Designing the antenna coil

AN2866

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4

Designing the antenna coil

In the paragraphs below, the antenna inductance is calculated for different types of antenna

coils.

4.1

Inductance of a circular loop

, where:

●

r is the mean coil radius in millimeters

●

●

N is the number of turns

●

●

L is measured in Henry

4.2

Inductance of a spiral coil

, where:

●

d is the mean coil diameter in millimeters

●

c is the thickness of the winding in microns

●

N is the number of turns

●

●

L is measured in Henry

Figure 8.

Spiral coil

4.3

Inductance of an antenna with square coils

, where:

●

d is the mean coil diameter

●

●

K1 and K2 depend on the layout (refer to Table 2 for values)

L

ant

μ

0

N

1.9

r

×

r

r

0

----

⎝⎠

⎛⎞

ln

×

×

=

L

ant

31.33

μ

0

×

N

2

×

d

8d

11c

+

-----------------------

×

=

ai15812

L

ant

K1

μ

0

×

N

2

×

d

1K2

p

⋅

+

----------------------------

×

=