Ka波段行波管线性化器研究

模拟预失真技术是补偿行波管放大器非线性失真的一种重要方法,为了精确补偿放大器的非线性失真,需要同时保证预失真器的幅度和相位特性满足补偿要求,然而目前大多数的预失真器无法实现幅度和相位特性独立调节使得这个要求难以满足。本文提出了一种工作于Ka波段的模拟预失真线性化器,它采用矢量合成式结构,通过同时调节两条支路中二极管的偏置电压可以实现幅度和相位特性的独立调节。该预失真器工作于29~31 GHz,根据理论分析和仿真结果加工制作了实际电路并进行了测试,测试结果表明:在30 GHz时,该预失真器可以在相位扩张恒定的情况下在2.2~9.1 d B范围内调节增益扩张,同时可以在增益扩张恒定的情况下在19.7°~42.5°的范围内调节相位扩张。与行波管放大器的联测结果表明,线性化后的行波管放大器的非线性失真明显降低,在输出功率回退6 d B时,三阶互调系数提高了约9 d B。     

用于Ka波段行波管的反射式可调预失真线性化器

为了解决目前模拟预失真器存在的可调性差,增益和相位斜率补偿不够的问题,减小预失真器增益扩展和相位扩张之间的相互影响。本文介绍一种工作于Ka波段的反射式模拟预失真电路,该电路基于90°电桥、肖特基二极管、变容二极管产生预失真信号,利用90°电桥的特性实现电路的匹配,同时通过改变肖特基二极管及变容二极管两端的偏置电压实现对预失真电路的增益扩展和相位扩张特性的控制调节。接着对预失真电路进行非线性分析与仿真验证,在此基础上,将所设计的电路加工为实际的预失真线性化器并与Ka波段的空间行波管联合测试,测试结果表明,线性化后的行波管增益和相位特性从之前的-7 dB和-45°改善到-0.5 dB和-3.5°,三阶交调改善了7.5 dB。     

用于行波管放大器的预失真线性化技术研究

本文第一部分介绍了行波管的非线性特性,给出了Saleh提出的行波管非线性模型,用其对某行波管的实测数据拟合,拟合均方误差小,结果好.第二部分首先介绍了预失真技术的原理与基本方法,在Saleh模型的基础上,通过级联网络的理论,得出与行波管配用预失真线性化器的幅度和相位预失真函数.第三部分利用二极管的变阻特性,提出了一种利用肖特基二极管构成的预失真电路.通过计算该电路交流通路的等效二端口网络散射参数S21的幅度和相位,得出其随输入功率的变化趋势与行波管配用预失真线性化器的幅度和相位预失真函数变化趋势相同.调节二极管的直流偏压及电阻,即可与实际行波管配用.最后通过ADS软件对电路进行仿真,得出其增益和相移特性与理论分析的结果一致.     

一种端口匹配的行波管预失真线性化器

模拟预失真是补偿行波管非线性失真的一种非常重要的方法.不过,目前大多数的预失真器需要在输入输出端加隔离器,增加了系统的复杂性.本文介绍一种工作在L波段的基于二极管的预失真线性化器.这种预失真线性化器利用3dB分支线耦合器的特性,实现输入输出端的良好匹配.随着输入功率的增加,该预失真线性化器可以达到不同的增益扩张和相位扩张.级联行波管后的测试表明,采用这种预失真线性化器,使得行波管在额定输入功率范围内的增益压缩和相位压缩从以前的6dB和40°改善到0.5dB和5°.     

基于肖特基二极管和移相器的超宽带线性化器

基于ADS软件设计并加工了一款2~6 GHz的超宽带线性化器。实测结果表明,该线性化器在2,4和6 GHz这三个频点分别既可提供约9.5 dB和55°,8.3 dB和55°,8.8 dB和73°增益和相位扩张量,用于改善行波管的非线性失真,也能提供约7.8 dB和42°,8.4 dB和42°,5.1 dB和56°增益扩张和相位压缩量,用于改善固态功率放大器的非线性失真。将该线性化器应用到某S波段行波管的线性化中,可将行波管饱和点相对于小信号点的增益和相位压缩量分别从5 dB和36°改善到1.2 dB和5°以内。双音5 MHz的测试结果表明,为了达到通信中载波与三阶交叉调制分量比(C/IM3)25 dBc的要求,单独行波管需回退13 dB,而加入线性化器后的行波管,只需回退7 dB,也即加线性化器可改善6 dB,极大地提升了行波管的线性度。     

一种补偿量可调的反射式预失真线性化器北大核心CSCD

提出一种改进的反射式预失真电路,使其在相同功率区间上具有在线的补偿量调节能力。该电路对肖特基二极管不施加偏置电压,避免了因偏压改变而引起的补偿区间变化;在非线性产生电路中串联变容二极管,通过调节变容管的偏置电压,实现预失真器补偿量的调节。采用该方案设计加工了工作于29~31 GHz频段的反射式预失真器,实测结果表明:将变容管偏置电压由0调节至6 V,在相同功率区间内,该预失真器的增益扩张由4.5增大至7.6 d B,相位扩张由3.4°增大至51.1°。     

