1. 1 Design of RFID Tags for the Real World (and how to test you got it right) Ian J Forster Clive P Hohberger

2. 2 Tag requirements In designing a tag for the ‘real world’ we have to start somewhere with... The REQUIREMENT AT BEST A well researched detailed description of exactly what is needed, where it will work, on what, when… AT WORST On napkins… Summarised as two key parameters: Cost and Performance

3. 3 Inlay cost and performance drivers Inlay Cost drivers Area of silicon Cost of chip Cost of antenna Assembly technique Test methodology Quality of roll Wafer yield – chips Volume + But… its like pushing on Jell-O, all parameters interact Inlay Performance drivers Process size used Parasitic effects Antenna Conductivity Assembly technique Antenna size Target product range +

4. 4 The blob of Jell-O With cost and performance, everything affects everything else Can I ever say ‘YES’ or ‘NO’… without a ‘BUT’? Smaller Chip Higher assembly cost Lower threshold sensitivity Lower cost antenna to achieve a given performance

5. 5 OK, now what? The key is making the right trade-offs in cost and performance to be “good enough” Robust antenna designs can be made which work well over a wide range of applications We’ll talk about one such design later.

6. 6 Transponders are perfect in free space Nothing is physically there to distort their field or detune their antennas Reader is so far away that it interacts with the transponder only through the RF signal (“far field”, typically a few wavelengths away– UHF wavelength ~0.34m, so 3 meters is far field) In the free space and far field, the tag acts like the spec sheet says Then some idiot goes and slaps it on a carton…

7. 7 RF properties of things… What’s in YOUR carton? 100%RF Reflecting 100% RF Absorbing 100% RF Transparent ● Canned hams ● Potato chips in foil bags ● Jars of pickles ● Bottled water ● Bubble wrap ● Dried foods

8. 8 Real products in cartons Alien squiggle transponder, horizontally polarized Measured distance at which good read rate drops to 50%

9. 9 We’re not in free space any more, Toto.. ‘Real World’ influences Conductors Dielectrics ‘Mixtures’ Results in changes in: Antenna bandwidth Operating Frequency Impedance Match Antenna Efficiency… =

10. 10 And its worse than that… ‘Real World’ Products have a 3D shape T T T T C C Layer of corrugated cardboard Pack of canned goods Antenna position dramatically changes electrical environment tag is operating in

11. 11 Still worse… Connectivity between conductive objects matter T T C Layer of corrugated cardboard Pack of canned goods Electrically isolated when pack is bent, in contact at other times So, shape, materials, connectivity all interact with mounting position to determine how well a deployed label works And we can’t design a different antenna for each situation…

12. 12 Special antenna technology approach Avery’s Carton Content Insensitive Technology ‘Near field interaction of specific elements in the antenna design re-tunes the far field response’ H field Interaction E field Interaction When placed 1.7mm away from a set of cans the operating frequency changes by >100MHz When placed 1.7mm away from a set of cans the operating frequency changes by <10MHz IN BOTH CHIP CENTRE AND CHIP GAP Carton Contents Insensitive (CCI) technology is intended to reduce the number of different designs we need to cope with a diverse range of products

13. 13 Special antenna technology approach Avery’s CCI Technology allows a single tag design to work on a larger group of products Works well with metal objects, conductive liquids are a challenge but progress is being made More difficult to design than a tag specifically tuned for one position and one product More difficult to test

14. 14 Avery’s testing systems for real world products Provides optimal trade-off between –Accuracy –Cost –Speed –Flexibility Ensures repeatability & traceability to National Standards through –Calibration routines –Test RFID devices –Defined procedures

15. 15 Avery primary response testing system VECTOR SIGNAL GENERATOR REAL TIME SPECTRUM ANALYZER DEVICE UNDER TEST LOW DIELECTIC SUPPORT CONTROL AND DISPLAY SYSTEM ROTATOR MOTOR COMPACT ANECHOIC CHAMBER IMPORTANT! Does NOT use a reader Test Distance Establishes a ‘Baseline’ for all other test systems

16. 16 Zebra primary response testing system Built in a G-TEM horn antenna with anechoic foam in bottom Uniform field in 6x6x6 inch volume 3-axis motion stepping tests 3-D transponder response field Uses calibrated UHF reader with PC-controlled step attenuators to measure transponder sensitivity

17. 17 Avery tag testing on real world products Secondary Reader Based System Calibrated To Primary System

18. 18 Avery “sweet spot” tag position testing READER SYSTEM AND DISPLAY COAXIAL CABLE NEAR FIELD COUPLER TEST TAG COMPLIANT FOAM POLYSTYRENE BLOCK Tertiary Reader Based System Calibrated To Primary System via secondary system

19. 19 Can I test my own cartons? Some simple test procedures are in Annex C of: Proposed Guidelines for the Use of RFID-Enabled Labels in Military Logistics: Recommendations for Revision of MIL-STD-129 Written by the AIM RFID Experts Group Free from AIM at: https://www.aimglobal.org/estore/ProductDetails.aspx?productID=241 https://www.aimglobal.org/estore/ProductDetails.aspx?productID=241

20. 20 19 mm (0,75 in) minimum from either vertical edge 25 mm (1 in) min from natural bottom 430 mm (17 in) max from natural bottom 25 mm (1 in) min from top Target area for RFID transponder DoD recommended smart label placement Problem: Where is the best spot to put the label in the allowed target area?

21. 21 Reader threshold power test Start in the center Test same tag at different points on case at a fixed distance from a reader with programmable power Find relative reader power to activate tag at each position Find position or region requiring minimum power Put label there! DJDJ L +6 F-3F-3 G +1 H 0dB J -2 K M no E C D -3 B +1 A +2 N +2 P0P0 Q +1

22. 22 Thanks! Questions?