Multi-frequency point supported LLRF front-end for CiADS wide-bandwidth application

The China initiative Accelerator Driven System,CiADS,physics design adopts 162.5 MHz,325 MHz,and 650 MHz cavities,which are driven by the corresponding radio frequency(RF)power system,requiring frequency translation front-end for the RF station.For that application,a general-purpose design front-end prototype has been developed to evaluate the multi-frequency point supported design feasibility.The difficult parts to achieve the requirements of the general-purpose design are reasonable device selection and balanced design.With a carefully selected low-noise wide-band RF mixer and amplifier to balance the performance of multi-frequency supported down-conversion,specially designed LO distribution net to increase isolation between adjacent channels,and external band-pass filter to realize expected up-conversion frequencies,high maintenance and modular front-end generalpurpose design has been implemented.Results of standard parameters show an R2 value of at least 99.991%in the range of-60-10 dBm for linearity,up to 18 dBm for P1dB,and up to 89 dBc for cross talk between adjacent channels.The phase noise spectrum is lower than 80 dBc in the range of 0-1 MHz;cumulative phase noise is 0.006°;and amplitude and phase stability are 0.022%and 0.034°,respectively.

基于硅工艺的12GHz单片接收RF Front-End设计

提出了一种基于硅材料的、工作在12 GHz频率的用于接收卫星数字图像广播的单片射频前端系统,该系统含有低噪声放大器、混频器和第二级放大器,所有的电路都集成在硅材料工艺中,可以用于频率在12GHz的卫星通信频段信号的接收。

RF front-end for digital beam position monitor signal processor

RF circuit board has a significant impact on performance of the Digital Beam Position Monitor (DBPM) in storage ring of a synchrotron radiation facility.In this paper,a front-end RF board is designed for DBPM,and schematics of the RF board and the test results are given.In view of the inevitable inconsistency in the multi-channel circuit,a calibration circuit is designed to reduce such an influence.The test results show that the calibration method is useful for beam current dependence which is sensitive to channels inconsistency.

Design and Analysis of Analog Front-End of Passive RFID Transponders

An analog front-end of HF passive RFID transponders compatible with ISO/IEC 18000-3 is presented.Design considerations, especially the power transmission in the RFID transponder, are analyzed. Based on these considerations,an analog front-end is presented with novel architecture, high power conversion efficiency, low voltage, low power consumption, and high performance in an environment of noise and power fluctuation. The circuit is implemented in a Chartered 0.35μm standard CMOS process. The experimental results show that the chip can satisfy the design target well.

An RF front-end with an automatic gain control technique for a U/V band CMMB receiver

This paper presents a fully integrated RF front-end with an automatic gain control（AGC） scheme and a digitally controlled radio frequency varied gain amplifier（RFVGA） for a U/V band China Mobile Multimedia Broadcasting（CMMB） direct conversion receiver.The RFVGA provides a gain range of 50 dB with a 1.6 dB step. The adopted AGC strategy could improve immunity to adjacent channel signal,which is of importance for CMMB application.The front-end,composed of a low noise amplifier（LNA）,an RFVGA,a mixer and AGC,achieves an input referred 3rd order intercept point（IIP3） of 4.9 dBm with the LNA in low gain mode and the RFVGA in medium gain mode,and a less than 4 dB double side band noise figure with both the LNA and the RFVGA in high gain mode.The proposed RF front-end is fabricated in a 0.35μm SiGe BiCMOS technology and consumes 25.6 mA from a 3.0 V power supply.

Noise-canceling and IP3 improved CMOS RF front-end for DRM/DAB/DVB-H applications

A CMOS RF（radio frequency） front-end for digital radio broadcasting applications is presented that contains a wideband LNA,I/Q-mixers and VGAs,supporting other various wireless communication standards in the ultrawide frequency band from 200 kHz to 2 GHz as well.Improvement of the NF（noise figure） and IP3（third-order intermodulation distortion） is attained without significant degradation of other performances like voltage gain and power consumption.The NF is minimized by noise-canceling technology,and the IP3 is improved by using differential multiple gate transistors（DMGTR）.The dB-in-linear VGA（variable gain amplifier） exploits a single PMOS to achieve exponential gain control.The circuit is fabricated in 0.18-μm CMOS technology.The S11 of the RF front-end is lower than -11.4 dB over the whole band of 200 kHz-2 GHz.The variable gain range is 12-42 dB at 0.25 GHz and 4-36 dB at 2 GHz.The DSB NF at maximum gain is 3.1-6.1 dB.The IIP3 at middle gain is -4.7 to 0.2 dBm.It consumes a DC power of only 36 mW at 1.8 V supply.

