CN101606315B - Predistortion method and device with constant time delay of power amplifier - Google Patents

Abstract

The predistortion method and apparatus that the time delay of the power amplifier is invariable is based on the storage-compensation or memory-compensation principle through using the addressing method of combined time delay, therefore the framework of this apparatus has inherent self-calibration time delay compensation function. The architecture uses only a look-up table (33) for correction of the non-linear response of the power amplifier (12) and compensation for any time delay effects present in the same device. Due to the time delay invariant nature, the predistortion design has the advantage of wider dynamic range processing for wireless RF signals and therefore can be implemented in multicarrier and multichannel wireless systems.

Description

Translated fromChinese

功率放大器时间延迟不变的预失真方法和装置Predistortion method and device with constant time delay of power amplifier

相关申请related application

本申请是标题为System and Method for Digital MemorizedPredistortion for Wireless Communication、提交于2005年10月27日的美国专利申请序列号11/262,079的部分继续申请，该美国专利申请又是标题为System and Method for Digital Memorized Predistortionfor Wireless Communication的美国专利申请序列号10/137,556、现为美国专利第6,985,704号的继续申请，通过引用将这两个申请结合于此。本申请要求前述申请的优先权并且也要求如下申请的优先权：提交于2007年4月30日的美国专利申请序列号11/799,239及其有关的标题为High Efficiency Linearization Power Amplifier ForWireless Communication、提交于2006年4月28日的美国临时专利申请序列号60/795,820；标题为Power Amplifier Predistortion Methodsand Apparatus、提交于2006年12月22日的美国临时专利申请第60/876,640号和提交于2007年12月20日的有关非临时美国专利申请11/962,025；标题为Power Amplifier Time-Delay InvariantPredistortion Methods and Apparatus、提交于2007年1月26日的美国临时专利申请序列号60/897,746；标题为Power AmplifierTime-Delay Invariant Predistortion Methods and Apparatus、提交于2007年1月29日的美国临时专利申请序列号60/898,312号，通过引用将所有这些申请结合于此。This application is a continuation-in-part of U.S. Patent Application Serial No. 11/262,079, filed October 27, 2005, entitled System and Method for Digital Memorized Predistortion for Wireless Communication, which in turn is titled System and Method for Digital US Patent Application Serial No. 10/137,556 for Memorized Predistortion for Wireless Communication, now a continuation of US Patent No. 6,985,704, both applications are hereby incorporated by reference. This application claims priority to the foregoing applications and also claims priority to U.S. Patent Application Serial No. 11/799,239, filed April 30, 2007, and its related titles, High Efficiency Linearization Power Amplifier For Wireless Communication, filed at U.S. Provisional Patent Application Serial No. 60/795,820, filed April 28, 2006; U.S. Provisional Patent Application No. 60/876,640, filed December 22, 2006, and entitled Power Amplifier Predistortion Methods and Apparatus, filed December 2007 Related NonprovisionalU.S. Patent Application 11/962,025 of the 20th; titled Power Amplifier Time-Delay Invariant Predistortion Methods and Apparatus, U.S. Provisional Patent Application Serial No. 60/897,746 filed January 26, 2007; titled Power Amplifier Time-Delay Invariant Predistortion Methods and Apparatus, U.S. Provisional Patent Application Serial No. 60/898,312, filed January 29, 2007, all of which are hereby incorporated by reference.

技术领域technical field

本发明涉及用于使用预失真将比如无线传输系统中所用功率放大器(PA)这样的PA的输出线性化的系统和方法。具体而言，本发明使用自适应时间延迟调节方法来校正PA的非线性。具体而言，本发明涉及使用时间延迟不变的预失真架构将无线传输系统中的功率放大器(PA)的输出线性化的系统和方法。The present invention relates to systems and methods for linearizing the output of a PA, such as a power amplifier (PA) used in a wireless transmission system, using predistortion. Specifically, the present invention uses an adaptive time delay adjustment method to correct PA non-linearities. In particular, the present invention relates to systems and methods for linearizing the output of a power amplifier (PA) in a wireless transmission system using a time delay invariant predistortion architecture.

背景技术Background technique

在用于功率放大器线性化的典型的现有技术的预失真系统中，该系统通常包含多个信号传输路径，比如参考路径和反馈路径。在预失真线性化系统中，当信号穿过不同信号传输路径如参考路径和反馈路径时，出现由不同信号路径造成的定时差异是不可避免的。通常称为时间延迟的这一差异带来与预失真校正的准确性有关的明显问题。这些问题由于时间延迟可能随着包括温度、系统条件(包括信号功率电平、系统老化)等变化这一事实而变得更糟。因此难以在实验室中测量这样的固有时间延迟参数，另外不能将用于校正时间延迟的参数设计为常数。在现有技术中已经付出诸多努力以补偿、减少或者消除这一时间延迟。传统上，两种方法已经使用在现有技术的预失真电路中用来解决由时间延迟造成的问题。In a typical prior art predistortion system for power amplifier linearization, the system usually includes multiple signal transmission paths, such as a reference path and a feedback path. In a predistortion linearized system, when a signal passes through different signal transmission paths such as a reference path and a feedback path, timing differences caused by different signal paths are unavoidable. This difference, commonly referred to as time delay, poses obvious problems with the accuracy of the predistortion correction. These problems are exacerbated by the fact that time delays can vary with changes including temperature, system conditions (including signal power levels, system aging), and the like. It is therefore difficult to measure such an inherent time delay parameter in a laboratory, and in addition the parameters for correcting the time delay cannot be designed to be constant. Efforts have been made in the prior art to compensate, reduce or eliminate this time delay. Traditionally, two methods have been used in prior art predistortion circuits to solve the problems caused by time delay.

