Texas Instruments RFM003B Inductive Reader Module User Manual RI RFM 003B Series 2000 Reader System Mini RFM

Texas Instruments Inc Inductive Reader Module RI RFM 003B Series 2000 Reader System Mini RFM

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1November ’00 PrefaceSeries 2000 Reader SystemMini-RFM RI-RFM-003BReference Guide11-06-29-030 November 2000
2Mini-RFM - Reference Guide November ’00Edition Three - November 2000This is the third edition of this manual, it describes the following equipment: TIRIS Mini-Radio Frequency Module RI-RFM-003BTexas Instruments (TI) reserves the right to make changes to its products or servicesor to discontinue any product or service at any time without notice. TI provides cus-tomer assistance in various technical areas, but does not have full access to dataconcerning the use and applications of customer's products. Therefore, TI assumes no liability and is not responsible for customer applications orproduct or software design or performance relating to systems or applications incor-porating TI products. In addition, TI assumes no liability and is not responsible forinfringement of patents and/or any other intellectual or industrial property rights ofthird parties, which may result from assistance provided by TI. TI products are not designed, intended, authorized or warranted to be suitable for lifesupport applications or any other life critical applications which could involve poten-tial risk of death, personal injury or severe property or environmental damage. The TIRIS logo and the word TIRIS are registered trademarks of Texas InstrumentsIncorporated. Copyright  2000 Texas Instruments Incorporated (TI) This document may be downloaded onto a computer, stored and duplicated as nec-essary to support the use of the related TI products. Any other type of duplication,circulation or storage on data carriers in any manner not authorized by TI representsa violation of the applicable copyright laws and shall be prosecuted.
PREFACE3Read This FirstAbout This GuideThis manual describes the TIRIS Mini-Radio Frequency Module (Mini-RFM), it pro-vides the information that you will need in order to install the Mini-RFM into your RFIDsystem. It is generally targeted at systems integrators or value added resellers. Regulatory, safety and warranty notices that must be followed are given inChapter 6. ConventionsIf You Need AssistanceApplication Centers are located in Europe, North and South America, the Far Eastand Australia to provide direct support. For more information, please contact yournearest TIRIS Sales and Application Center. The contact addresses can be found onour home page: http://www.tiris.comWARNING:A WARNING IS USED WHERE CARE MUST BE TAKEN, OR A CERTAINPROCEDURE MUST BE FOLLOWED IN ORDER TO PREVENT INJURY ORHARM TO YOUR HEALTH.CAUTION:This indicates information on conditions which must be met, or a procedure which must be followed, which if not heeded could cause permanent damage to the equipment or software.Note:Indicates conditions which must be met, or procedures which must be followed, to ensure proper functioning of the equipment or software.Information:Indicates information which makes usage of the equipment or soft-ware easier
4Mini-RFM - Reference Guide November ’00Document OverviewPageChapter 1: Product Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.1 General............................................................................................... 61.2 System Overview ............................................................................... 61.3 Product Description ............................................................................ 61.4 Mechanical Construction .................................................................... 7Chapter 2: Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.1 General............................................................................................... 92.2 Transmitter ......................................................................................... 92.3 Receiver ........................................................................................... 112.4 Antenna Circuit................................................................................. 11Chapter 3: Connectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133.1 Connector Location .......................................................................... 143.2 Connector ST1 ................................................................................. 153.3 Connector ST2 ................................................................................. 16Chapter 4: Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174.1 Recommended Operating Conditions .............................................. 184.2 Electrical Characteristics .................................................................. 184.3 Timing Characteristics...................................................................... 204.4 Mechanical Data............................................................................... 21Chapter 5: Installation and Use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225.1 Mechanical Mounting ....................................................................... 235.2 Supply Voltage ................................................................................. 235.3 Receiver Signal Strength Output RXSS-.......................................... 255.4 Programming a Transponder ........................................................... 275.5 Antenna Requirements..................................................................... 275.6 Antenna Tuning ................................................................................ 29Chapter 6: Warnings, Cautions and Notices . . . . . . . . . . . . . . . . . . . . . . . . . . 316.1 FCC / Telecommunications Regulations.......................................... 326.2 Important Note to Purchasers/Users of the Mini-RFM in the USA ... 326.3 Warning ............................................................................................ 326.4 Cautions ........................................................................................... 32List of Figures PageFigure 1: The RI-RFM-003B........................................................................... 6Figure 2: Mini-RFM Block Diagram.............................................................. 10Figure 3: Mini-RFM’s Antenna Circuit .......................................................... 12Figure 4: Top View ....................................................................................... 14Figure 5: Bottom View.................................................................................. 14Figure 6: Maximum Supply Current I_VSP versus t_off (Power Stage)....... 