一种补偿量可调的反射式预失真线性化器

提出一种改进的反射式预失真电路,使其在相同功率区间上具有在线的补偿量调节能力。该电路对肖特基二极管不施加偏置电压,避免了因偏压改变而引起的补偿区间变化;在非线性产生电路中串联变容二极管,通过调节变容管的偏置电压,实现预失真器补偿量的调节。采用该方案设计加工了工作于29~31 GHz频段的反射式预失真器,实测结果表明:将变容管偏置电压由0调节至6 V,在相同功率区间内,该预失真器的增益扩张由4.5增大至7.6 d B,相位扩张由3.4°增大至51.1°。     

氮化镓功率放大器功率增益非线性的预失真电路设计

提供一种可实现氮化镓(GaN)功率放大器功率增益非线性预失真校正电路,克服了现有的氮化镓功率放大器的功率增益非线性或线性输出功率低的问题,使其在功率增益特性方面与砷化镓(GaAS)功放性能相似。该预失真电路具有性能优越、通用性强和灵活性好等特点。     

基于等效采样的数字预失真方法

为降低数字预失真系统对反馈回路ADC采样速率的要求,提出一种基于等效采样的预失真线性化方法,首先将周期性训练序列送入功放系统,然后采用等效采样的方式对反馈回路信号进行采样,最后使用等效采样数据设计预失真器。实验证明:文中提出的方法正确可行,能达到与实时采样方法相当的线性化效果。该方法可应用于小体积、低功耗、低成本的数字预失真功放线性化系统。     

基于改进记忆多项式的预失真技术研究

基于记忆效应的非线性放大器的预失真算法是预失真技术的关键点和难点。传统的记忆多项式模型运算复杂度高,实时性差,实际应用困难。本文对记忆多项式模型进行了改进,并对基于该模型的预失真方法的有效性进行了仿真验证。仿真结果表明,改进的记忆多项式功放模型能较好地表征宽带射频功率放大器的动态非线陛行为特性,且显著提高了运算速度。利用本文所提出的记忆效应的预失真算法能在保证线性化眭能的前提下,较大程度的提高了预失真算法的实时性。’     

Automatic Transformation of Curved-to-Flat Calibration Lines by a Normalizer

In high-accuracy swept-frequency insertion-loss testing, antenna-pattern measurement, and many other applications, significant measurement-system output variations are caused by the system itself. These variations can be recorded and subtracted from the measurement results to provide the required accuracy generally by recording system calibration lines with attenuation standards in the test position and reading the measurement results against these calibration lines. However, the procedure is tedious, costly, and does not lend itself to automation. The linearizer is a device for storing the system calibration and correcting for it before displaying the results. With no loss in accuracy, it provides an output curve that can be read on an ordinary rectilinear graph, used to actuate GO-NO GO switches, or automaticaly compare a test piece against a standard. Details of operation and some performance data are given for a particular analog-type linearizer and associated swept-frequency measurement system for insertion-loss or scattering coefficients. The linearizer can readily display a scale of 0.02 dB/inch with adequate stability and reproducibility. Two such linearizers can be used together to display two components of a vector or phase and amplitude, etc. Other applications are discussed and several possible approaches to an ideal system shown.     

Error Characteristics of a Nonlinear Sensor Used with a Linearizer

A formula is derived for the basic error of a measurement channel containing a nonlinear sensor and a linearizer matched to it. It is shown that a two-term formula is unsuitable for standardizing the error of such a combination.     

Adaptive compensation for position error signal nonlinearity

The magnetoresistive (MR) magnetic head is a poor positioning transducer for a disk file's servo control system because its positioning response is nonlinear with radial displacement. This paper shows how the MR head's poor positioning properties are alleviated by a self-adjusting adaptive algorithm that allows a disk file to linearize its own servo position error signal (PES). The adaptive linearizer uses a nonlinear state estimator whose nonlinearity adjusts to match the nonlinearity of the PES. As the match between the two nonlinearities adaptively improves, the state estimator gives increasingly accurate estimates of the true actuator position     

Hybrid predistortion to compensate third- and fifth-order intermodulation of a 2 GHz power amplifier using cuber predistortion and second harmonics injection

A new circuit construction technique that actively utilises second harmonics injection (HI) to realise fifth-order predistortion (PD) for power amplifiers (PAs) with memoryless AM/AM and AM/PM conversions is proposed. Applying a combination of the proposed technique and cuber predistortion (CPD) to third-order distortion yields the simultaneous compensation of both third- and fifth-order intermodulation distortion (IM3 and IM5); capabilities are not possible with the conventional third-order PD approach. Since the proposed method can be implemented as a simple analogue circuit, it betters compactness and lowers cost. In order to derive the PA bias condition at which second HI works most effectively, a complex power series nonlinear model that allows both amplitude and phase nonlinearities to be dealt with simultaneously is used. To confirm the author's compensation theory, a 2 GHz band PA and a hybrid lineariser that employs second HI and CPD are fabricated and experiments are performed. About a 20 dB simultaneous reduction in IM3 and IM5 is achieved with the two-tone test. A W-CDMA one-carrier test is also conducted to verify the improvement in adjacent channel leakage power ratio compared with CPD only.     

