射频宽带低噪声放大器的设计与仿真

介绍了一种射频宽带低噪声放大器的设计过程,包括稳定性分析、偏置电路设计和匹配电路设计等内容.设计采用E-PHEMT晶体管(ATF-55143)器件模型和其他元件模型.通过采用ADS技术进行电路和电磁仿真,结果表明设计的放大器完全满足性能指标要求.     

有源滤波器设计中运算放大器的设计考虑

本文分析了对含有强高频信号分量、选出小低频信号的有源滤波器设计中，运算放大器的设计考虑。     

便携式心电监护系统设计

采用基于ARM7内核的LM3S811处理器为核心设计了便携式心电监护系统。通过输入保护电路、前置放大电路、带通滤波电路、50Hz限波电路、主放大电路,主要实现对心电信号的前级采集和调理;通过LM3S811控制A／D转换、S卡D数据扩展存储、LCD显示,实现对心电信号的模数转换、存储、显示和传输。     

评估COA放大性能的方法

本文提出直接评估电流反馈运算放大器放大性能的方法。     

高效率线性RF功放的研究与设计

应用EER(Envelope Elimination and Restoration)线性功放技术和高效率D类音频放大技术，实现了一个高效率线性RF功率放大器。该线性放大器为AM调制，7MHz时效率优于75％。     

实用运算放大器网络中的虚地性质

本文提出用一个理想电压控制电流源(VCCS)并接于嵌在一个倒相放大器电路中的实际运算放大器(OP.amp)输入端,虚地性质(VGP)可以扩展到使用的运算放大器单位增益带宽那样高的频率.文中给出用真正运算放大器的VCCS的实用电路.用互补变换法可得出非倒相放大电路图.     

音频功率放大器

本设计是一款基于模电知识的音频放大器,功率放大器的作用是将声音源输入的信号进行放大,然后输出驱动扬声器。声音源的种类有很多种,故输出信号的电压差别很大,从零点几毫伏到几百毫伏。一般动率放大器的输入灵敏度是一定的,这些不同的声音源信号如果直接输入到功率放大器的话,对于输入信号过低的,功率放大器功率输出不足,不能充分发挥功放的作用;加入输入信号的幅值过大,功率放大器的输出信号将严重过载失真。这样就失去了音频放大的意义了,所以一个实用音频功率放大系统必须设置前置放大器,以便使放大器适应不同的输入信号,或放大,或衰减,或进行阻抗变换,使其与功率放大器的输入灵敏度相匹配。     

浅谈大功率ocl放大器的调试及保护

大功率ocl放大器的调试与保护时电力工程中十分重要的环节,而实际工作中由于技术人员的专业水平或电力条件的限制,常会出现各种异常情况.本文首先分析了放大器电路的集中常见形式,并重点研究了大功率ocl放大嚣的设计与制作,在此基础上对其调试与保护工作进行分析.     

A/D转换器的前置放大器电路

NE5539适合作视频信号的高频带信号放大器,具体电路如图所示。它是用作A/D转换器PNA7507的电平移位放大器。PNA7507输入信号电平最大为5.0V最小为2.5V,则放大     

微波反馈放大器匹配及增益带宽的研究

本文介绍的是小信号微波反馈放大器的分析与综合。放大器是采用通常的增益级的框图,并取并联反馈。文中提供全部网络元件值的估算和预测闭环宽频带增益、带宽和双端口的匹配值。简述匹配值与增益用图解法的权衡。最后描述了综合方法并举例说明设计实例。     

用微变等效法分析差动放大电路

传统对差动放大电路的动态分析,均多是根据输入、输出信号的特点,利用特定条件下的微变等效分析,这种方法易于得出结论,但不容易理解其物理含义,这是认识和理解差动放大电路的难点之一。文中从典型的电路出发,根据连接方式的不同,得出相应的指标,从而解决了这个难题。     

Competition in the LM market

This paper considers the competition in the LM (land-to-mobile) market mainly by focusing on how access charges are determined in a competitive environment. Contrary to the widely held belief, the main beneficiary to introducing competition into the LM market (except consumers) is the mobile network operator if LM services are homogeneous. This is due to its ability to charge differentiated access fees to each of the LM service providers thereby inducing them to compete for LM retail prices. Also, competition in the LM market raises social welfare by eliminating double marginalization. Thus, the regulation imposing uniform access charges is socially undesirable in the sense that it hinders LM service providers from effectively competing for retail prices.     

