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1、 11-08-26-001 Jan 2004Radio Frequency Identification SystemsHF Antenna CookbookTechnical Application ReportContentsEdition Two Jan 2004. i About this Manual.ii Conventions. ii If You Need Assistance.iiAbstract. 11 Construction Details.21.1 Copper Tape.21.2 Copper Tube.31.2.1 Mounting tuning componen

2、ts.3 2 Copper Tube Antenna (500mm x 500mm.42.1 Matching Components.52.1.1 Gamma matching the Antenna.5 3 Tape Antenna (1000 mm x 600 mm.73.1 Tuning to Resonance.83.2 Damping the Q.83.3 Matching the Loop to 50 Ohms.103.4 Tuning. 113.5 Adding a Common Mode Choke.124 Copper Tube Antenna (1 m x 1 m. 134

3、.1 Matching Circuit Layout.134.2 Matching Components.145 Double Loop Antenna.155.1 The Matching Board.165.2 Matching Components.165.3 Winding the BALUN.176 Small Antenna 1 (40 mm × 30 mm.186.1 Circuit Layout.186.2 The Matching Components.187 Small Antenna 2 (50 mm × 30 mm.197.1 Circuit Lay

4、out.197.2 The Matching Components.198 Small Antenna 3 (60 mm × 30 mm.208.1 Circuit Layout.208.2 Matching Components.209 Small Antenna 4 (150 mm × 100 mm.219.1 Circuit Layout.219.2 Matching Components.2210 Conclusion . 23FiguresFigure 1. Soldered Antenna Corners.2Figure 2. Picture showing c

5、opper tube and the joining material.3Figure 3. Assembled Tube with Damping Resistor.3Figure 4.Copper Tube Antenna 500mm x 500mm.4Figure 5.Resonance Tuning Components.4Figure 6.Thick Film Damping Resistor. 5 Figure 7.Gamma Matching Arm.5 Figure 8.Soldered Copper Tape Main Loop.7Figure 9. Variable Mic

6、a Capacitor.8Figure 10.Air Gap Variable Capacitor.8 Figure 11.10K Thick Film Resistor.9 Figure 12.Resonant Capacitors and Damping Resistor.9 Figure 13.Dimensions of Matching arms.10 Figure 14.Completed Antenna.11 Figure 15.VSWR Meter.12 Figure 16.Common Mode Choke.12 Figure 17.The 1 m Loop with Spac

7、er.13 Figure 18.Artwork for Matching Board.14 Figure 19.1 m × 1 m Antenna Matching Circuit.14 Figure 20.Double Loop Antenna.15 Figure 21.Clinch Nuts.15 Figure 22.Artwork and Completed Board.16 Figure 23.How to Wind The BALUN.17 Figure 24.Matching Board Connected.17 Figure 25.40 mm × 30 mm

8、Antenna Artwork.18 Figure 26.Completed Antenna.18 Figure 27.50 mm × 30 mm Antenna Artwork.19 Figure 28.Completed Antenna.19 Figure 29.60 mm × 30 mm Antenna Artwork.20 Figure 30.Completed Antenna.20 Figure 31.150 mm × 100 mm Antenna Artwork.21 Figure 32.Completed Antenna.22 Figure 33.R

9、oller Conveyor Read Gate.23Edition Two Jan 2004This is the second edition of this Technical Application Report called HF Antenna Cookbook.It contains descriptions of how to build and tune antennas for use at 13.56MHz which can be used in conjunction with:S4100, S6350, S6400, and S6500 Series Readers

10、This document has been created to help support Texas InstrumentsCustomers in designing in and /or using TI*RFID products for their chosen application. Texas Instruments does not warrant that its products will be suitable for the application and it is the responsibility of the Customer toensure that

11、these products meet their needs, including conformance toany relevant regulatory requirements.Texas Instruments (TI reserves the right to make changes to its products or services or to discontinue any product or service at any time withoutnotice. TI provides customer assistance in various technical