飞机训练拟器视景系统非线性失真校正技术研究

柱面实像投影是飞机训练模拟器视景系统采用的主要投影方式之一，可以得到很大的观察视野，但是不可避免地会产生非线性失真。根据具体的工程背景，针对大视场角的柱面实像投影的非线性失真，分析了其产生的原因，并设计了投影仪的离轴安装方案，从而提出了基于预失真的柱面投影非线性失真校正算法。实际的校正结果表明，采用预失真的方法进行柱面非线性失真校正，是一种行之有效的方法。通过相应的数据结构设计，保证了程序执行的实时性。     

飞机训练模拟器视景系统非线性失真校正技术研究

柱面实像投影是飞机训练模拟器视景系统采用的主要投影方式之一,可以得到很大的观察视野,但是不可避免地会产生非线性失真。根据具体的工程背景,针对大视场角的柱面实像投影的非线性失真,分析了其产生的原因,并设计了投影仪的离轴安装方案,从而提出了基于预失真的柱面投影非线性失真校正算法。实际的校正结果表明,采用预失真的方法进行柱面非线性失真校正,是一种行之有效的方法。通过相应的数据结构设计,保证了程序执行的实时性。     

A look-up-table digital predistortion technique for high-voltage power amplifiers in ultrasonic applications

In this paper, we present a digital predistortion technique to improve the linearity and power efficiency of a high-voltage class-AB power amplifier (PA) for ultrasound transmitters. The system is composed of a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), and a field-programmable gate array (FPGA) in which the digital predistortion (DPD) algorithm is implemented. The DPD algorithm updates the error, which is the difference between the ideal signal and the attenuated distorted output signal, in the look-up table (LUT) memory during each cycle of a sinusoidal signal using the least-mean-square (LMS) algorithm. On the next signal cycle, the error data are used to equalize the signal with negative harmonic components to cancel the amplifier's nonlinear response. The algorithm also includes a linear interpolation method applied to the windowed sinusoidal signals for the B-mode and Doppler modes. The measurement test bench uses an arbitrary function generator as the DAC to generate the input signal, an oscilloscope as the ADC to capture the output waveform, and software to implement the DPD algorithm. The measurement results show that the proposed system is able to reduce the second-order harmonic distortion (HD2) by 20 dB and the third-order harmonic distortion (HD3) by 14.5 dB, while at the same time improving the power efficiency by 18%.     

基于新型伸缩因子的PMSM模糊自适应反步控制

目的 为了解决包装机驱动控制系统在非线性因素的影响下,工作效率和产品质量大大降低的问题,提出一种基于新型伸缩因子的模糊自适应反步控制策略。方法 在传统自适应反步控制算法的基础上加入转速误差积分值对电流进行补偿,引入积分重置环节防止积分饱和引起调速时的超调和振荡,设计一种新的变论域伸缩因子,优化模糊推理模块,以在线整定转速反馈增益和自适应增益。结果 通过MATLAB/SIMULINK仿真结果表明,改进后的控制器通过对交轴电流值进行补偿,使参数摄动对系统的影响大大降低,并根据转速误差及其变化率自适应调整增益,进一步提高了控制系统的转速动态响应性能。结论 与常规传统PID控制系统和未优化的反步控制系统相比,文中优化后的控制器能增强被控系统的稳定性,缩短速度响应时间,具有更优的鲁棒性和动静态性能。     

外推法天线增益测量的核心算法及实验研究

基于外推法测量原理研究了外推法天线增益测量核心算法,重点在于天线互耦的滤波抑制、功率级数展开式的拟合和任意距离下的天线增益求解。此外,还基于以上核心算法设计了一款外推法天线增益测量界面,为外推法天线增益的精密测量提供便利。最后,开展了W波段标准天线的增益校准实验,增益测量结果与NPL的测量偏差小于0.04 dB,实现了较好的等效一致性。     

一种新的神经网络预失真器及其算法

针对高功率放大器(High Power Amplifier,HPA)的神经网络(Neural Network,NN)预失真器非直接学习方法中存在的预失真性能缺陷和直接学习方法中存在的计算复杂的弊端,本文基于非直接方法得到HPA后逆滤波器的精确辨识,利用非线件算子的运算性质及一种近似方法分别推导出了新的NN预失真器学习结构及其相应的自适应算法.该算法由HPA的后逆滤波器辅助,直接产生HPA的前逆滤波器的输出.与直接学习方法相比,它大大简化了计算复杂度.仿真结果表明,本文提出的NN预失真器学习方法可以有效地改善非直接学习方法的顶失真效果,进一步降低邻信道功率比约5dB.