19Figure 7: Mechanical Dimensions - Top View.............................................. 21Figure 8: Mechanical Dimensions - Side View............................................. 21Figure 9: PCB Mounting Proposal................................................................ 23Figure 10: Supply Line Wiring for Short Supply Lines.................................. 24Figure 11: Supply Line Wiring for a Separated Power Supply ..................... 25Figure 12: Synchronization output Control - Digital Adjustment................... 26Figure 13: Synchronization output Control - Analog Adjustment ................. 26Figure 14: Write Pulse Timing for TXCT- ..................................................... 27Figure 15: Stick Antenna RI-ANT-P02A....................................................... 28List of Tables PageTable 1: Module Connector - ST1 ................................................................ 15Table 2: Antenna Tuning Connector - ST2 .................................................. 16
CHAPTER 15IntroductionChapter 1: Product DescriptionThis chapter introduces you to the Mini-RFM. It tells you what the module is for, pro-vides an overview of the complete system and the product itself. It also provides amechanical description of the construction of the Mini-RFM. Topic Page1.1 General..........................................................................................................61.2 System Overview .........................................................................................61.3 Product Description.....................................................................................61.4 Mechanical Construction ............................................................................7
6Mini-RFM - Reference Guide November ’001.1 General This manual provides information about the TIRIS Mini-Radio Frequency Module RI-RFM-003B. It describes the module and how to integrate it into your RFID system. This guide should be used in conjunction with the RFM Sequence Control ReferenceManual (document number 11-06-21-049) which describes the timing and sequenceof radio communications between the TIRIS transponder and the radio frequencymodule. 1.2 System OverviewThe three major parts of a TIRIS system are the transponder, antenna and reader. When a transponder is to be read, the reader sends out a 134.2 kHz power pulselasting approximately 50 ms to the antenna. The field generated by this power pulseis “collected” by the antenna in the transponder that is tuned to the same frequency.This received energy is stored in a small capacitor within the transponder. When thepower pulse has finished, the transponder immediately transmits its data back to thereader, using the energy stored within its capacitor as the power source. 1.3 Product DescriptionThe Mini-Radio Frequency Module is an integral part of a TIRIS system, togetherwith a control module or unit and an antenna it is used for wireless identification ofTIRIS transponders. Main tasks of the RF module are to send an energizing signal via the antenna to ini-tialize a TIRIS transponder, to demodulate the received transponder identificationsignal and to write to a transponder. The RF module delivers a digital data streamand a clock signal for further processing to its control unit or module. Furthermore afield strength dependent digital output is available for synchronization purposes. Figure 1: The RI-RFM-003B
7November ’00 Chapter 1. IntroductionIts small size and low supply voltage makes the Mini-RFM well suited for portableReading/Writing Units, as well as for stationary equipment where medium read/writerange and speed is sufficient. The data input and output lines are compatible with the HCMOS- logic family. 1.4 Mechanical ConstructionThe RF module has a simple mechanical construction where all the components aremounted on the Printed Circuit Board (PCB). The components of the upper and lowerside of the PCB are protected by metal shields. The PCB also carries the connectorsST1, ST2 and the antenna terminals A1 to A3 which are captive nuts soldered to thePCB. These captive nuts allow durable low resistance connection with the ring ter-minals of the antenna.
CHAPTER 28Electrical DescriptionChapter 2: Functional DescriptionThis chapter provides an electrical description to block diagram level of how the Mini-RFM works. Topic Page2.1 General..........................................................................................................92.2 Transmitter ...................................................................................................92.3 Receiver ......................................................................................................112.4 Antenna Circuit ..........................................................................................11
9November ’00 Chapter 2. Electrical Description2.1 General The RF module is the interface between the TIRIS transponder and the data pro-cessing unit of a TIRIS Reader. It contains circuitry to:- send a charge-up signal to a TIRIS transponder- program a read/write transponder- to receive the signal from the transponder and to prepare the received signalfor digital decoding. Figure 2 shows the block diagram of the RF module and unless otherwise noted thefollowing description refers to this schematic.2.2 TransmitterThe transmitter control logic generates the transmitter output frequency from acrystal-controlled oscillator. This signal is amplified by the push-pull transmitterpower stage which is connected to the antenna terminal A1. The supply currentI_VSP of the transmitter output stage depends on the quality factor of the antennabeing used and the supply voltage VSP. The Mini-RFM’s antenna circuit is shown inFigure 3. The transmitter control signal TXCT- activates the transmitter as long as it is “low”.In receive mode when TXCT- is “high” the antenna terminal A1 has a low impedancepath to the ground.The transmitter power control signal TPC controls the intensity of the transmittercharge pulse by changing the duty cycle of the power stage control signal. The levelof the RF power output can be reduced by setting the TPC signal to “low”. TPC con-trols the power setting of the RF signal which is used to make-up the “power-burst”.Both input signals TXCT- and TPC have internal pull-up resistors.Because of the limited heatsink possibilities of the transmitter power transistors theduty cycle of the power pulse must not be allowed to exceed that shown in Figure 6. CAUTION:Because of the necessarily low impedance of the output stage, a short-circuit from antenna terminal A1 either to the ground or to the supply voltage can damage the output stage if the supply current is not limited.
