Specifications

5-24
5.8 Resonator measurement
The resonator is the key component in an oscillator circuit. Crystal and ceramic resonators are com-
monly used in the kHz and MHz range. Figures 5-34 (a) and (b) show typical equivalent circuit and
frequency response for a resonator. A resonator has four primary elements: C, L, R, and Co. C and L
determine the series resonant frequency (fr) and Co and L determine the parallel resonant frequency
(fa.) Qm (mechanical Q) is another measurement parameter used to describe the performance of
resonators. An impedance analyzer or network analyzer is used to measure the resonator character-
istics.
Figure 5-34. Typical resonator characteristics
In the following methods, note the impedance analyzer has an advantage in the accuracy of the
measurement results.
Impedance analyzer advantages
• The impedance value at resonant frequency can be read directly. (Network analyzers generally
read in units of dB.)
• Measurement accuracy for low impedance at series resonance and for high impedance at paral-
lel resonance are better than in network analysis.
• Measurement is made by simply connecting the resonator to the test fixture, and residuals can
be removed using the compensation function. (Network analyzers require a π network circuit to
be connected and cannot compensate for all the residuals.)
• By using the equivalent circuit analysis function, all resonator parameters are easily known.
(Network analyzers require complicated calculation or special analysis software to be used.)
Network analyzer advantages
• Faster measurement speed.
• Higher measurement frequency range.