Linearization system

• US 10,581,470 B2
• Filed: 06/11/2018
• Issued: 03/03/2020
• Est. Priority Date: 06/09/2017
• Status: Active Grant

• Current Assignee: NanoSemi, Incorporated (Maxlinear Incorporated)
• Original Assignee: NanoSemi, Incorporated (Maxlinear Incorporated)
• Inventors: Megretski, Alexandre, Mahmood, Zohaib, Chuang, Kevin, Li, Yan, Kim, Helen H.
• Primary Examiner(s): Panwalkar, Vineeta S
• Application Number:
  US16/004,594
• Publication Number:
  US 20190260401A1
• Time in Patent Office: 631 Days
• CPC Class Codes: H03F 1/3258 based on polynomial terms
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 2001/0425 with linearisation using predistortion

Abstract

A linearization system computes a robust set of quantities characterizing a nonlinearity of a transmit chain including a power amplifier by combining a current set of quantities characterizing the nonlinearity of the transmit chain with a weighted combination of prior sets of quantities characterizing the nonlinearity of the transmit chain.

Claims

1. A method for digital compensation of a signal chain comprising at least one analog electronic amplification element, the method comprising:

receiving an input signal to the signal chain, the input signal comprising a plurality of batches of the input signal, each batch of the input signal corresponding to a different time interval of the input signal;

receiving an output signal of the signal chain, the output signal comprising a plurality of batches of the output signal, each batch of the output signal corresponding to a different batch of the input signal;

computing coefficient values for a digital compensator from the plurality of batches of the input signal and the corresponding batches of the output signal, including

evaluating, for each batch of the input signal, output of application of a plurality of basis functions to said batch of the input signal,

computing a first average over the plurality of batches of the input signal of a first function of the output of the application of the plurality of basis functions to corresponding batches of the input signal,

computing a second average over the plurality of batches of the input signal of a second function of the output of the application of the plurality of basis functions to corresponding batches of the input signal and corresponding batches of the output signal, and

computing the coefficient values from the first average and the second average; and

processing a desired input signal with the digital compensator configured according to the coefficient values to produce the input signal for the signal chain.

2. The method of claim 1 wherein the first average comprises a decaying average, and the second average comprises a decaying average.

3. The method of claim 2 wherein each decaying average corresponds to an exponentially decaying average according to weighting proportional to λ

<sup>−

i</sup> where i is an increasing index of the batches over time and 0<

λ

<

1 is a real quantity characterizing the rate of exponential decay.

4. The method of claim 1 wherein application of the plurality of basis functions to an i^th batch of the input signal is equivalent to a matrix A_i having a number of columns equal to a number of the basis functions and a number of rows equal to a number of samples in the batch of the input signal, and the first function is equivalent to A_i^HA_i+ρ

I, where A_i^H is a transpose of complex conjugate of A_i and I is an identity matrix, where ρ

is a real number that is zero or is positive.

5. The method of claim 4 wherein the plurality of batches of the input signal comprises n batches of the input signal and the first average comprises a matrix, G_Lⁿ, and wherein computing the first average includes updating a previous value of the first average, G_L⁻

1, computed without the n^th batch of the input signal, using the n^th batch of the input signal G_L^n-1 n^th according to an update equation G_Lⁿ=λ

G_L^n-1+(1−

λ

)(A_n^HA_n+ρ

I).

6. The method of claim 4 wherein an i^th batch of the output signal is equivalent to a vector b_i, having a number of rows equal to a number of samples in the batch of the output signal, and the second function is equivalent to A_i^Hb_i.

7. The method of claim 6 wherein the plurality of batches of the output signal comprises n batches of the output signal and the second average comprises a vector, G_Rⁿ, and wherein computing the second average includes updating the second average using the n^th batch using a previous value of the first average, G_R^n-1, computed without the n^th batch according to an update equation G_Rⁿ=λ

G_R^n-1+(1−

λ

)A_n^Hb_n.

8. The method of claim 1 wherein the first average comprises a matrix, G_Lⁿ, the second average comprises a vector, G_Rⁿ, and computing the coefficient values from the first average and the second average is according to an equation.

9. The method of claim 8 wherein computing the coefficient values from the first and the second averages includes determining said values α

=(G_Lⁿ)⁻

G_Rⁿ subject to bounds on the magnitudes of the coefficient values α

_L≤

α

≤

α

_U.

10. The method of claim 1 wherein each batch of the input signal corresponds to a time interval of the input signal having a same duration.

11. The method of claim 1 wherein the plurality of basis functions comprise products of delayed values or conjugates or magnitudes of delayed values.

12. The method of claim 1 wherein processing the desired input signal with the digital compensator configured according to the coefficient values includes weighting the outputs of application of the basis functions to the desired input signal by the computed coefficient values.

13. A non-transitory machine-readable medium comprising instructions stored thereon, execution of the instructions causing a data processing system to digitally compensate a signal chain comprising at least one analog electronic amplification element by performing operations comprising:

receiving an input signal to the signal chain, the input signal comprising a plurality of batches of the input signal, each batch of the input signal corresponding to a different time interval of the input signal;

receiving an output signal of the signal chain, the output signal comprising a plurality of batches of the output signal, each batch of the output signal corresponding to a different batches of the input signal;

computing coefficient values for a digital compensator from the plurality of batches of the input signal and the corresponding batches of the output signal, including

evaluating, for each batch of the input signal, output of application of a plurality of basis functions to said batches of the input signal,

computing a first average over the plurality of batches of the input signal of a first function of the output of the application of the plurality of basis functions to corresponding batches of the input signal,

computing a second average over the plurality of batch the input signal of a second function of the output of the application of the plurality of basis functions to corresponding batches of the input signal and corresponding batches of the output signal, and

computing the coefficient values from the first average and the second average; and

processing a desired input signal with the digital compensator configured according to the coefficient values to produce the input signal for the signal chain.

