EP-4742531-A1 - DIGITAL PRE-DISTORTION

EP4742531A1EP 4742531 A1EP4742531 A1EP 4742531A1EP-4742531-A1

Abstract

An apparatus for digital pre-distortion of a real valued signal in a real domain not a complex domain to produce a pre-distorted real valued signal (30), wherein digital pre-distortion is performed based on a comparison between a feedback real-valued signal signal (123), a real-valued signal to be transmitted (121) and/or the pre-distorted version of this signal (30).

Inventors

STEDILE-RIBEIRO, Thales
JELONNEK, Björn
FELGENTREFF, TILMAN

Assignees

Nokia Solutions and Networks Oy

Dates

Publication Date: 20260513
Application Date: 20251105

Claims (15)

An apparatus comprising: a digital signal processor circuitry (112) comprising a digital predistortion circuitry; a power amplifier (60); at least one processor (402); and at least one memory (404) comprising instructions which, when executed by the at least one processor, cause the apparatus at least to: determine a pre-distorted real valued signal 30, wherein the determination of the pre-distorted real valued signal (30) comprises: (i) applying a digital pre-distortion (20) in the real domain to a real-valued input signal (121) to obtain the pre-distorted real valued signal (30) to be transmitted to the power amplifier; (ii) measuring an output of the power amplifier representative of a distorted real-valued signal (61); (iii) determining an error based on the distorted real-valued signal (61) and at least one of the a) the real-valued input signal (121) b) the digital pre-distorted signal (30); (iv) modifying the digital pre-distortion in the real domain based on the determined error.
The apparatus as claimed in claim 1, wherein the apparatus is further caused to transmit the pre-distorted real valued signal over a first bandwidth of transmission frequencies and to adapt a real valued signal for transmission at at least frequencies outside the first bandwidth that have a capability to have an effect within the first bandwidth.
The apparatus as claimed in claim 1, wherein the real valued signal is a time-variable real valued signal and has a bandwidth from zero frequency, DC, to half the sampling frequency.
The apparatus as claimed in any preceding claim, wherein the pre-distorted real valued signal is provided, as a controlled waveform, directly from a digital signal processing block to a digital to analogue converter at a target frequency as a real valued signal.
The apparatus as claimed in any preceding claim, wherein the pre-distorted real valued signal is provided directly to a digital to analogue converter from a digital signal processor block, bypassing up-sampling and up-conversion blocks used for complex valued signals.
The apparatus as claimed in any preceding claim, wherein the pre-distorted real valued signal is configured to cancel at least one of i) even-order distortion ii) odd-order distortion at a power amplifier for a transmitting frequency, to linearize an output of the power amplifier at the transmitting frequency.
The apparatus as claimed in any preceding claim, wherein the apparatus is further caused to adapt the digital predistortion coefficients for a model that generates the distorted components with an amplitude and phase capable of cancelling distortion generated by a power amplifier.
The apparatus as claimed in any preceding claim, wherein the apparatus is further caused to transmit the pre-distorted real valued signal over a first bandwidth of transmission frequencies, and to adapt a signal for transmission at at least frequencies below a frequency of the transmitted carrier of lowest frequency or above a frequency of the transmitted carrier of highest frequency.
The apparatus as claimed in any preceding claim, comprising an input path for the pre-distorted real valued signal to a power amplifier wherein the input path is configured to have a bandwidth that is extended significantly beyond a transmission bandwidth.
The apparatus as claimed in claim 9, wherein the input path is configured to have a bandwidth that is extended significantly beyond a transmission bandwidth at frequencies below the transmission bandwidth.
The apparatus as claimed in claim 10, wherein the input path is configured to have a bandwidth that is extended to include DC.
The apparatus as claimed in any preceding claim, comprising a matching network configured to allow low frequencies to reach a gate node of a power amplifier transistor.
The apparatus as claimed in any preceding claim, comprising a transistor bias circuit configured to allow low frequencies coming from a power amplifier input to reach a gate node of a transistor of the power amplifier.
An electronic device comprising the apparatus as claimed in any preceding claim.
A method comprising: determining a pre-distorted real valued signal 30, wherein the determination of the pre-distorted real valued signal (30) comprises: applying a digital pre-distortion (20) in the real domain to a real-valued input signal (121) to obtain the pre-distorted real valued signal (30) to be transmitted to be transmitted to a power amplifier; measuring an output of the power amplifier representative of a distorted real-valued signal (61); determining an error based on the distorted real-valued signal (61) and at least one of the a) the real-valued input signal (121) b) the digital pre-distorted signal (30); modifying the digital pre-distortion in the real domain based on the determined error.

