HTRM800SLASHEED datasheet(14/20 Pages) PHILIPS

14 / 20 page

2001 Oct 04

Philips Semiconductors

Product speciﬁcation

HITAG long range reader module

hardware

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) <10V.

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.

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