US-20260128752-A1 - Increasing Bandwidth for Digital Predistortion in Multi-Channel Wideband Communication Systems

Abstract

A method of operating a communications system includes receiving a signal at a digital predistorter (DPD), introducing predistortion to the signal using the DPD, and converting the predistorted signal to an analog signal using a digital-to-analog converter having a first bandwidth. The method also includes amplifying the analog signal, sampling the amplified signal using an analog-to-digital converter having a second bandwidth less than the first bandwidth, and extracting coefficients of the DPD from the sampled signal.

Inventors

• Wan-Jong Kim
• Shawn Patrick Stapleton

Assignees

• DALI SYSTEMS CO., LTD.

Dates

Publication Date

20260507

Application Date

20250826

Claims (7)

1. 1 . A method comprising: receiving a signal at a digital predistorter (DPD) having a DPD bandwidth; introducing predistortion to the signal using the DPD; converting the predistorted signal to an analog signal using a digital-to-analog converter having a first bandwidth; modulating the analog signal using a modulator; amplifying the modulated signal; filtering the amplified signal using a bandwidth less than the first bandwidth; and transmitting the filtered signal using an antenna; and extracting coefficients of the DPD from the sampled signal.
2. 2 . The method of claim 1 comprising: translating a first frequency of the amplified signal to a second frequency signal, different from the first frequency; and sampling the second frequency signal using an analog-to-digital converter having a second bandwidth, different from the first bandwidth.
3. 3 . The method of claim 1 wherein the digital-to-analog converter comprises a first bandwidth.
4. 4 . The method of claim 1 wherein the analog-to-digital converter comprises a second bandwidth that is less than the first bandwidth.
5. 5 . The method of claim 1 wherein the DPD comprises a DPD bandwidth.
6. 6 . The method of claim 1 wherein the digital predistorter adds predistortion to the signal.
7. 7 . The method of claim 1 wherein the digital predistorter adds distortion components associated with the third order and fifth order expansion of the signal.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of the co-pending U.S. patent application titled, “SYSTEM AND METHOD FOR INCREASING BANDWIDTH FOR DIGITAL PREDISTORTION IN MULTI-CHANNEL WIDEBAND COMMUNICATION SYSTEMS” filed on Mar. 22, 2023 and having Ser. No. 18/188,216, now U.S. Pat. No. 12,407,368, issued Sep. 2, 2025, which is a continuation of U.S. patent application titled, “SYSTEM AND METHOD FOR INCREASING BANDWIDTH FOR DIGITAL PREDISTORTION IN MULTI-CHANNEL WIDEBAND COMMUNICATION SYSTEMS” filed on Feb. 7, 2022 and having Ser. No. 17/666,357, which is a continuation of U.S. patent application title, “SYSTEM AND METHOD FOR INCREASING BANDWIDTH FOR DIGITAL PREDISTORTION IN MULTI-CHANNEL WIDEBAND COMMUNICATION SYSTEMS” filed on Jul. 30, 2020 and having Ser. No. 16/943,227, now U.S. Pat. No. 11,245,429, issued Feb. 8, 2022, which is a continuation of U.S. patent application title, “SYSTEM AND METHOD FOR INCREASING BANDWIDTH FOR DIGITAL PREDISTORTION IN MULTI-CHANNEL WIDEBAND COMMUNICATION SYSTEMS” filed on Feb. 19, 2019 and having Ser. No. 16/279,535, now U.S. Pat. No. 10,749,553, issued Aug. 18, 2020, which is a continuation of U.S. patent application title, “SYSTEM AND METHOD FOR INCREASING BANDWIDTH FOR DIGITAL PREDISTORTION IN MULTI-CHANNEL WIDEBAND COMMUNICATION SYSTEMS” filed on Oct. 20, 2015 and having Ser. No. 14/918,371, now U.S. Pat. No. 10,256,853, issued Apr. 9, 2019, which is a continuation of U.S. patent application title, “SYSTEM AND METHOD FOR INCREASING BANDWIDTH FOR DIGITAL PREDISTORTION IN MULTI-CHANNEL WIDEBAND COMMUNICATION SYSTEMS” filed on Sep. 8, 2014 having Ser. No. 14/480,267, now U.S. Pat. No. 9,197,259, issued on Nov. 24, 2015, which is a continuation of U.S. patent application title, “SYSTEM AND METHOD FOR INCREASING BANDWIDTH FOR DIGITAL PREDISTORTION IN MULTI-CHANNEL WIDEBAND COMMUNICATION SYSTEMS” filed on Sep. 24, 2012, having Ser. No. 13/625,760, now U.S. Pat. No. 8,873,674, issued on Oct. 28, 2014, which claims priority to U.S. Provisional patent application filed on Sep. 22, 2011 having Ser. No. 61/538,042. The subject matter of these related applications is hereby incorporated herein by reference. BACKGROUND OF THE INVENTION The present invention generally relates to wideband communication systems using multiplexing modulation techniques. More specifically, the present invention relates to a method of increasing instantaneous or operational bandwidth for digital predistortion linearization in order to compensate for nonlinearities and/or memory effects in multi-channel wideband wireless transmitters. The linearity and efficiency of radio frequency (RF) power amplifiers (PAs) have become critical design issues for non-constant envelope digital modulation schemes with high peak-to-average power ratio (PAR) values. This has happened as a result of the increased importance of spectral efficiency in wireless communication systems. RF PAs have nonlinearities which generate amplitude modulation-amplitude modulation (AM-AM) distortion and amplitude modulation-phase modulation (AM-PM) distortion at the output of the PA. These undesired effects may create spectral regrowth in the adjacent channels, as well as in-band distortion which may degrade the error vector magnitude (EVM). Commercial wireless communication systems may for example employ a bandwidth in the range of 20 MHz to 25 MHz. In such an example, these spectral regrowth effects create an undesired impact over a frequency band which is more than 100 MHz to 125 MHz wide. The potential impacts may include inter-system and intra-system interference. Therefore, there is a need in the art for improved methods and systems related to communications systems. BRIEF SUMMARY OF THE INVENTION It is advisable to employ a linearization technique in RF PA applications in order to eliminate or reduce spectral regrowth and in-band distortion effects. Various RF PA linearization techniques have been proposed in the literature such as feedback, feedforward and predistortion. One of the most promising linearization techniques is baseband digital predistortion (DPD), which takes advantage of recent advances in digital signal processors. DPD can achieve better linearity and higher power efficiency with a reduced system complexity when compared to the widely-used conventional feedforward linearization technique. Moreover, a software implementation provides the digital predistorter with a re-configurability feature which is desirable for multi-standards environments. In addition, a PA using an efficiency enhancement technique such as a Doherty power amplifier (DPA) is able to achieve higher efficiencies than traditional PA designs, at the expense of linearity. Therefore, combining DPD with a DPA using an efficiency enhancement technique has the potential for maximizing system linearity and overall efficiency. Requirements for instantaneous bandwidth (for example, exceeding 25 MHz) for next generation wireless system