UHF-Technology

UHF-Technology
Vorlesung RFID Systems
Benno Flecker, Michael Gebhart
TU Graz, Sommersemester 2014
RFID System
A traditional passive label (tag) is queried and it responds with it’s ID
accordingly. Power and commands are transferred with different
frequencies (UHF [860 – 960MHz], HF [13.56MHz], LF [125 & 134.2kHz].
Power & Commands
0101011011010111010
1010101100110101011
RFID Systems
Serial Number / Data
Seite 2
Interactive RFID | I2C devices
I2C serial interface to traditional RFID
Enables bidirectional communications between electronics and the
traditional RF interface
RFID tag would typically be incorporated in the electronic PCB
RFID
I2C
Electronic
Device
Bidirectional Communications
RFID Systems
Seite 3
RFID Technology Elements
•Slotted Aloha
•Binary Tree
•One Time Programmable (OTP)
•Read Only (RO)
•Read / Write (R/W)
Anti-collision
Handling
Memory
•Sensors
•Localization
•Cryptography
Special
Features
Power
Supply
RFID
System
Operating
Frequency
•125 /134.2 kHz
•13.56 MHz
•860 - 960 MHz
•2.45 GHz
•(5.6 GHz)
RFID Systems
•Passive
•Semi-passive
•Active
ID Format
•UID
•EPC 96bit
Protocol
Transponder
Type
•Tag (rigid)
•Label (flexible)
•Reader Talks First (RTF)
•Tag Talks First (TTF)
Seite 4
Used RFID technology and its properties
Low frequency (125kHz)
–
–
–
–
Read Range ~ 1m – one tag each time
Works well in harsh environment
Transponder cost
System cost
High frequency (13.56MHz)
–
–
–
–
Read Range ~ 1.5m – 40 tags at the same time
Works well in harsh environment
Transponder cost
System cost
Ultra high frequency (840-960MHz)
–
–
–
–
Very long read ranges of up to 10+m – 1000 tags/sec
Susceptible to harsh environment
Transponder cost
System cost
RFID Systems
Seite 5
LF Technology
 Physical concept:
 Inductive coupling
 Operating frequency:
 125/134.2 kHz
 Antenna:
 Coil
 Operating distance:
 Up to 1m
 Environmental influences:
 Standards:
 ISO 11784/85 Animal ID, TTF
 ISO 14223 RTF & TTF
 ISO 18000-2 Item Management
 National Regulations:
 Worldwide harmonized
RFID Systems
 Weak influence on operating
distance
 Works in metal environment
 Application:
 Animal identification
 Industrial environment
 Access Control
Seite 6
HF Technology
 Physical concept:
 Inductive coupling
 Operating frequency:
 13.56 MHz
 Antenna:
 Coil
 Operating distance:
 Vicinity: up to 1.5m
 Proximity: up to 10cm
 Standards:




ISO 15693 Vicinity Card
ISO 14443 Proximity Card
ISO 18000-3 Item Management
HF EPC Gen2
 National Regulations:
 Worldwide harmonized
RFID Systems
 Environmental influences:
 Weak influence on operating
distance
 Works in metal environment
 Application:




Libraries
Public transport
Product identification
Access control, …
Seite 7
UHF Technology
 Physical concept:
 EM – wave propagation
 Operating frequency:
 860 – 960 MHz
 Antenna:
 Dipole and/or loop
 Operating distance:
 Far field: up to 7m
 Near field: up to 10cm
 Environmental influences:
 Standards
 EPC Class I Gen2
 ISO 18000-6 Item Management
 National Regulations:
 No worldwide harmonized
RFID Systems
 Influence on operating distance
by reflection and absorption
 Application:




Pallets and container ID
Fashion
Retail
Electronics
Seite 8
Information from EPCglobal HP (Free Download)
Class 1 Generation 2 UHF Air Interface Protocol Standard "Gen 2"
http://www.gs1.org/gsmp/kc/epcglobal/uhfc1g2
EPC Tag Data Standard (TDS)
http://www.gs1.org/gsmp/kc/epcglobal/tds/
EPC Tag Data Translation (TDT) Standard
http://www.gs1.org/gsmp/kc/epcglobal/tdt/
Mask Designer ID Assignment (MDID)
http://www.gs1.org/epcglobal/standards/mdid
Frequency Regulations UHF
http://www.gs1.org/docs/epcglobal/UHF_Regulations.pdf
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Seite 9
Frequency allocation by countries
Frequency Regulations UHF
http://www.gs1.org/docs/epcglobal/UHF_Regulations.pdf
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Seite 10
PEIRP - Equivalent Isotropic Radiated Power
vs. PERP - Effective Radiated Power
PERP... transmitted power compared to a dipole antenna
ERP: Effective radiated power. The amount of power that would be necessary at the
input terminals of a reference half-wave dipole antenna in order to produce the same
maximum field intensity.
PEIRP... transmitted power compared to an isotropic antenna
EIRP:Equivalent isotropically radiated power (EIRP). The amount of power that a
theoretical isotropic antenna would need to emit to produce the peak power density
observed in the direction of maximum antenna gain.
PERP
PEIRP
=
1.64
1.64 is equivalent to 2.15dB
Gain and Directivity
Ptransmitted
G=
⋅D
Pconducted
– if the antenna has no electrical losses, then G = D
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Seite 11
Maximum Radiated by countries (PEIRP)
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Seite 12
Energy Transmission from Reader to TAG
Transferred power from a reader antenna to the chip
PChip
λ2
= PEIRP ⋅
⋅ ϑMatching ⋅ϑPolarisation ⋅ ϑ Antenna ⋅ GLabel
2
(4 ⋅ π ⋅ R)
– ϑMatching ... Antenna matching factor(1− | Γ |2 )
– ϑPolarisation ... Polarisation losses
– ϑAntenna ... efficiency of the label antenna (Pradiated / Pin)
RFID Systems
Seite 13
Read Range of an UHF/GHz Chip
Rmax
PEIRP ⋅ GLabel ⋅ λ2
⋅ ϑMatching ⋅ϑPolarisation ⋅ ϑ Antenna
=
2
(4 ⋅ π ) ⋅ PChip
Example I (UHF)
under US regulations:
PEIRP = 4 W; GLabel = 1.64; f = 915MHz; PCHIP = 35µW
ϑMatching = 0.8; ϑPolarisation = 1; ϑAntenna = 0.5
Rmax
4W ⋅1.64 ⋅ 0.33m 2
=
⋅ 0.8 ⋅ 1 ⋅ 0.5 = 7.19m
2
−6
(4 ⋅ π ) ⋅ 35 ⋅10 W
RFID Systems
Seite 14
Read Range of an UHF/GHz Chip
Example II (UHF)
under EN 302 208 European regulation:
PERP = 2 W equals PEIRP = 3.28W; GLabel =1.64
f = 869MHz; PCHIP = 35µW
ϑMatching = 0.8 ; ϑPolarisation = 1 ; ϑAntenna = 0.5
Rmax
3.28W ⋅1.64 ⋅ 0.35m 2
=
⋅ 0.8 ⋅ 1 ⋅ 0.5 = 6.90m
−6
2
(4 ⋅ π ) ⋅ 35 ⋅10 W
RFID Systems
Seite 15
UHF Memory structure
Reserved
Memory
EPC
Memory
TID
User
Memory
RFID Systems
• Access and Kill Password
• EPC Electronic Product Code
• Code can be written by user
• TID Tag Identifier (preprogrammed & locked)
• IC Manufacturer information, Unique serial number
• Manufacturing, quality and product related data
storage
• User related data storage
Seite 16
Anti collision algorithm
RFID Systems
Seite 17
Communication with the tag
Inventory
(1 Communication step)
Command
(e.g. READ TID)
RFID Systems
Seite 18
Tag Inventory flag
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Seite 19
Tag persistence
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Effect on search mode and sessions
Tag in the field
Dual Target
Reader A&B
Tag out of the field
A B A B A B A B A B A B A B A B A
R R R R R R R R R R R R R R R R R
Singel Target
Session 1
A
R
PT S1
B
A
R
PT S1
B
A
R
PT S1
B
A
R
PT S1
B
A
R
Reader only A
PT S2 or S3
Singel Target
Session 2 or 3
A
R
B
Reader only A
R: READ
PT S1: Persistance Time Session 1
PT S2 or S3: Persistance Time Session 2/ 3
RFID Systems
Seite 21
Environmental Influence - Overview
UHF-Characteristics
– Absorption/Damping
– Reflection
– Refraction
– Diffraction
– Penetration into Liquids
– Interference
– Polarisation
RFID Systems
Seite 22
Environmental Influence - Overview
Absorption/damping
– Only vacuum is passed by electromagnetic energy without
absorption
– Absorbed energy is typically converted to heat
– Absorbing materials between the reader antenna and the label