第一种方法是通过测量和计算穿过不同传输路径的相同信号的差异来制作特殊时间延迟线缆以便补偿时间延迟效应，比如模拟前馈预失真系统中的处理。这一方式受困于如下限制：时间延迟线缆施加固定的时间延迟，因此在实际系统的操作期间自然出现信号和环境的改变时，该固定的时间延迟却不能进行调节。The first method is to make special time-delay cables to compensate for time-delay effects by measuring and calculating the difference of the same signal passing through different transmission paths, such as the processing in analog feed-forward predistortion systems. This approach suffers from the limitation that the time delay cable imposes a fixed time delay, which cannot therefore be adjusted as signal and environmental changes naturally occur during operation of the actual system.

第二种方法是使用特殊数字信号处理(DSP)算法和电路来计算并且自适应地调节穿过不同传输路径的相同信号的时间差异、然后使用所得到的时间延迟信息来校正功率放大器的非线性。这一方式通常实施于数字反馈方式和无线环境中。然而，需要通常为锁存器的额外电路和相关联算法，并且时间延迟计算的准确性也与算法的收敛速率有关。The second method is to use special digital signal processing (DSP) algorithms and circuits to calculate and adaptively adjust the time difference of the same signal passing through different transmission paths, and then use the resulting time delay information to correct the nonlinearity of the power amplifier . This approach is usually implemented in digital feedback and wireless environments. However, additional circuitry, usually a latch, and associated algorithm is required, and the accuracy of the time delay calculation is also related to the convergence rate of the algorithm.

发明内容Contents of the invention

下一代无线通信系统将需要用于各种宽带和多媒体服务的改进的发送信号质量和改进的整体RF发送器系统性能。对高级RF发送器系统的这些需求将至少部分地由具有比当前可获得的更高的功率效率和频谱效率的功率放大器来满足。为了获得更好的预失真结果，本发明将时间延迟参数作为由特殊算法和电路估计和计算的变量来评估。Next generation wireless communication systems will require improved transmitted signal quality and improved overall RF transmitter system performance for various broadband and multimedia services. These demands on advanced RF transmitter systems will be met, at least in part, by power amplifiers with higher power and spectral efficiencies than currently available. In order to obtain better predistortion results, the present invention evaluates the time delay parameter as a variable estimated and calculated by special algorithms and circuits.

具体而言，本发明在一种实施中使用一种组合的预失真和时间延迟查找表结构来为PA的非线性失真和系统的时间延迟提供校正因子。这允许本发明的系统和方法成为一种用于无线RF发送器系统中的性能改进和非线性校正的自校准解决方案。Specifically, the present invention in one implementation uses a combined predistortion and time delay look-up table structure to provide correction factors for nonlinear distortion of the PA and time delay of the system. This allows the system and method of the present invention to be a self-calibrating solution for performance improvement and nonlinearity correction in wireless RF transmitter systems.

这一设计可以由优良简易电路结构便利地实施并且可以用于几乎所有无线射频(RF)传输系统以改进功率效率和频谱效率。一些适用的RF传输系统的例子包括无线基站、接入点、移动手机(包括但不限于蜂窝和GPRS协议)、移动无线终端、便携无线设备和其它无线通信系统如微波和卫星通信。This design can be conveniently implemented by an excellent simple circuit structure and can be used in almost all wireless radio frequency (RF) transmission systems to improve power efficiency and spectral efficiency. Some examples of suitable RF transmission systems include wireless base stations, access points, mobile handsets (including but not limited to cellular and GPRS protocols), mobile wireless terminals, portable wireless devices, and other wireless communication systems such as microwave and satellite communications.

这里呈现的新型时间延迟不变的方法使用如下组合：(i)自适应时间延迟调节方法用于处理PA的非线性；并且同时(ii)时间延迟补偿而无需针对特殊时间延迟调节而定制的附加电路和/或算法。这一新颖的基于算法的方法可以由预失真处理单元实施，该单元包括可以存储和记忆PA的非线性、时间延迟信息和系统中的其它干扰如噪声的时间延迟寻址查找表。The novel time-delay-invariant approach presented here uses a combination of: (i) an adaptive time-delay adjustment approach to deal with PA nonlinearities; and simultaneously (ii) time-delay compensation without the need for additional circuits and/or algorithms. This novel algorithm-based approach can be implemented by a predistortion processing unit that includes a time-delay addressed look-up table that can store and memorize PA nonlinearity, time-delay information, and other disturbances in the system such as noise.

