AN3178

Read range considerations

Doc ID 17256 Rev 2

9/11

5

Read range considerations

The read range is the maximum distance between an RF reader and the M24LRxx antenna.

First and foremost, you must choose the right inductor value so that the resulting antenna is

properly tuned to your application.

However, for a given inductance value, the read range varies depending on the actual size of

the inductor. The bigger the inductor, the bigger the active surface of the inductance, the

more energy and data are captured by the M24LRxx devices and the better the read range.

To illustrate this, ST has measured the effect of various sizes of inductor on the ANT3-

M24LR64 reference antenna, using a Feig MR101 ISO15693 reader. The inductance value

is the same for all inductors: 4.7 µH.

Figure 7.

Read range (cm) vs inductor diameter (mm) using a Feig MR101 reader

ai15782