Prediction of Gain Expansion and Intermodulation Performance of Nonlinear Amplifiers

A mathematical model for the input‐output characteristic of an amplifier exhibiting gain expansion and weak and strong nonlinearities is presented. The model, basically a Fourier‐series function, can yield closed‐form series expressions for the amplitudes of the output components resulting from multisinusoidal input signals to the amplifier. The special case of an equal‐amplitude two‐tone input signal is considered in detail. The results show that unless the input signal can drive the amplifier into its nonlinear region, no gain expansion or minimum intermodulation performance can be achieved. For sufficiently large input amplitudes that can drive the amplifier into its nonlinear region, gain expansion and minimum intermodulation performance can be achieved. The input amplitudes at which these phenomena are observed are strongly dependent on the amplifier characteristics.     

射频包络消除与恢复功率放大器性能分析

从双频信号模型出发,分析了包络通道带宽和相位包络间信号延时差对交调失真的共同影响,得出了一个更符合测试结果的通用简化模型.该简化模型克服了Raab模型只能处理零延时差和无穷包络通道带宽这两个特例的局限性;采用本文模型得出的交调失真等高线图还可以帮助设计者快速准确地选择电路参数.最后,基于GSM/EDGE射频信号,用一个935MHz的射频功放示范了本文提出的设计方法.     

射频包络消除与恢复功率放大器性能分析

从双频信号模型出发,分析了包络通道带宽和相位包络间信号延时差对交调失真的共同影响,得出了一个更符合测试结果的通用简化模型.该简化模型克服了Raab模型只能处理零延时差和无穷包络通道带宽这两个特例的局限性;采用本文模型得出的交调失真等高线图还可以帮助设计者快速准确地选择电路参数.最后,基于GSM/EDGE射频信号,用一个935MHz的射频功放示范了本文提出的设计方法.     

Impact of second harmonic injection on the linearity and linear gain of RF/microwave amplifiers

This article reviews the development and applications of harmonic injection technique. It discusses the impact of second harmonic injection on the linearity and linear gain of amplifiers. It reveals that amplifier characteristics and input drive level determine whether second harmonic injection enhances or reduces the linear gain of an amplifier. Furthermore, a method has been developed to predict this behaviour which can be used to identify amplifiers that are best suited to harmonic injection or build amplifiers that may particularly be used with harmonic injection. For experimental investigation, a second harmonic injected amplifier was used that employs a frequency-doubler. In laboratory experiments, third-order intermodulation distortion was suppressed by 18?dB at the expense of 0.7?dB linear gain whereas theoretical analysis has predicted that second harmonic injection could compromise the linear gain of the amplifier by up to 1.3?dB for 20?dB distortion suppression.     

Performance analysis and comparison of multi-level hard limiters

A general formula, using a Fourier sine-series representation, is derived for the input–output characteristic of multilevel hard limiters (MHLs) with unequal output jumps occurring at unequally spaced inputs. Using this formula, closed-form expressions involving ordinary Bessel functions are obtained for the harmonic and intermodulation performance of MHLs excited by multisinusoidal inputs with arbitrary amplitudes. The results show that, compared to the ideal hard limiter, MHLs can result in a reduction in the relative third harmonic distortion of about 40 dB, and a reduction in relative third-order intermodulation distortion of about 19 dB depending on the amplitude of the input sinusoids and the shape of the MHL characteristic. Using the proposed model it is possible to generate a database for the harmonic and intermodulation performance of any MHL with arbitrary values of jumps and their locations. Simulation results obtained using the harmonic balance simulator controller in the advanced design system design automation software confirm the accuracy of the proposed technique.     

AB类功率放大器驱动电路的研究与设计

功率放大器是无线系统的重要组成部分,驱动电路是任何一类功放都必不可少的。各类功放的设计已有大量的文献发表,但只有较少的专利和文献涉及驱动电路的设计。AB类功率放大器是目前应用比较多的一种,因此AB类功放驱动电路的研究具有重要意义。针对MOS管的BSIM3模型,提出和分析了AB类经典功放的多种驱动电路方案,最后用HSpice对每个所设计的驱动电路进行了精确的仿真,验证了其可行性及正确性。     

