RM310 NXP Semiconductors, RM310 Datasheet - Page 9

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

HT RM310
2.4.2.
The inductance of the coil should be in the range of 350 and 500 µH.
The quality factor of the antenna should be approximately Q = 40.
If the Q factor is too high, it must be reduced by using an additional resistor. Generally speaking it
is better to have a smaller diameter of the wire for the coil rather than using an additional resistor.
The following equation shows the approximate calculation of the number of coil windings for a
required inductance and antenna geometry:
The abbreviations read as follows:
L
a
D
N
K
Please note:
The factor K is usually much smaller than the quotient a/D and can thus be neglected.
Htrm310.doc/HS
Antenna Coil
required inductance (nH)
circumference of the antenna (cm)
diameter of the wire (cm)
number of windings
geometrical constant
circle antenna:
square antenna:
L
N
Page 9 of 41
2
Q
Rev. 2.3
a
1 9
.
K= 1.01
K= 1.47
ln
2
2
a
D
a
R
ln(
f L
S
L
K
a D
S
)
N
1 9
.
02-10-1998