Magnetic Absorber in RFID Systems

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27 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Magnetic Absorber in RFID Systems
ARC Wave-X® Magnetic Absorber in RFID Systems
The problem: communication failure induced by nearby metals
In a 13.56MHz RFID system, metals near an antenna degrade communication performance.
For example:
• With an RFID tag, the antenna is placed on or near printed circuit
boards or a battery pack surrounded by metals
• The RFID tag is attached directly to a metallic surface
• A reader/writer is placed on a metal table or the antenna is
positioned near metals in an enclosure
• System performance is deteriorated because when magnetic
flux from a reader/writer encounters metals, eddy currents flow
on the metal surfaces.
• These eddy currents generate a demagnetizing field which
cancels the magnetic field passing through the RFID tag
The solution: ARC Technologies Wave-X® absorber
• When a magnetic absorber sheet is inserted between the
metal surfaces and the antenna of an RFID tag and/or a reader/
writer the magnetic flux is drawn toward the absorber.
• Interference with metal surfaces is suppressed and system
communication distance is enhanced.
• This solution also reduces null problems within the system.

Demagnetizing Field
RFID TAG
Eddy Current
Magnetic Flux
METAL
ANTENNA
Reader / Writer
Figure 1a — Communication Malfunction
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Optimal absorber characteristics:
• The ideal absorber choice for antenna performance enhancement in
13.56MHz RFID systems will exhibit both high magnetic flux
convergence and low loss.
• Magnetic flux convergence is expressed and measured as high real
permeability (μ’) while low loss is expressed as low imaginary
permeability or μ”.
• An excellent choice for RFID performance enhancement is
Wave-X WD-NRC from ARC Technologies.
• WD-NRC exhibits a μ’ value of 50 and μ” of <1 at 13.56MHz. The
ratio of μ”/μ’ is the magnetic loss tangent or “Q”.
• The very high Q of WD-NRC ensures metal objects will not
interfere with optimal RFID reading and/or writing.
METAL
WAVE-X
ANTENNA
MAGNETIC SHEET
Reader / Writer
Figure 1b — Improved Communication with a Magnetic Sheet
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Permeability
Frequency (MHz)
1
0
20
10
30
40
50
60
70
10 100 1000 10000
Computation (mm)
130120110100
135
130
125
120
115
110
105
100
Measurement (mm)
WD-SPV
WD-H
WD-NRC
WAVE-X WD-NRC Permeability
Communication distance with magnetic sheets
ARC Technologies, Inc. 11 Chestnut Street • Amesbury, MA 01913
Tel: (978) 388-2993 • Fax: (978) 388-6866 • www. arc-tech.com
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Because of their high real permeability and high
magnetic loss tangent (Q factor) Wave-X WD-NRC
and WD-H enhanced effective RFID range significantly.