行波管功率放大器在卫星地球站的应用

概述了目前卫星地球站常用的高功率放大器的种类,对CPI VZC-6965B5行波管功率放大器工作原理和性能特点作一介绍。     

EVM simulation and analysis in digital transmitter

The error vector magnitude (EVM) is extensively applied as a metric for digital transmitter signal quality compliance in modern communication systems. This article is focused on the effects of local oscillator (LO) phase noise and nonlinear distortion of power amplifier on EVM. This article contributes to below aspects. First, the relationships between EVM and two effects, LO phase noise and nonlinear distortion of power amplifier, are derived and expressed. Second, to simplify the expression, the third-order intermodulation distortion (IMD3) is used to calculate the EVM. Then, an expression for the EVM is derived based on the digital transmitter model that considers local oscillator phase noise and nonlinear distortion of power amplifier. Finally, the math formula of bit error rate (BER) versus EVM is given which can be easier and more useful to predict BER, according to analysis of the relationship between EVM and signal to noise rate (SNR), inspired by the works of Rishad, Md. Shahriar and AHM, 2006. Simulations are carried out to display the performance of EVM based on these relationships.     

宽带增益平坦光纤Raman放大器的研究进展

宽带增益平坦光放大器是密集波分复用光通信系统提高信息容量的基本需求。在总结宽带掺铒光纤放大器的基础上 ,介绍了展宽光纤Raman放大器平坦增益带宽的基本方法和研究现状。     

Large Signal Analysis of Harmonic and Intermodulation Distortion in Switched-Current Audio Memory Cells

Closed-form expressions are presented for the harmonic and intermodulation performance of SI audio memory cells excited by large amplitude multisinusoidal current signals. Effects of the threshold-voltage mismatch, the output conductance and the clock-injection are taken into consideration. The results show that under certain conditions, the second-harmonic components resulting from these three sources may be out of phase and thus cancellation, resulting in minimum distortion, may result.     

光波导放大器中的光场与铒浓度分析之间重迭的分析

本文在忽略放大自发辐射（ASE）和上转过程影响的情况下,用重迭因子的方法,得到了980nm波段泵浦的掺饵光波导放大器增益的隐式解析解、泵浦光沿波导方向分布的函数关系式和泵浦阈值功率的解析表达式。详细讨论了重迭因子对增益、泵浦阈值功率和波导中任意位置泵浦光分布的影响。     

前馈技术在改善功率放大器线性中的应用

推导并分析了存在增益和相位跟踪等误差情况下,功率放大器前馈技术对三阶线性失真的改善情况,并从原理上论述了前馈技术的工作原理.前馈技术一般可将三阶互调降低10～30 dB,在新一代的抗干扰跳/扩频电台中有广泛应用.     

功率放大器数字基带自适应预失真技术研究进展

阐述了目前国内外功率放大器（PA）线性化技术的研究状况,重点研究了其中最有应用前景的数字基带自适应预失真技术及其最新研究进展,分析并指出了相关方法的优缺点,并对其发展前景进行了展望。     

宽带OFDM功放自适应数字预失真算法的研究与实现

针对宽带OFDM功放的线性化问题,本文提出了一种基于训练序列的递推最小二乘算法和最小均方算法的组合算法.并将其应用到基于多项式的数字预失真系统中以实现自适应数字预失真滤波器系数的估计和更新.本文首先介绍了整个数字预失真系统的组成架构;然后是自适应数字预失真算法的实现,使用MATLAB软件对其算法进行仿真验证;最后还组建了实验系统,进行了ACLR测试实验.仿真结果和测试结果均表明基于自适应数字顶失真算法的宽带线性化功放具有良好的性能,OFDM功放输出的线性度改善6dB.     

High Power SiGe X-Band (8～10GHz) Heterojunction Bipolar Transistors and Amplifiers

Limited by increased parasitics and thermal effects as device size increases, current commercial SiGe power HBTs are difficult to operate at X-band (8～ 12GHz) frequencies with adequate power added efficiencies at high power levels. We find that, by changing the heterostructure and doping profile of SiGe HBTs, their power gain can be significantly improved without resorting to substantial lateral scaling. Furthermore, employing a common-base configuration with a proper doping profile instead of a common-emitter configuration improves the power gain characteristics of SiGe HBTs, thus permitting these devices to be efficiently operated at X-band frequencies. In this paper,we report the results of SiGe power HBTs and MMIC power amplifiers operating at 8～10GHz. At 10GHz,a 22.5dBm (178mW) RF output power with a concurrent gain of 7.32dB is measured at the peak power-added efficiency of 20.0%, and a maximum RF output power of 24.0dBm (250mW) is achieved from a 20 emitter finger SiGe power HBT. The demonstration of a single-stage X-band medium-power linear MMIC power amplifier is also realized at 8GHz. Employing a 10-emitter finger SiGe HBT and on-chip input and output matching passive components, a linear gain of 9.7dB,a maximum output power of 23.4dBm,and peak power added efficiency of 16% are achieved from the power amplifier. The MMIC exhibits very low distortion with 3rd order intermodulation (IM) suppression C/I of -13dBc at an output power of 21.2dBm and over 20dBm 3rd order output intercept point (OIP3).     