10Mini-RFM - Reference Guide November ’00Figure 2: Mini-RFM Block Diagram
11November ’00 Chapter 2. Electrical Description2.3 ReceiverThe receiver comprises three parts: the RF part, the interface and the logic. The selective amplifier in the RF Part of the receiver: - amplifies the RF signal received from the antenna circuit, then - demodulates the FSK signal from the TIRIS transponder, and - generates an analog voltage (RSSI) that provides an indication of the receivedsignal strength. The demodulated FSK signal, carrier signal and analog signal strength voltage areall connected to the receiver interface. The demodulated data signal and the carriersignal are converted to logic signals, and connected to the receiver logic for furtherprocessing. The signal strength indicator voltage is converted into RXSS- which isfed directly to the module connector ST1. The function of the RXSS- signal is ex-plained in more detail in section 5.3. The receiver logic generates the receiver data signal RXDT and the receiver clocksignal RXCK to allow a simple data processing. The NRZ data stream of RXDT con-tains the identification data, the protection data and the framing bits. The clock signalRXCK is used as time reference for the data stream of RXDT. The RXCK signalchanges from “low” to “high” level in the middle of each data bit. 2.4 Antenna Circuit Figure 3 shows a simplified schematic of the antenna circuit. The antenna coil L_ANTis not part of the module but together with the antenna circuit’s built-in capacitors itforms a resonance circuit. The resonant current through the antenna coil generatesthe magnetic field which charges (and programs) the transponder.For the system to transmit and receive correctly, the antenna must be precisely tunedto the transmitter output frequency f_TXO to compensate for the (allowed) tolerancesof the antenna coil L_Ant and the antenna capacitors C_A1 and C_A2. To enable thistuning, six tuning capacitors C_AT1 to C_AT6 have been added to the antenna cir-cuit. Their values are binary weighted in normalized steps of 1, 2, 4, 8 16 and 32.C_AT1 has the smallest value corresponding to the normalized value 1. C_AT2 hasthe double capacitance of C_AT1, so that C_AT2 corresponds to the normalized val-ue 2 and so on. With this capacitance array and six jumpers, 64 different capacitancevalues can be tuned. Each of the five tuning pins has its adjacent antenna ground pinfor a simple short circuit with jumpers. The antenna terminal A3, which is not used in normal applications and the antennaground pins of ST2 have same potential as GNDP but should be used only for an-tenna purposes and not as a convenient ground connection.The damping circuit is part of the antenna circuit and damps the antenna circuit byreducing the quality factor of the built-in antenna circuit capacitor connected to theterminal A2. The quality factor is reduced during the receive mode when the TXCT-signal is “high”. Information about the tuning of the antenna circuit is given in section 5.6.
12Mini-RFM - Reference Guide November ’00Figure 3: Mini-RFM’s Antenna Circuit
CHAPTER 313ConnectorsChapter 3: ConnectorsThis chapter contains a listing of the module’s two connectors (ST1 and ST2) togeth-er with a list of the signals contained on each pin. Topic Page3.1 Connector Location ...................................................................................143.2 Connector ST1............................................................................................153.3 Connector ST2............................................................................................163.4 Antenna Connector....................................................................................16
14Mini-RFM - Reference Guide November ’003.1 Connector LocationFigure 4 and Figure 5 show the location of the terminals on the PCB from the top andfrom the bottom. Figure 4: Top ViewFigure 5: Bottom View
15November ’00 Chapter 3. Connectors3.2 Connector ST1 Table 1: Module Connector - ST1Pin Number Signal Name Purpose1 VSP Supply Voltage for Power Stage (+)2 VSP Supply Voltage for Power Stage (+)3 VSP Supply Voltage for Power Stage (+)4 VSP Supply Voltage for Power Stage (+)5 GNDP Ground for Power Stage (-)6 GNDP Ground for Power Stage (-)7 GNDP Ground for Power Stage (-)8 GNDP Ground for Power Stage (-)9 GNDL Ground for Logic (-)10 VSRL Regulated Supply voltage for Receiver and Logic (+)11 N.C. Not connected12 N.C. Not connected13 N.C. Not connected14 TXCT- Transmitter Control Input, inverted15 TPC Transmitter Power Control Input16 RXCK Receiver Clock Output17 RSCA Receiver Synchronization Level Control Input, weighted 118 RXDT Receiver Data Output19 RSCB Receiver Synchronization Level Control Input, weighted 220 RXSS- Receiver signal strength output, inverted Important Note:Supply terminals GNDP and GNDL must be connected externally.
