iCLASS SE Reader Module Hardware Developer’s Guide, SE3200-902, Rev. C.1
Page 31 of 52 February 2014
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 of read performance.
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 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.
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