根据结合附图进行的下文具体描述实施可以更好地理解本发明的这些和其它方面。These and other aspects of the invention can be better understood from the following detailed description when taken in conjunction with the accompanying drawings.

附图说明Description of drawings

图1图示了根据本发明的系统和装置；Figure 1 illustrates a system and device according to the present invention;

图2以简化形式图示了用于查找表串行寻址以及将积累的历史录入到查找表中的一种实施；Figure 2 illustrates, in simplified form, one implementation for serial addressing of a lookup table and logging of accumulated history into the lookup table;

图3以简化形式图示了不同于图2中所示的一种查找表并行寻址实施。Figure 3 illustrates in simplified form a lookup table parallel addressing implementation different from that shown in Figure 2 .

具体实施方式Detailed ways

在本发明的一种实施中，根据在通过引用均结合于此并且作为附录A和B来附带的未决的、提交于2005年10月27日的美国专利申请序列号11/262,079和提交于2007年4月30日的美国专利申请序列号11/799,239中描述的技术来开发用于查找表的条目。本领域技术人员将理解在现实系统中出现的误差范围是有界的；也就是说，有具有最小值和最大值的范围，并且在几乎所有的境况中在任何给定样本的时间适用的校正因子将落在该范围内。通过选择适当大小的查找表并且用如由上述专利中的方法确定的适当值(这些值是在PA和相关联系统的整个操作频谱内选择的)来填充查找表，适合于输入信号各采样的校正因子将是查找表中已有的值之一。因此，一旦已经完全地填充查找表，本发明的校正因子不会随时间变化；也就是说，它们是不随时间变化的。虽然查找表的大小可以随着特定实施而明显地变化并且对于一些系统可以如十六个条目一样小，但是对于更复杂的实施，比如适合于无线RF传输系统的实施，该表将具有级别为2¹²个或者更多的条目而且可以根据可允许的功率消耗、成本和有关系统因素而具有明显更多的条目。对于某些实施，已经发现在2¹²个与2¹⁴个条目之间的表大小是可接受的。In one implementation of the present invention, according to pending U.S. Patent Application Serial No. 11/262,079, filed October 27, 2005, which is hereby incorporated by reference and attached as Appendices A and B, and filed at The techniques described in US Patent Application Serial No. 11/799,239, April 30, 2007 to develop entries for lookup tables. Those skilled in the art will understand that the range of error that occurs in real systems is bounded; that is, there are ranges with minimum and maximum values, and the corrections applicable at any given sample time in nearly all circumstances Factors will fall within this range. By selecting an appropriately sized look-up table and populating the look-up table with appropriate values as determined by the methods in the above-mentioned patents (the values are selected over the entire operating spectrum of the PA and associated system), a value suitable for each sample of the input signal The correction factor will be one of the values already in the lookup table. Therefore, once the look-up table has been completely populated, the correction factors of the present invention are not time-varying; that is, they are time-invariant. While the size of the lookup table can vary significantly with a particular implementation and can be as small as sixteen entries for some systems, for more complex implementations, such as those suitable for wireless RF transmission systems, the table will have levels of 2¹² or more entries and can have significantly more entries depending on allowable power consumption, cost and related system factors. For some implementations, table sizes between²¹² and²¹⁴ entries have been found to be acceptable.

在一种实施中，预失真处理单元或者预失真器的查找表通过可以由移位寄存器构造的与时间有关的地址集来寻址，尽管如下文具体讨论的那样可以在一些方案中实施并行寻址。出于当前目的，将使用移位寄存器技术进行说明。查找表的寻址是基于如下存储-补偿或者记忆-补偿原理，该原理通过矢量形式在不同时间存储信息并且将输入矢量映射到查找表中的条目之一。查找表中的寻址条目集将得到如下输出信号，该输出信号是对应输入矢量的映射函数。由于输入地址矢量包括不同时间信号，所以查找表的输出信号实际上与不同时间信息相关，包括当前信号和先前N个发送信号，其中N＞1并且N为整数。结果可以将查找表的各条目中所存储的信号视为所有以往发送信号的组合而不是当前输入信号的仅有响应。通常，查找表中的地址矢量的位长度确定待覆盖的时间延迟信号的持续时间。In one implementation, the predistortion processing unit or look-up table of the predistorter is addressed by a set of time-dependent addresses that can be constructed from shift registers, although parallel addressing can be implemented in some schemes as discussed in detail below. site. For present purposes, shift register technology will be used for illustration. The addressing of the look-up table is based on the store-offset or memory-offset principle, which stores information at different times in the form of a vector and maps the input vector to one of the entries in the look-up table. The set of addressed entries in the lookup table will result in an output signal that is a mapping function for the corresponding input vector. Since the input address vector includes different time signals, the output signal of the lookup table is actually related to different time information, including the current signal and the previous N transmitted signals, where N>1 and N is an integer. As a result, the signal stored in each entry of the look-up table can be considered as a combination of all past sent signals rather than as the only response to the current incoming signal. In general, the bit length of the address vector in the look-up table determines the duration of the time-delayed signal to be overwritten.