16Mini-RFM - Reference Guide November ’003.3 Connector ST23.4 Antenna Connector Table 2: Antenna Tuning Connector - ST2Pin Number Signal Name Purpose1 C_AT6 Antenna Tuning Capacitor 5, (weighted value 32)2 GNDP Antenna Ground 3 C_AT5 Antenna Tuning Capacitor 5, (weighted value 16)4 GNDP Antenna Ground 5 C_AT4 Antenna Tuning Capacitor 4, (weighted value 8)6 GNDP Antenna Ground 7 C_AT3 Antenna Tuning Capacitor 3, (weighted value 4)8 GNDP Antenna Ground 9 C_AT2 Antenna Tuning Capacitor 2, (weighted value 2)10 GNDP Antenna Ground 11 C_AT1 Antenna Tuning Capacitor 1, (weighted value 1)12 GNDP Antenna Ground Table 3: Antenna Connector Pin Number PurposeA1 Antenna Terminal 1A2 Antenna Terminal 2A3 Antenna Ground (GNDP)CAUTION:Never try to connect the antenna between A1 and A3, or A2 and A3; as this will damage the module.
CHAPTER 417SpecificationsChapter 4: SpecificationsThis chapter provides the specific details that you will need in order to use the TIRISMini-Radio Frequency Module RI-RFM-003B correctly. It includes general data, elec-trical characteristics, timing characteristics and mechanical data. Topic Page4.1 Recommended Operating Conditions......................................................184.2 Electrical Characteristics ..........................................................................184.3 Timing Characteristics ..............................................................................204.4 Mechanical Data.........................................................................................21
18Mini-RFM - Reference Guide November ’004.1 Recommended Operating ConditionsOperating free-air temperature range.......................... 0 to +50 °CStorage temperature range........................................ -25 to +85 °C4.2 Electrical Characteristicsat Tamb=25 °C, VSRL=5.0V (unless otherwise noted)Note:Free-air temperature: air temperature immediately surrounding the Mini-RFM. If the module is incorporated into a housing, it must be guaranteed by proper design or cooling that the internal temperature does not exceed the ratings given here. Parameter Description Condition Pin No. of ST1 min. max UnitVSRL Supply voltage for logic - 10 4.75 5.25 VVSP Supply voltage for transmitter power stage - 1,2, 3, 4 4.5 6.0 V VIL Low level input voltage for TXCT- and TPC VSRL=5.0 14, 15 0 1.0 VVIH High level input voltage for TXCT- and TPC VSRL=5.0 14, 15 4.0 5.0 VNote:The voltage difference between GNDL and GNDP must not exceed 0.5 V. Parameter Description Condition Pin No. of ST1 min. nom. max UnitI_VSRL Supply current for logic and receiver - 10 - - 80 mAI_VSP Supply current for transmitter power stage with antenna Ri-ANT-P02AVSP=5VTXCT-=”low”TPC=”high” 1,2,3,4 0.5 - 1.2 AI_VSP_L Leakage current for transmitter power stage with antenna Ri-ANT-P02A VSP=5VTXCT-=”high” 1,2,3,4 - - 50 µAR_up Pull-up resistor from TXCT- and TPC to VRSL ---22-kOhmI_IL Low level input current for TCXT- and TPC V_IL=0V 14, 15 -180 - -300 µAI_IH High level input current for TCXT- and TPC V_IL=4V 14, 15 -30 - -60 µA
19November ’00 Chapter 4. SpecificationsFigure 6: Maximum Supply Current I_VSP versus t_off (Power Stage)Time t_off between 2 charge pulses of 50 ms [ms]Values in brackets ( ) are for time t_off between 2 write cyclesI_IL Low level input current for RSCA and RSCB V_IL=0V 17, 19 - -30 µAI_IH High level input current for RSCA and RSCB V_IH=5V 17, 19 - - 30 µAV_OH High level output voltage for RXCK, RXDT and RXSS- I_OH=-2mA 16, 18, 20 2,4--VV_OH High level output voltage for RXCK, RXDT and RXSS- I_OH=-1mA 16, 18, 20 4.0--VV_OL Low level output voltage for RXCK, RXDT and RXSS- I_OL=-2mA 16, 18, 20 --0.5VR_GND Decoupling resistor between GNDL and GNDP -9 to 5,6,7,8 -33-OhmParameter Description Condition Pin No. of ST2 min. nom. max UnitC_A1 +C_A2 Antenna capacity without tuning cap. A2 10.6 - 11.8 nFC_AT6 Antenna tuning capacity weighted 32 - 1 1425 1500 1575 pFC_AT5 Antenna tuning capacity weighted 16 - 3 740 780 820 pFC_AT4 Antenna tuning capacity weighted 8 - 5 370 391 410 pFC_AT3 Antenna tuning capacity weighted 4 - 7 209 220 231 pFC_AT2 Antenna tuning capacity weighted 2 - 9 95 100 105 pFC_AT1 Antenna tuning capacity weighted 1 - 11 50 56 64 pFParameter Description Condition Pin No. of ST1 min. nom. max Unit1.81.51.20.90.60.3 050(250) 100(400) 150(550) 200(700) 250(850)0I_VSP_max [A]
