HTRM800 データシートの表示（PDF） - Philips Electronics
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HTRM800 Datasheet PDF : 20 Pages
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Philips Semiconductors
HITAG long range reader module
hardware
Product specification
HTRM800 family
10.5.2 RECOMMENDED ANTENNA CABLE AND LENGTH
The length of the antenna cable should be limited with five
meters. In case of longer cables a type with low
capacitance and resistance must be used. For standard
applications a 50 Ω coaxial cable is recommended and a
75 or 95 Ω coaxial cable for special applications.
10.5.3 TUNING OF THE ANTENNA CURRENT
Potentiometer R72 (see Fig.2) is used to tune the current
driven through the antenna. The default setting is 200 mA.
It is not customary to change this value. However, if you
want to change the current for a special application, it
should be noted that Vo(peak) < 10 V.
10.5.4 TUNING OF THE ANTENNA PHASE
The signal from a transponder is delayed by the decay
time of the antenna. To achieve optimal performance this
signal and the digital signal processing unit of the reader
module must be synchronous. Thus it is necessary to store
a phase information called Bit Clock Delay (BCD), which is
a function of the quality factor and the inductance
(reactance) of the antenna.
The default setting is 7 which is suitable in most of the
cases. Apart from that, the user is able to change the BCD
value. The reader module includes a non volatile memory
(EEPROM) to store the bit clock delay. To load the BCD
value to the reader module the command SetBCD is used.
10.5.5 HITAG ANTENNA TUNING DEVICE
Especially for the HITAG product line the HITAG antenna
tuning device HTOT840 was designed. This tuning device
can be used for tuning long range and proximity antennas.
10.5.6 ANTENNA MALFUNCTION INDICATION
If the antenna is broken or badly detuned, the antenna
overload bit is set. This bit can be read by the host system
via the serial interface by using the command
ReadLRStatus.
10.5.7 ADDITIONAL REMARKS
The following list is a summary about HITAG long range
antennas:
• Philips lays high emphasis on the research of antenna
development
• The choice of various antenna shapes (the electrical
parameters) is characteristic to 125 kHz systems
• The knowledge is transferred to Philips customers, in
order to enable them to design and build antennas which
fit best for the particular applications (antenna training)
• Solutions can be found for almost every environmental
scene (metal, periodic disturbers, special antenna
shapes, etc.).
10.6 Antenna arrangements
Various arrangements are suitable for different
applications (see Fig.6):
• The single loop antenna is used for standard
arrangements
• The gate antenna is used for typical access control
applications such as access control during passing
through the gate
• The double gate antenna is similar to the gate using two
rows
• The antenna multiplex system is a cost efficient
application, because one reader module drives many
antennas and the number of multiplexed antennas is
only limited by timing restrictions.
By changing the arrangement of the antenna, the total
system performance and reliability can be significantly
improved. As an example: building gate antennas with
opposite magnetic orientation leads to a very reliable
system.
2001 Oct 04
14
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