Crystals for quartz resonators

Abstract

This paper briefly describes the hydrothermal growth process and then discusses the important defects in quartz (twins, inclusions, dislocations, and impurities) and the correlations among them. The properties of quartz are reviewed and tabulated under the headings of intrinsic properties and defect-related properties. Resonator theory and fabrication techniques are outlined, with particular reference to aspects related to defects in the crystals. At this stage, it is possible to list the circuit design factors which must be taken into account when the application calls for very high performance. The paper then looks at the approach of a device maker faced with problems caused by impurities, inclusions, dislocations, and other nonideal properties of real crystals. This question leads to a specification of the crystals suitable for device use. The major parameter of this specification is the infrared Q, which must exceed about 1.8 million for satisfactory performance and yield. Acceptance test procedures are discussed, and finally the present state of the subject and the future prospects are briefly described.

On the 1/f frequency noise in ultra-stable quartz oscillators

“…This conclusion results from a set of selected articles, which includes the measurement of the frequency stability [WW75,RGBG00] and the interpretation of the flicker noise of crystal resonators [Kro98,Kro05]; the design fundamentals of the nowadays BVA resonators [Bes77]; some pioneering works on the low-frequency noise in quartz oscillators [BOM75,Dri75]; more recent articles focusing on specific design solutions for ultra-stable oscillators [Nor91, Nor96, CCG + 98, CCL + 03, TJA97]; and, as a complement, a thorough review of the SiO 2 crystal for the resonator fabrication is found in [Bri85]. Conversely, in everyday-life oscillators, which span from the low-cost XOs to the OCXOs used in telecommunications and instrumentation, the relative simplicity of the low-noise electronics required indicates that the frequency flicker is chiefly the 1/f fluctuation of the resonator.…”

Highly Sensitive Dual Quartz Reactance-to-Frequency Transducer

“…This expands the possibility of the use of the frequency stable quartz crystal oscillator by influencing quartz crystal equivalent circuit as a capacitive transducer whose capacitance is in the range 4−8 pF. Stable oscillation and high sensitivity in this range [6,[37][38][39][40][41] are thus one of this method's major advantages.…”

“…The data of the electrical quartz crystals' equivalent elements are f 0 = 4 MHz, R = 10 Ohm, C = 25 fF, L = 64 mH, C o = 4 pF, quality Q = 80 k. The frequency f 0 was selected due to a greater oscillation amplitude and a higher Q value for the selected oscillation circuit. The new method (Figure 3) allows the AT-cut crystal temperature characteristics compensation (under 0.02 Hz) in the above temperature range through the switching circuit compensating this characteristics and reducing its influence to a minimum [22,37,42].…”

Acoustic Microscopy Applied to Acoustic Resonator Characterization

“…Apart from the intrinsic quality of the crystals (inclusions, impurities, dislocations, etc.) [1], the nature of the vibration pattern is an important characteristic of such resonators [2], which directly affects their performance. Although there exist numerous methods for visualising the standing wave patterns in these crystals, all of these methods are indirect in nature and suffer from different limitations.…”