为了根据本发明利用查找表单元在时间延迟环境中校正PA的非线性而不利用锁存器或者其它辅助校正电路，预失真算法利用函数来并入时间延迟信号组合。查找表将从PA导出的非线性信息与由不同信号传输路径造成的时间延迟因子一起存储。通过响应于样本对查找表适当地进行寻址，查找表提供既包括适当的预失真校正也包括适当的时间延迟补偿的校正因子。查找表的输出然后与原始输入信号相组合以向PA提供输入而该PA获得线性化输出而基本上无时间延迟误差。In order to correct PA non-linearities in a time-delay environment using a look-up table unit according to the present invention without using latches or other auxiliary correction circuits, the predistortion algorithm utilizes functions to incorporate time-delayed signal combinations. The look-up table stores the non-linear information derived from the PA together with the time delay factors caused by the different signal transmission paths. By appropriately addressing the look-up table in response to the samples, the look-up table provides correction factors that include both appropriate pre-distortion correction and appropriate time delay compensation. The output of the lookup table is then combined with the original input signal to provide input to the PA which obtains a linearized output substantially free of time delay errors.

由于查找表的记忆和存储功能，PA的将由查找表校正的非线性特性不受基于时间的数据限制。查找表的自适应处理的与时间无关的特性是查找表的寻址布置的至少一些实施的一个益处。通过包括当前输入信号以及先前N个输入信号的N位矢量数据的集来实施查找表的寻址。因此，查找表的地址是长度为N的连串输入序列的组合。查找表的地址越长(因此查找表越大)，系统可以容纳的时间延迟信息的范围越宽、即系统可以容许的时间延迟效应的持续时间越长。然而，尽管更大的表可以允许存储更多信息，但是条目在某一点变为重复，从而更大的表赋予递减边际回报、浪费存储器资源并且不必要地增加功率消耗。Due to the memory and storage function of the look-up table, the non-linear characteristics of the PA to be corrected by the look-up table are not limited by time-based data. The time-independent nature of the adaptive processing of the look-up table is a benefit of at least some implementations of the addressing arrangement of the look-up table. Addressing of the look-up table is implemented by a set of N-bit vector data comprising the current input signal as well as the previous N input signals. Therefore, the address of the lookup table is a combination of consecutive input sequences of length N. The longer the address of the lookup table (and thus the larger the lookup table), the wider the range of time delay information the system can accommodate, ie the longer the duration of the time delay effect the system can tolerate. However, while larger tables may allow more information to be stored, at some point the entries become duplicated such that larger tables confer diminishing marginal returns, waste memory resources and unnecessarily increase power consumption.

预失真处理器的查找表是基于将输入矢量集映射到实际信号输出的存储-补偿原理。由于查找表的地址包含从不同时间存储的输入信息，所以由查找表生成的各输出信号与发送的多信号组合密切相关。因此，基于查找表的布置，表更新条目也与从不同时间点存储的输入信号的组合信息密切有关。The look-up table of the predistortion processor is based on the store-and-compensate principle of mapping the input vector set to the actual signal output. Since the addresses of the look-up table contain input information stored from different times, each output signal generated by the look-up table is closely related to the transmitted multi-signal combination. Therefore, based on the arrangement of the look-up table, the table update entries are also closely related to the combined information of the input signals stored from different time points.

接着参照图1，可以具体地理解本发明的一个实施例。具体而言，图示的实施例包括模拟乘法器11，该乘法器从基站的RF调制器部分10接收调制的RF信号v_RF并且也从查找表和可以广义地描述为预失真处理器(下文具体讨论)的有关部件接收预失真校正信号v_p。一般而言，预失真处理器可以视为在ADC 21和25与DAC 30之间的所有部件。模拟放大器11的输出作为输入V_in提供给功率放大器(PA)12，该PA又将输出信号V_o发送到天线13。RF调制器10虽然并非必然但是通常为正交调制器。将理解乘法器11可以实施为各自与一个或者多个正交信号相关联的多个乘法器。Referring next to FIG. 1, an embodiment of the present invention can be specifically understood. In particular, the illustrated embodiment includes ananalog multiplier 11 which receives the modulated RF signal_vRF from theRF modulator section 10 of the base station and which also reads from a look-up table and can be broadly described as a predistortion processor (hereinafter Discussed in detail) the relevant components receive the predistortion correction signal v_p . In general, the predistortion processor can be considered as everything between the ADCs 21 and 25 and theDAC 30 . The output of theanalog amplifier 11 is provided as input V_in to a power amplifier (PA) 12 which in turn sends an output signal V_o to anantenna 13 .RF modulator 10 is typically, though not necessarily, a quadrature modulator. It will be appreciated thatmultiplier 11 may be implemented as a plurality of multipliers each associated with one or more quadrature signals.