Design of a low-power 433/915-MHz RF front-end with a current-reuse common-gate LNA

This paper presents a wideband RF front-end with novel current-reuse wide band low noise amplifier （LNA）, current-reuse V-I converter, active double balanced mixer and transimpedance amplifier for short range device （SRD） applications. With the proposed current-reuse LNA, the DC consumption of the front-end reduces considerably while maintaining sufficient performance needed by SRD devices. The RF front-end was fabricated in 0.18μm RFCMOS process and occupies a silicon area of just 0.11 mm^2. Operating in 433 MHz band, the measurement results show the RF front-end achieves a conversion gain of 29.7 dB, a double side band noise figure of 9.7 dB, an input referenced third intercept point of -24.9 dBm with only 1.44 mA power consumption from 1.8 V supply. Compared to other reported front-ends, it has an advantage in power consumption.

A wideband large dynamic range and high linearity RF front-end for U-band mobile DTV

A wideband large dynamic range and high linearity U-band RF front-end for mobile DTV is introduced, and includes a noise-cancelling low-noise amplifier （LNA）, an RF programmable gain amplifier （RFPGA） and a current communicating passive mixer. The noise/distortion cancelling structure and RC post-distortion compensation are employed to improve the linearity of the LNA. An RFPGA with five stages provides large dynamic range and fine gain resolution. A simple resistor voltage network in the passive mixer decreases the gate bias voltage of the mixing transistor, and optimum linearity and symmetrical mixing is obtained at the same time. The RF front-end is implemented in a 0.25 #m CMOS process. Tests show that it achieves an IIP3 （third-order intercept point） of -17 dBm, a conversion gain of 39 dB, and a noise figure of 5.8 dB. The RFPGA achieves a dynamic range of-36.2 to 23.5 dB with a resolution of 0.32 dB.

A 5.4mW Low-Noise High-Gain CMOS RF Front-End Circuit for Portable GPS Receivers

This paper describes a CMOS low noise amplifier （LNA） plus the quadrature mixers intended for use in the front-end of portable global positioning system （GPS） receivers. The LNA makes use of an inductively degenerated input stage and power-constrained simultaneous noise and input matching techniques. The quadrature mixers are based on a Gil- bert cell type. The circuits are implemented in a TSMC 0.18μm RF CMOS process. Measurement results show that a voltage conversion gain of 35dB is achieved with a cascade noise and an input return loss of - 22.3dB. The fully differential figure of 2.4dB,an input ldB compression point of - 22dBm, circuits only draw 5.4mW from a 1.8V supply.

基于改进KNN-RF的信息补全算法

针对室内指纹定位指纹库数据在实际环境中存在数据缺失导致定位误差大的问题,本文提出了一种改进距离公式的K近邻-随机森林的信息补全算法。首先,采用高斯滤波对收集的指纹数据进行预处理,去除干扰数据项,提高数据可靠性。其次,在将指纹数据划分为训练集和测试集的基础上,采用结合欧氏距离和曼哈顿距离的KNN算法获得近邻集合样本,随后用RF算法对近邻集合训练进行优化,再把各个决策树的预测结果取平均值,得到缺失数据的预测值。最后,将改进的补全算法与KNN、改进的KNN、RF和KNN-RF补全算法进行对比。实验结果表明,本文的改进补全算法的预测准确率和精度均优于其他算法,预测的准确率达91.3%。同时本文补全算法的指纹库平均定位误差为1.82 m,相较于其他补全算法的指纹库定位误差降低了1.6%~7.2%,定位性能更好。

Analysis and Design of a Low-Cost RFID Tag Analog Front-End

A new,low-cost RFID tag analog front-end compatible with ISO 14443A and ISO 14443B is presented. By substituting conventional multi-circle antenna with single-circle antenna, the package cost of the tag is greatly reduced. Based on this exasperate antenna performance,a new rectifier with high power conversion efficiency and low turn-on voltage is presented. The circuit is implemented in an SMIC 0.18μm EEPROM process. Measurement results show that with a 120kΩ load,the power conversion efficiency reaches as high as 36%. For a sinusoidal wave with magnitude of 0. 5V, the output DC voltage reaches IV,which is high enough for RFID tags. The read distance is as far as 22cm.