20Mini-RFM - Reference Guide November ’004.3 Timing Characteristics at Tamb=0-50 °C, VSRL=5.0 V, VSP=5.0 VParameter Description Condition Pin No. of ST1 min. nom. max. Unitf_TX Transmitter frequency - A1 134.1 134.2 134.3 kHzf_OSC Internal oscillator frequency - - - 4294.4 - kHzf_mRX Center frequency of receiver - - - 128.2 - kHzb_RX Bandwidth of receiver - - - 22 - kHzt_rin, t_finRise and fall time of the input signals TXCT- and TPC - 14, 15 - - 100 nst_rout, t_foutRise and fall time of the output signals RXCK, RXDT, RXSS- -17, 18, 20 --1µs f_REPwrt Repetition rate to program with Antenna = RI-ANT-P02At_wrt=310msTPC=”high ---1Hzf_REPrd Repetition rate to read with Antenna = RI-ANT-P02At_charge= 50msTPC=”high” ---4Hzt_offL Transmitter OFF-time for databit = “L” t_bit=2ms - - 0.5 - mst_offH Transmitter OFF-time for databit=”H” t_bit=2ms - - 1.2 - ms
21November ’00 Chapter 4. Specifications4.4 Mechanical DataLength......................................................................... 60.2 mmWidth........................................................................... 55.1 mmHeight, body................................................................ 10.4 mmHeight, at connector.................................................... 11.5 mmWeight......................................................................... 40 gFigure 7 shows the top view and Figure 8 shows the side view of the RF module, bothdrawings show the most important dimensions. The center of the upper right mount-ing hole serves as reference point for all dimensions.Figure 7: Mechanical Dimensions - Top ViewFigure 8: Mechanical Dimensions - Side View
CHAPTER 522Installation and UseChapter 5: Installation and UseThis chapter provides the specific details that you will need in order to install the TIRIS Mini-RFM correctly. It includes a detailed description of the power supply re-quirements, the antenna characteristics, the connecting cable and how to tune theantenna to resonance.Topic Page5.1 Mechanical Mounting...............................................................................235.2 Supply Voltage .........................................................................................235.3 Receiver Signal Strength Output RXSS-................................................255.4 Programming a Transponder..................................................................275.5 Antenna Requirements............................................................................275.6 Antenna Tuning........................................................................................295.6.1 To Switch-ON the Transmitter..............................................................295.6.2 To Tune the Antenna Circuit ................................................................295.6.3 To Detect the Correct Tuning...............................................................295.6.4 Tuning Procedure.................................................................................30
23November ’00 Chapter 5. Installation and Use5.1 Mechanical MountingTo protect the RF module from strong mechanical shock and vibration, grommets areinserted into the mounting hole of the PCB as shown in Figure 9. Because the grom-mets are made of soft material, eyelets or spacers must be inserted into them whenthe RF module is mounted with screws. Figure 9: PCB Mounting Proposal5.2 Supply VoltageThe module uses two different supply lines each with a separate ground line. The re-ceiver and the logic are supplied via the VSRL and GNDL pins from a voltage regu-lated power supply. The transmitter power stage with its relatively high currentconsumption is supplied via the VSP and GNDP pins. The supply voltage range forVSP is wider than for VSL. This allows the direct connection of VSP to a four cellNiCd battery, if the variation of the power pulse field strength caused by the variationof the battery voltage is acceptable.Both ground lines GNDL and GNDP are decoupled inside the RFM with the resistorR_GND and the capacitor C_GND and have to be connected together externally asshown in Figure 10 or Figure 11 (depending on your power supply). This techniqueallows the power ground level GNDP to float in a certain range against the logicground level GNDL without creating adverse effects to the control signals from andto the control unit. Floating GNDP can happen during transmit time if you are usinga long supply line between the RF module and a control module.Note:Take care when disconnecting ST1 that you pull the plug straight out and do not apply any sideways strain to the plastic guides.
