Digital pre-distortion for high bandwidth signals

Patent metadata

Field	Value
Publication number	US-9385764-B2
Application number	US-201214651920-A
Country	US
Kind code	B2
Filing date	Dec 13, 2012
Priority date	Dec 13, 2012
Publication date	Jul 5, 2016
Grant date	Jul 5, 2016

Abstract

A digital pre-distortion arrangement is disclosed. The arrangement comprises a respective filter bank for each of two or more initial signals to be amplified simultaneously by a non-linear power amplifier, N combiners, N pre-distorters and a multiplexer. Each respective filter bank comprises N interrelated filters. Multiplexed impulse responses of the interrelated filters define an overall filter function comprising a pass band associated with a transmission frequency of the initial signal. Each respective filter bank is configured to filter the respective initial signal in each of the interrelated filters to produce N digital filtered signals. The initial signal and each of the digital filtered signals have sample rate R. Each of the combiners is configured to combine corresponding digital filtered signals of each of the two or more initial signals to produce a composite digital signal having sample rate R. Each of the pre-distorters is configured to apply digital pre-distortion at a processing rate R to a respective one of the composite digital signals to produce a pre-distorted composite digital signal having sample rate R. The multiplexer is configured to multiplex the N pre-distorted composite digital signals to produce a pre-distorted digital signal having a sample rate N times R, wherein the pre-distorted digital signal comprises a signal component of each of the two or more initial signals and N times R is greater or equal to a total bandwidth comprising the transmission frequencies of the two or more initial signals. Corresponding method, transmitter and wireless communication device are also disclosed.

First claim

The invention claimed is:

1. A digital pre-distortion method comprising:
for each of two or more initial signals to be amplified simultaneously by a non-linear power amplifier, filtering the initial signal in each of N interrelated filters of a respective filter bank to produce N digital filtered signals, N being an integer greater than 1, wherein the initial signal and each of the digital filtered signals have a first sample rate R and multiplexed impulse responses of the interrelated filters of the respective filter bank define an overall filter function comprising a pass band associated with a transmission frequency of the initial signal;
combining corresponding digital filtered signals of each of the two or more initial signals to produce N composite digital signals having the first sample rate R;
applying digital pre-distortion at a processing rate R to each of the composite digital signals to produce N pre-distorted composite digital signals having the first sample rate R; and
multiplexing the N pre-distorted composite digital signals to produce a pre-distorted digital signal having a second sample rate N times R,

wherein:
the pre-distorted digital signal comprises a signal component of each of the two or more initial signals;
the processing rate R and the sample rate R, are equal; and
the second sample rate N times R is greater than or equal to a total bandwidth comprising the transmission frequencies of the two or more initial signals.

2. The method of claim 1 further comprising:
digital-to-analog converting the pre-distorted digital signal to a pre-distorted analog signal; and
amplifying the pre-distorted analog signal in the non-linear power amplifier to produce an amplified signal.

3. The method of claim 1 further comprising:
digital-to-analog converting the pre-distorted digital signal to a pre-distorted analog signal;
mixing the pre-distorted analog signal with a first radio frequency modulation signal to produce a radio frequency pre-distorted analog signal; and
amplifying the radio frequency pre-distorted analog signal in the non-linear power amplifier to produce an amplified signal.

4. The method of claim 2 further comprising transmitting the amplified signal over a transmission medium.

5. The method of claim 1 wherein each of the two or more initial signals is a baseband signal.

6. The method of claim 5 further comprising mixing each of the two or more initial signals with a respective positioning frequency before filtering the initial signal.

7. The method of claim 5 further comprising:
delaying each of the initial signals to produce delayed initial signals;
comparing the delayed initial signals with a digital feedback signal to produce a pre-distortion error estimation, wherein the digital feedback signal represents the pre-distorted digital signal influenced by the non-linear power amplifier; and
adapting the digital pre-distortion based on the pre-distortion error estimation.

