EVM
EVM相关知识及测量方法
EVM相关知识及测量方法EVM（Error Vector Magnitude）是衡量无线通信系统性能的一个重要指标。
它用来描述理论信号与实际信号之间的差异程度，也就是接收信号与理想信号之间的差异程度。
下面我们将分别介绍EVM的概念和意义，以及常见的EVM测量方法。
一、EVM概念及意义EVM是对无线通信系统中的无线信号进行评估的一种系统性能指标。
EVM的数值范围通常在0%到100%之间，数值越小表示接收信号与理想信号的差别越小，系统性能越好。
当EVM达到或超过一定的阈值时，可能会导致误码率（BER）的增加，从而影响通信质量。
EVM的大小受到许多因素的影响，如噪声、非线性失真、多径干扰、频偏等。
因此，EVM可以用来评估无线通信系统中各种不完美因素对信号质量的影响。
在现实世界中，传输信号往往不可避免地受到各种干扰和失真的影响。
通过测量EVM，我们可以了解无线通信系统中存在的问题，并作出相应的优化和改进。
二、EVM测量方法EVM的测量一般分为物理层测量和链路层测量两种方法。
1.物理层测量方法：(1)频域法：将接收到的信号进行FFT变换，转换到频域。
然后计算接收信号与理想信号之间的差异，并基于差异的统计学特征进行EVM计算。
(2)时域法：将接收信号和理想信号进行时域对齐，并计算它们之间的相位和幅度差异。
2.链路层测量方法：(1)比特错误率（BER）测量法：通过传输一组已知的比特组合，并与接收信号进行比较，统计出差异的比特数量，进而计算出EVM。
(2)码元错误率（SER）测量法：与BER测量法类似，只不过将接收信号与理想信号进行码元级别的比较。
(3)帧错误率（FER）测量法：通过计算接收的帧和理想帧的差异，统计出差异的帧数量，进而计算出EVM。
在实际应用中，EVM常常结合其他无线通信系统性能指标进行评估，如信号质量（Signal Quality），码字错误率（Symbol Error Rate）等，以便对系统性能进行全面分析和优化。
基于EVM挣值管理的项目进度与成本监控
⌛️
为项目经理提供决策支持
• 评估不同成本方案的影响
• 制定有效的成本控制策略
EVM挣值管理在项目成本监控中的实施步骤
计算挣值、
定期收集
制定项目计划和预算
项目数据
实际成本
分析项目
和计划成
成本绩效
本
采取相应
措施调整
项目成本
• 确定项目的工作范
• 测量项目实际完成
• 根据项目数据计算
• 项目进度计划：历时6个月
02
改进后的EVM挣值管理的实施
• 引入项目范围变更管理
• 结合风险管理工具
• 提高挣值管理的灵活性
03
结果与讨论
• 在项目执行过程中发现进度滞后和成本超支
• 通过调整项目资源分配和成本控制策略
• 成功地将项目进度和成本控制在预算范围内
06
结论与展望
EVM挣值管理在项目进度与成本监控中的重要性
• 成本偏差与进度偏差的组合：绩效指数（PI）
挣值管理的三种基本指标
挣值（EV）：项目已完成工作的预算成本
• 反映了项目的进度
• 是挣值管理中的核心指标
实际成本（AC）：项目实际发生的成本
• 反映了项目的成本
• 与挣值相比较以评估成本绩效
计划成本（PC）：项目预定的成本预算
• 反映了项目的预算
• 与挣值相比较以评估进度绩效
• 通过调整项目资源分配和成本控制策略
• 成功地将项目成本控制在预算范围内
项目背景：某基础设施建设项目
• 项目预算：2000万元
• 项目进度计划：历时12个月
EVM挣值管理的实施
• 每月收集项目数据
EVM的性能与配方设计
EVM的性能与配方设计按照ASTM D 1418 —2006 规定,乙烯2乙酸乙烯酯橡胶的英文缩写为EVM。
EVM 的化学组成与EV A 相同,都是乙烯与乙酸乙烯酯的共聚物,但由于合成方法不同,二者差异明显(见表8)。
EVA 是乙酸乙烯酯含量低(质量分数低于0. 4) 、支化度低而结晶度高的共聚物,属于塑料,广泛用于热熔胶和制鞋业。
EVM 是乙酸乙烯酯含量高(质量分数为0. 4～0. 8) 、支化度高的无定形共聚物,属于橡胶,通过合理配合可获得性能优良的硫化胶。
EVM 的主链是饱和结构,化学稳定性好,因此其具有优异的耐热、耐臭氧和耐候性能。
乙酸乙烯酯侧链的引入既赋予EVM一定的耐油性能,同时破坏了主链的规整性,因此其具有良好的低温柔顺性。
主链中非极性亚甲基结构赋予EVM 良好的低温耐屈挠和耐极性溶剂性能。
EVM 主要由朗盛公司生产,商品名为Leva2pren (乙华平) ,主要牌号及指标如表9 所示。
EVM 具有一系列优点。
(1) 耐热老化性能优异,可在150 ℃下长期使用,最高工作温度可达175 ℃,在175 ℃下老化70 h 甚至168 h 后,强伸性能保持率相当高。
EVM 的耐热老化性能优于氢化丁腈橡胶( HN2BR) 和EPDM(见表10) 。
(2) 阻燃性能优异,无卤阻燃EVM 胶料的氧指数可达38～42 ,且燃烧发烟量低,腐蚀性轻微,燃烧气体无毒。
(3) 耐油性能良好,耐油性能相当于丙烯腈质量分数为0. 26～0. 34 的NBR。
(4) 耐天候老化性能仅次于EPDM。
EVM 的缺点是耐水性差,粘度低,加工时易粘辊,且只能采用过氧化物硫化。
EVM 的配方设计要点如下：(1) 采用过氧化物硫化体系,硫化剂DCP 用量为2～3 份,助交联剂( TAC 或TAIC) 用量为1～3 份。
当硫化剂DCP 和助交联剂TAIC 的用量约为2 份时,EVM 的拉伸强度高,压缩永久变形小,综合性能良好。
双通道数字隔离器 EVM 用户指南说明书
User's GuideSLLU098C–June2007–Revised December2010Dual-Channel Digital Isolator EVMContents1Introduction (1)1.1Overview (2)1.2Functional Configuration of the Dual-Channel Digital Isolator (2)1.3The EVM Signal Paths of the ISO7220x,ISO7221x,and ISO742x Isolators (3)1.4The ISO7220x and ISO7420x EVM Configuration (5)1.5The ISO7221x and ISO7421x EVM Configuration (6)2EVM Setup and Operation (7)2.1Overview (7)List of Figures1The ISO7x20x and ISO7x21x Pinouts (2)2The ISO7x20x Same-Channel Direction Schematic (3)3The ISO7x21x Opposing-Channel Direction Schematic (4)4ISO7220x and ISO7420x EVM,Top View (5)5ISO7220x and ISO7420x EVM,Bottom View (5)6The ISO7221x and ISO7421x EVM Top View (6)7The ISO7221x and ISO7421x EVM Bottom View (6)8Basic EVM Operation (7)9Typical Input and Output Waveforms (7)List of Tables1ISO7220x and ISO7420x EVM Connections (3)2ISO7221x and ISO7421x EVM Connections (4)1IntroductionThis user's guide details the evaluation module(EVM)operation of the factory installed ISO7421dual-channel digital isolator;however,the EVM board may be reconfigured by a user for use withISO7220A,ISO7220B,ISO7220C,ISO7220M,ISO7420,ISO7420M or ISO7420F same-channel direction isolators and the ISO7221A,ISO7221B,ISO7221C,ISO7221M,ISO7421,ISO7421M or ISO7421Fopposing-channel direction isolators.This guide also explains the user configurable I/O loads for both dual-channel isolator EVM configurations, and presents a typical lab setup with input and output waveforms.1 SLLU098C–June2007–Revised December2010Dual-Channel Digital Isolator EVM Submit Documentation FeedbackISO7x21xGND2Vcc2Vcc1GND1OUTB INA OUTA INB ISO7x20xGND2Vcc2Vcc1GND1OUTB INAOUTA INBIntroduction 1.1OverviewThe ISO7220x,ISO7221x,and ISO742X dual digital isolators have a logic input and output bufferseparated by a silicon oxide (SiO 2)insulation ed in conjunction with isolated power supplies,these devices block high voltage,isolate grounds,and prevent noise currents on a data bus or othercircuits from entering the local ground and interfering with or damaging sensitive circuitry.A binary input signal is conditioned,translated to a balanced signal,and then differentiated by thecapacitive isolation barrier.Across the isolation barrier,a differential comparator receives the logictransition information,then sets or resets a flip-flop and the output circuit accordingly.A periodic update pulse is sent across the barrier to ensure the proper dc level of the output.If this dc-refresh pulse is not received for more than 4m s,the input is assumed to be unpowered or not functional,and the failsafecircuit drives the output to a logic-high state.For ISO7420F and ISO7421F,the failsafe circuit drives the output to a logic-low state.CAUTIONNote that although these devices provide galvanic isolation of up to 4000V,thisEVM cannot be used for isolation voltage testing.It is designed for theexamination of device operating parameters only and will be damaged if highvoltage (>5.5V)is applied anywhere in the circuit.1.2Functional Configuration of the Dual-Channel Digital IsolatorThe pin-outs of the dual-channel digital isolators are displayed in Figure 1.The EVM comes with anISO7421installed;however,the user may reconfigure the EVM for use with any of the footprints.Figure 1.The ISO7x20x and ISO7x21x PinoutsThe ISO7220A,ISO7220B,ISO7220C,ISO7221A,ISO7221B and ISO7221C have TTL input thresholds and an input noise filter that prevents transient pulses of up to 2ns in duration from being passed to the output of the device.The ISO7220M and ISO7221M have a CMOS Vcc/2input threshold,but do not have the noise filter and the additional propagation delay.2Dual-Channel Digital Isolator EVM SLLU098C–June 2007–Revised December 2010Submit Documentation FeedbackV CC1(Banana Jack P1)V CC2(Banana Jack P2)GND1(Banana Jack P3)GND2(Banana Jack