Model of crystal
This model was determined from bench measurements on 9.83MHz microporcessor crystals. The 1000 GigOhm resistor is there simply to prevent SPICE from becoming confused with complete opens at DC.
Crystal filter, four sections
This latter filter design is symmetric. Both ends have the same termination impedance.
The Response
In the plot below, Blue is the SPICE simulation result and red is measured result.
The measured response is more narrow than the simulated response. This may be related to a problem with the model.