24Mini-RFM - Reference Guide November ’00Figure 10 shows an example of how to supply the RF module in a battery suppliedreading unit where short lines are possible. Figure 11 shows an example of how to wire a stationary application where long sup-ply lines (over 15 cm) are used. The capacitor C_E1 between the VSP and GNDPpins is necessary to reduce the RF ripple voltage and EMI on the supply line andmust have low impedance at the transmit frequency (ESR = Equivalent Serial Resis-tor). In addition the common mode choke coil (choke) and the capacitor C_E2 alsoreduce the EMI during transmit time. These components should be placed as closelyas possible to the RF module connector ST1. The capacitor values shown in Figure 10 and Figure 11 are for general use and canvary according to different application requirements. Regardless of which kind of power supply you use, we recommend that you build infuses or electronic current limitations in between the RF module and the power sup-plies to avoid any damage in case of short circuit. The value of the fuse depends verymuch on the application, for example: the current consumption of the module whichin turn depends on several factors, such as: the antenna used, whether or not a ca-pacitor is connected and its size. Figure 10: Supply Line Wiring for Short Supply LinesNote:The fuse load for VSP under normal conditions is less than 1 A. However, if the Mini-RFM is connected into an application where the power is permanently on (hot” connecting), the load could surge by several amps due to the current in capacitor CS1 inside the Mini-RFM.
25November ’00 Chapter 5. Installation and UseFigure 11: Supply Line Wiring for a Separated Power Supply 5.3 Receiver Signal Strength Output RXSS-If you are going to operate more than one TIRIS reader in a local area, the systemsshould be synchronized to each other. An intelligent control unit achieves this syn-chronization by sampling for the presence or absence of the field strength indicatorsignal RXSS-. A power pulse in the area will cause RXSS- to be active. If the signalRXSS- is present the control unit ensures that the RF module transmits either simul-taneously or sequentially to any other RFMs in the area.The RXSS- output switches to “low” if the received signal strength exceeds the inter-nal reference level. This reference level can be adjusted with the two receiver signalstrength control inputs RSCA and RSCB. Figure 12 and Figure 13 show the basic schematic of the signal strength indicatorand two methods of adjusting the switching level. The circuit shown in Figure 12 works as a simple D/A converter where the digital in-puts RSCA and RSCB are switched either to the ground GNDL or to the supply volt-age VSRL. Because of the high input impedance of RSCA and RSCB, the switchescan be replaced by computer controlled outputs. Such a circuit can adjust the sensi-tivities in four steps. A fifth step is given if both inputs are open.
