@MAXX
PRIME
R
EFERENCE
M
ANUAL
14
3.5.2. Internal RF antenna
The internal RF antenna is connected with the pins C4 / C8 of the smartcard reader for the
usage of dual interface cards.
When a dual interface card is inserted in the @MAXX and the @MAXX is put in the magnetic
field of any contactless reader, the internal RF antenna couples with the reader and an
induction current appears in the antenna thus providing power to the integrated circuit. The
generated current is proportional to the magnetic flux going through the antenna of @MAXX
reader
The carrier frequency of the magnetic field is used as a fundamental clock signal for the
communication between the reader and the card. It is also used as a fundamental clock input
for the integrated circuit microprocessor to function.
To send data to the user token the reader modulates the amplitude of the field. There are
several amplitude modulation and data encoding rules defined in ISO/IEC 14443. The reader
should should be ISO 14443 compliant reader.
To answer to the reader, the integrated circuit card of the @MAXX modulates its way of loading
(impedance) the field generated by the reader. Here also further details can be found in
ISO/IEC 14443.
The best communication between the @MAXX (with inserted dual interface card) and a
contactless reader can be established if the @MAXX is placed on the contactless reader with
the @MAXX bottom side in direction to the contactless reader. The bottom side of the @MAXX
is the side where the label and the smartcard insertion slot can be found. Depending on the
used contactless reader and the used dual interface card, the @MAXX prime establishes a
read out distance between 2cm – 3cm. A little bit bigger antenna within the @MAXX pime A
results to a bigger read out distance up to 3.5cm.
The communication between the reader and the @MAXX with dual interface card is sensitive to
the presence of material or objects interfering with the magnetic field generated by the reader.
The presence of conductive materials like metal in the vicinity of the reader and the user token
can severally degrade the communication and even make it impossible. The magnetic field of
the reader generates Eddy or Foucault’s currents in the conductive materials; the field is
literally absorbed by that kind of material.
The presence of multiple @MAXXs in the field of contactless readers also interferes with the
communication. When several @MAXXs are in the field of a contactless reader, load of the
field increases which implies that less energy is available for each of them and that the system
is detuned.
The communication between a contactless reader and the @MAXX is sensitive to the geometry
of the system {reader, @MAXX}. Parameters like the geometry and specially the relative size of
the reader and @MAXX antennas directly influence the inductive coupling and therefore the
communication.
