向量开关模型的数字预失真改进方法

射频功率放大器的向量开关数字预失真模型存在因所在区域样本点不足而引起的不连续问题。提出一种基于向量开关模型的数字预失真改进方法,该方法通过加入区域权重的约束条件以及交叠的区域划分方法对向量开关模型进行优化,达到消除向量开关模型不连续问题,提高模型的稳定性。仿真实验中采用30MHz的LTE信号进行实验,当原方法出现不连续时新方法可消除间断点,同时在邻道泄漏比(ACLR)指标上有近6dB改善,结果表明其具有更好的鲁棒性。     

基于相移PWM调制的多电平D类功率放大器谐波分析

介绍了一种新颖的基于级联型多电平拓扑结构的开关型功率放大器,采用单极倍频相移PWM技术,其开关频率为单个单元开关频率的2N倍,总的输出电压波纹小.分析了级联型多电平技术的特点,重点研究了采用单极倍频相移PWM技术的多电平输出信号的谐波,最后研制了一台级联型多电平的D类功率放大器.研究结果证明了所研究的级联型多电平D类功率放大器输出电压谐波的正确性,表明该放大器具有良好的跟踪性和稳定性.     

Robust design of CMOS amplifiers oriented to settling‐time specification

In this paper, we propose a new approach for the robust design of complementary metal‐oxide‐semiconductor amplifiers based on settling‐time specifications. The approach is based on the definition of the separation factors and on the analysis of their role in the settling time. We define a design strategy for being certain that an OTA satisfies the settling‐time constraint under any statistical variation of process or design parameters. The proposed strategy is applied to the transistor level design of a two‐stage amplifier and a three‐stage one. Simulation results, in good agreement with theory, confirm the validity of the proposed approach. Copyright © 2016 John Wiley & Sons, Ltd.     

Alternative Realizations of CMOS Current Feedback Amplifiers for Low Voltage Applications

Two variants of a new current feedback amplifier (CFA) are presented in this paper. These CFAs are realized in CMOS technology and both are capable of working at low voltages. It is shown that one circuit performs better than the other by virtue of an increased impedance at its Z terminal achieved through the use of additional transistors. Analysis of both variants of the current conveyor and buffer that form the current feedback amplifier gives an insight into the location of primary poles and zeros of the CFAs. Simulation results indicate an overall gain bandwidth product in excess of 59 MHz and 102 MHz for each circuit at a gain of –10 and with a 3.3 V supply. Experimental results from a chip fabricated in a 0.35 m CMOS technology agree closely with the simulation results.     

基于前馈线性化的研究及改进

对前馈功率的线性化原理从时域上和频域上进行了综述。基于对相位、幅度、延时的失配影响的系统级分析对如何具体设计各部分电路给出了步骤和参数限制,对进一步电路实现选择元器件提供指导。最后基于前馈信号对消的原理提出了一种简化电路的方法,给出了该方法对处理器件的工作速度要求、精度和非线性性能提高的关系。     

宽频带光电隔离跟随器

本文给出了一种频带宽度为500kHz的光电隔离跟随器,分析了这种隔离跟随器的传递函数、频带宽度和温度漂移,以及电路设计和实验结果.分析和实验表明,本隔离跟随器具有频带宽、非线性失真小、体积小和成本低的特点,可用于仪表放大器的后置隔离跟随.     

A Self-Calibrated Pipeline ADC with 200 MHz IF-Sampling Frontend

A 13-bit, 50-MS/s pipeline ADC with IF-sampling capability is presented. A high sampling linearity is obtained through the use of bootstrapped switches. A digital self-calibration algorithm with modified capacitor measurement scheme is employed to improve the accuracy of the first two pipeline stages. The prototype, implemented with a 0.35-m BiCMOS (SiGe) technology, shows a 76.5-dB SFDR at a 194.2-MHz signal frequency and dissipates 715 mW power from a 2.9-V supply.     

A combined optical–wireless indoor communication system

This new combined optical–wireless indoor communication system provides an economic and flexible approach for local area networks mainly in large buildings or in a group of several buildings. The radiation from the radio base stations of mobile networks cannot penetrate into large buildings completely. That problem is more serious at higher frequencies. The present approach offers a good solution to this problem. In this approach the wireless communication serves small picocells which are interconnected by an optical backbone. The performance of the system is enhanced by assigning a specific radio frequency for each picocell which enables the transmission of the wireless channels without altering their modulation formats. This method allows for a simple, and low-cost indoor communication system.     

Behavioral modeling of power amplifiers for wireless applications

In this paper, an improved empirical behavioral model for radio‐frequency power amplifiers (RF‐PAs) is presented. The model was implemented in a commercial nonlinear microwave simulator. It belongs to the category of bandpass PA models, which exhibits memory effects due to the low frequency dependence of bias and temperature. Additionally, it facilitates accurate and efficient system level simulations of RF‐PA large‐signal behaviors such as self‐bias, AM‐AM, AM‐PM, gain expansion effects, and intermodulation distortion (IMD) sweet‐spots. The model was validated using measurement data obtained from a commercial CDMA PA at 1.88 GHz. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

组合结构设计的双频带数字预失真方法

双频带射频功放的数字预失真技术(DPD)要求支持更宽的带宽.为了保证功放输出的线性指标并降低预失真系统的实现开销,设计一种组合结构的双频带宽带数字预失真方法.该方法采用一维整频带数字预失真模型与四个一维分频带数字预失真模型的组合结构来综合处理双频带的发射信号.仿真实验结果表明,采用90 MHz的双频带LTE信号,临道泄露比(ACLR)指标较改进的二维记忆多项式DPD有1 dB提升,与二维DPD有0.5 dB差别,满足系统指标要求.