How to check the M24LRxx antenna tuning

AN2972

20/25

Doc ID 15629 Rev 6

Figure 22. Setting up the standard laboratory equipment

Experiments

Set the signal generator to output a sine wave with a peak-to-peak amplitude in the range of

200 mV. Starting from 5 MHz, increase the signal generator frequency until you reach the

maximum amplitude of the signal measured with the oscilloscope. The signal generator

frequency then corresponds to the resonant frequency of the [antenna+M24LRxx] pair.

Figure 23 provides the frequency response curve of the prototype antenna, based on

measurements of the received signal amplitude at different frequencies.

Figure 23. Example of a frequency response measurement of a prototype antenna

Synchronization frequency

Prototype antenna to be measured

Loop antennas

ai16085

Signal generator

Oscilloscope

12

12.5

13

13.5

14

14.5

15

Frequency (MHz)

Resonant frequency = 13.56 MHz

Voltage on

the second

ISO 10373-7

antenna

ai17300