输入下变频转换器电路20从基站中的调制器接收理想化的参考信号V_RF并且由本地振荡器40进行偏置，从而它将输出V_d提供给模拟到数字转换器21。ADC 21将信号V_d转换成数字形式(作为I和Q信号)，其中它作为一对输入提供给数字预失真处理器并且具体地分别提供给变量22I和22Q。Theinput downconverter circuit 20 receives an idealized reference signal_VRF from a modulator in the base station and is biased by alocal oscillator 40 so that it provides an output_Vd to an analogue-to-digital converter 21 . ADC 21 converts signal_Vd into digital form (as I and Q signals), where it is provided as a pair of inputs to a digital predistortion processor and specifically to variables 22I and 22Q, respectively.

也由本地振荡器40偏置的反馈下变频转换器电路26从PA的输出接收原始反馈信号V_o(t)并且将反馈信号V_f提供给反馈ADC 25。该ADC 25的数字输出然后将第二输入、即反馈信号提供给数字预失真处理器并且具体地提供给变量24I和24Q。下文具体讨论的数字预失真将数字输出信号Vr提供给DAC 30，该DAC30将数字信号转换成模拟形式，其中它在乘法器11中与调制的RF信号组合。Feedback downconverter circuit 26 , also biased bylocal oscillator 40 , receives raw feedback signal V_o (t) from the output of the PA and provides feedback signal V_f to feedback ADC 25 . The digital output of this ADC 25 then provides the second input, the feedback signal, to the digital predistortion processor and in particular to variables 24I and 24Q. Digital predistortion, discussed in detail below, provides a digital output signal Vr to aDAC 30 which converts the digital signal into analog form where it is combined in amultiplier 11 with the modulated RF signal.

如图1中所示，地址数据形成器32I-32Q从ADC21I/Q接收输入并且被设计成生成用于查找表33I/Q的所需信号格式。数据形成器32I/Q对查找表33I/Q内的记忆单元进行寻址，其中查找表将单独I和Q输出提供给加法器31。将理解查找表33可以实施为一个或者多个查找表。由地址形成器32I-32Q提供的地址可以视为查找表关键字或者地址。As shown in Figure 1, address data formers 32I-32Q receive input from ADC 21I/Q and are designed to generate the required signal format for lookup table 33I/Q. Data former 32I/Q addresses memory locations within a lookup table 33I/Q which provides separate I and Q outputs to adder 31 . It will be appreciated that lookup table 33 may be implemented as one or more lookup tables. The addresses provided by address formers 32I-32Q may be considered lookup table keys or addresses.

预失真控制器查找表33I-33Q是设计成存储用于高功率放大器线性化的预失真信号的记忆单元。表中的预失真信号是基于通过比较理想信号v_d和反馈信号v_f来生成的误差以及呈现的自适应算法。存储于表33I-Q中的数据可以通过如下文所述自适应迭代来更新并且形成反映功率放大器非线性特性的数字索引的数据。The predistortion controller lookup tables 33I-33Q are memory units designed to store predistortion signals for linearization of the high power amplifier. The predistortion signals in the table are based on the errors generated by comparing the ideal signal v_d with the feedback signal v_f and the adaptive algorithm presented. The data stored in Tables 33I-Q can be updated by adaptive iteration as described below and form numerically indexed data reflecting the non-linear characteristics of the power amplifier.

通过在理想化信号V_RF(t)与反馈信号V_o(t)之间的AM-AM和AM-PM信息比较，数字预失真处理器计算由高功率放大器12的非线性传输特性造成的输出信号V_o(t)的幅度和相位分量的误差。By comparing the AM-AM and AM-PM information between the idealized signal V_RF (t) and the feedback signal V_o (t), the digital predistortion processor calculates the output due to the nonlinear transfer characteristic of thehigh power amplifier 12 The error in the magnitude and phase components of the signal V_o (t).

基于由前述比较获得的误差信息，预失真处理器基于在美国专利第6,985,704，号中公开的查找表算法来计算并且自适应地生成具有与PA 12的变换函数相反的特性的补偿信号以预失真由PA 12造成的AM-AM和AM-PM失真。Based on the error information obtained from the aforementioned comparison, the predistortion processor calculates and adaptively generates a compensation signal having the inverse characteristics of the transfer function of thePA 12 based on the look-up table algorithm disclosed in US Patent No. 6,985,704 to predistort AM-AM and AM-PM distortion caused byPA 12.

预失真查找表33I-33Q的输出v_p在加法器31和数字到模拟转换器30之后馈送到乘法器11以修改来自调制器10的调制的RF信号。乘法器的输出是用以向高功率放大器的输入产生预补偿的、其非线性与功率放大器12的非线性相反的所需预失真信号v_in(k)。The output_vp of the predistortion look-up tables 33I-33Q is fed to themultiplier 11 after theadder 31 and the digital-to-analog converter 30 to modify the modulated RF signal from themodulator 10 . The output of the multiplier is used to generate a precompensated desired predistorted signal v_in (k) whose nonlinearity is inverse to that of thepower amplifier 12 to the input of the high power amplifier.