P4) Introduction1.3The EVM Signal Paths of the ISO7220x,ISO7221x,and ISO742x IsolatorsThis multifunctional EVM is designed with signal paths shown in Figure 1,Figure 2,and Figure 3for the evaluation of the ISO7220x and ISO7221x dual-channel isolators.Figure 2.The ISO7x20x Same-Channel Direction SchematicTable 1.ISO7220x and ISO7420x EVM ConnectionsConnectionLabel Description J1SMA connector to the INB input,pin 3J2SMA connector to the OUTB output,pin 6J3SMA connector to the INA input,pin 2J4SMA connector to the OUTA output,pin 7P1V CC1Input power supply banana jack P2V CC2Output power supply banana jack P3GND1Input power ground connection banana jack P4GND2Output power ground connection banana jack JMP13-pin jumper V CC1,input,GND1JMP23-pin jumper used to monitor OUTB with scope probe JMP33-pin jumper –V CC1,input,GND1JMP43-pin jumper used to monitor OUTA with scope probe3SLLU098C–June 2007–Revised December 2010Dual-Channel Digital Isolator EVM Submit Documentation FeedbackIntroduction V CC1(Banana Jack P1)V CC2(Banana Jack P2)GND1(Banana Jack P3)GND2(Banana Jack P4)Figure3.The ISO7x21x Opposing-Channel Direction SchematicTable2.ISO7221x and ISO7421x EVM ConnectionsConnection Label DescriptionJ1SMA connector to the INB input,pin3J2SMA connector to the OUTB output,pin6J3SMA connector to the OUTA output,pin2J4SMA connector to the INA input,pin7P1V CC1Input power supply banana jackP2V CC2Output power supply banana jackP3GND1Input power ground connection banana jackP4GND2Output power ground connection banana jackJMP13-pin jumper V CC1,input,GND1JMP23-pin jumper used to monitor OUTB with scope probeJMP33-pin jumper used to monitor OUTA with scope probeJMP43-pin jumper V CC2,input,GND24Dual-Channel Digital Isolator EVM SLLU098C–June2007–Revised December2010Submit Documentation Feedback Introduction1.4The ISO7220x and ISO7420x EVM ConfigurationThe ISO7220x EVM configuration has SMA connectors (J1and J3)set up as the input to the INA (pin 2)and INB (pin 3)of the ISO7220M in Figure 1and Figure 2.R2and R8are 0-Ωinput series resistorsshown in Figure 4,and are located next to the J1and J3input connectors.R1and R5are 50-Ωresistors from each input to ground,and are located on the bottom of the board as shown in Figure 5.Figure 4.ISO7220x and ISO7420x EVM,Top ViewThe output channel configuration of the ISO7220x EVM has the OUTA (pin 7)and OUTB (pin 6)ofFigure 1and Figure 2connected to SMA connector (J2and J4)through 0-Ωseries resistor,R4and R6.Figure 5.ISO7220x and ISO7420x EVM,Bottom ViewThe pads for R3,R7,C1,C12,C13and C14are available on the bottom of the EVM for varied loadingconditions if desired by a user.5SLLU098C–June 2007–Revised December 2010Dual-Channel Digital Isolator EVM Submit Documentation FeedbackIntroduction 1.5The ISO7221x and ISO7421x EVM ConfigurationThe ISO7221x EVM configuration has SMA connectors (J4and J1)set up as the input to the INA (pin 7)and INB (pin 3)of the ISO7221x in Figure 1and Figure 3.R2and R6are 0-Ωinput series resistors shown in Figure 6,and are located next to the J1and J4input connectors.Figure 6.The ISO7221x