短波高线性前馈放大器的设计

提出了一种采用前馈线性化技术的短波放大器设计方法,介绍了前馈线性化技术的基本原理,研究了该方法在放大器设计中的应用,探讨了在工程实现中存在的问题及解决办法,使用仿真软件ADS构建电路模型,对放大器进行了仿真及优化设计,制作了一个短波高线性前馈放大器样件,对样件进行了指标测试并与主放大器进行对比,详细分析了测试结果,验证了这种方法的可行性.     

Compensating combustion forces for automotive electromagnetic valves

Electromagnetic actuators show considerable promise in replacing camshafts in automotive combustion engines. Most research published to date focuses on reducing valve seating velocity. This is usually achieved using a current feed-forward controller during most of the valve travel and a trajectory controller with a fixed trajectory close to the end of travel. Such systems face considerable challenges in the presence of varying combustion forces, since the feed-forward strategy cannot ensure constant starting conditions for the tracking controller. The work shown here replaces the feed-forward controller with an energy based feedback controller. For the tracking controller with feedback linearization at the end of the valve travel, real-time trajectories that adapt to different starting conditions are derived. The algorithms can adapt to large changes in combustion pressure without relying on a priori combustion information. The algorithms are validated using simulations and on an experimental test bed.     

Reduction of noise and distortion in amplifiers using adaptivecancellation

Application of adaptive cancellation techniques to feed-forward networks for amplifier linearization is discussed. Results of a test showing over 25 dB reduction in third order intermodulation products are presented     

前馈功率放大器的常用自适应方法

提出了功率放大器中使用线性化技术的必要性。介绍了前馈功率放大器的设计方案和基本原理。针对前馈放大器的线性度因外部工作环境条件变化而产生恶化的问题,引入了功率放大器的自适应方法。提出了3种常用的前馈功率放大器自适应方法:导频法、最小功率检测法和相关检测法。分别讲述了这3种自适应方法的基本原理及其优缺点,并提出最小功率检测法是一种简便易行有效的自适应方法。     

BUCK变换器的一种多环控制研究

文中研究了一种具有快速动态响应的多环控制方法,介绍了多环控制方法的工作原理,并建立了器件模型,利用Matlab的Power System Blockset对该模型的特性进行了时域仿真,并将仿真结果与传统的电压型。电流型控制方法进行比较,对分析结果进行了验证。     

多环路交叉眼干扰的波前相位畸变研究

多环路交叉眼干扰能够有效改善交叉眼干扰严苛的实施条件而成为角度欺骗的研究热点。该文提出中心畸变程度和有效畸变区两个指标对多环路交叉眼干扰系统的波前相位畸变特性进行研究。首先，推导建立多元干扰信号的合成场模型，并以中心畸变程度和有效畸变区为目标函数建立约束模型；其次，通过MOEA/D算法对各环路干扰信号幅度比、相位差、环路数等参数进行优化分析；最后，结合对雷达的跟踪角干扰效果进行仿真验证。结果表明，相比于单环路干扰系统，多环路交叉眼干扰系统能够有效提高中心畸变程度和增大有效畸变区，同时随着环路数增加，干扰系统对单脉冲雷达的干扰效果减小, 使干扰系统更多地表现为雷达指示器的作用。      

一种新的用于射频功率放大器的预失真法

改善射频功率放大器非线性的方法通常有功率回退法、负反馈法、前馈法和预失真法。预失真技术与其他线性化技术相比具有电路结构简单、性能优良、成本低等优点,因而受到设计者的青睐。设计了一种利用混频器和滤波器分别产生三阶和五阶交调分量的预失真器,采用复增益调节器控制预失真器产生的IMD3,IMD5幅度和相位。并从理论上对其特性进行了分析,利用专用的微波电路仿真工具进行仿真验证,仿真结果表明双音测试在2 GHz频段,IMD3和IMD5分别改善了17 dBc和12 dBc。     

Multitone power and intermodulation load-pull characterization ofmicrowave transistors suitable for linear SSPA's design

In this paper, an experimental load-pull characterization of microwave transistors operated under N-tone-excitations (2⩽N⩽32) is presented. Such characterization is very useful to investigate the linearity of high-power amplifiers via intermodulation distortion analysis. All the measurements were carried out using a newly developed multiline measurement system which uses an arbitrary waveform generator (AWG) to generate the spectrum of any N desired tones and a microwave transition analyzer (MTA) as a vector receiver. The measured intermodulation rejection (IMR) behavior, as the number of tones increases, is compared with previously published theoretical results. Constant output power contours and IMR contours in the Γ_L (f₀) plane for different number of tones are presented and discussed. The dependency of the IMR on the biasing conditions and the carriers' phase distribution is also investigated     

