WCDMA系统中功放的数字预畸变技术的研究
摘要
WCDMA系统具有多载波,多电平等特点,对功率放大器的线性度提出了较高的要求,线性化技术可分负反馈,前馈和线性预畸变技术,本文主要讨论其中的数字预畸变技术。
对于功率放大器线性度的改善,传统预失真算法存在低效率和弱自适应性的缺点,尤其是在高峰均比的WCDMA,系统中。本文重点研究一种新型的基于有记忆多项式的数字基带预失真算法,该算法有效的改善了功放的非线性性,抵消了高阶互调失真,具有较强的适应性。首先,讨论了功放非线性性对WCDMA系统信号传输的影响,定量的分析了信号幅度,相位,功率谱密度,传输误比特率等指标的变化。其次,完成了模拟预畸变和数字预畸变的比较,最后对数字预畸变系统的实现进行了讨论,构建了整个数字预畸变系统框架,并通过浮点实验和定点实验,验证了该算法的高效性和实用性。
The WCDMA system, with the multi-carrier and multi-level, requires high linearity of power amplifier. The linearity technologies can be classified into three classes. This paper deals with the digital baseband predistortion technology.
Low efficiency and poor adaptive ability are the main problems of the traditional predistortion algorithm in improving the linearity of power amplifier, especially in WCDMA system where peak-to-average power ratio is high. Firstly, we discussed how the nonlinearity affects the transmission of the WCDMA signals, illustrating the effects of the nonlinearity to the signal amplitude, the signal phase, the power spectrum density and the bits error ratio. Secondly, compared the radio predistortion and DLP technology. Finally, we discussed some key details in implementing the DLP module and the hardware framework. The results of floating-point test and fixing-point test both verify the validity and practicability of this algorithm.
对于功率放大器线性度的改善,传统预失真算法存在低效率和弱自适应性的缺点,尤其是在高峰均比的WCDMA,系统中。本文重点研究一种新型的基于有记忆多项式的数字基带预失真算法,该算法有效的改善了功放的非线性性,抵消了高阶互调失真,具有较强的适应性。首先,讨论了功放非线性性对WCDMA系统信号传输的影响,定量的分析了信号幅度,相位,功率谱密度,传输误比特率等指标的变化。其次,完成了模拟预畸变和数字预畸变的比较,最后对数字预畸变系统的实现进行了讨论,构建了整个数字预畸变系统框架,并通过浮点实验和定点实验,验证了该算法的高效性和实用性。
The WCDMA system, with the multi-carrier and multi-level, requires high linearity of power amplifier. The linearity technologies can be classified into three classes. This paper deals with the digital baseband predistortion technology.
Low efficiency and poor adaptive ability are the main problems of the traditional predistortion algorithm in improving the linearity of power amplifier, especially in WCDMA system where peak-to-average power ratio is high. Firstly, we discussed how the nonlinearity affects the transmission of the WCDMA signals, illustrating the effects of the nonlinearity to the signal amplitude, the signal phase, the power spectrum density and the bits error ratio. Secondly, compared the radio predistortion and DLP technology. Finally, we discussed some key details in implementing the DLP module and the hardware framework. The results of floating-point test and fixing-point test both verify the validity and practicability of this algorithm.
引文
[1]S.Boumaiza and F.M.Ghannouchi,"Realistic Power-Amplifiers Characterization with Application to Baseband Digital Predistortion for 3G Base Stations",IEEE Trans.Microwave Theory and Techniques,Vol.50,No.12,pp.3016-3021,Dec.2002.
[2]L.Ding,Digital Predistortion of Power Amplifiers for Wireless Applications,Ph.D Dissertation,Georgia Institute of Technology,Mar.2004.
[3]D.B.Chester,"Digital IF Filter Technology for 3G Systems:An Introduction",IEEE Com.Maga.pp.102-107,Feb.1999.