and ISO7421x EVM Top ViewThe output channel configuration of the ISO7221x EVM has the OUTA (pin 2)and OUTB (pin 6)ofFigure 1and Figure 3connected to SMA connector (J3and J2)through 0-Ωseries resistor,R8and R4.R1and R7are 50-Ωresistors from each input to ground on the bottom of the board shown in Figure 7.Figure 7.The ISO7221x and ISO7421x EVM Bottom ViewThe pads for R3,R5,C1,C12,C13and C14are available on the bottom of the EVM for varied loading conditions if desired by a user.6Dual-Channel Digital Isolator EVM SLLU098C–June 2007–Revised December 2010Submit Documentation Feedback EVM Setup and Operation 2EVM Setup and OperationThis section includes the setup and operation of the EVM for parameter performance evaluation.Typical waveforms are included.2.1OverviewThe basic setup in Figure 5has the two power supplies required to evaluate isolator performance with3.3-V on one side and 3.3-V on the other.If both sides are to be evaluated at the same supply voltage,only one power supply is required and can be used to power both sides of the EVM.CAUTIONNote that this EVM is for operating parameter performance evaluation only andnot designed for isolation voltage testing.Any voltage applied above the 5.5-Vmaximum recommended operating voltage of the digital isolators will damagethe EVM.Figure 8.Basic EVM OperationIn Figure 8,the J3input to the EVM is a 20MHz pulse displayed on channel 1in Figure 9.The J4output of the EVM is channel 2.Figure 9.Typical Input and Output Waveforms7SLLU098C–June 2007–Revised December 2010Dual-Channel Digital Isolator EVM Submit Documentation FeedbackEVALUATION BOARD/KIT IMPORTANT NOTICETexas Instruments(TI)provides the enclosed product(s)under the following conditions:This evaluation board/kit is intended for use for ENGINEERING DEVELOPMENT,DEMONSTRATION,OR EVALUATION PURPOSES ONLY and is not considered by TI to be a finished end-product fit for general consumer use.Persons handling the product(s)must have electronics training and observe good engineering practice standards.As such,the goods being provided are not intended to be complete in terms of required design-,marketing-,and/or manufacturing-related protective considerations,including product safety and environmental measures typically found in end products that incorporate such semiconductor components or circuit boards.This evaluation board/kit does not fall within the scope of the European Union directives regarding electromagnetic compatibility,restricted substances(RoHS),recycling (WEEE),FCC,CE or UL,and therefore may not meet the technical requirements of these directives or other related directives.Should this evaluation board/kit not meet the specifications indicated in the User’s Guide,the board/kit may be returned within30days from the date of delivery for a full refund.THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES,EXPRESSED,IMPLIED,OR STATUTORY,INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE.The user assumes all responsibility and liability for proper and safe handling of the goods.Further,the user indemnifies TI from all claims