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• 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)

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• Down link : data transfer from the reader to the transponder

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Power supply to passive transponders

Reader

Transponder

Magnetic field H

Rectification

DC Power Generation

weak transformer-type coupling

Resonance Capacitor

Resonance

Capacitor

135 kHz Typical 100-1000 windings

13.56MHz Typical 3-10 windings

trimming cap. to compensate for resonance frequency manufacturing tolerances

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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)

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Reader for inductively coupled transponder in the frequency range <135 kHz

with integral antenna (reproduced by permission of easy-key System, micron, Halbergmoos)

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: transponderreader

Load modulation

Binary Code Signal, subcarrier freq. (fs)

TransponderMagnetic field H

signal Modulation

product by load modulation with

subcarrierGeneration of load modulation in the transponder by switching the drain-source resistance of an FET on the chip.

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Example : circuit-load modulation with subcarrier

13.56MHz

Subcarrier(212 kHz)

/64Divider

NAND

Full-wave

Rectifier

SW w.r.t output of IC3a

Q : TP 가 Reader 기로 너무 가까이 가면 ?

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Example : Subharmonic Procedure

128 kHz

64 kHz

Subcarrier (64 kHz)

128 kHz

Basic circuit of a transponder with subharmonic back frequency

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Long-range systemsRFID 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 의 인식거리를 넓히고자 한다 . 사용 주파수와 인식거리와의 관계는 ?

Free space path loss

Free space path loss aF at different frequencies and distances.

the transponder’s antenna gain : 1.64 (dipole),

the reader’s antenna gain : 1 (isotropic)

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antenna

Lithium batteries

Active transponder for the frequency range 2.45 GHz.

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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

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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

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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

ElectricalField E

Reader’s coupling surface

Transponder’s coupling surface

: transponderreader

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Capacitive coupling

An electrically coupled system

1m 의 거리에서 전극 크기 a×b=4.5cm×7cm

( 스마트 카드에 대응하는 형태 ) 를 갖는 트랜스폰더 읽기를 위해 필요한 전극 전압 (f=125kHz)

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2 Full and Half Duplex Procedure

Equivalent circuit diagram of an electrically coupled RFID system

3.2.5 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.

: transponderreader