antenna strongly determines the operating range of the label
Absorbing materials
– Water, water absorbing materials
– Rubber, adhesives, …
RFID Systems
Seite 23
Environmental Influence - Overview
Reflections
– A pure reflection of the travelling wave, will conserve the
energy
of the field
– Will lead to interferences
– Constructive interference may lead to super ranges
– Destructive interferences may lead to „holes“ in the
operational area
– Reduce this no-read situations with multiple antennas
Reflecting materials
– Metal, water, concrete
– Metallic paints - films - foils
RFID Systems
Seite 24
Environmental Influence - Overview
Refraction
– caused by the velocity difference of the EM wave
between one propagation medium and a second
– lead to a change of the wave direction
medium border
εr
RFID Systems
εr1
Seite 25
Environmental Influence - Overview
Diffraction
– occurs by passing a sharp corner
– Huygens’ principle is based on this process
Representation of Radio
Waves as Wavelets
RFID Systems
Seite 26
Environmental Influence - Overview
Penetration into Liquids
– Depending on the electrical conductivity of the liquid
– Water has a high electrical conductivity and will tend to absorb and
reflect EM waves
– Oil derivates allows an EM wave to pass with a low level of
attenuation, if no additives are used.
RFID Systems
Seite 27
Environmental Influence - Reflections
Application Effects
Expanding operation range
– guiding travelling waves with the help of e.g. metal (Truck, ...)
Shielding
– wanted
• separation from places of identification
• hiding items from being identified (wrapping into conducting foil)
– unwanted
• e.g. labels inside a pallet of tin cans may not be recognized
RFID Systems
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Environmental Influence - Interferences
Example
– Propagation of travelling waves in free space
Z
Y
ideal dipole
X
Different field-strength
RFID Systems
Idealized linear polarized dipole
Polarisation: y - axis
Picture: xz - plane
Seite 29
Environmental Influence - Interferences
Example
– Propagation of travelling waves in free space
Z
Y
ideal dipole
X
Idealized linear polarized dipole
Polarisation: y - axis
Picture: xy - plane
RFID Systems
Seite 30
Environmental Influence - Interferences
Example
– Propagation of travelling waves with reflecting floor
field-holes
Idealized linear polarized dipole
Polarisation: z - axis
Picture left: zy - plane / Picture right: xy - plane
Z
Y
X
RFID Systems
Seite 31
Environmental Influence - Interferences
Example
– Propagation of travelling waves with reflecting floor
Z
Y
X
RFID Systems
Idealized linear polarized dipole
Polarisation: y - axis
Picture left: xz - plane / Picture right: xy plane
super-range
field-hole
Seite 32
Environmental Influence - Interferences
Example
– Propagation of travelling waves with reflecting wall
Z
Y
X
...wall
Idealized linear polarized dipole
Polarisation: y - axis
Picture: xz - plane
RFID Systems
Seite 33
Environmental Influence - Interferences
Application Effects
Close to reflecting planes, interferences will lead to standing waves
•Moving labels may cross spots
of „field nulls“ and may loose it´s
internal states
Z
Y
X
Idealized linear polarized dipole
Polarisation: y - axis
Picture: xz - plane
RFID Systems
...wall
Seite 34
Multi Antenna Arrangements
A single reader antenna will in many cases not be sufficient for desired
applications
Preferred way to use more than one reader antenna is multiplexing,
controlled by the reader
The reader starts its task (e.g. identify all tags in the field) at the first
antenna. After finishing this job the next antenna can be used ....
RFID Systems
Seite 35
Multi Antenna Arrangements
Positioning
A given operational space has to be covered by the sum of
the operational spaces of all individual antennas
– The more overlap the antenna arrangement has, the more reliable
the identification will be
– For applications with many, fast moving items the antenna
switching may be improved by external detectors e.g light barrier
– Operational spaces may be a affected by the items that have to be
identified (shielding, absorbing)
RFID Systems
Seite 36
Multi Antenna Arrangements
Positioning
Parallel mounted
Gate antennas
RFID Systems
Seite 37
Content