本领域技术人员将理解当理想信号v_RF和反馈信号V_o(t)这两个信号到达预失真控制器时在这些信号之间可能有信号差异。时间差异归因于由各自在去往控制器时行进的不同路径造成的在两个信号之间的时间延迟差异。这一信号时间延迟可以基于电路和部件的参数以及其它环境因素而随机地变化。结果是难以估计、计算和调节现场应用环境中这样的信号差异。为了克服这一问题，本发明通过使用由先前引用的美国专利第6,985,704号教导的一种算法来自适应地调节这一时间延迟。Those skilled in the art will understand that there may be signal differences between the ideal signal v_RF and the feedback signal V_o (t) when these two signals arrive at the predistortion controller. The time difference is due to the difference in time delay between the two signals caused by the different paths each takes to travel to the controller. This signal time delay may vary randomly based on circuit and component parameters, as well as other environmental factors. The result is that it is difficult to estimate, calculate and adjust for such signal differences in field application environments. To overcome this problem, the present invention adaptively adjusts this time delay by using an algorithm taught by previously referenced US Patent No. 6,985,704.

对查找表33的使用允许将记忆函数引入到本发明的至少一些实施例中。预失真控制器的查找表是基于将输入数据集映射到数字输出并且自适应更新的存储补偿原理。基于存储的函数，查找表的各输出信号实际上与当前和先前发送信号均有关、因此具有以下记忆功能：其不仅补偿PA的非线性并且避免了对于比如现有技术中通常使用的特殊时间延迟补偿电路的需要。The use of look-up tables 33 allows for the introduction of memory functions into at least some embodiments of the invention. The look-up table of the predistortion controller is based on the principle of memory compensation that maps the input data set to the digital output and updates adaptively. Based on a stored function, each output signal of the look-up table is actually related to both the current and previous transmitted signals, thus having the following memory function: it not only compensates the non-linearity of the PA but also avoids special time delays such as those commonly used in the prior art compensation circuit needs.

基于图1中所示预失真架构，功率放大器的非线性由预失真处理器的输出信号v_p校正。信号v_p与调制的RF信号相乘以生成预失真信号作为功率放大器的输入。实际上，功率放大器的输入信号是可以在幅度/包络方面可控而在相位方面可调的复增益信号。输入和输出的关系可以描述为以下复增益表达式：Based on the predistortion architecture shown in Figure 1, the nonlinearity of the power amplifier is corrected by the output signal_vp of the predistortion processor. The signal_vp is multiplied with the modulated RF signal to generate the predistorted signal as input to the power amplifier. In practice, the input signal to the power amplifier is a complex gain signal that can be controlled in amplitude/envelope and adjustable in phase. The relationship between input and output can be described as the following complex gain expression:

v_in＝v_RFv_p＝v_RFF(V)  (1)v_in ＝v_RF v_p ＝v_RF F(V) (1)

其中v_p是由查找表的映射函数F生成的预失真处理器输出。通常，映射函数F未知并且难以用数学方式表达。然而，可以通过根据自适应算法更新查找表中的条目以实现与{0，1}^N→v_p这些关系对应的所有可能映射来自适应地确定F。where v_p is the output of the predistortion processor generated by the mapping function F of the lookup table. In general, the mapping function F is unknown and difficult to express mathematically. However, F can be determined adaptively by updating the entries in the lookup table according to an adaptive algorithm to achieve all possible mappings corresponding to these relations {0, 1}^N →_vp.

查找表因此将各N位输入地址矢量集V映射到实际输出v_p。事实上，N维地址矢量代表由下式表达的从当前时间到先前N个时间的经过功率放大器的发送信号序列：The look-up table thus maps each N-bit input address vector set V to the actual output_vp . In fact, the N-dimensional address vector represents the transmitted signal sequence through the power amplifier from the current time to the previous N times expressed by the following formula:

V(k)＝(d₁(k)，d₂(k)，...，d_N(k))^T    (2)V(k)=(d₁ (k), d₂ (k), . . . , d_N (k))^T (2)

其中上述矢量V中的各数据d_i是表达如下的1或者0：Each data d_i in the above vector V is 1 or 0 expressed as follows:

d_i(k)＝0或者1，其中1≤i≤N    (3)d_i (k)=0 or 1, where 1≤i≤N (3)

在图2中所示一种实施中，查找表200的地址由在预失真过程期间对查找表的各对应条目进行寻址的串行移位寄存器205形成。由于寻址的信息与当前和先前N个发送信号有关，所以查找表的输出信号210可以视为最后N个发送数据的函数、因此并入时间延迟校正要素。通过在组合器225中组合自适应误差215和查找表更新220来自适应地更新查找表。即使当相同信号穿过不同传输路径时呈现时间延迟效应，配置为预失真处理器的查找表的布置仍然可以将组合的校正信号系统地用于PA的非线性校正和时间延迟补偿的处理。In one implementation shown in FIG. 2, the address of the look-up table 200 is formed by a serial shift register 205 that addresses each corresponding entry of the look-up table during the pre-distortion process. Since the addressed information is related to the current and previous N transmissions, theoutput signal 210 of the look-up table can be considered as a function of the last N transmissions, thus incorporating a time delay correction element. The lookup table is adaptively updated by combining adaptive error 215 andlookup table update 220 incombiner 225 . Even if the same signal exhibits time delay effects when passing through different transmission paths, the arrangement of the look-up table configured as a predistortion processor can still systematically use the combined correction signal for the processing of non-linear correction and time delay compensation of the PA.

