How to design an antenna on a PCB

AN2972

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Doc ID 15629 Rev 6

Figure 12. Rectangular planar antennas

Once the antenna coil inductance has been calculated, a prototype coil is realized. The

value of the so-obtained prototype must then be validated by measurement. This can be

done using either a contactless or a non-contactless method.

2.5

PCB layout

2.5.1

M24LRxx-antenna distance

The M24LRxx must be laid out as close as possible to the antenna (a few millimeters). Any

additional wire/trace would change the antenna characteristics and tuning.

2.5.2

Ground layer considerations

Designing an inductive antenna on a PCB means that special attention must be paid to

ground plane design:

●

no ground plane above or below the antenna

●

no ground plane surrounding the antenna

Figure 13 shows a correct layout.

Width

Length

s

w

1

1

8

10

3 turns, 10 segments

2 turns, 8 segments

ai15815

thickness

(cross-section)