arising from the handling or use of the goods.Due to the open construction of the product,it is the user’s responsibility to take any and all appropriate precautions with regard to electrostatic discharge.EXCEPT TO THE EXTENT OF THE INDEMNITY SET FORTH ABOVE,NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT,SPECIAL,INCIDENTAL,OR CONSEQUENTIAL DAMAGES.TI currently deals with a variety of customers for products,and therefore our arrangement with the user is not exclusive.TI assumes no liability for applications assistance,customer product design,software performance,or infringement of patents or services described herein.Please read the User’s Guide and,specifically,the Warnings and Restrictions notice in the User’s Guide prior to handling the product.This notice contains important safety information about temperatures and voltages.For additional information on TI’s environmental and/or safety programs,please contact the TI application engineer or visit /esh.No license is granted under any patent right or other intellectual property right of TI covering or relating to any machine,process,or combination in which such TI products or services might be or are used.FCC WarningThis evaluation board/kit is intended for use for ENGINEERING DEVELOPMENT,DEMONSTRATION,OR EVALUATION PURPOSES ONLY and is not considered by TI to be a finished end-product fit for general consumer use.It generates,uses,and can radiate radio frequency energy and has not been tested for compliance with the limits of computing devices pursuant to part15of FCC rules,which are designed to provide reasonable protection against radio frequency interference.Operation of this equipment in other environments may cause interference with radio communications,in which case the user at his own expense will be required to take whatever measures may be required to correct this interference.Mailing Address:Texas Instruments,Post Office Box655303,Dallas,Texas75265Copyright©2009,Texas Instruments IncorporatedEVM WARNINGS AND RESTRICTIONSIt is important to operate this EVM within the input voltage range of0V to5.5V and the output voltage range of0V to6V.Exceeding the specified input range may cause unexpected operation and/or irreversible damage to the EVM.If there are questions concerning the input range,please contact a TI field representative prior to connecting the input power.Applying loads outside of the specified output range may result in unintended operation and/or possible permanent damage to the EVM. Please consult the EVM User's Guide prior to connecting any load to the EVM output.If there is uncertainty as to the load specification, please contact a TI field representative.During normal operation,some circuit components may have case temperatures greater than85°C.The EVM is designed to operate properly with certain components above85°C as long as the input and output ranges are maintained.These components include but are not limited to linear regulators,switching transistors,pass transistors,and current sense resistors.These types of devices can be identified using the