Dual-Mode Crystal Oscillator with Simultaneous Excitation of Two Overtones in a Stress Compensated Quartz Resonator

Abstract

The paper introduces novel dual-mode crystal oscillator (DMXO) that employs a standard 10-MHz 3 rd overtone stress compensated (SC) quartz resonator. In the DMXO, the two overtones (c-modes) of the SC-cut resonator are simultaneously excited: the 3 rd overtone and the 5 th overtone. The ability of utilization of the two excited overtones to implement the resonator self-thermometry we have evaluated. The resonator self-temperature-sensing method eliminates temperature offset and lag effects, since no external temperature sensor is used [1], [2], [3]. Eventual applications of the DMXO with excitation of the two overtones include the stabilization of the SC-cut resonator's temperature as well as compensation for frequency shifts due to the variations of the ambient temperature. I. INTRODUCTIONStress compensated (SC) quartz resonator selftemperature-sensing utilizing simultaneous excitation of two slow thickness-shear modes (i.e. c-modes) has been introduced by Schodowski in 1989 [1]. Processing of both c-mode actual frequencies enables prediction of their frequency shifts due to ambient temperature variations in a wide range. Temperature offset and lag effects are eliminated, since no external temperature sensor is used. For example, in microcomputer compensated crystal oscillator (MCXO) that operates in temperature range between -55 o C and +85 o C, a dual-mode crystal oscillator (DMXO) utilizes simultaneous excitation of fundamental c-mode and 3 rd overtone c-mode of special SC-cut resonator. In the case of the optimum MCXO SC-cut resonator, the lower turnover temperature of the 3 rd overtone is close to +20 o C [2], [3]. The minimization of the differences between aging rates of the two excited c-mode's frequencies is very important for MCXO, since the different aging rates cause an offset with a tilt in the MCXO frequency output over the operating temperature range [4].

Multi-mode crystal oscillator for simultaneous excitation of three thickness-shear modes in stress compensated resonator

“…In [7], [8], we investigated an impact of instabilities due to temperature variations of different types of inductors on the oscillator frequencies: -the air-core wire-wound inductors; -and the miniature multilayer ceramic inductors (HK1608 series from Taiyo Yuden Co. Ltd.). To be the influence more obvious, we replaced the SC-cut resonator in the particular bridge-type oscillator by the resistor with the resistance approximately equal to motional resistance of the appropriate mode, normally excited in the SC-cut.…”

“…To be the influence more obvious, we replaced the SC-cut resonator in the particular bridge-type oscillator by the resistor with the resistance approximately equal to motional resistance of the appropriate mode, normally excited in the SC-cut. Inductance of multilayer ceramic inductors is more temperature dependent (approximately, three times) in comparison with the wirewound air-core inductors [7], [8].…”

“…Different combinations of two overtones (c-modes) simultaneously excited in 10-MHz 3 rd overtone SC-cut resonators with lower turnover temperature of the 3 rd overtone between +80 o C and +85 o C we investigated in [7], [8], [9].…”

Mathematical Model of Multi-Frequency Piezoresonance Oscillation System

“…However, the research in such field [5][6][7][8][9][10][11][12][13][14][15] do not take into account the whole spectrum of specific conditions of modern PRD functioning, which reveals in sharp changes in temperature rate and substantial vibration and mechanical effects, which makes the task of providing the invariance in the conditions of parametrical non-stationarity essentially difficult. At that the following mechanisms, which define the dynamics of multifrequency PRD, can be defined [16,17]:…”