RM310 NXP Semiconductors, RM310 Datasheet - Page 12

• Manufacturer Part Number: RM310
• Description: Ht Rm 310 Hitag Tm Mini Reader Module
• Manufacturer: NXP Semiconductors

02-10-1998
2.4.7.
The procedure how to design a HITAG Proximity antenna has been described in the previous
chapters. Generally speaking the following steps have to be considered:
1. The required antenna inductance can be chosen in the range of 350 H and 500 H
2. The number of turns N can be calculated with the following formula:
3. Now the antenna can be build according to the required dimensions (circumference a) with the
4. Measuring the inductance L of the antenna is described in Chapter 2.4.3.
5. Determination of the serial capacitor C
6. Now the antenna has to be tuned according to the instructions given in Chapter 2.4.4.
7. The serial resistance R
(e.g. L=420 H).
for L=420 H:
Please note:
Usually the factor K is much smaller than the quotient from a/D and can thus be neglected.
calculated number of turns.
Please note:
The antenna coil must not be changed afterwards because with the mechanical dimensions the
electrical specifications are changing, too. That means the number of turns, the shape, the ar-
rangement of the coil windings and the antenna supply cable must be used in their final form.
Please note:
Metal influences considerably the electric characteristics of the antenna. If metal is close to the
antenna when it is set up, all instructions below must be followed (distance from
metal < maximum diameter of the antenna).
Please note:
The capacitance of the antenna supply cable can be determined according to the specifications
given in the data sheet of the cable (e.g. Cp = 180 pF/m).
The tuning of the antenna is finished when the phase of impedance is within the range of
+/- 10°.
resistance at the resonance frequency (f=125 kHz). It can be calculated according to the for-
mula given in Chapter 2.4.5.
Procedure for Practical Antenna Design
s
of the antenna is the impedance of the tuned antenna and is an ohms
N
1 9
.
2
N
Page 12 of 41
a
Rev. 2.3
S
420 000
1 9
ln (
.
is described in Chapter 2.4.4.
2
a D K
a
ln (
L nH
a D K
)
1 9
.
a
)
633
ln(
a D
)
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