5G光载无线通信前传系统数字预失真线性化研究

第五代移动通信系统新空口(5G NR)的信号带宽、调制度和峰均比相比4G信号高很多。用于小蜂窝或微蜂窝基站组网的光载无线通信(Radio-over-Fiber, RoF)前传系统的非线性失真也更加严重。为了使5G NR信号线性传输,采用记忆多项式(Memory Polynomial, MP)和广义记忆多项式(Generalized Memory Polynomial, GMP)模型构建数字预失真器,矫正5G RoF前传系统的非线性。在实验中搭建了2 km光纤的RoF前传系统,并采用100 MHz带宽5G NR信号作为测试信号对其进行线性化测试。实验结果表明,采用MP和GMP数字预失真器进行线性化时,5G RoF前传系统的邻信道功率比(Adjacent Channel Power Ratio, ACPR)可分别改善13 dB和17 dB以上。这说明MP和GMP数字预失真器对5G RoF前传系统的非线性具有显著的抑制作用。因此基于MP和GMP两个模型的数字预失真器均可用于5G RoF前传系统的线性化,而且GMP预失真器比MP预失真器对该系统线性化的能力更强。     

74 dB SNDR Multi-Loop Sturdy-MASH Delta-Sigma Modulator Using 35 dB Open-Loop Opamp Gain

This paper presents a new multi-loop delta-sigma modulator which overcomes the necessity of high DC gain opamps that were needed in previous multi-loop modulators. Enabling the use of low gain opamps also allows low-voltage operation due to the reduced number of transistors between the power supply rails. In addition, all the digital filters are removed from the output of this modulator to minimize the overall system requirement. Instead, an in-loop digital addition facilitates the desired noise transfer functions of both loops. This combines stability advantage of the multi-loop structure with relaxed circuit requirement of the single-loop modulator. A fourth order modulator is implemented in a 0.18 $mu$m CMOS technology to demonstrate this concept. Measurement results show that, with open-loop opamp gain of less than 35 dB, the implemented prototype IC achieves over 74 dB SNDR at an oversampling ratio of 16. The sampling frequency is 20 MHz and the total power dissipation is 3.2 mW at 1.2 V supply.      

雷测数据动态滞后误差修正新思路

针对动态目标过捷近点时引起的雷测数据动态滞后误差,分析了雷达伺服系统产生动态滞后误差的原因,采用前馈网络的功能,提出前馈滤波系统,从理论上讨论和仿真试验验证了该系统的有效性,为提高数据处理精度提供可靠的数据源。     

Digital Predictive Feed-Forward Controller for a DC–DC Converter in Plasma Display Panel

This paper describes a new digital control method to enhance the dynamic performance of a dc-dc converter used in plasma display panel (PDP). A simple digital PID compensator with duty ratio feed-forward control is proposed to minimize the output voltage variation while the load current is continuously changing. The duty ratio feed-forward is calculated using noise-free load current information which is predicted by the available video data of the PDP. No separate current sensing circuit is required. A small signal z-domain feed-forward model is derived for the performance analysis and controller design. The proposed control method is experimentally verified on an asymmetrical half bridge dc-dc converter which supplies power to a 42 in PDP.     

新构型下多环路反向交叉眼干扰分析

提出一种由四个干扰阵元呈线阵不等间隔排布而构成的全新多环路反向交叉眼干扰构型,并借助通道回波、矢量合成和角度因子,分别对新构型下多环路反向交叉眼干扰的诱骗角度、诱骗距离和参数容限进行了详细的理论推导和仿真验证.仿真结果表明,在Ku波段,搭载于大型平台上的新环路构型不仅可产生很大的交叉眼增益,引导单脉冲雷达产生更大的诱骗距离和诱骗角度,而且在给定角度因子的情况下,随着干扰距离和干扰机转角的增大,角度因子等高线明显减小,多环路反向交叉眼干扰对参数容限的要求也越来越严苛.     

