RIID硬件原理及其实现.ppt

RFID硬件原理简介 以AS3990阅读器芯片为例 涉及的一些基础概念RFID硬件结构及各部分作用AS3990阅读器芯片介绍 基带 指信号的频谱从零频率附近开始 频带 指信号的频谱具有带通形式且中心频率远离零频 携带有消息 适合在信道中传输 ASK调制和PSK调制 PSK ASK信号波形 OOK RFID使用的ASK信号的调制度是80 100 ASK解调 非相干解调 包络检波法 相干解调 PLL 锁相环 混频 器件的非线性 光的颜色 RFID中发射机混频结构 低中频超外差零中频中频选为0 本振与载波同频 时的超外差结构 GEN2协议 EPCphysicallayerInterrogator tag Carrier 860 960Mhz dependingonlocalregulations EU 865 5 867 6Mhz US 902 928Mhz dividedintochannels 200kHz 500kHz yes FDMAispossible Modulation ASK DSB ASK SSB ASK PR ASK tagundestandsall Encoding PIEBandwidth 26 7 128kbit sTag interrogator Modulation ASKorPSK readerunderstandsall Encoding readerdecidesFM0baseband 40 640kbit s Millerofasubcarrier 5 320kbit s DataratedependsonDivideRatioandTRcal selectedbyreaderQUERYcommand RFID系统工作原理 1 读写器开始工作之后 先内向空间发送860 960MHz频率范围的载波 激活标签 2 标签从射频信号获得能量后 响应读写器发送的指令 3 读写器开始发送带调制的命令信息 标签从载有信息的调制信号获取能量的同时得到指令 标签依照指令做出响应 相互认证通过之后 阅读器会向电子标签发出读 写 锁定 kill 盘存等操作指令 阅读器发射未调载波信号作用 为标签供电 为标签反向散射信号提供载 为零中频接收机提供本振 电磁反向散射 阅读器发出的射频信号传播标签的天线上 标签需要向将阅读器发送信息时 就通过调整天线的复阻抗 改变天线对电磁波的反射系数 从而对反射波进行相位或振幅的调制 一种反射调制的电路实现 RFID系统工作波形 RFID读写器硬件组成 AS3990 AS3991芯片简介 各部分硬件结构各部分功能 工作原理只涉及少芯片引脚各部分相关寄存器设置单独由word文档列出 Compriseof analoganddigitalfunctionalitywithcompleteEPCGen2orISO18000 6Cdigitalprotocolsupport on boardPLLsectionwithintegratedVCOsupplysectionDACandADCsectionHostinterfacesectionConfigurationregisters configuresoperationofallblocks Powerupandoperations Needstobecorrectlysuppliedvia VEXTandVEXT2pinsandenabledvia ENpinAtpower up Theconfigurationregistersarepresettoadefaultoperationmode Accessandchangeregisters P23 tochooseotheroptions Communication Communication Thecommunicationbetweenthereaderandthetransponderfollowsthereadertalkfirstmethod Afterpower upandconfiguringIC thehostsystemstartscommunicationbyturningontheRFfieldbysettingoptionbitrf on Transmittingandreceivingmodes NormalDataMode theTXandRXdataistransferredthroughtheFIFOregisterandallprotocoldataprocessingisdoneinternally DirectDataMode thedataprocessingisdonebythehostsystem 接口总线 interfacebus parallel10 pinbuscanbeconfiguredandusedasaserialperipheralinterface SPI exclusive cannotswitchbetweentheminasingleapplication TheparallelmodeisselectedifallIOpinsarelowduringlowtohightransitionoftheENpin enable Thereaderwillalwaysbehaveasthe slave connectedtothehostsystem MCU whichbehavesasthe master device Thehostsysteminitiatesallcommunications ThereaderhasanIRQpintoaskforhostsystemattention CommunicationisinitializedbyaStartcondition whichshouldbefollowedbyanAddressorCommandword TheAddressandCommandwordsare8 bitslong Communicationisclosedbyanappropriatestopcondition 命令 地址格式 Continuousaddressmodenoncontinuousaddressmodecommandmode ContinuousaddressmodeneedstobeclosedbyStopContconditionwhiletheothertwomodesneedtobeterminatedbyStopSglcondition communicationmodes Continuousaddressmode Contmode 1 thefirstdatathatfollowstheaddressiswritten orread to from thegivenaddress Foreachadditionaldata theaddressisincrementedbyone canbeusedtowritepartofthecontrolregistersinasinglestreamwithoutchangingtheaddress 组合模式 Registers12 14 15 16 and17arethreebytesdeep TheycanbeaccessedbyContinuousaddressmodeonly Theleastsignificantbyteisaccessedfirst Itispossibletoaccessonlydeepregisterinasinglecommunicationstream