Performance of feed‐forward linearizers of power amplifiers in OFDM systems under complex gain errors

Adaptive feed‐forward (FF) linearization schemes of power amplifiers provide high distortion cancelation and adjacent channel power ratio (ACPR) reduction. However, FF schemes are very sensitive to imbalances in the circuit parameters used to achieve signal cancelation. In this paper, an FF linearization circuit is analyzed using the orthogonalization of the nonlinear model and considering the effects of complex gain errors in the signal and distortion cancelation loops on the overall performance of the FF linearizer. The analysis enables the effective signal‐to‐distortion ratio (SDR) and ACPR to be estimated from FF circuit model. It is shown that complex gain errors in the distortion cancelation loop have a more significant effect on in‐band distortion than out‐of‐band distortion, which means that the design of FF linearizers based on ACPR improvement is not optimal. Copyright © 2015 John Wiley & Sons, Ltd.     

基于ADS平台不对称Doherty功率放大器的仿真设计

为在高线性的前提下提高WCDMA基站系统中功率放大器的效率,仿真设计了一款工作于2.14 GHz频段不对称功率驱动的Doherty功率放大器。基于ADS平台,采用MRF6S21140H LDMOS晶体管,通过优化载波放大器和峰值放大器的栅极偏置电压改善三阶互调失真(IMD3),同时通过调节输入功率分配比例改善由于峰值放大器对载波放大器牵引不足导致的失配问题,从而改善不对称Doherty功率放大器的输出性能。仿真结果表明,当载波放大器的栅极偏置电压为2.84 V,峰值放大器的栅极偏置电压为0.85 V并且输入功率比例为1:2.3,输出功率为44 dBm时其功率附加效率(PAE)为24.21%,IMD3为-44.46 dBc,和传统AB类平衡功率放大器相比PAE提高了8.58%,IMD3改善了6.98 dBc。     

Trade-off between efficiency and linearity in an RF-power amplifier

RF-power amplifiers are used in a variety of applications including radio and TV transmitters, wireless communications, satellite communication systems and RF-power heating. Power efficiency and amplifier linearity are two key parameters which play a significant role in the design of modern power amplifiers. It is well known that driving the amplifier into its non-linear region, e.g. Class C operation, may improve efficiency, but it will also lead to increased distortion. This article examines the trade-off between efficiency and linearity quantitatively and advances a useful design rule.     

Statistics of the Carrier-to-Interference Ratio in C/TDMA Cellular Mobile Radio Systems Applying Multi-User Detection

In cellular mobile radio systems, interference is a limiting factor with respect to both system performance and system capacity. Therefore, profound knowledge of the statistics of the carrier-to-interference ratio C/I, given by the received carrier power C and the sum I of received powers associated with various interferers, is essential. In this communication, a general approach allowing the calculation of C/I for both the up- and the downlink of any interference limited mobile radio system is presented. Power control algorithms are explicitly considered. The general approach is used to provide insight into the statistics of C/I of C/TDMA systems applying multi-user detection, which are promising candidates for third generation mobile radio systems. For these C/TDMA systems applying multi-user detection, a representative selection of results is collected from the general approach and presented in this communication. Furthermore, results concerning the composition of the intercell interference are given. These results are of particular interest when plumbing potential benefits of worthwhile future enhanced multi-user detection schemes which explicitly incorporate a given number of intercell interferers.     

“软件无线电”在雷达系统中的应用和前景

“软件无线电”技术是一种新的通信系统结构，它以其开放性、灵活性给使用者带来前所未有的优秀性能。本文介绍“软件无线电”在雷达数字系统中的应用，分析了它的优缺点，展望了它的发展前景。