NXP Semiconductors
AN145715
PN544 Antenna Design Guide
145715
© NXP B.V. 2006. All rights reserved.
Application Note
Rev. 1.5 — 28th August 2009
28 of 43
8.1.3
36B36B
Rectangular antennas
76H76H75H
Fig 28 shows a typical rectangular antenna.
g
w
b
0
a
0
b
avg
a
avg
Fig. 23 Rectangular antenna
Variables:
a
o
, b
o
Overall dimensions of the coil
a
avg
, b
avg
Average dimensions of the coil
t Track
thickness
w Track
width
g
Gap between tracks
N
a
Number of turns
d
Equivalent diameter of the track
The inductance can be calculated by:
[
]
8
.
1
4
3
2
1
0
a
a
N
x
x
x
x
L
⋅
+
−
+
⋅
=
π
μ
With:
(
)
π
w
t
d
+
⋅
=
2
(
)
w
g
N
a
a
a
o
avg
+
⋅
−
=
(
)
w
g
N
b
b
a
o
avg
+
⋅
−
=
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛
+
+
⋅
⋅
⋅
⋅
=
2
2
1
2
ln
avg
avg
avg
avg
avg
avg
b
a
a
d
b
a
a
x
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛
+
+
⋅
⋅
⋅
⋅
=
2
2
2
2
ln
avg
avg
avg
avg
avg
avg
b
a
b
d
b
a
b
x