26Mini-RFM - Reference Guide November ’00Figure 12: Synchronization output Control - Digital AdjustmentAn analog adjustment of the sensitivity level can be realized if a potentiometer isused as shown in Figure 13 or if a variable voltage source is used to bias one or bothof the control inputs RSCA and RSCB. Figure 13: Synchronization output Control - Analog Adjustment
27November ’00 Chapter 5. Installation and Use5.4 Programming a TransponderTo write data to a read/write transponder the transmitter of the RF module must beswitched off and on periodically after the power pulse is completed. As shown in Fig-ure 14 each data bit has the same length t_bit, but the duration t_offL or t_offH duringwhich the transmitter is switched off, determines the value of the bit. Because the an-tenna circuit of the module and the connected antenna form a resonance circuit witha specific rise and fall characteristic of the resonance voltage, different RF moduleand antenna combinations might need different t_offL and t_offH timing. The valuest_offL and t_offH shown in section 4.3 'Timing Characteristics' are the times appliedto TXCT-. A high Q antenna such as RI-ANT-P02A is used.Figure 14: Write Pulse Timing for TXCT-A detailed description of the complete programming sequence is given in the Se-quence Control Manual (document number 11-06-21-049).5.5 Antenna RequirementsThe antenna for a TIRIS RF module is a coil with the inductance L_ANT and the Q-factor Q_ANT. To ensure that the antenna can be tuned to resonance with the tuningcapacitors inside the RF Module, the inductance L_ANT for an air coil antenna canvary in the limits given below: L_ANT = 115 to 117 µH (at f=134.2 kHz, V=1V)Q_ANT = 200 or better is recommended for good read/write range.Some factors which often influence each other, are listed below.a. The size and the construction of the antenna coil is a key factor for the generated magnetic field strength. The larger the area of an air coil antenna or the longer a ferrite core antenna is, the higher the field strength for a given RFM set-up and a given Q-factor of the antenna coil. b. The quality factor of the antenna coil is a parameter indicating its efficiency. The quality depends on the construction and the wire used for the coil. Because of the high frequency, litze-wire is needed for a high Q-factor. The higher the Q-factor of the antenna coil the more energy can be “pulled” from the RF module for a given RF module set-up. If an antenna with ferrite core is used, it must be kept in mind that it may have a very high quality factor under test conditions, but the quality factor will drop if a high magnetic field is applied to the ferrite core.c. A very important factor for a good read/write range is the correct orientation / polarization between the transponder antenna and the antenna of the read/write unit.
28Mini-RFM - Reference Guide November ’00d. Noise, i.e. magnetic interference energy in or close to the TIRIS frequency range can reduce the read range remarkably. Sources of interference can be, for example: electronic equipment with built-in switch mode power supplies, monitors and TV-sets with their magnetic deflection, which are not shielded enough. In such conditions you may be able to obtain better read/write ranges with a smaller antenna rather than a large one. The reason for this is that a large antenna collects signals within a larger area and therefore produces a stronger interference signal compared with the relatively small transponder signal. Under some conditions, charging and/or writing to the transponder works excellently, but the reading unit cannot detect the transponder signal.Figure 15 shows the dimensions of the ferrite stick antenna RI-ANT-P02A availablefor the RF Module RI-RFM-003B.Figure 15: Stick Antenna RI-ANT-P02A
29November ’00 Chapter 5. Installation and Use5.6 Antenna TuningIn order to get all the available field strength from the antenna, it must be tuned toresonance. To do this, the following set-up and equipment are required.5.6.1 To Switch-ON the TransmitterThe reading/writing unit or test set up should be able to switch the RF module’s trans-mitter to a fast repeating reading mode or continuous wave mode. If a continuouswave mode is applied, care must be taken not to exceed the duty cycle limitation asgiven in section 4.3. Time when the transmitter is switched on but during which thecurrent consumption is less than I_VSPcont, does not add to the duty cycle.5.6.2 To Tune the Antenna CircuitThe built-in tuning capacitors C_AT1 to C_AT6 which are available at ST2 should beused to tune the resonance frequency of the antenna circuit to the output frequencyof the transmitter. The most simple method of tuning is to use a “Switch Box” con-nected to the antenna tuning connector ST2, this will allow the capacity of the anten-na resonant circuit to be increased by connecting the built-in tuning capacitors to theground. The “Switch Box” in its simplest version is an array of six well isolated, high voltageproof ON/OFF switches, which are connected to the antenna tuning connector ST2(Antenna Tuning Switch Box RI-ACC-ATS1). If you have to tune a lot of Mini-RFMs (for example on a production run) it would behelpful to build a computer (or electronically) controlled tuning box which allows youto start the tuning procedure and then set the jumpers according to the result of thetuning. The cable from the “switch box” to the connector ST2 should be as short aspossible (less that 20 cm) in order to get the same tuning results as with the jumpers. 5.6.3 To Detect the Correct TuningThere are two basic methods to detect the correct tuning point, they are: One method is to tune the antenna circuit to maximum current consumption ofthe transmitter power stage by inserting a current meter into the VSP-linewhich is an easy way for production. The lines of the meter should be as shortas possible, or they must be RF decoupled close to the RF module.The second method is to tune the antenna circuit to the maximum of the mag-netic field strength generated by the antenna.
