Korea University Ubiquitous LAB. Chapter 5. Characteristics of tags Ph.D Chang-Duk Jung

Korea University Ubiquitous LAB. Components of RFID tags The chip and the antenna reside on the substrate, which is made of either rigid or flexible material. The antenna is made up of a metal or a metal-based material. The chip, which is an integrated circuit (IC) made of silicon, has an electrical connection with the antenna.

Korea University Ubiquitous LAB. Types of tags Active –Have an internal power source, such as a battery Battery powers the IC and transmits a signal to the reader –Read range from 20 meters through 100 meters Passive –Have no internal power supply –Activated by the reader –Read distances ranging from 2 millimeters through 4.6 meters Semi-passive –Passive tags with batteries –Battery constantly powers the IC –Larger reading distance than passive tags

Korea University Ubiquitous LAB. Active tags vs. passive tags FunctionalityActive tagsPassive tags PowerPowered by a battery; have an active transmitter Powered by the radio signal of an RFID reader, which activates them Read rangeDesigned for communications up to 100 feet from the RFID Reader Can be read from a distance of about 15 feet. (Semi-passive RFID tags contain a small battery that boosts the range.) Input / OutputCan be read/writeCan be read-only or read/write Data storageMemory size varies according to application requirements; some system can use up to 1 MB of memory Memory size varies from 32 bits through 128 bits of data DurabilityLarge and heavy; dependent on battery life Lighter and more durable CostExpensiveCheap

Korea University Ubiquitous LAB. Inductive vs. backscatter coupling Inductive coupling –LF and HF passive tags use inductive coupling –A coil in the reader antenna and a coil in the tag antenna form an electromagnetic field –Readers can read LF tags from within 1 foot and HF tags up to 3 feet Backscatter coupling –UHF passive tags use backscatter coupling –A reader antenna emits radio waves but does not form any electromagnetic field –Readers can read UHF passive tags up to 10 feet or more

Korea University Ubiquitous LAB. Antenna Polarization –The principle of changing the direction of the magnetic field Radiation patterns –A radiation pattern is a three-dimensional plot of its radiation from the source.

Korea University Ubiquitous LAB. Radiation patterns Elevation pattern –A graph of the energy radiated from the antenna as you view it from the side Azimuth pattern –A graph of the energy radiated from the antenna as if you were looking at it directly from above the antenna

Korea University Ubiquitous LAB. Radiation patterns 3D pattern

Korea University Ubiquitous LAB. Antenna types Dipole antenna Linear polarized antenna Circular polarized antenna Omnidirectional antenna Monopole antenna Crossed-dipole antenna Helical antenna Slotted antenna

Korea University Ubiquitous LAB. Dipole antenna

Korea University Ubiquitous LAB. Dipole antenna (cont’) Half-wavelength dipole –The total length of the antenna is half the wavelength of the used frequency to optimize the energy transfer from the reader antenna signal to the tag Quarter-wavelength dipole –It relies on the reflective ground plane to provide an image of the antenna to complete the dipole. The gain of the antenna varies considerably depending on its deployment. Dual dipole antenna –It consists of two dipoles that can greatly reduce the tag’s orientation sensitivity, a reader can read this tag at different tag orientations Folded dipole –It consists of two or more straight electric conductors that are connected in parallel, each electric conductor being half the wavelength of the used frequency

Korea University Ubiquitous LAB. Linear polarized antenna The RF waves emanate in a linear pattern from the antenna These waves have only one energy field

Korea University Ubiquitous LAB. Circular polarized antenna RF waves radiate from a circular polarized antenna in a circular pattern These waves have two component energy fields that are equal in amplitude and magnitude, but have a phase difference of 90 degrees Therefore, when a wave of one energy field is at its highest value, the wave of the other field is at its lowest

Korea University Ubiquitous LAB. Omnidirectional antenna A non-directional antenna Radiates maximum power uniformly in all directions A perfectly omnidirectional antenna is an isotropic antenna. The isotropic antenna is a theoretical construct derived from actual antenna radiation patterns

Korea University Ubiquitous LAB. Antenna types (cont’) Monopole antenna –Single antenna with applied source feed ground plane –Uses reflection from the ground plane The other end of its pole is an RF reflection from the ground Crossed-dipole antenna –Transmitting and receiving antennas oriented orthogonally to each other Slotted antenna –Exhibits radiation characteristics that are similar to those of the dipole –Provides little antenna gain –Doesn’t exhibit high directionality

Korea University Ubiquitous LAB. Helical antenna Consists of a conducting wire wound in the form of a helix The direction of the coil determines its polarization The space between the coils and the diameter of the coils determine its wavelength

Korea University Ubiquitous LAB. Integrated circuit The power control/rectifier converts AC power from the reader antenna signal to DC power. It also supplies power to other components of the microchip The clock extractor extracts the clock signal from the reader antenna signal The modulator modulates the received reader signal. The tag’s response is embedded in the modulated signal, which is then transmitted back to the reader The logic unit implements the communication protocol between the tag and the reader. The microchip memory stores data. You can generally segment this memory into several blocks or fields.

Korea University Ubiquitous LAB. Substrate A plastic or Mylar layer that the metal of the transponder antenna adheres to. Some of the materials used for a substrate are polyethylene terephthalate (PET), paper, and polyvinyl chloride (PVC) or glass epoxy material. Substrate materials can be rigid or flexible. It is the support structure for the RFID tag

Korea University Ubiquitous LAB. Smart labels

Korea University Ubiquitous LAB. Smart labels (cont’) A semiconductor wafer processed into chips that have the ability to store data. These chips are small with enough data storage capacity An antenna made of a conductive material –permits the chip to receive and send data to and from an RFID reader A substrate on which the antenna –can be printed, and to which the chip can be adhered A label face stock –covers the inlay and provides a readable print area A release liner –serves as the bottom layer for the inlay. By using this layer, you can convert the pressure-sensitive face and inlay into rolls for easy distribution, and remove the layer when you place the smart label on the carton or pallet An adhesive –attaches the inlay to the face stock and the release liner to the inlay and face stock

Korea University Ubiquitous LAB. Insert RFID inserts are available in different sizes for various applications: –Postage stamp-sized inserts are fixed into a case or package to be applied to a video cassette –Paper-thin inserts are inserted into pressure-sensitive labels that are applied to packages for parcel tracking –Rugged credit cards are thick inserts, which are used to create intelligent labels intended for use in harsh environments

Korea University Ubiquitous LAB. Packing items Effects of material on RFID system Material compositionEffects on RF signals Corrugated cardboardAbsorption from moisture Conductive liquidAbsorption GlassAttenuation (weakening) Group of cansMultiple propagation effects; reflection Human body/animalAbsorption; detuning; reflection MetalReflection PlasticDetuning (dielectric effect)

Korea University Ubiquitous LAB. Unit summary RFID tags consist of three components: chip, antenna, and substrate The types of tags, such as passive, active, and semi-passive The difference between inductive and backscatter coupling. Different types of tag antennas, such as dipole, linear polarized, circular polarized, omnidirectional, monopole, crossed-dipole, and helical Antenna properties, such as polarization and radiation patterns, which will help you to select an antenna Two components of the tag, integrated circuit and substrate. Labels and inserts The various considerations that you need to take care of when packing tagged items

Korea University Ubiquitous LAB. Review questions List the components of an RFID tag. What are the different types of tags and how are they categorized? How do passive, active, and semi-passive tags differ from each other? What are the various types of tag antennas and configurations that are widely deployed? What are the basic components of an IC attached to a tag antenna? What are the key components of a smart label?