HID Global Corporation SE3210 Manuel D’Utilisation
iCLASS SE Reader Module Hardware Developer Guide, SE3200-902, Rev B.0
October 2012
Page 29 of 42
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7
Antennas
All antennas offered for the iCLASS SE Reader Module are optimized for a free air
environment. A free air environment is one in which there are no external effects on the field
produced by the antenna and which might degrade its performance (for example, metal or
stray capacitance).
When an air-tuned antenna is placed near metal, its tuning is affected causing a degradation
When an air-tuned antenna is placed near metal, its tuning is affected causing a degradation
of read performance.
All air-tuned antennas are optimized for a 50mm interconnect cable length. Different cable
All air-tuned antennas are optimized for a 50mm interconnect cable length. Different cable
lengths may also lead to performance degradation and optimization may be required.
Environment deviations (from free air, as well as antenna interconnect cable length and
Environment deviations (from free air, as well as antenna interconnect cable length and
routing the HF antenna interconnect cable along metal) require performing antenna
optimization to ensure that the RF interface operates optimally within the integrated
environment. It is suggested that the antenna and antenna interconnect cable be integrated
into the end product to mirror a free air environment.
7.1
Basic Antenna Operation
Credentials obtain their power from the magnetic field generated by the antenna of the
reader. At the operating frequency of the reader, this interaction is similar to the operation of
an air core transformer. When an antenna is energized by an alternating current, the induced
magnetic field is directly proportional to the area enclosed by the antenna loop. The larger
the loop, the more excitation current is required to produce the same level of magnetic flux.
That flux covers a larger area and so the read range is extended. Other external factors
affect the magnitude of this induced magnetic field. Magnetic lines of flux when generated by
a loop antenna are oriented perpendicular to the plane of the loop. This is known as the
right-hand rule, the magnetic field wraps around the wire in the direction of current flow.