AN2972

How to check the M24LRxx antenna tuning

Doc ID 15629 Rev 6

19/25

Figure 20. Example of the resonant frequency response of a prototype antenna

3.2

Antenna measurements with standard laboratory tools

The antenna resonant frequency can also be measured with standard laboratory equipment

like:

●

a signal generator

●

an oscilloscope

●

two standard loop antennas

Experiment setup

Connect the first ISO 10373-7 standard loop antenna (see Figure 21) to the signal generator

to provide the RF electromagnetic field.

Connect the second ISO 10373-7 standard loop antenna to the oscilloscope (see Figure 22)

by using either a standard oscilloscope probe (1M or 10M input impedance) or a 50

Ω BNC

cable (oscilloscope input set to 50

Ω in this case).

Place the [antenna+M24LRxx] inside the RF electromagnetic field.

Figure 21. ISO standard loop antenna

S11 Log

magnitude

(dB)

ai17199

12

12.5

13

13.5

14

14.5

15

13.56 MHz

Frequency (MHz)

Resonant frequency (13.56 MHz)

i15819

ISO/IEC 7810 ID-1 outline

connections

72 mm × 42 mm coil

1 turn