对具有组合的预失真和时间延迟校正的查找表进行使用的技术使得没有必要使用附加时间延迟处理和相关的电路。由于查找表的地址包含当前和先前发送的校正信息，所以来自查找表的各输出信号固有地是包含从当前时间到先前N个时间的丰富信号分量的多时间信息组合。结果预失真算法具有用以补偿信号延迟效应的内置机制。这获得一种比传统解决方案明显更简易和更有效的预失真处理结构。The technique of using a look-up table with combined predistortion and time delay correction eliminates the need for additional time delay processing and associated circuitry. Since the address of the look-up table contains current and previously sent correction information, each output signal from the look-up table is inherently a multi-time information combination containing rich signal components from the current time to the previous N times. The resulting predistortion algorithm has a built-in mechanism to compensate for signal delay effects. This results in a significantly simpler and more efficient predistortion processing structure than conventional solutions.

在如图1和图2中所示具有查找表的预失真架构中，记忆表由它的地址寄存器寻址。移位寄存器的位数长度确定查找表的大小并且因此确定覆盖的时间延迟范围、即时间延迟效应的最大限制。查找表中存储的各数据集具有唯一的地址索引。数据集的这一地址索引对应于数据集的输入数据采样时间点。然后利用地址索引作为用于PA的非线性误差校正计算的时间校准这一目的的时间戳。换而言之，在各预失真计算时间点，预失真算法选择来自具体寻址条目的仅一个数据集作为查找表的输出以供进一步PA的非线性误差校正处理。如果所选输出信号仅与当前时间发送信号有关而与其它发送信号无关，则在预失真处理期间必须考虑由通过不同传输路径的当前发送信号造成的时间延迟以便提供参考与反馈信号之间的准确信号匹配。In a predistortion architecture with a look-up table as shown in Figures 1 and 2, the memory table is addressed by its address register. The bit length of the shift register determines the size of the look-up table and thus the covered time delay range, ie the maximum limit of the time delay effect. Each data set stored in the lookup table has a unique address index. This address index of the dataset corresponds to the input data sampling time point of the dataset. The address index is then used as a time stamp for the purpose of time calibration of the PA's nonlinear error correction calculation. In other words, at each predistortion calculation time point, the predistortion algorithm selects only one data set from a specific addressed entry as the output of the lookup table for further nonlinear error correction processing of the PA. If the selected output signal is only related to the current time transmit signal and not to other transmit signals, the time delay caused by the current transmit signal through different transmission paths must be taken into account during the predistortion process in order to provide an accurate correlation between the reference and feedback signals. Signal match.

将由查找表覆盖的时间延迟范围与地址寄存器的位数有关。对于具有N位地址寄存器的查找表，查找表条目的大小为M＝2^N-1。这意味着在查找表中有M个条目并且存储于条目中的所有数据是覆盖当前时间k到先前k-M+1个时间的地址矢量的函数。输入地址矢量集A可以表达为：The range of time delays to be covered by the lookup table is related to the number of bits in the address register. For a lookup table with an N-bit address register, the size of the lookup table entry is M=^2N-1 . This means that there are M entries in the lookup table and all data stored in the entries is a function of the address vector covering the current time k to the previous k-M+1 times. The input address vector set A can be expressed as:

A＝{V(k)，V(k-1)，...，V(k-M+1)}(4)A={V(k), V(k-1), ..., V(k-M+1)} (4)

其中V(k)是在时间k的输入地址矢量，该矢量记录针对PA非线性的M个可能预失真信息而各信息记录当前发送的信号和时间延迟信号分量。where V(k) is the input address vector at time k, which vector records M possible predistortion information for PA nonlinearity and each information records the currently transmitted signal and the time-delayed signal component.

基于记忆-补偿原理，组合的时间延迟查找表结构涉及到用以捕获穿过不同传输路径的信号时间延迟的简易逻辑运算和信号处理。具体而言，由于时间延迟不变的特性，这一预失真架构可以在更宽的动态范围内并且无需附加电路和算法来处理和校正PA非线性。Based on the memory-compensation principle, the combined time-delay look-up table structure involves simple logic operations and signal processing to capture the time delay of signals passing through different transmission paths. Specifically, due to the time-delay invariant property, this predistortion architecture can handle and correct PA nonlinearity over a wider dynamic range without additional circuits and algorithms.