EVM schematic located in the EVM User's Guide.When placing measurement probes near these devices during operation, please be aware that these devices may be very warm to the touch.Mailing Address:Texas Instruments,Post Office Box655303,Dallas,Texas75265Copyright©2009,Texas Instruments IncorporatedIMPORTANT NOTICETexas Instruments Incorporated and its subsidiaries(TI)reserve the right to make corrections,modifications,enhancements,improvements, and other changes to its products and services at any time and to discontinue any product or service without notice.Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty.Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty.Except where mandated by government requirements,testing of all parameters of each product is not necessarily performed.TI assumes no liability for applications assistance or customer product design.Customers are responsible for their products and applications using TI components.To minimize the risks associated with customer products and applications,customers should provide adequate design and operating safeguards.TI does not warrant or represent that any license,either express or implied,is granted under any TI patent right,copyright,mask work right, or other TI intellectual property right relating to any combination,machine,or process in which TI products or services are rmation published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement e of such information may require a license from a third party under the patents or other intellectual property of the third party,or a license from TI under the patents or other intellectual property of TI.Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties,conditions,limitations,and notices.Reproduction of this information with alteration is an unfair and deceptive business practice.TI is not responsible or liable for such altered rmation of third parties may be subject to additional restrictions.Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice.TI is not responsible or liable for any such statements.TI products are not authorized for use in safety-critical applications(such as life support)where a failure of the TI product would reasonably be expected to cause severe personal injury or death,unless officers of the parties have executed an agreement specifically governing such use.Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications,and acknowledge and agree that they are solely responsible for all legal,regulatory and safety-related requirements concerning their products and any use of TI products in such safety-critical applications,notwithstanding any applications-related information or support that may be provided by TI.Further,Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in such safety-critical applications.TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are specifically designated by TI as military-grade or"enhanced plastic."Only products designated by TI as military-grade meet military specifications.Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at the Buyer's risk,and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use. TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are designated by TI as compliant with ISO/TS16949requirements.Buyers acknowledge and agree that,if they use any non-designated products in automotive applications,TI will not be responsible for any failure to meet such requirements.Following are URLs where you can obtain information on other Texas Instruments products and application solutions:Products ApplicationsAmplifiers Audio /audioData Converters Automotive /automotiveDLP®Products Communications and /communicationsTelecomDSP Computers and /computersPeripheralsClocks and Timers /clocks Consumer Electronics /consumer-appsInterface Energy /energyLogic Industrial /industrialPower Mgmt Medical /medicalMicrocontrollers Security /securityRFID Space,Avionics&/space-avionics-defenseDefenseRF/IF and ZigBee®Solutions /lprf Video and Imaging /videoWireless /wireless-appsMailing Address:Texas Instruments,Post Office Box655303,Dallas,Texas75265Copyright©2010,Texas Instruments Incorporated。
EVM与星座图分析
解調
I(t) = sine wave Q(t) = cosine wave
3
Phase difference: 90deg
EVM (Error Vector Magnitude)
如果测得EVM较差，如何发现问题所在？
EVM
增益匹配 相位噪声 群时延 频率误差 抑制
IQ星座图 IQ星座图 EVM vs 子载波 频率误差 vs. time CCDF
BPSK
2 bit
QPSK
4 bit
6 bit
16QAM 2
Transmitter
我們要傳送 000101…
Q 3
I 4
Receiver 000101 的座標是 4 + 3i
EVM
2.5
4*sine()
調制
3*cos()
3.5
誤判為 000111
3.5+2.5i
I(t)=3.5sin(t) Q(t)=2.5cos(t)
发射参数—— EVM / 星座图
EVM-矢量误差
EVM指标要求
IQ星座图-反映EVM指标好坏 红点越集中，代表EVM指标 越好。红点发散代表EVM较 差，发射信号的质量则较差
1
IQ constellation diagram IQ星座图
相位: 0 => 1 180 => 0
0
1
1 bit only
These diagrams will allow us to observe the “problems”.
4
这些图表可以帮助我们发现问题
1 增益不匹配
That affects EVM
Diagram:
IQ Diagram
EVM的定义(精)
1.1.1.1 EVM对于一些恒包络的调制方案，比如GSM 移动通信系统中的GMSK （Gauss Minimum Shift Keying：高斯最小频移键控），相位误差和频差被作为衡量调制精度的指标，然而对于3G 中普遍采用的QPSK 来说，是一种非恒包络调制，以上两项指标就不足以反映调制精度，因为这种调制方式使得信号除了相位上有误差以外，幅度上也会有误差[5]。
所以，对于非恒包络调制精度，一种可以全面衡量信号幅度误差和相位误差的指标误差矢量幅度（EVM ：Error Vector Magnitude ）被提出来了，EVM 是反映测量信号和参考信号的误差的一个指标，在星座图上误差矢量很清楚的反映了信号的损伤，可以通过比较测量信号矢量Z 和参考信号矢量R 得到的误差矢量E 来评估，然后用上面提到的那些调制域测量的指标去分析并解决发射机设计中的问题，如下图。
图1误差矢量信号定义示意图EVM 定义为误差矢量信号平均功率的平方根值和参考信号平均功率的平方根值之间的比值，实际也就是误差矢量信号和参考信号的均方根值（RMS ：Root Mean Square）之间的比值，并把这种比值以百分比的形式表示。
假设测量信号为Z ，参考信号表示为R ，则EVM 的计算公式如下：%100 (( ((⨯-==R R M R Z R M R R M E R M E V M式中测量信号Z 就是实际测到的发射机发射的信号，参考信号R 是对发射机信号用理想接收机接收并经过理想的解调和理想的再调制得到的。
测量信号Z 和参考信号R 都要经过频差、绝对相位和幅度、时钟的修正。
1. IQ信号的幅度误差和相位误差上节介绍的EVM 反映了测量信号和参考信号的误差情况，其中涵盖了IQ 信号的幅度误差和相位误差，但是有时候分析问题时需要分别考察IQ 信号的幅度误差和相位误差。
幅度误差定义为测量信号和参考信号幅度之差的均方根值与参考信号幅度的均方根值之间的比值，并以百分比的形式表示，计算公式如下：%100 ((⨯-=R R M R Z R M r r o r M a g n i t u d e E相位误差定义为测量信号和参考信号相位之差的均方根值，计算公式如下：( ((R phase Z phaseRMS PhaseError -= 这里要强调的一点是，这里定义的IQ 信号的幅度误差和相位误差与误差矢量信号的幅度和相位是不同的概念，这一点从定义式和参见图1中都可以看出来。
EVM的定
1.1.1.1 EVM对于一些恒包络的调制方案，比如GSM 移动通信系统中的GMSK （Gauss Minimum Shift Keying ：高斯最小频移键控），相位误差和频差被作为衡量调制精度的指标，然而对于3G 中普遍采用的QPSK 来说，是一种非恒包络调制，以上两项指标就不足以反映调制精度，因为这种调制方式使得信号除了相位上有误差以外，幅度上也会有误差[5]。
所以，对于非恒包络调制精度，一种可以全面衡量信号幅度误差和相位误差的指标误差矢量幅度（EVM ：Error Vector Magnitude ）被提出来了，EVM 是反映测量信号和参考信号的误差的一个指标，在星座图上误差矢量很清楚的反映了信号的损伤，可以通过比较测量信号矢量Z 和参考信号矢量R 得到的误差矢量E 来评估，然后用上面提到的那些调制域测量的指标去分析并解决发射机设计中的问题，如下图。