基于LSTM-RF的电动钻机绞车齿轮箱故障诊断

针对提高石油电动钻机绞车齿轮箱故障诊断的准确性和效率,提出了一种基于长短期记忆网络(long short-term memory,LSTM)和随机森林(random forest,RF)融合模型。首先,运用LSTM能够从大规模数据中学习复杂特征,将这些特征作为随机森林的输入。然后,通过随机森林处理非线性和高维数据以及对特征的分类,以实现对齿轮不同故障状态的识别。最后,利用电动钻机绞车齿轮箱运行过程中的实时数据,建立了一个包含多种齿轮故障类型的综合数据集。试验结果表明,LSTM齿轮故障诊断准确率为94.67%,RF齿轮故障诊断准确率为94.34%,支持向量机齿轮故障诊断准确率为82.00%,K近邻齿轮故障诊断准确率88.33%,而融合模型LSTM-RF在齿轮故障诊断准确率方面达到了98.33%,克服了单一模型的局限性,提高了诊断准确性。研究表明了融合模型具有更优的电动钻机绞车齿轮箱故障诊断能力。

基于VPNRS-RF的飞机液压系统故障诊断模型

针对飞机液压系统故障诊断特征值冗余难以精准获取和准确率不高的问题,提出一种基于变精度邻域粗糙集(Variable Precision Neighborhood Rough Set,VPNRS)和随机森林(Random Forest,RF)相结合的特征选择算法,并以此为基础建立飞机液压系统故障诊断模型。VPNRS-RF算法主要是利用随机森林算法分别对变精度邻域和模糊熵粗糙集约简后的特征进行重要度排序,再次筛选后确定最优特征子集,使用最优特征子集对在线贯序极限学习机(OSELM)分类模型进行训练,从而提高故障信息获取准确率。最后以飞机起落架收放系统为例进行仿真研究,验证了VPNRS-RFOSELM模型的优越性。

基于RF-SFLA-SVM的装配式建筑高空作业工人不安全行为预警

为有效预警装配式建筑高空作业工人不安全行为的发生趋势或状态,增强对装配式建筑工人不安全行为(PBWUBs)的管控,采用随机森林(RF)-混合蛙跳算法(SFLA)-支持向量机(SVM)模型,开展工人不安全行为预警研究。首先,采用SHEL模型分析处于高空作业危险中的PBWUBs的影响因素,并通过RF确定关键预警指标;然后,采用SFLA对SVM的参数进行寻优改进;最后,利用RF-SFLA-SVM预警高空作业PBWUBs,提出应对措施,并与其他预警模型对比。研究结果表明:基于RF-SFLA-SVM预警高空作业PBWUBs,准确率最高,为91.67%,与其他模型的预警性能相比,最高提升14%。研究结果可为高空作业PBWUBs的防控提供参考。

基于DBSCAN-RF洪水分类的洪水预报应用研究

【目的】洪水分类预报能有效提高洪水预报准确性,为防灾减灾工作提供科学依据。【方法】针对分类因子和分类算法优选问题,以海河流域徒骇河宫家闸上游为例进行研究,(1)充分考虑产汇流影响因素与洪水特征,选取洪峰流量、洪水总量、时段洪量、洪水历时、起历时、落历时、峰度、偏度、涨水仰角、落水仰角、C_(s)、C_(v)、前3 d面雨量、前10 d面雨量、累计面雨量及最大面雨量等16维分类因子,使用主成分投影法(Principal Component Analysis,PCA)对分类因子降维提高计算效率;(2)基于密度聚类(Density-Based Spatial Clustering of Applications with Noise,DBSCAN)-随机森林(Random Forest,RF)算法进行洪水分类,减少对分类先验知识的依赖,提高了分类精度;(3)在徒骇河流域进行了方法应用,选择适用于半干旱半湿润地区的超渗-蓄满同时作用的产流模型及单位线汇流模型进行洪水分类预报研究,分别针对各类洪水进行模型率定。【结果】结果表明:轮廓系数为0.7015,表明DBSCAN算法聚类效果理想,基于RF算法的洪水分类准确率为91.67%,分类效果理想;经洪水分类预报,NSE系数均高于0.8,分类预报结果优于直接预报。【结论】结果说明:基于DBSCAN-RF洪水分类的洪水预报能较好地反映研究区域洪水演进过程,为研究区域洪水预报及防灾减灾工作提供依据。