Delay Dynamics in a Classical IS‐LM Model with Tax Collections

An IS‐LM model is developed for the dynamics of income, interest rate and money stock with delay in tax revenue. The main aim is to show that the delay matters in macro dynamics. Two different delays, fixed time delays and continuously distributed time delays, are considered explicitly and described by delay‐differential equations and integro‐differential equations, respectively. Conditions for the local stability of the two models are derived and compared. The destabilizing effects caused by the delay are numerically examined. Appearance of wide spectrum of dynamics ranging from simple cyclic oscillations to complex dynamics is described through Hopf bifurctions.     

高分辨雷达的一种新的波形设计

频率步进合成高分辨雷达体制受目标径向运动速度的影响极大,为了获取目标准确的高分辨距离像,需要做运动补偿。目标运动速度的估计精度直接决定速度补偿效果。首先分析了顺序跳频和随机跳频两种高分辨信号的特点,然后概述了相参合成处理实现高分辨的方法,最后研究了目标运动对这两种信号合成一维距离像的影响,并在此基础上提出了一种新波形的设计方法,从而大大提高了目标速度的估计精度。     

Window on Eastern Europe: Teaching Ethics in Gdańsk

Against the background of a new Ten Commandments for the Polish business community a new course in business ethics is now being offered to students in the Faculty of Management and Economy of the Technical University of Gdańsk, ul. G. Narutowicza 11/12, 80-952 Gdańsk, Poland. Dr Kinach-Brzozowska, who introduced the course last year, describes its content and her students'needs and reactions.     

Do Brands Serve as Reliable Signals of Nutritional Quality? The Case of Breakfast Cereals

Organic and national brand manufacturers position their offerings as nutritious meals for adults and children. Do these brands serve as reliable signals of nutritional quality? To find an answer, this study analyzed a very popular, ready-to-eat breakfast cereal food category based on all the available data from 2011 (324 offerings) from a large UK grocery comparison website, mysupermarket.co.uk. The study shows that it is possible to find store and basic brand offerings that are almost identical to national brand offerings, but much cheaper and with less sugar (the main concern in cereal). Hedonic price regression analysis further confirms that brand and size explain most of cereal’s price variability, regardless of nutritional quality. The findings also reveal that low-sugar cereals are hard to find regardless of price, and almost all cereals targeted at children have high levels of sugar. A replication study (337 offerings in 2012) revealed that, on average, cereal sugar levels and prices increased, while nutritional value decreased.     

放大器估计器的查表法自适应预失真器设计

非线性功放特性随温度,供电电压等因素的变化而改变,为保证其稳定工作,预失 真系统的自适应性能就显得非常重要。当前的自适应预失真算法每次都对其参数进行更新, 计算量很大。针对这个问题提出了一种放大估计器的查表法自适应预失真算法,将查表法和 放大器估计器法结合在一起,以误码率为指标在系统允许的误差范围内可以大大减少参数的 迭代次数。同时针对不同的输入回退,可以选择采用不同的预失真算法,从而使其更加接近 功放特性,进一步减少迭代次数。     

基于角度重构和差分飞行时间的室外多站定位

针对当前室外定位基站和目标之间的信号收发不同步,以及非视距(Non-Line of Sight,NLOS)环境下定位困难的问题,提出了一种基于角度重构和差分飞行时间(Time of Flight,TOF)的室外NLOS多站定位方法。首先,基于单次散射模型给出了一种关于散射体波达角(Angle of Arrival,AOA)的粗略重构方法,再利用多径信号的差分TOF并结合模型中目标、散射体、基站之间的几何位置关系构建定位方程;然后,结合先验信息添加约束区间并结合定位方程将定位问题转化为最小二乘优化问题,并利用列文伯格-马奈尔特法(Levenberg Marquardt,LM)算法进行初始解算得到基站到目标的初始估计距离;最后,将每个基站的距离估计结果进行联合多边定位得到最终目标位置。仿真结果表明,该方法利用多个基站能在室外NLOS环境中实现较高定位精度。     

Bank lending,misleading signals,and the latin american debt crisis

This article explores the microfoundations of bank and borrower behavior in the Latin American debt crisis. In the model developed, less developed countries attract loans by signaling their ability and willingness to pay. Some of the signals are “coercive” because they indicate that if income targets are not met, income will be redistributed in order to honor debt obligations. Implicit in such coercive signaling is the borrower's expectation that redistribution will not damage economic productivity. A coercive signal is misleading when feedback effects on social stability and work effort—and thus on the ability to pay—are underestimated or ignored; in this case, it inaccurately predicts repayment prospects. We estimate two equations: (1) private lending to Latin borrowers as a function of our specified signals, and (2) the probability of payments problem as a function of the same set of signals. The results support our borrowing model: coercive signals do enhance lending, and at least one of these signals is misleading.