Chapter 6. Tag implementation Ph.D Chang-Duk Jung

Interaction between tags and interrogators

Tag selection and implementation depends on four key performance areas: Communication link margin : Measures how efficiently each tag uses RF power Distance performance : Measures the maximum distance at which you can successfully read a tag Read rate performance : Measures whether a tag can be successfully read while moving at varying speeds Orientation sensitivity : Measures how the tag’s orientation affects readability when the tag is attached to different materials depends on the type of reader that you are using : Read range - Reading volume geometry Tag size and geometry - Tag velocity Number of tags - Anti-collision strategy Operating power level - Operating frequency

Communication link margin Refers to the amount of power the tag extracts from the RF signal before the reader-tag communication weakens Used to calculate the distance between the tag and reader antenna

Relationship between frequency and read range Low frequency (LF) Tags operate at 125 KHz, and have a range between 3 feet and 4 feet High frequency (HF) Tags operate at 13.56 MHz, and have a range between 3 feet and 6 feet Ultra-high frequency (UHF) Tags operate in the range of 400 MHz and 1 GHz (depending on the geographical location), and have a range of nearly 7 feet Microwave frequency Tags operate in the range of 2.35 GHz and 2.45 GHz

Factors affecting tag performance Tag sensitivity Tag size Tag shape Number of tag antennas Speed Tight tag stacking Interference Materials to which the tags are attached

IC performance Chip memory Power circuitry Impedance mismatch Impedance alteration Collision-free channels

Effects of operating frequency The choice of operating frequency affects Reading distance Interference with other radio systems Communication data speed Antenna size Low frequency RFID systems use passive tags High- and ultra-high frequency systems operate with active tags

Packaging material The four principal effects that a material can have on a tag are: Absorption Reflection/refraction Dielectric effects Multipath

Packaging design considerations Variations in package dimensions can change signal propagation Air pockets help the tag use more RF energy to increase its power Altering the processing and composition of the existing packaging material can improve tag performance Changing the chemical formula of a product can enhance RFID compatibility

Tag and antenna orientation

Tag sensitivity map

Polarization continued

Polarization( con’t )

Polarization & tag orientation continued

Polarization & tag orientation, continued

Substrate A substrate that contains a metal antenna and an IC is known as an inlay Substrates are either rigid or flexible

Media selection for tags The common RFID-enabled media configurations: Pressure-sensitive labels RFID-enabled tickets Tie-on tags

Adhesive selection for tags Effective tag adhesives depend on Ease of initial adhesion Settling time Ultimate bond strength Environmental stability Resistance to deterioration over time Two basic adhesive families Acrylic adhesives Rubber-based adhesives

Movement of tags

Tag stacking You can resolve tag stacking by Placing tags farther apart from each other Placing tags in an alignment where they cause the least amount of interference

Tag placement

Unit summary The interaction between tags and interrogators The factors affecting tag performance and the effects of packaging materials on a tag Tag orientation and placement, the movement of tags, and the issues caused by tag stacking

Review questions How would you define a link margin? Why should you be concerned about antenna polarization? What type of tag can be read through human or animal skin and why? What is the purpose of an IC chip in the tag? Explain how the link margin influences the performance of an RFID