基于RF-RNN模型的DNS隐蔽信道检测方法

为提高检测隐蔽信道的灵敏度,提出一种基于随机森林(Random Forest,RF)和循环神经网络(Recurrent Neural Network,RNN)的域名系统(Domain Name System,DNS)隐蔽信道检测方法。该方法采用域名检测作为主要手段,使用RF模型对域名进行分类,通过深度学习方法挖掘更高阶的特征表示。实验结果表明,与单一模型相比,该方法在检测准确性和健壮性方面均取得了显著提升。

RIS辅助的混合RF/FSO系统物理层安全性能分析

【目的】针对自由空间光(FSO)链路和射频(RF)链路的保密信息容易被外部窃听者窃听的问题,为提升混合RF/FSO通信系统的保密性能,同时考虑到实际工程中FSO链路往往无法满足视距条件且不同天线分支之间会由于收发模块小型化产生相关性,需要对可重构智能表面(RIS)辅助的混合RF/FSO系统的安全性能进行研究,以得到系统安全性能与RIS部署位置和天线相关性程度等参数的关系。【方法】文章考虑单个窃听者,分别针对RF和FSO链路进行窃听,RF链路服从任意相关的Nakagami-m分布,FSO链路服从Gamma-Gamma分布。采用解码转发协议,推导得到了两种窃听场景下通信系统的安全中断概率(SOP)和严格正安全容量概率(SPSC)的闭合表达式,并对SOP进行了渐近分析。此外还利用Matlab软件进行了仿真实验,通过蒙特卡洛仿真来验证所推导公式的准确性。【结果】仿真结果表明,将RIS部署在靠近接收端的位置可以降低系统的SOP,RF主信道的信道质量与窃听信道相比较好时,天线相关性程度的增加会使系统的SOP上升。【结论】RIS辅助的FSO链路相比RF链路具有更好的安全性,虽然多天线分集技术能够有效提高系统的安全性能,但是类似指向误差和大气湍流引起的衰落,天线相关性也会对系统的安全性能造成损害,通过降低天线相关性程度能有效提升系统的安全性。

基于RF-GWO的水利工程地质渗透系数智能反演分析

地质渗透系数是准确分析水利工程渗流的关键参数。针对传统反演方法计算效率低、精度差的问题,采用有限元正演模型和正交试验设计构建渗透系数反演样本集,建立了基于随机森林(RF)算法的渗流计算代理模型;在此基础上,引入灰狼优化(GWO)算法,提出了基于RF-GWO的渗透系数智能反演方法,并以Z抽水蓄能电站为研究案例进行了验证。结果表明:RF模型对各钻孔水位预测结果均接近实测值,性能优于CART和BP模型;GWO可搜寻到地质最佳渗透系数,钻孔水位反演结果合理,相对误差最大为0.42%,精度满足工程要求,计算的天然渗流场分布形态也符合一般山体渗流场分布规律。建立的反演模型能够快速准确地推断工程区地层渗透系数,具有实际工程应用价值。

基于RF-GA的热磨机生产参数优化方法

热磨机是纤维板生产中最重要的设备之一;热磨机的综合能耗在纤维板生产的整体能源消耗中占比显著,优化生产参数以降低热磨机能耗一直是纤维板生产的要求之一。以华北某纤维板企业采集的数据为依据,针对影响比能耗(SEC)和纤维质量(QF)的多个生产参数,用粒子群算法优化的BP神经网络、支持向量机(SVM)和随机森林(RF)建立比能耗和纤维质量预测模型,经对比确定最佳比能耗和纤维质量预测模型;后基于最佳预测模型构建生产参数优化模型,采用遗传算法(GA)对其求解得到最佳生产参数,以此提出基于RF-GA模型的热磨机生产参数优化方法。结果表明,热磨机各生产参数之间存在较强耦合关系,且与比能耗和纤维质量为非线性关联;粒子群算法对机器学习算法中超参数的优化是必要的,可以有效降低机器学习算法误差;选取5组不同纤维质量下的数据,采用建立的热磨机生产参数优化方法优化后,比能耗平均下降6.9kW·h/t、降幅为5.22%。该研究验证了RF-GA热磨机生产参数优化方法的可行性,能够应用于生产参数的优化,有效地实现节能降耗的目标,并为热磨机生产参数的设定提供依据。