8. The method of claim 7 wherein comparing the delayed initial signals with a digital feedback signal comprises:
mixing each of the delayed initial signals with a respective feedback positioning frequency to produce respective frequency shifted delayed initial signals;
combining the respective frequency shifted delayed initial signals to produce a composite reference signal;
for each transmission frequency of the two or more initial signals, filtering the digital feedback signal with a respective receiver filter to produce a filtered feedback signal and mixing the filtered feedback signal with the respective feedback positioning frequency to produce a frequency shifted baseband feedback signal;
combining the frequency shifted baseband feedback signals to produce a composite feedback signal; and
comparing the composite reference signal with the composite feedback signal to produce the pre-distortion error estimation.

9. The method of claim 8 , wherein adapting the digital pre-distortion based on the pre-distortion error estimation comprises:
determining correction parameters based on the pre-distortion error estimation; and
adapting the digital pre-distortion based on the correction parameters.

10. A digital pre-distortion arrangement comprising:
a respective filter bank for each of two or more initial signals to be amplified simultaneously by a non-linear power amplifier, wherein each respective filter bank comprises N interrelated filters and is configured to filter the initial signal in each of the interrelated filters to produce N digital filtered signals, N being an integer greater than 1, wherein the initial signal and each of the digital filtered signals have a first sample rate R and wherein multiplexed impulse responses of the interrelated filters of the respective filter bank define an overall filter function comprising a pass band associated with a transmission frequency of the initial signal;
N combiners, each configured to combine corresponding digital filtered signals of each of the two or more initial signals to produce a composite digital signal having the first sample rate R;
N pre-distorters, each configured to apply digital pre-distortion at a processing rate R to a respective one of the composite digital signals to produce a pre-distorted composite digital signal having the first sample rate R; and
a multiplexer configured to multiplex the N pre-distorted composite digital signals to produce a pre-distorted digital signal having a second sample rate N times R;

wherein:
the pre-distorted digital signal comprises a signal component of each of the two or more initial signals;
the processing rate R and the first sample rate R are equal; and
the second sample rate N times R is greater or equal to a total bandwidth comprising the transmission frequencies of the two or more initial signals.

11. The arrangement of claim 10 further comprising:
a digital-to-analog converter configured to convert the pre-distorted digital signal to a pre-distorted analog signal; and
the non-linear power amplifier configured to amplify the pre-distorted analog signal in the non-linear power amplifier to produce an amplified signal.

12. The arrangement of claim 11 further comprising a mixer configured to mix the pre-distorted analog signal with a first radio frequency modulation signal before amplification.

13. The arrangement of claim 10 wherein each of the two or more initial signals is a baseband signal.

14. The arrangement of claim 13 further comprising, a mixer for each of the two or more initial signals, each mixer configured to mix the initial signal with a respective positioning frequency before filtering of the initial signal.

15. The arrangement of claim 13 further comprising:
one or more delay elements configured to delay each of the initial signals to produce delayed initial signals; and
an adaptor circuit configured to compare the delayed initial signals with a digital feedback signal to produce a pre-distortion error estimation, wherein the digital feedback signal represents the pre-distorted digital signal influenced by the non-linear power amplifier, and to adapt the digital pre-distortion based on the pre-distortion error estimation.

16. The arrangement of claim 15 wherein the adaptor circuit comprises:
a mixer for each of the two or more initial signals configured to mix the delayed initial signal with a respective feedback positioning frequency to produce a respective frequency shifted delayed initial signal;
a combiner configured to combine the respective frequency shifted delayed initial signals to produce a composite

Assignees

• Ericsson Telefon Ab L M
• Ericsson Telefon Ab L M

Inventors

• Rexberg Leonard
• Malmqvist Håkan

Classifications

• H03F2201/3233

  Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion · CPC title

• H03F1/3247 Primary

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

• H04B1/0475 Primary

  with means for limiting noise, interference or distortion (H04B1/0483 takes precedence) · CPC title

• H03F3/24

  of transmitter output stages · CPC title

• H04B2001/0425

  with linearisation using predistortion · CPC title