12、areas, butdoes not have full access to data concerning the use and applications of customers products.Therefore, TI assumes no liability and is not responsible for Customerapplications or product or software design or performance relating tosystems or applications incorporating TI products. In addit

13、ion, TI assumes no liability and is not responsible for infringement of patents and / or any other intellectual or industrial property rights of third parties, which mayresult from assistance provided by TI.TI products are not designed, intended, authorized or warranted to besuitable for life suppor

14、t applications or any other life critical applicationswhich could involve potential risk of death, personal injury or severeproperty or environmental damage.TIRIS and TI*RFID logos, the words TI*RFID and Tag-it are trademarks or registered trademarks of Texas Instruments Incorporated (TI.Copyright (

15、C 2001 Texas Instruments Incorporated (TIThis document may be downloaded onto a computer, stored and duplicated as necessary tosupport 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 represents a violation

16、of the applicable copyright laws and shall be prosecuted.Lit. Number 11-08-26-001PREFACERead This FirstAbout this Manual This Technical Application Report 11-08-26-001 is designed for use by TI-RFID partnerswho are engineers experienced with TI-RFID and Radio Frequency Identification Devices (RFID.C

17、onventionsCertain conventions are used in order to display important information in this manual, these conventions are: WARNING:A warning is used where care must be taken or a certain procedure must be followed, in order to prevent injury or harm to your health.CAUTION:This indicates information on

18、conditions, which must be met, or a procedure, which must be followed, which if not heededcould cause permanent damage to the system.Note:Indicates conditions, which must be met, or procedures, which must be followed, to ensure proper functioning of any hardware orsoftware.Information:Information wh

19、ich makes setting up, or procedures, that makes the use of the equipment or software easier, but is not detremental toits operation.If You Need AssistanceFor more information, please contact the sales office or distributor nearest you. This contact information can be found on our web site at: .HF An

20、tenna Cook BookJ A GoulbourneRFID Systems, NorthamptonAbstractDuring the past years it has become clear that with each application of smart labels then a new antenna system has to be designed. A few off the shelf HF Antennae are available but many antennae have to be designed from scratch, in order

21、to meet the system requirements.The HF Antenna Cook Book is the result of this need to build different antenna systems and has been written to show the RFID Engineer how to design various HF antennas for use with Texas Instruments Tag-it and ISO 15693 transponder inlays. The descriptions within this

22、 document are based on actual designs which have been completed at Texas Instruments RFID laboratories and used to demonstrate antenna configurations during various trials that have subsequently taken place.The document is full of pictures and constructional details for a variety of antennae operati

23、ng at 13.56MHz and which are primarily matched to the characteristics of Texas Instruments RFID readers. This is not an exhaustive list of antenna types that could be used, but it does offer the RF antenna design engineer an insight into some of them that have been used.Note: Because antenna loops m

24、ay be slightly different in size to those shown in this document, and because of component tolerances,the RF Engineer may have to fine-tune individual antenna designsto achieve the correct matching.1 Construction DetailsAn antenna loop can be constructed from any conductive material but in this note

25、, three common methods involve using either copper PCB tracks, copper tape or copper tube.1.1 Copper TapeAdhesive copper tape is available in a number of widths and with conductive and non-conductive adhesive. It is recommended to use the non-conductive type because it is much less expensive. As a g

26、eneral rule, as the size of the antenna increases, the width of the tape should increase to keep the antennae inductance to a minimum.For example to build a 150mm x 150mm (6" x 6" antenna - 10mm wide tape would be satisfactory but for a 1m x 1m (40" x 40" antenna 50mm (2" ta

27、pe is required. The backing board must also be stiff enough, for the size of antenna, to prevent the tape rippling or stretching when applied.All the joints should be soldered as shown in Figure 1 with minimum overlap, to avoid adding parasitic capacitance. For the best results, the corners of recta