Description

TECHNOLOGICAL FIELD Examples of the disclosure relate to digital pre-distortion (DPD). Examples of the disclosure relate to digital pre-distortion (DPD) before power amplification. BACKGROUND Power amplifiers (PAs) are efficient at nonlinear operating points. It is desirable to linearize the PA output so that they operate efficiently while meeting linearity specifications. One way to achieve a linearized PA output is by pre-distorting the input signal to the PA, so that the signal output from the PA meets the specified linearity. Pre-distortion can, for example, create signal distortion components with controlled (frequency dependent) amplitude and phase that is the complement of the signal distortion inherent at the PA. The objective is that distortion at the PA negates the introduced distortion producing a near linear transfer characteristic. BRIEF SUMMARY The scope of protection sought for various example embodiments of the invention is set out by the independent claims. The example embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various example embodiments of the invention. According to various, but not necessarily all, examples there is provided an apparatus. The apparatus may comprise a digital signal processor circuitry comprising a DPD circuitry; a power amplifier; at least one processor; and at least one memory comprising instructions which, when executed by the at least one processor, cause the apparatus at least to: determine a pre-distorted real valued signal, wherein the determination of the pre-distorted real valued signal comprises: applying a digital pre-distortion in a real domain to a real-valued input signal to obtain the pre-distorted real valued signal to be transmitted to the power amplifier; measuring an output of the power amplifier representative of a distorted real-valued signal; determining an error based on the distorted real-valued signal and at least one of the a) the real-valued input signal b) the digital pre-distorted signal; modifying the digital pre-distortion in the real domain based on the determined error. In some but not necessarily all examples, the pre-distorted real valued signal is transmitted over a first bandwidth of transmission frequencies. And wherein the digital pre-distortion of the real valued signal in the real domain is configured to adapt a real valued signal for transmission at at least frequencies outside the first bandwidth that have a capability to have an effect within the first bandwidth. In some but not necessarily all examples, wherein the real valued signal is a time-variable real valued signal and has a bandwidth from zero frequency (DC) to half the sampling frequency. In some but not necessarily all examples, the pre-distorted real valued signal is provided, as a controlled waveform, directly from a digital signal processing block to a digital to analogue converter (DAC) at a target frequency as a real valued signal. In some but not necessarily all examples, the pre-distorted real valued signal is provided directly to a digital to analogue converter (DAC) from a digital signal processor block, bypassing up-sampling and up-conversion blocks used for complex valued signals. In some but not necessarily all examples, the pre-distorted real valued signal is configured to cancel even-order distortion at a power amplifier for a transmitting frequency, to linearize an output of the power amplifier at the transmitting frequency. In some but not necessarily all examples, the pre-distorted real valued signal is configured to cancel even-order distortion and odd-order distortion at a power amplifier for a transmitting frequency, to linearize an output of the power amplifier at the transmitting frequency. In some but not necessarily all examples, the pre-distorted real valued signal is configured to cancel odd-order distortion at a power amplifier for a transmitting frequency, to linearize an output of the power amplifier at the transmitting frequency. In some but not necessarily all examples, the digital predistortion adapts coefficients for a model that generates the distorted components with an amplitude and phase capable of cancelling distortion generated by a power amplifier. In some but not necessarily all examples, the pre-distorted real valued signal is transmitted over a first bandwidth of transmission frequencies, and, the digital pre-distortion in the real domain is configured to additionally adapt a signal for transmission at least at least frequencies below a frequency of the transmitted carrier of lowest frequency or above a frequency of the transmitted carrier of highest frequency. In some but not necessarily all examples, the apparatus comprises: an input path for the pre-distorted real valued signal to a power amplifier wherein the input path is configured to have a bandwidth that is extended significantly