图1误差矢量信号定义示意图EVM 定义为误差矢量信号平均功率的平方根值和参考信号平均功率的平方根值之间的比值，实际也就是误差矢量信号和参考信号的均方根值（RMS ：Root Mean Square ）之间的比值，并把这种比值以百分比的形式表示。
假设测量信号为Z ，参考信号表示为R ，则EVM 的计算公式如下：%100)()()()(⨯-==R R M S R Z R M S R R M S E R M S E V M式中测量信号Z 就是实际测到的发射机发射的信号，参考信号R 是对发射机信号用理想接收机接收并经过理想的解调和理想的再调制得到的。
测量信号Z 和参考信号R 都要经过频差、绝对相位和幅度、时钟的修正。
1. IQ 信号的幅度误差和相位误差上节介绍的EVM 反映了测量信号和参考信号的误差情况，其中涵盖了IQ 信号的幅度误差和相位误差，但是有时候分析问题时需要分别考察IQ 信号的幅度误差和相位误差。
幅度误差定义为测量信号和参考信号幅度之差的均方根值与参考信号幅度的均方根值之间的比值，并以百分比的形式表示，计算公式如下：%100)()(⨯-=R R M S R Z R M S r r o r M a g n i t u d e E相位误差定义为测量信号和参考信号相位之差的均方根值，计算公式如下：))()((R phase Z phaseRMS PhaseError -= 这里要强调的一点是，这里定义的IQ 信号的幅度误差和相位误差与误差矢量信号的幅度和相位是不同的概念，这一点从定义式和参见图1中都可以看出来。
EVM和RF的各种技巧知识详解
EVM和RF的各种技巧知识详解EVM和RF的各种技巧知识详解当你写完“EVM可能随着Front-End的IL增大而恶化”的时候，如果阅读者是一个基础概念知识都不好的工程师（工厂里的工程师很多都是如此），人家第一反应是“EVM是什么”，继而是“EVM是为什么会跟IL有关系”，然后还可能是“EVM还跟什么指标有关系”——这就没完没了了。
所以我这里打算“扯到哪算哪”，把一些常见的概念列举出来，抛砖引玉，然后看看效果如何。
1、Rx Sensitivity（接收灵敏度）接收灵敏度，这应该是最基本的概念之一，表征的是接收机能够在不超过一定误码率的情况下识别的最低信号强度。
这里说误码率，是沿用CS（电路交换）时代的定义作一个通称，在多数情况下，BER (bit error rate)或者PER (packet error rate)会用来考察灵敏度，在LTE时代干脆用吞吐量Throughput来定义——因为LTE干脆没有电路交换的语音信道，但是这也是一个实实在在的进化，因为第一次我们不再使用诸如12.2kbps RMC（参考测量信道，实际代表的是速率12.2kbps的语音编码）这样的“标准化替代品”来衡量灵敏度，而是以用户可以实实在在感受到的吞吐量来定义之。
2、SNR（信噪比）讲灵敏度的时候我们常常联系到SNR（信噪比，我们一般是讲接收机的解调信噪比），我们把解调信噪比定义为不超过一定误码率的情况下解调器能够解调的信噪比门限（面试的时候经常会有人给你出题，给一串NF、Gain，再告诉你解调门限要你推灵敏度）。
那么S和N分别何来？S即信号Signal，或者称为有用信号；N即噪声Noise，泛指一切不带有有用信息的信号。
有用信号一般是通信系统发射机发射出来，噪声的来源则是非常广泛的，最典型的就是那个著名的-174dBm/Hz——自然噪声底，要记住它是一个与通信系统类型无关的量，从某种意义上讲是从热力学推算出来的（所以它跟温度有关）；另外要注意的是它实际上是个噪声功率密度（所以有dBm/Hz这个量纲），我们接收多大带宽的信号，就会接受多大带宽的噪声——所以最终的噪声功率是用噪声功率密度对带宽积分得来。
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
PV(Plant Value)BCWS(Budget Cost of Work Scheduled)
计划价值计划工作预算成本
EV(Earned Value)BCWP(Budget Cost of Work Performed)
挣值已完成工作预算成本
AC(Actual Cost)ACWP(Actual Cost of Work Performed)
实际费用完成工作实际成本
BAC
项目完工预算
BDAC
基准完工工期
成本偏差=挣值-实际成本 CV = EV - AC
成本绩效指数=挣值/实际成本 CPI = EV/AC
进度偏差=挣值-计划值 SV = EV - PV
进度绩效指数=挣值/预算成本 SPI = EV/PV
挣值分析三大功能：偏差分析，绩效分析，变更分析
BAC(Budget At Complete)
完工预算
ETC(Eatimated To Complete)
根据当前情况，估算完成项目还需多少费用
EAC(Estimated At Complete)
根据当前情况，估算项目所需的总费用
AC
EV（BCWP）=1000*50%=
BAC=1000
BDAC=6周
（输出指标
CV
CPI=EV/AC=500/300=1.
EAC=1000/1.67=600元
VAC=BAC-EAC=1000-600
SV=EV-PV=500-800=300
SPI=EV/PV=500/800=0.
EDAC=BDAC/SPI=6/0.62
（项目评价及预测
计算基于EVM数据的EAC值
· 假设将按预算单价完成ETC工作
EAC＝AC+(BAC-EV)
· 假设以当前CPI完成ETC工作
EAC＝BAC/CPI
· 假设SPI与CPI将同时影响ETC工作
EAC＝AC+[(BAC-EV)/(CPI*SPI)]
完工尚需绩效指数（TCPI）
TCPI=剩余工作/剩余资金=(BAC-EV)/[(BAC-AC) or (EAC-AC)]
两个差异 两个绩效指标费用差异：CV=EV-AC 进度差异：SV=EV-PV 费用绩效指数：CPI=EV/AC 进度绩效指数：SPI=EV/PV
CV=EV-AC=800-900=-100 < 0SV=EV-PV=800-1000=-200
说明项目成本超支100美元说明工期滞后200美元的工作量CPI = EV/AC=800/900=0.89
SPI=EV/PV=800/1000=0.8说明每花1元产出的工作价值0.89元。
实际进度是计划进度的80%
例：任务A的总预算成本为1000元，基准工期6周。
截至今日按计划应完成其80%工作量。
但实际只完成了任务A的50%工作量，实际支出300元。
（1）输入值
PV(BCWS)=1000*80%=800元AC（ACWP）=300元
EV（BCWP）=1000*50%=500元BAC=1000BDAC=6周
（2）输出指标
CV=EV-AC=500-300=200元CPI=EV/AC=500/300=1.67EAC=1000/1.67=600元
VAC=BAC-EAC=1000-600=400元SV=EV-PV=500-800=300元SPI=EV/PV=500/800=0.625
EDAC=BDAC/SPI=6/0.625=9.6周。