14. A digital compensator for compensating a signal chain comprising at least one analog electronic amplification element, the compensator comprising:

a storage for coefficient values for configuration of the digital compensator;

an input for receiving an input signal to the signal chain, the input signal comprising a plurality of batches of the input signal, each batch corresponding to a different time interval of the input signal;

an output for receiving an output signal of the signal chain, the output signal comprising a plurality of batches of the output signal, each batch of the output signal corresponding to a different batches of the input signal; and

a computation element configured to compute coefficient values for a digital compensator from the plurality of batches of the input signal and the corresponding batches of the output signal by

evaluating for each batch of the input signal output of application of a plurality of basis functions to said batch of the input signal,

computing a first average over the plurality of batches of the input signal of a first function of the output of the application of the plurality of basis functions to corresponding batches of the input signal,

computing a second average over the plurality of batch the input signal of a second function of the output of the application of the plurality of basis functions to corresponding batches of the input signal and corresponding batches of the output signal, and

computing the coefficient values from the first average and the second average; and

wherein the digital compensator is configured by storing the computed coefficient values in the storage for the coefficient values to process a desired input signal to produce the input signal for the signal chain.

15. A non-transitory machine-readable medium, comprising a design structure encoded thereon, said design structure comprising elements, when processed in a computer-aided design system, generate a machine-executable representation of a digital compensator for compensating a signal chain comprising at least one analog electronic amplification element, wherein said digital compensator in operation is configured to perform operations comprising:

receiving an input signal to the signal chain, the input signal comprising a plurality of batches of the input signal, each batch of the input signal corresponding to a different time interval of the input signal;

receiving an output signal of the signal chain, the output signal comprising a plurality of batches of the output signal, each batch of the output signal corresponding to a different batch of the input signal;

computing coefficient values for a digital compensator from the plurality of batches of the input signal and the corresponding batches of the output signal, including

evaluating for each batch of the input signal output of application of a plurality of basis functions to said batches of the input signal,

computing a first average over the plurality of batches of the input signal of a first function of the output of the application of the plurality of basis functions to corresponding batches of the input signal,

computing a second average over the plurality of batch the input signal of a second function of the output of the application of the plurality of basis functions to corresponding batches of the input signal and corresponding batches of the output signal, and

computing the coefficient values from the first average and the second average; and

processing a desired input signal with the digital compensator configured according to the coefficient values to produce the input signal for the signal chain.

16. The medium of claim 15 wherein the first average comprises a decaying average, and the second average comprises a decaying average.

17. The medium of claim 16 wherein each decaying average corresponds to an exponentially decaying average according to weighting proportional to λ

<sup>−

i</sup> where i is an increasing index of the batches over time and 0<

λ

<

1 is a real quantity characterizing the rate of exponential decay.

18. The medium of claim 15 wherein application of the plurality of basis functions to an i^th batch of the input signal is equivalent to a matrix A_i having a number of columns equal to a number of the basis functions and a number of rows equal to a number of samples in the batch of the input signal, and the first function is equivalent to A_i^HA_i+ρ

I, where A_i^H is a transpose of complex conjugate of A_i and I is an identity matrix, where ρ

is a real number that is zero or is positive.

19. The medium of claim 15 wherein the first average comprises a matrix, G_Lⁿ, the second average comprises a vector, G_Rⁿ, and computing the coefficient values from the first average and the second average is according to an equation α

=(G_Lⁿ)<sup>−

1</sup>G_Rⁿ.

20. The medium of claim 15 wherein:

application of the plurality of basis functions to an i^th batch of the input signal is equivalent to a matrix A_i having a number of columns equal to a number of the basis functions and a number of rows equal to a number of samples in the batch of the input signal, and the first function is equivalent to A_i^HA_i+ρ

I, where A_i^H is a transpose of complex conjugate of A_i and I is an identity matrix, where ρ

is a real number that is zero or is positive;

the plurality of batches of the input signal comprises n batches of the input signal and the first average comprises a matrix, G_Lⁿ, and wherein computing the first average includes updating a previous value of the first average, G_L^n-1, computed without the n^th batch of the input signal, using the n^th batch of the input signal according to an update equation G_Lⁿ=λ

G_L^n-1+(1−

λ

)(A_n^HA_n+ρ

I);

an i^th batch of the output signal is equivalent to a vector b_i, having a number of rows equal to a number of samples in the batch of the output signal, and the second function is equivalent to A_i^Hb_i; and

the plurality of batches of the output signal comprises n batches of the output signal and the second average comprises a vector, G_Rⁿ, and wherein computing the second average includes updating the second average using the n^th batch using an previous value of the first average, G_R^n-1 computed without the n^th batch according to an update equation G_Rⁿ=λ

G_R^n-1+(1−

λ

)A_n^Hb_n.