Antenna Design

Antenna design Inputs

Antenna design Parameter

Direct chip assembly

Pmin measurement

Identify the right tag

Label / Tag provider

RFID PCB antenna designer
RFID Systems
Seite 38
Antenna design inputs
IC
Dimensions, coating
Size
Label Size, Antenna Size
Antenna Substrate
Material; Thickness
Antenna Conductive materials
Material; Thickness; Line width; Gap width; min. corner radius
Performance
Required Frequency Bands; US; EU
Application
Free Air; Cardboard; Plastic; Other material
Stacked tags
Max. no. of tags; Min. distance of tags
Chip Attachment - Direct Attach:
Expected Assembly Capacitance
RFID Systems
Seite 39
Assembling –Parasitic Capacitances
Cparasit
Cchip
R
C tot = C parasit + C chip
RFID Systems
Seite 40
Reference antenna design FF9510
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Seite 41
FF9510 – Change loop size
7
6
Range [m]
5
4
3
Delta Loop = 0
mm
Delta Loop = 0.57 mm
Delta Loop = 1.05 mm
Delta Loop = 1.52 mm
Delta Loop = 2.00 mm
2
Loop Size
Increase
1
0
0.7
0.75
RFID Systems
0.8
0.85
0.9
0.95
FREQ [GHz]
1
1.05
1.1
1.15
1.2
Seite 42
FF9510 – Change dipole length
7
dL dipole =
dL dipole =
dL dipole =
dL dipole =
dL dipole =
6
0
mm
- 0.75 mm
- 1.75 mm
- 2.25 mm
- 3.00 mm
Rang [m]
5
4
3
2
L decrease
1
0
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
1.15
1.2
Freq [GHz]
RFID Systems
Seite 43
FF9510 – Change connection dipole loop
7
6
Range [m]
5
4
3
2
Distance
Reduction
Distance
Reduction
1
0
0.7
0.75
RFID Systems
0.8
0.85
0.9
0.95
FREQ [GHz]
1
1.05
Delta Dipole =
0 mm
Delta Dipole = - 1.2 mm
Delta Dipole = - 2.4 mm
Delta Dipole = - 3.6 mm
Delta Dipole = - 4.8 mm
Delta Dipole = - 6.0 mm
1.1
1.15
1.2
Seite 44
FF9510 – Total Gain 868 MHz
RFID Systems
Seite 45
Direct Chip attach
150µm, 120µm with
18µm gold bumps
Pressure
Temperature
ACP/ACF
Anisotropic Conductive Paste/Foil
(Adhesive with conducting particles
10k - 40k particles per mm2)
Antenna Structure
Pressure
Temperature
Material: Al, Cu, Ink
Etched, Printed, Laser cutted
Substrate
Material: Paper, PET, PC;
Thickness 38µm or 50µm
RFID Systems
Seite 46
Antenna gap
A… Maximum antenna gap (average distance + tolerance)
IC placement accuracy MB +/-50µm
Remark: Add etching tolerances - Check with the antenna supplier!
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Seite 47
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Seite 48
Assembled die
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Seite 49
Pmin – Measurement setup
EPC global document “Tag Performance Parameters and Test Methods
Version 1.1.1”.
RFID Systems
Seite 50
Pmin - Anechoic chamber
RFID Systems
Seite 51
FF9510 120 µm Reference materials
Measured with Voyantic Tagformance (http://www.voyantic.com/)
RFID Systems
Seite 52
Identify the right tag
Size
Application
Memory
Read / Write Sensitivity
Write cycles
Data retention
RFID Systems
Seite 53
Label / Tag provider
Avery Dennison (http://rfid.averydennison.com/)
Smartrac (http://www.smartrac-group.com/en/)
Confidex (http://www.confidex.net/)
…
RFID Systems
Seite 54
RFID PCB Antenna Designer
Target:
Easy access to customized PCB
antennas
Supported ICs:
• UCODE G2iL (SL3S1203)
• UCODE G2iM (SL3S1013)
• UCODE I2C (SL3S4011)
• Link:
http://www.nxp.com/documents/design_tools/re
direct_transim_rfid.html
RFID Systems
Seite 55
RFID PCB Antenna Designer - Design flow
IC Selection Specification
Synthesis
EM
Validation
Simulation
Step 1
Step 2
Step 3
Step 4
Step 5
Choice of three
different RFID
UHF ICs
UHF frequency
selection
Available space
for antenna
Antenna type
Antenna topology
PCB board
dimensions
PCB board
material
Start CST
Simulation
After simulation
report and
download
RFID Systems
Seite 56
Design flow – Step 1 - IC selection
Supported ICs:
• UCODE G2iL (SL3S1203)
• UCODE G2iM (SL3S1013)
• UCODE I2C (SL3S4011)
• Access Product Info
• Access datasheet
RFID Systems
Seite 57
Design flow – Step 2 - Specification
UHF Selection:
• Region
• Power level
Available antenna space
PCB top layer type
RFID Systems
Seite 58
Design flow – Step 3 - Synthesis
Topology selection
Topology - Geometry
RFID Systems
Seite 59
Design flow – Step 4 – EM Validation
Board Dimensions
PCB Specification
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Seite 60
Design flow – Step 5 - Simulation
Login required for starting the
simulation!
Simulation time counter
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Seite 61
Design flow – Step 6 - Results
Download:
• CST file
• DXF file
• Summary PDF
• Summary XLS
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Seite 62
Thank you for your
Audience!
Please feel free to ask questions...
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