Electronic Activity Dip Measurement

Abstract

Abstract-The frequency-or immittance-temperature anomalies occurring in quartz-crystal resonators are generically called activity dips. Because of their potentially disastrous effects on oscillator and filter performance, testing for their presence can represent a considerable addition to the manufacturing cost. An electronic method is described, in several variations, that is rapid, simple, and well adapted to microprocessor control. The electronic method obviates tedious and costly temperature runs. It makes use of the fact that the desired mode of vibration is shifted in frequency by a variable series capacitor, while interfering modes, that cause activity dips, are nearly unaffected. INTRODUCTIONA NOMALIES in the frequency-or admittancetemperature characteristic of a resonator are called "activity dips" or "bandbreaks." At least two distinct species exist: "design-related" dips and "process-related" dips. The latter type arise from shortcomings in the processing phases where, for example, an improperly deposited electrode film peels or blisters in a reversible, temperature-dependent manner; these are not considered further here. "Design-related" activity dips are those for which the structural configuration remains unaffected by temperature changes, but instead depend solely upon geometry and material constants. The presence of "designrelated" activity dips is a persistent problem and necessitates a good deal of costly testing for medium-and

Correlation of Electrical Properties and Acoustic Loss in Single Crystalline Lithium Niobate-Tantalate Solid Solutions at Elevated Temperatures

“…The frequencies of the measurements correspond to the first, and fifth harmonics of the resonator that is operated in the TSM mode. A substantial number of sharp peaks were observed in the raw data for the first harmonic of LNT88-01 between 250 and 350 • C. These peaks are understood to originate from the "activity dips" phenomenon, caused by the coupling of the main mode with other spurious (parasitic) modes [62]. Such coupling does not allow for correct determination of the Q-factor.…”

Studying Soft Interfaces with Shear Waves: Principles and Applications of the Quartz Crystal Microbalance (QCM)

“… The vibration of interest may couple to other modes of vibration of the crystal, where the exact mechanism of coupling is unclear and where even the nature of the other mode is unclear. These so-called “activity dips”, which sometimes occur when ramping temperature up or down, can be a problem in time and frequency control [ 173 ]. An activity dip lets the bandwidth increase at a certain temperature and lets the frequency go through a corresponding antisymmetric pattern.…”

A Quartz Crystal Microbalance, Which Tracks Four Overtones in Parallel with a Time Resolution of 10 Milliseconds: Application to Inkjet Printing

“…Such cross-talk has been seen in other cases. Coupling between modes gives rise to the “activity dips”, much feared in time-and-frequency control [ 10 ]. Mode coupling was not observed here.…”