrature pre-distorted signal;

producing an error signal between said in-phase input signal and said in-phase feedback signal and between said quadrature input signal and said quadrature feedback signal;

producing a complex multiplication term from said error signal, said in-phase input signal, and said quadrature input signal; and

multiplying said complex multiplication term by said in-phase input signal and said quadrature input signal to produce said in-phase pre-distorted signal and said quadrature pre-distorted signal.

7. The method of claim 6 further comprising generating input signal difference values from said in-phase input signal and said quadrature input signal.

8. The method of claim 7 further comprising processing said input signal difference values to produce recursive complex multiplication terms.

9. The method of claim 8 further comprising processing said input signal difference values to produce quotient values.

10. The method of claim 9 further comprising processing said recursive complex multiplication terms and said quotient values to generate said complex multiplication term.