[4]M.C.Jeruchim,P.Balaban,and K.S.Shanmugan,Simulation of Communication Systems Modeling,Methodology,and Techniques,KLUWER ACADEMIC,2000.
[5]S.M.McBeath,D.T.Pinckley,and J.R.Cruz,"W-CDMA Power Amplifier Modeling",pp.2243-2247,VTC 2002 Fall.
[6]B.Widrow and J.R.Glover et.al.,"Adaptive Noise Cancelling:Principles and Applications",Proc.IEEE,Vol.63,No.12,pp.1692-1715,Dec.1975.
[7]F.Zavosh,M.Thomas et.al.,"Digital Predistortion Techniques for RF Power Amplifiers with CDMA Applications",Microwave Journal,1999.
[8]UE Radio Transmission and Reception(FDD),3GPP 25.101.
[9]P.B.Kenington,High-Linearity RF Amplifier Design,Arrech House,Boston,London,2000
[10]P.B.Kenington,et.al."An Ultra-Broadband Power Amplifier using Dynamically Controlled Linearisation" Proc.of IEEE International Symposium on Microwave Theory and Techniques,Anaheim,California,USA,Vol.1,13-19 June 1999,pp.355-358
[11]Nojima,T.,and T.,Konno,"Cuber predistorter linaerizer for relay equipment in 800MHz band land mobile telephone system," IEEE Trans.on Vehicular,Vol.VT-34,November 1985,pp169-177
[12]Joyce Van de Vetge,Fundamentals of Digital Signal Processing,Publishing House of Electronics Industry,Beijing,2003.
[13]C.R.Anderson,S.Krishnamoorthy et.al.,"Antenna Isolation,Wideband Multipath Propagation Measurements,and Interference Mitigation for On-frequency Repeaters",Globalcomm,2004.
[2]L.Ding,Digital Predistortion of Power Amplifiers for Wireless Applications,Ph.D Dissertation,Georgia Institute of Technology,Mar.2004.
[3]D.B.Chester,"Digital IF Filter Technology for 3G Systems:An Introduction",IEEE Com.Maga.pp.102-107,Feb.1999.
[4]M.C.Jeruchim,P.Balaban,and K.S.Shanmugan,Simulation of Communication Systems Modeling,Methodology,and Techniques,KLUWER ACADEMIC,2000.
[5]S.M.McBeath,D.T.Pinckley,and J.R.Cruz,"W-CDMA Power Amplifier Modeling",pp.2243-2247,VTC 2002 Fall.
[6]B.Widrow and J.R.Glover et.al.,"Adaptive Noise Cancelling:Principles and Applications",Proc.IEEE,Vol.63,No.12,pp.1692-1715,Dec.1975.
[7]F.Zavosh,M.Thomas et.al.,"Digital Predistortion Techniques for RF Power Amplifiers with CDMA Applications",Microwave Journal,1999.
[8]UE Radio Transmission and Reception(FDD),3GPP 25.101.
[9]P.B.Kenington,High-Linearity RF Amplifier Design,Arrech House,Boston,London,2000
[10]P.B.Kenington,et.al."An Ultra-Broadband Power Amplifier using Dynamically Controlled Linearisation" Proc.of IEEE International Symposium on Microwave Theory and Techniques,Anaheim,California,USA,Vol.1,13-19 June 1999,pp.355-358
[11]Nojima,T.,and T.,Konno,"Cuber predistorter linaerizer for relay equipment in 800MHz band land mobile telephone system," IEEE Trans.on Vehicular,Vol.VT-34,November 1985,pp169-177
[12]Joyce Van de Vetge,Fundamentals of Digital Signal Processing,Publishing House of Electronics Industry,Beijing,2003.
[13]C.R.Anderson,S.Krishnamoorthy et.al.,"Antenna Isolation,Wideband Multipath Propagation Measurements,and Interference Mitigation for On-frequency Repeaters",Globalcomm,2004.
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