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UHF Gen2 RFID Propagation View. Prof. Roland Kueng. 0. 0. 1. 2. 3. 4. 5. 6. 7. 8. 9. 5. Starting Motivation. Wanted: Smart Wireless Electronic Barcode which allows to create and operate an Internet-of-Things
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UHF Gen2 RFIDPropagation View Prof. Roland Kueng
0 0 1 2 3 4 5 6 7 8 9 5 Starting Motivation Wanted: Smart Wireless Electronic Barcode which allows to create and operate an Internet-of-Things Needs: Ultra low cost Tags with a Global Standard behind to tag all goods and items Future: Upgrade Tag with Sensors
RFID Systems up to Edgeware RFID Reader System Decoupling Line to RFID - Application Enterprise Application Integration
Example: Dock Door Application Reader related risks • Mutual interference among readers • Co-channel interference • Adjacent channel interferences • Intersystem interferences
UHF Reader Block Diagram power amp TX antenna modulation switch RADIATING ANTENNA RX antenna signal processor synthesizer I Q D A direct conversionreceiver • Air Interface Options: • 2 Separated Antennas • 1 Antenna and Circulator • 1 Antenna and Directional Coupler
Details Reader Architecture Signal Processing - Sample Level on FPGA - Symbol Level on DSP - Air Protocol on DSP • RISC Processor • MAC • Reader Protocol • Interfaces • UHF Frontend • Direct Conversion Receiver • Carrier Suppression • Multi Antenna
FPGA ADC DAC DSP Synthesizer DC-RX Xscale TX Amp Supply Circulator Ethernet USB RS232 4 Antenna Ports Modern Reader Example
UHF Passive Tag Block Diagram RADIATING ANTENNA DC power control & signal sub carrier with processing data from reader unit memory backscatter modulator sub carrier with data from tag
Best what Radiation can do • The fundamental formula (d>> ) : • Pr = received power • Pt = transmitted power • Gt = transmit antenna gain • Gr = receive antenna gain • = wavelength • d = distance • n = propagation exponent • L = system loss factor • do = breakpoint distance for n>2 G = 4·Ae/2 Pt ·Gt = EIRP (limited by regulations*) 2/(4)2d2 Free space attenuation, n = 2 *Regulations: ETSI EN 320 208 US FCC Part 15
Path Loss 49 dB @ 8 m Path Loss 49 dB @ 8 m PassiveUHF RFID: Limited by Tag Power Consumption * EPC Class 1 Gen 2 -13…-17 dBm - 16 dBm received at tag * S/N= 35 dB + 33 dBm (2 W) - 71 dBm (0.1 nW) Gain = 7 dB • 22 dBm (6 μW)backscatter signal Receiver Noise: -99 dBm (F = 25 dB, B = 100 kHz) Reality: Additionally orientation losses, system losses, fading, n > 2 ... Additional noise sources, amplitude phase, TX to RX coupling
Fading - Problem for Passive Solutions Simple 2-Ray Model
UHF Signal Propagation Material Orientation • Test fixture with 73 Gen2 tags, equally spaced in air medium • Target read time: < 1 second
UHF Signal Propagation Multi-path reflections from metal (reinforcing in floors/ dock levellers and other objects), cause nulls and peaks that get worse with distance from the antenna.