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11-06-21-068, March 2003

Radio Frequency Identification Systems

Series 2000

Antenna Design Guide

Application Note

Содержание 2000 LF Series

Страница 1: ...11 06 21 068 March 2003 Radio Frequency Identification Systems Series 2000 LF Antenna Design Guide Application Note...

Страница 2: ......

Страница 3: ...easurement 10 4 2 Antenna Q 11 4 2 1 Determing the Antenna s Q Value 12 4 2 1 1 By Measurement 12 4 2 1 2 By Calculation 12 4 3 Controlling the Antenna s Q 13 4 3 1 Wire Selection 13 4 3 1 1 Skin Effe...

Страница 4: ...20 Windings Vs Inductance 17 Figure 21 Single Loop Vs 27 H Inductance 17 Figure 22 Out of Tune Conditions 18 Figure 23 Polypropylene Capacitor De rating 20 Figure 24 Polypropylene capacitors 0 01 F 0...

Страница 5: ...applications of customers products Therefore TI assumes no liability and is not responsible for Customer applications or product or software design or performance relating to systems or applications i...

Страница 6: ...a certain procedure must be followed in order to prevent injury or harm to your health CAUTION This indicates information on conditions which must be met or a procedure which must be followed which i...

Страница 7: ...taching to Texas Instruments Low Frequency LF Radio Frequency RF modules and readers It looks at the matching circuits of the standard RFMs and details the antenna requirements for each one The issues...

Страница 8: ...The size and shape of the transponder s antenna The size and shape of the reader s antenna The electrical noise in the environment The transmitter power limited by legislation Metal in the environmen...

Страница 9: ...quire antennas with different inductances Texas Instruments have three categories of antennas available 2 1 27 H Inductance Antennas These antennas are used with the RFM 104B RFM 007B and RFM 008B RF...

Страница 10: ...5 mm2 14 SWG wire is used a 4m 12 tail can be added and still be capable of being tuned to resonance Information The antenna tail is an integral part of the RF Module s matching circuit Changing the...

Страница 11: ...a matching circuit on Series 2000 readers Changing any part has an impact on the total system e g lengthening the feeder cable Each module requires antennas of a certain Inductance to ensure the match...

Страница 12: ...to resonance by varying the capacitance whilst the RFM 104B and the Remote Antenna Tuning Boards both vary the inductance 3 1 1 The RFM 104B Module The RFM 104B standard RF module is shown in Figure...

Страница 13: ...ng using jumpers for the fine tuning This circuit is represented in Figure 7 Figure 7 Capacitance Fine Tuning 3 1 3 The RFM 008B Tuning Board The RFM 008B Remote Antenna Module s resonant components h...

Страница 14: ...Figure 9 The MicroReader Unlike the other RF modules already described which need high Q antennas for optimum performance the MicroReader is designed for low Q antennas Antenna Q is described in more...

Страница 15: ...of measurement for inductance is the Henry H The values for Series 2000 antennas are in the micro Henry H range 4 1 1 By Calculation For S2000 Series readers antenna inductance can be calculated using...

Страница 16: ...d and by adjusting the number of windings or the size you can decide what size antenna will give you the correct inductance 4 1 2 By Measurement Relatively low cost LCR Inductance Capacitance and Resi...

Страница 17: ...input power high Q antennas have a much greater RF output than lower Q antennas Figure 12 High Q Vs Low Q A high Q antenna also serves as a filter ignoring signals outside its bandwidth but high Q ant...

Страница 18: ...e of the resulting output is detected by a spectrum analyzer 0 this should be around 134 2 kHz The frequency of the input signal is then raised until a 3 dB drop in the amplitude of the spectrum analy...

Страница 19: ...ire Selection At RF frequencies the behavior of an AC current through a wire is different from the flow through a DC circuit What might be considered a low resistance wire in a DC circuit can become h...

Страница 20: ...le to break if vibration is present It is more difficult to work One re occurring issue is when a standard antenna connector breaks off The temptation is to strip off the silk and crimp a new connecto...

Страница 21: ...antennas get larger Texas Instrument s large gate antenna RI ANT G04C does not use Litze wire but oxygen free low resistance Jumbo Hi Fi speaker cable Figure 16 Jumbo Oxygen Free Hi Fi Wire This multi...

Страница 22: ...een mentioned that in electrically noisy situations large antennas can have less reading range than smaller ones Figure 19 Reading Range Reduction due to Noise From Figure 19 we can see how in low noi...

Страница 23: ...g antennas so although you may require a particular sized antenna you could have to compromise on shape The dimensions of Texas Instrument s own standard antennas are dictated by the number of winding...

Страница 24: ...that resonates at 134 2 kHz If the inductance value is not the expected value though we can modify the capacitance by adding external capacitors either in series or parallel to effectively increase or...

Страница 25: ...3 0 0 009 40 0 0 110 22 5 0 010 39 0 0 120 22 0 0 012 38 0 0 130 21 5 0 013 37 0 0 140 21 0 0 015 36 0 0 160 20 5 0 017 35 0 0 180 20 0 0 018 34 0 0 200 19 5 0 020 33 5 0 220 19 0 0 022 33 0 0 230 18...

Страница 26: ...mber of turns the antenna can have an inductance too low or too high always opt for too low From Table 2 if the inductance is just too high e g 30 H a 0 47 F capacitor in series is required If the ind...

Страница 27: ...d around 3 m of extra wire and still tune to resonance Unfortunately adding the extra tail also adds extra resistance and we have seen how as the R increases the Q drops To minimize the added resistan...

Страница 28: ...d is that it increases the resistance and inductance because of the extra wire 4 6 Ferrite Cored Antennas Ferrite cored antennas like Texas Instrument s stick antennas RI ANT S01C and RI ANT S02C prov...

Страница 29: ...na Field patterns The result is the field patterns shown in Figure 28 5 2 Opposing Antennas In Phase When two individual antennas are connected to the same RF module they act as one antenna but can gr...

Страница 30: ...27 H inductance and can be used with standard RF module Figure 30 Two 54 H Antennas Connected in Parallel In Phase Note Do not make your double inductance antennas too large As both loops are connecte...

Страница 31: ...tes where the badge is always worn at right angles to the antenna Changing the field means it will read across the width without a hole This technique is used for livestock applications where the elec...

Страница 32: ...some performance These antennas have multiple loops that are equal and opposite and any homogeneous signal arriving at all loops is cancelled whereas the tag signal will arrive at one loop and be rece...

Страница 33: ...tput capacitors may receive over voltage and long term damage could result The antenna may still be resonating when the response from the tag is received Without built in damping the data may not be r...

Страница 34: ...and the resistance reduced by a series resistor Figure 34 MicroReader Antenna 1 Antenna 2 This antenna is constructed on a 40 mm diameter plastic tube former Figure 35 MicroReader Antenna 2 47 H INDUC...

Страница 35: ...Lit Number 11 06 21 068 Page 29 Antenna 3 Antenna three is 75 mm in diameter and formed around a slice of plastic water pipe Figure 36 MicroReader Antenna 3 15 TURNS 0 2 mm Enamelled wire 75 mm...

Страница 36: ...nna 4 This antenna is constructed around a 6 mm thick MDF former Tip For such antennas double sided Scotch tape will retain the thin wire in position during winding Figure 37 MicroReader Antenna 4 200...

Страница 37: ...Lit Number 11 06 21 068 Page 31...

Страница 38: ...http www deeter co uk litz htm New England Electric Wire Corp 1 603 838 6625 Boston USA http www newenglandelectricwire com litzwire shtml Yu Seung Electronics Co Ltd 82 41863 8100 Korea http www yuse...

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