Method, Apparatus and Arrangement for Linearizing of a Transmitter Array

Patent metadata

Field	Value
Publication number	US-2020395662-A1
Application number	US-201816767390-A
Country	US
Kind code	A1
Filing date	Nov 23, 2018
Priority date	Dec 5, 2017
Publication date	Dec 17, 2020
Grant date	—

Abstract

Method, apparatus and arrangement for linearizing of a transmitter array having a plurality of non-linear branches for transmitting into a predetermined direction, wherein the non-linear branches may purposively be made different to obtain varying responses of the non-linear branches over the transmitter array. A combined array response is determined via a feedback structure that models an array response to the predetermined direction and predistortion coefficients are determined based on the measured array response. A feedback circuit with a plurality of feedback branches can be used for feeding back individual response signals at the outputs of the non-linear branches through phase shift and attenuation units of the feedback branches, and for combining the response signals at the outputs of the feedback branches, wherein phase shift and attenuation of each feedback branch is controlled to model a transmission channel of the individual response signals to a receiver in a predetermined direction.

First claim

1 . A method of linearizing a transmitter array having a plurality of non-linear branches for transmitting into a predetermined direction, the method comprising:
varying responses of individual non-linear branches over the transmitter array to increase variability of non-linearity of the non-linear branches in their output characteristics; determining predistortion coefficients based on a combined array response for the predetermined direction; and using the determined predistortion coefficients for applying predistortion to an input signal that is transmitted via the plurality of non-linear branches of the transmitter array.

2 . The method according to claim 1 , wherein the varying comprises at least one of:
providing different types or classes of amplifiers in the non-linear branches, providing phase shifters with phase-word dependent gains in the non-linear branches, varying bias points and/or input amplitudes and/or gains of amplifier blocks and/or operational voltages of respective amplifiers in the non-linear branches to provide a mixture of compressing and expanding amplifiers in the non-linear branches, or providing different couplings between amplifiers and/or antennas of the non-linear branches.

3 . The method according to claim 1 , further comprising measuring a combined array response via a feedback structure that models an array response to the predetermined direction.

4 . The method according to claim 1 , wherein the varying is adapted to provide a sufficient difference between the non-linear branches, that can be used for over-the-air linearization.

5 . The method according to claim 1 , wherein the measuring comprises feeding back individual response signals at the outputs of the non-linear branches via respective feedback branches of a feedback circuit, controlling phase shift and attenuation of each feedback branch to model a transmission channel of the individual response signals to a receiver in the predetermined direction, combining the response signals at the outputs of the feedback branches, and measuring the combined feedback signal.

6 . The method according to claim 1 , wherein the predetermined direction is not an intended transmission direction.

7 . The method according to claim 1 , wherein the determining comprises applying least squares fitting and/or adaptive methods comprising at least one of:
least mean squares, recursive least squares, or Kalman-filtering to solve the coefficients.

8 . An apparatus for controlling linearization of a transmitter array having a plurality of non-linear branches for transmitting into a predetermined direction, the apparatus comprising:
branch control circuitry configured to vary responses of the non-linear branches over the transmitter array to increase variability of non-linearity of the non-linear branches in their output characteristics; circuitry configured to determine a combined array response in the predetermined direction, coefficient setting circuitry configured to determine predistortion coefficients based on the determined array response and for supplying the determined predistortion coefficients to a common predistortion unit for applying predistortion to an input signal that is transmitted via the plurality of non-linear branches of the transmitter array.

9 . The apparatus according to claim 8 , wherein the branch control circuitry is adapted to control bias points and/or input amplitudes and/or gains of amplifier blocks and/or operational voltages of respective amplifiers in the non-linear branches to provide a mixture of compressing and expanding amplifiers in the non-linear branches.

10 . A method of determining predistortion coefficients for a group linearization of a plurality of non-linear branches of a transmitter array, the method comprising:
feeding back individual response signals at the outputs of the non-linear branches via respective feedback branches of a feedback circuit; controlling phase shift and attenuation of each feedback branch to model a transmission channel of the individual response signals to a receiver in a predetermined direction, combining the response signals at the outputs of the feedback branches; and determining the combined feedback signal to calculate the predistortion coefficients for the group linearization.

11 . The method according to claim 10 , wherein the combining of the response signals is done in the radio frequency domain.

12 . An arrangement for determining predistortion coefficients for a group linearization of a plurality of non-linear branches of a transmitter array, the arrangement comprising:
a feedback circuit comprising a plurality of feedback branches for feeding back individual response signals at the outputs of the non-linear branches through phase shift and attenuation circuitry of the feedback branches, and for combining the response signals at the outputs of the feedback branches; feedback control circuitry configured to control phase shift and attenuation of each feedback branch to model a transmission channel of the individual response signals to a receiver in a predetermined direction; and measuring circuitry configured to measure the combined feedback signal.

13 . The arrangement according to claim 12 , wherein the feedback circuit comprises a plurality of coupling elements for sampling the individual response signals before being fed back through the phase shift and attenuation circuitry.

14 . The arrangement according to claim 12 , wherein the feedback control circuitry is adapted to control the phase shift of each feedback branch to provide a phase value which has negative sign compared to a phase value selected for a related one of the non-linear branches to steer a transmission beam of the transmitter array into the predetermined direction.

15 . The arrangement according to claim 11 , wherein the feedback circuit comprises a plurality of coupling elements at the outputs of the non-linear branches for separately measuring neighbor coupling and impedance matching effects.

16 . A transmitter array having a plurality of non-linear branches for transmitting into a predetermined direction, the transmitter array comprising at least one of:
an apparatus according to claim 8 , or an arrangement for determining predistortion coefficients for a group linearization of a plurality of non-linear branches of a transmitter array, the arrangement comprising:
a feedback circuit comprising a plurality of feedback branches for feeding back individual response signals at the outputs of the non-linear branches through phase shift and attenuation circuitry of the feedback branches, and for combining the response signals at the outputs of the feedback branches;
feedback control circuitry configured to control phase shift and attenuation of each feedback branch to model a transmission channel of the individual response signals to a receiver in a predetermined direction; and
measuring circuitry configured to measure the combined feedback signal.

17 . A mobile device for communicating with a wireless communication network, the mobile device comprising a transmitter array according to claim 16 .

18 . A radio access device for providing access to a wireless communication network, the radio access device comprising a transmitter array according to claim 16 .

19 . A computer program product comprising a computer readable medium having code configured to cause the steps of claim 1 , when the code is run on a computer device.

Assignees

• Nokia Technologies Oy

Inventors

• Tervo Nuutti
• Parssinen Aarno Tapio
• Leinonen Marko

Classifications

• H04B2001/0425

  with linearisation using predistortion · CPC title

• H04B7/0617

  for beam forming · CPC title

• H01Q3/267 Primary

  Phased-array testing or checking devices · CPC title

• H03F1/3247

  using feedback acting on predistortion circuits (H03F1/3264 takes precedence) · CPC title

• H04B17/13 Primary

  of power amplifiers, e.g. gain or non-linearity · CPC title