28、ngular antennasshould be at 45º Figure 1. Soldered Antenna Corners1.2 Copper TubeAs with the copper tape antennae, as the size of the antenna increases, the diameter of x 500mm (20" x 20" loop requires 15mm (½” Ø copper tube, whilst larger loops should use 22mm (¾"

29、 Ø tube.To construct a rectangular copper antenna you can either bend the tube at 90, or use matching characteristics are unlikely to change (as can happen with ones constructed from wire.1.2.1 Mounting tuning componentsWhere a tube antenna has to be cut to attach tuning components, you should

30、maintain a minimum 10mm separation to prevent unwanted capacitive coupling. Figure 2. Picture showing copper tube and the joining materialA recommended method to achieve this is to solder straight joint connectors to each end of the copper loop and cut a PTFE or 'Tufnol' (resin bonded paper

31、rod 30mm (1.2" long x 12mm (½" to insert between, maintaining the 10mm separation. Insert the PTFE or Tufnol rod into the straight connectors and drill a 4mm (3/16" hole through the tube and the rod at each end. Then taking a M4 tap, tap the holes to take a M4 (3/16" screw.

32、These screws hold both the ends of the loop in place but also provide an easy method to attach the tuning components, see Figure 3 below. Figure 3. Assembled Tube with Damping Resistor2 Copper Tube Antenna (500mm x 500mmThis type of construction produces an antenna, which is self-supporting, easilyc

33、onstructed and when tuned gives a read range of approximately 650 mm (26”. Figure 4. Copper Tube Antenna 500mm x 500mmThe antenna loop is constructed from 15mm (½" Ø copper tube, which is bent into the form shown in the figure above. It is also acceptable to use soldered right angle c

34、onnectors but the sharper corners will slightly change the value of the resonancematching capacitance. The loop ends are connected together using PTFE or Tufnol rod giving 10mm separation. The tube ends are drilled and tapped through into the PTFE or Tufnol rod to take M4 (3/32" screws. This fi

35、xing also holds the PTFE or Tufnol rod inplace and allows easy attachment of the resonance tuning components. Figure 5. Resonance Tuning Components2.1 Matching ComponentsThe resonance tuning of the antenna to 13.56 MHz is achieved by using mica capacitorsapproximating to 100pF. The fixed element com

36、prises of 68pF with a 20 80pF variable mica capacitor; all connected in parallel. A 4K7, 20 Watt thick film resistor, adjusts theQ of the antenna (see Figure 6. Figure 6. Thick Film Damping Resistor2.1.1 Gamma matching the AntennaThe antenna is matched to 50 Ohms, the output impedance of the Readers

37、 transmitter, using the "Gamma" matching method.At the signal feed point of the antenna, usually opposite the tuning point, a clearance hole is drilled through the copper tube to accept a SMA solder spill bulkhead jack (the hole onthe inside of the tube will have to be enlarged to accept i

38、t. Figure 7. Gamma Matching ArmA wire link (shown red in Figure 7 is soldered to the SMA connector center lug before it is inserted into the copper tube. The outer of the SMA Connector is at ground potential when it is fitted to the copper tube.The other end of the wire link is connected (either sol

39、dered or by a crimp connector to a matching arm constructed from 5mm (3/16" Ø copper / nickel automotive brake pipe. The copper / nickel pipe is attached to the main tube by using a Tufnol plate which is screwed into the main tube. The Tufnol plate should be wide enough to ensure that the

40、copper / nickel pipe has a 30mm gap between it and the main tube to reduce induced capacitance effects.A tap is made from two copper clamps, one 5mm and the other 15mm in size; connected together by a solid wire soldered to each of them.In order to match the antenna to the reader output impedance of

41、 50 ohms and a VSWR of 1:1.0, the antenna is attached to an MFJ HF / VHF SWR Analyzer, Model MFJ-259. Using an iterative process, change the position of the tap along both tubes, adjusting the tuning variable capacitor to find where the 50 Ohms VSWR 1:1.0 point is. Once the tap position is found secure the clamps (it may be necessary to change the fixed capacitor should