The24bytesdeepFIFOregistercanbeaccessedbyContinuousaddressmodeonly Itisallowedtousecommunicationstreamcombinedofcommandmodeandaddressmode Example ResetFIFO Transmit writeto1D 1Efortransmissionlength andcontinuouslyto1FforfillingFIFOwithtransmissiondata Start startconditionAdr addresswithContbitlowAdrc addresswiththeContbithighCmd commandbyteData databyteStopSgl stopconditionforterminationofthecommandornon continuousaddressmodeStopCont stopconditionforterminationofthecontinuousaddressmode 命令后可以是地址 可以是命令 但不可以是数据 地址后只能是数据 地址和命令是定义的 数据是随机的 这样可以保证不会混淆 并行接口 以StopSgl结尾 VDD I0 此引脚很重要 定义了芯片与MCU的通信电平 1 8 5 5v 如果使用芯片内部高压器供电 VDD D 则应将VDD IO与VDD D相连 如果MCU单独供电 则应调节相关设置寄存器 SUPPLY Asetof3 4Vregulatorsisusedforsupplyingthereferenceblock ADandDAconverters lowfrequencyreceivercells theRFpart anddigitalpart ItispossibletousethedigitalpartsupplyVDD DforsupplyingtheexternalMCUwithacurrentconsumptionupto20mA Anadditional4 8VregulatorisusedfortheinputRFmixerssupply TheinputofthisregulatorisVEXT outputisVDD MIXpin TheVEXTvoltageneedstobebetween5 3Vand5 5V PowerDownMode ENpinlow EN L theOAD2pinnotbeconnected NormalMode EN H Thechipisreadytomovetotransmitorreceiveoperation StandbyMode stby H Inthestandbymodetheregulators referencevoltagesystem andcrystaloscillatorareoperatinginlowpowermode butthePLL transmitteroutputstagesandreceiverareswitchedoff PLL composedofavoltagecontroloscillator VCO prescaler mainandreferencedivider phasefrequencydetector chargepump andloopfilter Allbuildingblocksexcludingtheloopfilterarecompletelyintegrated externalRFsourcecanbeused ItisalsopossibletouseexternalVCOandinternalPLLcircuitry 使用于对相位噪声要求较高的场合 每次启动RF模块之前 主机都要先对PLL模块各项参数进行设置 主要是预定标 跳频 Frequencyhopping 主机以命令形式控制 相关命令参考手册 protocolprocessingdigitalpartshapingModulatoramplifiercircuitry 发射机 TRANSMITTER 三种工作模式 NormalMode 正常模式 DirectModeUsingParralleleInterfaceDirectModeusingSerialinterface SPI NormalMode Innormalmode allsignalprocessing protocolcoding addingpreambleorframe syncandCRC signalshaping andmodulation isdoneinternally Frame sync 帧同步 Thetransmissionisstartedbysendingthetransmitcommandfollowedbyinformationonthenumberofbytesthatshouldbetransmittedandthedata Thenumberofbytesneedstobewritteninthe TXlength registersandthedatatotheFIFOregister ThetransmissionactuallystartswhenthefirstdatabyteiswrittenintotheFIFO ThesecondpossibilityistostarttransmissionwithoneofthedirectGen2commands Query QueryRep QueryAdjust ACK NAK ReqRN Inthiscase thetransmissionisstartedafterreceivingthecommand Thereaderchipstartstransmissionandsendsaninterruptrequestwhenonly3bytesareleftintheFIFO Wheninterruptisreceived thehostsystemneedstoreadthe IRQstatusregister 0C Read Clear Attheendofthetransmitoperation theexternalsystemisnotifiedbyanotherinterruptrequestwithaflagintheIRQregisterthatsignalstheendoftransmission interrupt Modulator Normaldatamode Internallycodedandinternallyshaped Externallycodedandinternallyshapedmodulation 直接模式 Externallycodedandexternallyshapedmodulation 可以为外部提供所需参考信息 可以实现DSB ASKandPR ASK调制 实现机制是内部有两D A转换器 第一个定义座号高电平 第二个定义信号低电平 这两个电平也用作整形电路的参考电平 Receiver 混频器 INPUTMIXER RX滤波器 RXFilter RX增益 RXGain RSSI ReceivedSignalStrengthIndicator 回波信号电平指示 ReflectedRFLevelIndicator 电路泄露或环境影响 RXGAIN ManualAdjustment 手动调整 AGC 自动增益控制 AGL 自动电平控制 限于时间 篇幅 不能详细介绍各部分功能 及具体电路结构 如果有兴趣 欢迎一起探讨 共同进步