Digital pre-distortion systems in transmitters

Patent metadata

Field	Value
Publication number	US-9608676-B2
Application number	US-201313940263-A
Country	US
Kind code	B2
Filing date	Jul 12, 2013
Priority date	Jul 12, 2013
Publication date	Mar 28, 2017
Grant date	Mar 28, 2017

Abstract

Various digital pre-distortion systems for use in transmitters are disclosed. The digital pre-distortion system comprises an observing path, which performs either undersampling or radio frequency sampling of the output of a power amplifier. Undersampling may be performed at a rate, which causes aliasing to occur in the undersampled frequency domain. Both undersampling and radio frequency sampling reduces the complexity of the digital pre-distortion system by removing any down mixing modules or anti-aliasing modules, while maintaining reasonable performance of the digital pre-distortion systems.

First claim

What is claimed is:

1. A digital pre-distortion circuitry for observing and correcting non-linearity in a transmitter, the digital pre-distortion circuitry comprising:
an observing path configured to sample a multi-band output signal of a power amplifier, said observing path comprising a radio frequency (RF) analog-to-digital converter (ADC) configured to sample the multi-band output signal of the power amplifier at a first sampling rate that is equal to or more than twice a highest upper cut off frequency of a band centered at a highest frequency of the multi-band output signal to produce a multi-band digital signal without overlapping between bands, wherein the observing path does not convert the multi-band output signal of the power amplifier to an intermediate frequency; and
a digital signal processing circuit for down sampling, in a digital domain, the multi-band digital signal produced by the RF ADC to generate a down sampled multi-band digital signal having a sampling rate that matches the transmitter and is lower than the first sampling rate, and measuring the non-linearity of the power amplifier based on the down sampled multi-band digital signal.

2. The digital pre-distortion circuitry of claim 1 , wherein:
the observing path does not include an anti-aliasing filter.

3. The digital pre-distortion circuitry of claim 1 , wherein:
the digital signal processing circuit is configured to remove artifacts and/or noise caused by the sampling process of the RF ADC through an adaptive algorithms engine configured to compare known multi-band signals being transmitted in a path towards the power amplifier and the multi-band digital signal respectively.

4. The digital pre-distortion circuitry of claim 1 , wherein the digital signal processing circuit comprises:
a multi-band separation engine comprising bandpass filters configured to separate the multi-band digital signal into separated bands.

5. The digital pre-distortion circuitry of claim 4 , wherein the digital signal processing circuit further comprises at least two adaptive algorithms engines configured to process the separated bands in parallel to compare at least one known multi-band signals being transmitted in a path towards the power amplifier and at least one respective separated bands to measure and/or correct the non-linearity of the power amplifier.

6. The digital pre-distortion circuitry of claim 4 , wherein the digital signal processing circuit further comprises one or more adaptive engines configured to process the separated bands one band at a time or a subset of the separated bands at a time to compare at least one known multi-band signals being transmitted in a path towards the power amplifier and at least one respective separated bands to measure and/or correct the non-linearity of the power amplifier.

7. The digital pre-distortion circuitry of claim 1 , wherein:
the digital signal processing module comprises a multi-band separation engine configured to separate the multi-band digital signal into M separated bands using known multi-band signals being transmitted in a path towards the power amplifier respective to the M bands.

8. The digital pre-distortion circuitry of claim 7 , wherein the digital signal processing circuit further comprises at least two adaptive algorithms engines configured to process the separated bands in parallel to compare at least one known multi-band signals being transmitted in a path towards the power amplifier and at least one respective separated bands to measure and/or correct the non-linearity of the power amplifier.

9. The digital pre-distortion circuitry of claim 7 , wherein the digital signal processing circuit further comprises one or more adaptive engines configured to process the separated bands one band at a time or a subset of the separated bands at a time to compare at least one known multi-band signals being transmitted in a path towards the power amplifier and at least one respective separated bands to measure and/or correct the non-linearity of the power amplifier.

10. The digital pre-distortion circuitry of claim 1 , wherein the sampling rate is at least 2 gigahertz.

11. A digital pre-distortion method for observing and correcting non-linearity in a transmitter, the method comprising:
sampling a multi-band output signal of a power amplifier in an observing path by a radio frequency (RF) analog-to-digital converter (ADC) at a first sampling rate that is equal to or more than twice a highest upper cut off frequency of a band centered at a highest frequency of the multi-band output signal to produce a multi-band digital signal wherein sampling in the observing path does not include converting the multi-band the output signal of the power amplifier to an intermediate frequency, wherein sampling in the observing path does not include converting the multi-band the output signal of the power amplifier to an intermediate frequency; and
down sampling, by the digital signal processing circuit in a digital domain, the multi-band digital signal produced by the RF ADC to generate a down sampled multi-band digital signal having a sampling rate that matches the transmitter and is lower than the first sampling rate;
measuring, by the digital signal processing circuit, the non-linearity of the power amplifier using a signal being transmitted in a forward path and the down sampled multi-band digital signal; and
correcting, by the digital signal processing circuit, the non-linearity of the power amplifier.

12. The digital pre-distortion method of claim 11 , wherein sampling in the observing path does not include an anti-aliasing filter.

13. The digital pre-distortion method of claim 11 , further comprising:
removing, by the digital signal processing circuit, artifacts and/or noise caused by the sampling process of the RF ADC through an adaptive algorithms engine configured to compare known multi-band signals being transmitted in a path towards the power amplifier and the multi-band digital signal respectively.

14. The digital pre-distortion method of claim 11 , further comprising:
separating the multi-band digital signal into separated bands by a multi-band separation engine comprising bandpass filters.

15. The digital pre-distortion method of claim 14 , further comprising:
processing, by at least two adaptive algorithms engines of the digital signal processing circuit, the separated bands in parallel to compare at least one known multi-band signals being transmitted in a path towards the power amplifier and at least one respective separated bands to measure and/or correct the non-linearity of the power amplifier.

16. The digital pre-distortion method of claim 15 , further comprising:
processing, by one or more adaptive engines of the digital signal processing circuit, the separated bands one band at a time or a subset of the separated bands at a time to compare at least one known multi-band signals being transmitted in a path towards the power amplifier and at least one respective separated bands to measure and/or correct the non-linearity of the power amplifier.

17. The digital pre-distortion method of claim 11 , further comprising:
separating, by a multi-band separation engine in the digital signal processing module, the multi-band digital signal into M separated bands using known multi-band signals being transmitted in a path towards the power amplifier respective to the M bands.

18. The digital pre-distortion method of claim 17 , further comprising:
processing, by at least two adaptive algorithms engines of the digital signal processing circuit, th

Assignees

• Analog Devices Tech
• Analog Devices Global

Inventors

• Chen Dong

Classifications

• H03F2201/3209

  the amplifier comprising means for compensating memory effects · CPC title

• H03F2201/3206

  Multiple channels are combined and amplified by only one amplifier · CPC title

• H03F2201/3212

  Using a control circuit to adjust amplitude and phase of a signal in a signal path · CPC title

• H03F2201/3233

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

• H03F2201/3224

  Predistortion being done for compensating memory effects · CPC title