RIID硬件原理及其實(shí)現(xiàn).ppt

RFID硬件原理簡介 以AS3990閱讀器芯片為例,涉及的一些基礎(chǔ)概念 RFID硬件結(jié)構(gòu)及各部分作用 AS3990閱讀器芯片介紹,基帶：指信號(hào)的頻譜從零頻率附近開始。 頻帶：指信號(hào)的頻譜具有帶通形式且中心頻率遠(yuǎn)離零頻。攜帶有消息；適合在信道中傳輸。,ASK調(diào)制和PSK調(diào)制,PSK,ASK信號(hào)波形(OOK),RFID使用的ASK信號(hào)的調(diào)制度是80100%。,ASK解調(diào),非相干解調(diào)（包絡(luò)檢波法）,相干解調(diào),PLL(鎖相環(huán)),混頻（器件的非線性）,(光的顏色),RFID中發(fā)射機(jī)混頻結(jié)構(gòu),低中頻 超外差 零中頻 中頻選為0（本振與載波同頻）時(shí)的超外差結(jié)構(gòu)。,GEN2協(xié)議,EPC physical layer Interrogator!tag: Carrier: 860-960Mhz (depending on local regulations) EU:865.5-867.6Mhz, US: 902-928Mhz , divided into channels (200kHz, 500kHz) yes, FDMA is possible! Modulation: ASK (DSB-ASK,SSB-ASK, PR-ASK tag undestands all) Encoding: PIE Bandwidth: 26.7-128kbit/s Tag!interrogator: Modulation: ASK or PSK ( reader understands all) Encoding: reader decides FM0 baseband (40-640kbit/s) Miller of a subcarrier (5-320kbit/s) Data rate depends on Divide Ratio and TRcal, selected by reader QUERY command,RFID系統(tǒng)工作原理,1.讀寫器開始工作之后，先內(nèi)向空間發(fā)送860960 MHz頻率范圍的載波，激活標(biāo)簽。 2.標(biāo)簽從射頻信號(hào)獲得能量后，響應(yīng)讀寫器發(fā)送的指令。 3.讀寫器開始發(fā)送帶調(diào)制的命令信息，標(biāo)簽從載有信息的調(diào)制信號(hào)獲取能量的同時(shí)得到指令，標(biāo)簽依照指令做出響應(yīng)。,相互認(rèn)證通過之后，閱讀器會(huì)向電子標(biāo)簽發(fā)出讀、寫、鎖定、kill、盤存等操作指令。,閱讀器發(fā)射未調(diào)載波信號(hào)作用,為標(biāo)簽供電； 為標(biāo)簽反向散射信號(hào)提供載； 為零中頻接收機(jī)提供本振。,電磁反向散射,閱讀器發(fā)出的射頻信號(hào)傳播標(biāo)簽的天線上，標(biāo)簽需要向?qū)㈤喿x器發(fā)送信息時(shí)，就通過調(diào)整天線的復(fù)阻抗，改變天線對(duì)電磁波的反射系數(shù)，從而對(duì)反射波進(jìn)行相位或振幅的調(diào)制。,一種反射調(diào)制的電路實(shí)現(xiàn),RFID系統(tǒng)工作波形,RFID讀寫器硬件組成,AS3990/AS3991芯片簡介,各部分硬件結(jié)構(gòu) 各部分功能、工作原理 只涉及少芯片引腳 各部分相關(guān)寄存器設(shè)置單獨(dú)由word文檔列出,Comprise of,analog and digital functionality with complete EPC Gen2 or ISO18000-6C digital protocol support. on-board PLL section with integrated VCO supply section DAC and ADC section Host interface section Configuration registers( configures operation of all blocks),Power up and operations,Needs to be correctly supplied via. VEXT and VEXT2 pins and enabled via. EN pin At power-up. The configuration registers are preset to a default operation mode. Access and change registers(P23) to choose other options. Communication,Communication,The communication between the reader and the transponder follows the reader talk first method. After power-up and configuring IC, the host system starts communication by turning on the RF field by setting option bit rf_on。,Transmitting and receiving modes,Normal Data Mode: the TX and RX data is transferred through the FIFO register and all protocol data processing is done internally. Direct Data Mode: the data processing is done by the host system.,接口總線(interface bus),parallel 10-pin bus can be configured and used as a serial peripheral interface(SPI) exclusive , can not switch between them in a single application. The parallel mode is selected if all IO pins are low during low to high transition of the EN pin (enable).,The reader will always behave as the “slave” connected to the host system (MCU), which behaves as the “master” device. The host system initiates all communications. The reader has an IRQ pin to ask for host system attention.,Communication is initialized by a Start condition, which should be followed by an Address or Command word. The Address and Command words are 8-bits long. Communication is closed by an appropriate stop condition.,命令/地址格式,Continuous address mode noncontinuous address mode command mode. Continuous address mode needs to be closed by StopCont condition while the other two modes need to be terminated by StopSgl condition.,communication modes,Continuous address mode,Cont mode=1, the first data that follows the address is written (or read) to (from) the given address. For each additional data, the address is incremented by one. can be used to write part of the control registers in a single stream without changing the address.,組合模式,Registers 12, 14, 15, 16, and 17 are three bytes deep. They can be accessed by Continuous address mode only. The least significant byte is accessed first. It is possible to access only deep register in a single communication stream。