30Mini-RFM - Reference Guide November ’005.6.4 Tuning ProcedureEnsure that the reader is switched OFF.Connect the antenna to the RF Module.Remove all jumpers from the tuning connector ST2 and connect the “Switch Box”with all six switches in the OFF position.Switch the RF module transmitter ON (continuous or fast reading mode).While watching the current meter, increase tuning capacity with the “Switch Box”step-by-step until you find a peak. When you find a peak continue with two more steps and check in case you find an-other, higher peak. Looking for a possible second peak is necessary because the ca-pacitors of the tuning network have overlapping capacitance, which causesdiscontinuous capacitance steps.Check if the power stage supply current or the field strength has the correct value forthat application.Switch the transmitter OFF, disconnect the switch box and then plug-in jumpers atall the places where the switches are in the ON position.Switch ON the equipment again and check if the current or field strength are almostthe same as they were with the switch box connected. Switch OFF the transmitter or reading unit. Tuning is completed.WARNING:CARE MUST BE TAKEN WHEN HANDLING THE MINI-RFM. HIGHVOLTAGE ACROSS THE ANTENNA TERMINALS AND TUNING CONNEC-TORS COULD BE HARMFUL TO YOUR HEALTH. IF THE ANTENNAINSULATION IS DAMAGED IT MUST NOT BE CONNECTED TO THEMINI-RFM. Note:If you are using a switch box, do not forget that the capacitors attached to the jumpers are binary weighted, and that you should set the switches in a binary way: Switch 1 ONSwitch 1 OFF Switch 2 ONSwitch 1 ON Switch 2 ONSwitch 1 OFF Switch 2 OFF Switch 3 ONand so on.
CHAPTER 631Warnings, Cautions and NoticesChapter 6: Warnings, Cautions and NoticesThis chapter provides the Warnings, Cautions and Notices that are relevant to theMini-RFM. Topic Page6.1 FCC / Telecommunications Regulations .................................................326.2 Important Note to Purchasers/Users of the Mini-RFM in the USA ........326.3 Warning.......................................................................................................326.4 Cautions......................................................................................................32
32Mini-RFM - Reference Guide November ’006.1 FCC / Telecommunications RegulationsThe TIRIS RF Module generates RF emissions at 134.2 kHz. The radiation of thefundamental and the harmonics will vary with the type of antenna and other devicesor functions connected to the RF module.The required FCC or Telecommunications approvals must be obtained prior to oper-ating the TIRIS RF Module with antenna(s), power supply and a control module orother devices. Sale, lease or operation in other countries may be subject to prior approval by thegovernment or other organizations.6.2 Important Note to Purchasers/Users of the Mini-RFM in the USAThe TIRIS RF Module product is considered by the Federal Communications Com-mission (FCC) to be a “subassembly”. As such, no prior approval is required to im-port, sell or otherwise market the RF Module in the United States. In order to form afunctioning radio frequency RF device, the RF Module must be connected to a suit-able antenna, power supply, and control circuitry. A radio frequency device may notbe operated unless authorized by the FCC nor may a radio frequency device be mar-keted (i.e. sold, leased, imported, or advertised for sale or lease) without the priorgrant of an FCC equipment authorization.FCC authorization to operate an RF device may take one of two forms: first, the FCCmay grant the user an experimental license; second, the FCC may issue an equip-ment authorization permitting use of the RF device on an unlicensed basis. TI canassist the user in obtaining an experimental license that will cover a specific installa-tion of the RF Module in a specific site or sites. Experimental authorizations are ap-propriate to cover operations during the development of an RF device. A grant ofequipment authorization (known as “certification”) must be obtained from the FCCbefore RF devices are marketed or operated on a nondevelopment basis.An equipment authorization has already been issued for use of the RF Module andother TIRIS equipment (including antennas) in certain configurations. This authoriza-tion does not cover all possible combinations of equipment and, in particular, coversonly specific antenna configurations. Should a user desire to use the RF Module ina configuration not yet approved, TI can assist that customer to obtain the necessaryequipment approval.6.3 WarningCare must be taken when handling the RF Module. High voltage across the antennaterminals and tuning connector could be harmful to your health. If the antenna insu-lation is damaged it should not be connected to the RF Module.6.4 CautionsThe RF Module might be subject to damage by electrostatic discharge (ESD) andshould therefore only be handled by ESD protected personnel at ESD secured work-places.
33November ’00 Chapter 6. Warnings, Cautions and AbbreviationsThe transmitter power output stage can be damaged, if the antenna terminal A1 hasa short circuit either to the ground or to the supply voltage and no current limitationis applied.The transmitter power output stage can operate only with a limited duty cycle. Thissubject needs to be given attention especially during the antenna tuning procedure.The ground pins GNDL and GNDP have to be connected externally to avoid damageto the RF Module.
34Mini-RFM - Reference Guide November ’00

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