Now let's have a look at the measurement result:
Figure 8-10: Series and parallel resonance frequency of the quartz filter
To determine the series and parallel resonance frequencies check out the cursor grid as shown in
8-8 on page 56:
• Series resonance frequency (Cursor 1 - green): 11.996768 MHz
• Parallel resonance frequency (Cursor 2 - orange): 11.998572 MHz
• Offset between the series and parallel resonance frequency (Delta C2-C1): 1.8 kHz
Your measurement results can be slightly different since each quartz filter behaves a little bit
different.
One characteristic of resonance frequencies is that the inductances and capacitances compensate
each other. This means that at the series and parallel resonance the impedance of our quartz filter
should be purely resistive. An elegant way to check this is to display the quartz filters reflection curve
as a Smith chart.
58
OMICRON Lab
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