,The 24 bytes deep FIFO register can be accessed by Continuous address mode only.) It is allowed to use communication stream combined of command mode and address mode. Example: Reset FIFO, Transmit, write to 1D, 1E for transmission length, and continuously to 1F for filling FIFO with transmission data.,Start = start condition Adr = address with Cont bit low Adrc = address with the Cont bit high Cmd = command byte Data = data byte StopSgl = stop condition for termination of the command or non-continuous address mode StopCont = stop condition for termination of the continuous address mode,命令后可以是地址，可以是命令，但不可以是數(shù)據(jù)。 地址后只能是數(shù)據(jù)。 地址和命令是定義的，數(shù)據(jù)是隨機(jī)的。這樣可以保證不會(huì)混淆,并行接口（以StopSgl結(jié)尾）,VDD_I0,此引腳很重要，定義了芯片與MCU的通信電平(1.8-5.5v)。如果使用芯片內(nèi)部高壓器供電(VDD_D)，則應(yīng)將VDD_IO與VDD_D相連。如果MCU單獨(dú)供電，則應(yīng)調(diào)節(jié)相關(guān)設(shè)置寄存器。,SUPPLY,A set of 3.4V regulators is used for supplying the reference block, AD and DA converters, low frequency receiver cells, the RF part, and digital part. It is possible to use the digital part supply VDD_D for supplying the external MCU with a current consumption up to 20mA.,An additional 4.8V regulator is used for the input RF mixers supply. The input of this regulator is VEXT, output is VDD_MIX pin. The VEXT voltage needs to be between 5.3V and 5.5V.,Power Down Mode: EN pin low (EN=L). the OAD2 pin not be connected. Normal Mode: EN=H. The chip is ready to move to transmit or receive operation. Standby Mode: stby=H. In the standby mode the regulators, reference voltage system, and crystal oscillator are operating in low power mode; but the PLL,transmitter output stages and receiver are switched off.,PLL,composed of a voltage control oscillator (VCO), prescaler, main and reference divider, phasefrequency detector, charge pump, and loop filter. All building blocks excluding the loop filter are completely integrated.,external RF source can be used. It is also possible to use external VCO and internal PLL circuitry.(使用于對(duì)相位噪聲要求較高的場(chǎng)合),每次啟動(dòng)RF模塊之前，主機(jī)都要先對(duì)PLL模塊各項(xiàng)參數(shù)進(jìn)行設(shè)置（主要是預(yù)定標(biāo)）。 跳頻(Frequency hopping)：主機(jī)以命令形式控制。（相關(guān)命令參考手冊(cè)）。,protocol processing digital part shaping Modulator amplifier circuitry.,發(fā)射機(jī)(TRANSMITTER),三種工作模式,Normal Mode(正常模式) Direct Mode Using Parrallele Interface Direct Mode using Serial interface(SPI),Normal Mode,In normal mode, all signal processing (protocol coding, adding preamble or frame-sync and CRC, signal shaping, and modulation) is done internally. Frame-sync: 幀同步。,The transmission is started by sending the transmit command followed by information on the number of bytes that should be transmitted and the data. The number of bytes needs to be written in the TX length registers and the data to the FIFO register. The transmission actually starts when the first data byte is written into the FIFO.,The second possibility is to start transmission with one of the direct Gen2 commands (Query, QueryRep, QueryAdjust,ACK, NAK, ReqRN). In this case, the transmission is started after receiving the command.,The reader chip starts transmission and sends an interrupt request when only 3 bytes are left in the FIFO. When interrupt is received, the host system needs to read th