11.7.2 Fres-Q Calculation
For a fast and easy contactless measurement of the resonance frequency (Fres) and quality factor (Q)
of RFID and NFC transponders Bode Analyzer Suite includes the Fres-Q cursor calculation. By
automatically placing three cursors to the resonance peak, Bode Analyzer Suite automatically
calculates the resonance frequency and quality factor based on the shape of the resonance curve.
Fres-Q calculation works as follows: Cursor 2 is placed to the maximum y-value the curve which must
correspond to the resonance peak. Cursor 1 is placed to half the y-value at a lower frequency. Cursor
3 is placed to half the y-value at higher frequency.
The Cursor 2 frequency then equals the resonance frequency f
res
.
The distance between Cursor 1 and Cursor 3 equals the bandwidth B.
The quality factor Q is then calculated by:
To measure the resonance frequency and Q-factor of a resonance curve, go to the cursor ribbon and
select the Fres-Q calculation method as shown below:
As a next step, select the format (Real, Magnitude or Phase) and trace you want to use for the cursor
calculation from the ribbon interface as shown in the example below:
In this example we want to calculate the resonance frequency and Q-factor based on the Real part of
the values in Trace 1. As an alternative also the Magnitude or Phase can be used. If multiple traces
contain values or if a memory is linked to the cursor table, then the calculation can also be applied to
these curves.
Bode Analyzer Suite software features
OMICRON Lab
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