Presentation on theme: "1 Use an electronic microchip with data storage capacity of up to a few kilobytes Data-carrying device : Data transfer between the transponder and a reader."— Presentation transcript:
1 Use an electronic microchip with data storage capacity of up to a few kilobytes Data-carrying device : Data transfer between the transponder and a reader Full Duplex (FDX) Half Duplex (HDX) Transponder Reader HDX FDX < 30MHz Load modulation Simple circuitry Harmonic Procedure Similar to the modulated cross- section procedure in radar technology Sub-harmonic Procedure Sequential System (SEQ)
2 Down link : data transfer from the reader to the transponder
3 Power supply to passive transponders Reader Transponder Magnetic field H Rectification DC Power Generation weak transformer-type coupling Resonance Capacitor 135 kHz Typical windings 13.56MHz Typical 3-10 windings trimming cap. to compensate for resonance frequency manufacturing tolerances
4 Different designs of inductively coupled transponders. The photo shows half finished transponders, i.e. transponders before injection into a plastic housing (reproduced by permission of AmaTech GmbH & Co. KG, D-Pfronten)
5 Reader for inductively coupled transponder in the frequency range <135 kHz with integral antenna (reproduced by permission of easy-key System, micron, Halbergmoos)
6 : transponder reader Load modulation Binary Code Signal, subcarrier freq. (fs) Transponder Magnetic field H signal Modulation product by load modulation with subcarrier Generation of load modulation in the transponder by switching the drain-source resistance of an FET on the chip.
7 Example : circuit-load modulation with subcarrier 13.56MHz Subcarrier (212 kHz) /64 Divider NAND Full- wave Rectifier SW w.r.t output of IC3a Q : TP Reader ?
8 E xample : S ubharmonic P rocedure 128 kHz 64 kHz Subcarrier (64 kHz) 128 kHz Basic circuit of a transponder with subharmonic back frequency
9 Long-range systems RFID systems in which the gap between reader and transponder is greater than 1m UHF frequencies : 868 MHz (Europe), 915MHz (USA) 908.5~914MHz (Korea) Microwave frequencies : 2.5GHz, 5.8GHz Short Wavelength ANT size & Efficiency Q : RFID. ? Free space path loss Free space path loss a F at different frequencies and distances. the transponder s antenna gain : 1.64 (dipole), the reader s antenna gain : 1 (isotropic)
10 antenna Lithium batteries Active transponder for the frequency range 2.45 GHz.
11 reflection cross-sectionThe efficiency with which an object reflects electromagnetic waves. Operating principle of a backscatter transponder. The impedance of the chip is modulated by switching the chip s FET
12 2 Full and Half Duplex Procedure ranges between 0.1 cm and a maximum of 1 cm. Close coupling systems Close coupling transponder in an insertion reader with magnetic coupling coils frequency range : 1-10MHz Efficiency : Very good The mechanical and electrical parameters of contactless close coupling chip cards standard, ISO 10536
13 Magnetic Coupling Capacitive Coupling Load Modulation in close coupling systems Plate capacitors are constructed from coupling surfaces isolated from one another. Capacitive coupling in close coupling systems Electrical Field E Reader s coupling surface Transponder s coupling surface : transponder reader
14 Capacitive coupling An electrically coupled system 1m a×b=4.5cm×7cm ( ) (f=125kHz)
15 2 Full and Half Duplex Procedure Equivalent circuit diagram of an electrically coupled RFID system Data Transfer : Reader Transponder ASK: amplitude shift keying FSK: frequency shift keying PSK: phase shift keying Because of the simplicity of demodulation, the majority of systems use ASK modulation. : transponder reader