基于Matlab的BP神经网络结构与函数逼近能力的关系分析

人工神经网络是一种非线性动态数学模型,广泛应用于非线性系统建模、系统辨识、函数逼近等方面。介绍BP网络的结构和学习过程,并介绍利用Matlab人工神经网络工具箱设计BP网络的步骤,在此基础上设计了BP网络以验证其函数逼近能力,仿真结果说明了BP网络具有很强的函数逼近能力。并分析BP网络结构和函数逼近能力的关系,得出网络的结构直接影响网络对函数的逼近能力和效果。     

Source Coding With Feed-Forward: Rate-Distortion Theorems and Error Exponents for a General Source

In this work, we consider a source coding model with feed-forward. We analyze a system with a noiseless, feed-forward link where the decoder has knowledge of all previous source samples while reconstructing the present sample. The rate-distortion function for an arbitrary source with feed-forward is derived in terms of directed information, a variant of mutual information. We further investigate the nature of the rate-distortion function with feed-forward for two common types of sources- discrete memory- less sources and Gaussian sources. We then characterize the error exponent for a general source with feed-forward. The results are then extended to feed-forward with an arbitrary delay larger than the block length.     

Statistical control of VLSI fabrication processes. II. A softwaresystem

For pt.I see ibid., vol.1, no.2, p.62-71, 1988. The algorithms used to implement the CMU-CAM statistical control system for VLSI integrated circuit fabrication are presented. The CMU-CAM system performs three major operations: modeling; quality control; and feed-forward control. In order to increase the efficiency of modeling and control, the problem is decomposed using statistical factorization techniques. Algorithms for process modeling and algorithms used in quality control and feed-forward control are described. The CMU-CAM system performs profit maximization through statistical process control. Its capabilities are illustrated by a number of computational examples     

Linearity enhancement of TVGA based on adaptive sweep optimisation in monostatic radar receiver

The limited input dynamic power range of the radar receiver and the power loss due to the targets’ ranges are two potential problems in the radar receivers. This paper proposes a model based on the time-varying gain amplifier (TVGA) to compensate the power loss from the targets’ ranges, and using the negative impedance compensation technique to enhance the TVGA linearity based on Volterra series. The simulation has been done based on adaptive sweep optimisation (ASO) using advanced design system (ADS) and Matlab. It shows that the suppression of the third-order intermodulation products (IMR3) was carried out for two-tone test, the high-gain accuracy improved by 3 dB, and the high linearity IMR3 improved by 14 dB. The monostatic radar system was tested to detect three targets at different ranges and to compare its probability of detection with the prior models; the results show that the probability of detection has been increased for ASO/TVGA.     

有色噪声下的不敏卡尔曼滤波器

有色噪声干扰情况下非线性系统的状态估计是许多实际工程需要解决的问题。通常的方法是利用扩展卡尔曼滤波方法将非线性系统线性化后,再利用线性系统的方法对有色噪声系统进行估计。然而,模型的线性化误差往往会严重影响最终的滤波精度,甚至导致滤波发散。为了避免此类误差,先通过对测量方程进行变换的方法,将观测方程的有色噪声转换为白噪声后,再利用不敏卡尔曼滤波方法,对系统的状态进行估计。虽然,该方法也需要对观测方程进行线性化,但是由于此线性化过程是在求解新量测方程的测量误差中进行,因此对系统的误差影响不是很大。仿真结果表明新方法能够有效地对有色噪声环境下系统的状态进行估计,性能要优于现有的一些基于EKF的方法。     

Analysis of Adaptive Digital Feedback Linearization Techniques

A new lookup-table linearization technique is developed based on the digital feedback and digital feedback/predistortion (DFBPD) concepts. The linearization characteristics are investigated through system simulation of a real power-amplifier model with 90-W peak envelope power. The DFB suppresses forward-path nonlinear distortion as a gain reduction due to the FB effect, and this technique enhances the system tolerance without any bandwidth limitation. As the PD network is added to the FB loop, the linearization performance and system tolerance are further improved because of more accurate PD signal extraction. In addition, the gain is purely determined by the FB path, so the gain fluctuation in the forward path, including amplifier aging and temperature effects, is suppressed. The analysis and simulation allow experimental evaluation of the linearization mechanism and performance of the DFBPD technique for an 802.16e mobile Worldwide Interoperability for Microwave Access signal.      

结构光三维视觉检测系统的标定方法研究

提出了一种新的结构光三维视觉检测系统的标定方法,将BP神经网络和线性标定方法结合起来,用线性标定方法标定结构光系统的线性部分,用BP神经网络来描述该结构光系统的其他部分.结果表明:该方法结合了神经网络和线性标定方法的优点,不仅给出了结构光三维检测系统中CCD相机的内部和外部参数,而且利用神经网络的非线性逼近能力,补偿由于镜头径向畸变、切向畸变等因素引起的系统非线性误差,并且精度高、抗噪声能力强及鲁棒性好.