本领域技术人员也将理解对于一些实施例，通常是查找表更大而采样率相对更高的实施例，可以使用并行寻址方案，比如图3中所示并行寻址方案，该方案除了使用向查找表的并行输入300之外实质上与图2相同。如果一起接近地取得采样的数据点(即比较快的采样率)，从而用于样本t和样本t+1的校正因子有效地变得相同，则可以使用并行寻址方式对查找表进行寻址。在一些实施例中，如果查找表的大小充分地大并且满足计算能力和其它设备问题，则并行寻址方式可以在使用很快采样率的环境中赋予较串行寻址方式而言更佳的性能。Those skilled in the art will also appreciate that for some embodiments, typically those with larger look-up tables and relatively higher sampling rates, a parallel addressing scheme, such as that shown in FIG. The parallel input to the lookup table 300 is substantially the same as in FIG. 2 . The lookup table can be addressed using parallel addressing if the sampled data points are taken closely together (i.e. faster sampling rate) such that the correction factors for sample t and sample t+1 effectively become the same . In some embodiments, parallel addressing may give better performance than serial addressing in environments using very fast sampling rates if the size of the lookup table is sufficiently large and satisfies computing power and other device concerns. performance.

已经具体地完全描述包括若干实施例和替代实施例的本发明，本领域技术人员将理解存在着在本发明的范围内的诸多其它替代和等效实施例。因此本发明并非将由上述描述而实际上仅由所附权利要求来限制。Having specifically and fully described the invention including several embodiments and alternatives, it will be understood by those skilled in the art that there are many other alternatives and equivalents which are within the scope of the invention. It is therefore not intended that the invention be limited by the foregoing description, but actually only by the appended claims.

Claims (9)

1. for by a pre-distortion system for the linearization of power amplifier, comprising:

First signal, represents RF modulation signal,

Feedback signal, represents the nonlinear characteristic of power amplifier,

Predistortion controller, comprise at least one look-up table with pre-sizing, be suitable for receiving described first signal and described feedback signal and generate the correction factor of the described nonlinear characteristic for proofreading and correct described power amplifier, and the value of wherein said at least one look-up table drops on by the definite scope of the size of described at least one look-up table

Wherein said at least one look-up table be configured in response to the in-phase component of feedback signal described in the quadratic sum of the in-phase component from described first signal square between the difference input of deriving and the quadratic sum of the quadrature component of described first signal described in feedback signal quadrature component square between the difference input of deriving; And

Multiplier, is configured to:

Combine described RF modulation signal and the analog signal corresponding with described correction factor, described correction factor is generated and is depended on the output of described at least one look-up table by described predistortion controller, described output is fed into described multiplier after adder and digital-to-analog converter; And

By the signal provision of described combination to described power amplifier with by the linearization of described power amplifier.

2. pre-distortion system according to claim 1, also comprises serial shift register, is used to form the address for described at least one look-up table.

3. pre-distortion system according to claim 1, wherein said at least one look-up table carrys out addressing by parallel signal.

4. pre-distortion system according to claim 1, the value of wherein said at least one look-up table automatically compensates the time delay through the signal of different transmission path.

5. for by a pre-distortion system for the linearization of power amplifier, comprising:

First signal, represents RF modulation signal,

Feedback signal, represents the nonlinear characteristic of power amplifier,

Predistortion controller, comprises address shaper and look-up table, and the value in wherein said look-up table is temporal evolution and the operating characteristic based on described power amplifier and wireless RF transmission system not,

Wherein said look-up table be configured in response to the in-phase component of feedback signal described in the quadratic sum of the in-phase component from described first signal square between the difference input of deriving and from the quadrature component of feedback signal described in the quadratic sum of the quadrature component of described first signal square between the difference input of deriving; And

Multiplier, is configured to:

Combine described RF modulation signal and the analog signal corresponding with time-independent correction factor, described correction factor is generated and is depended on the output of described look-up table by described predistortion controller, described output is fed into described multiplier after adder and digital-to-analog converter.

6. by a method for the linearization of power amplifier, comprising:

The RF modulation signal that represents ideal signal is provided,

The feedback signal of the nonlinear characteristic that represents power amplifier is provided,

To representing described power amplifier and multiple samples of the error characteristics scope that comprises time delay of the transmission system that is associated are sampled,

Determine multiple time-independent error correction factor in response to described sample with look-up table,

Wherein said look-up table be configured in response to the in-phase component of feedback signal described in the quadratic sum of the in-phase component from described RF modulation signal square between the difference input of deriving and from the quadrature component of feedback signal described in the quadratic sum of the quadrature component of described RF modulation signal square between the difference input of deriving;

Combine described RF modulation signal and the analog signal corresponding with described time-independent error correction factor with multiplier, described multiplier arrangement becomes to receive from the output that is positioned at adder digital-to-analog converter afterwards, and described adder is configured to combine the output of described look-up table;

The simulation error correction signal that is provided for the output of power amplifier described in linearisation, described simulation error correction signal represents the combination of described RF modulation signal and described analog signal.

7. pre-distortion system according to claim 1, wherein said digital-to-analog converter is configured to convert the digital signal corresponding with described correction factor to the described analog signal corresponding with described correction factor.

8. pre-distortion system according to claim 5, wherein said digital-to-analog converter is configured to convert the digital signal corresponding with described correction factor to the described analog signal corresponding with described correction factor.

9. method according to claim 6, also comprises: by representative for the digital error correction signal of one of described correction factor of the linearization of described power amplifier being converted to representative for by the described simulation error correction signal of one of described correction factor of the linearization of described power amplifier.

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