Specifications

5-25
Agilent’s impedance analyzers are suitable for testing resonators. With their equivalent circuit
analysis function, each resonator parameter can be determined individually. Also the I-BASIC
programming function facilitates the calculation of Qm and the extraction of other parameters.
Figure 5-35 shows a resonator measurement setup using an auto-balancing bridge instrument for a
frequency range up to approximately 100 MHz. For higher frequency measurement, the same setup
can be used with RF I-V measurement instrument. Take the following precautions to ensure
accurate measurements:
1. It is often assumed that the series resonant frequency, fr, is coincident with the minimum
impedance point. This is practical for an approximate measurement, but it is not the true value
of fr. The true value of fr is given at θ = 0 and is typically 1 to 2 Hz above the minimum imped-
ance point. Search the 0°-phase angle point for fr measurement.
2. It is important to properly set the oscillator output level; resonators are test-signal dependent.
The minimum impedance value and the series resonant frequency may vary depending on the
applied test signal level. Decrease the test signal level while monitoring the test current (I-moni-
tor function) until the specified test level is obtained.
3. Perform an open/short compensation. Use All Point compensation mode instead of the interpo-
lation mode because the resonator measurements are narrowband. Also, pay special attention
to the short compensation procedure. Improper short compensation will result in measurement
error for fr and the minimum impedance value.
4. Keep the measurement temperature constant. Resonators are temperature sensitive. Place a
resonator into the test fixture with your hand and wait until the series resonant frequency
becomes constant.
Figure 5-35. Resonator measurement setup