At-cut crystal resonator

Details At-cut crystal resonator At-cut crystal resonator

1998-12-14

2000-09-05

Budd, Mark O.

Electrical generator or motor structure

Non-dynamoelectric

Piezoelectric elements and devices

310312, 310361, H01L 4108

Patent

active

061148016

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to an AT-cut quartz resonator which is adapted so that a deviation of its resonance frequency from a target value, which is attributable to an error of the angle of cutting out a quartz substrate from an artificially grown quartz crystal, can be corrected through a simple modification of the electrode structure and hence kept within acceptable limits, thereby eliminating the addition of a temperature compensating circuit to the incorporation of the quartz resonator into an oscillation circuit in consumer-oriented electronic products and negating the need for adjustment of the temperature compensating circuit in industrial equipment.
2. Description of the Prior Art
Heretofore, quartz oscillators have been widely used as reference frequency generators for communications equipment, industrial equipment, consumer-electronics products, and so forth because of their excellent characteristics such as small size, high frequency accuracy and high frequency stability. Quartz resonators are also used in a wide variety of communications equipment in large quantities; for example, a plurality of quartz resonators are used to form a crystal filter, or a quartz resonator, an amplifier circuit and a temperature compensating circuit are used, in combination, to form a temperature compensated crystal oscillator (TCXO). The oscillation frequency of the crystal oscillator depends on the resonance frequency of the quartz resonator forming the oscillator. The quartz is a physically stable piezoelectric crystal, whose resonance frequency also has extremely high stability. In particular, an AT-cut quartz resonator has excellent temperature-frequency characteristics, and for this reason, it is frequently used in various fields.
The AT-cut quartz resonator has, as is well-known in the art, a pair of opposed electrode patterns for excitation deposited on both sides of a quartz substrate. The quartz substrate of an AT-cut quartz resonator is a Y plate having an angle .theta. about the X axis of 35 degrees 15 minutes obtained by cutting out it of artificially grown quartz crystal. The resonance frequency of the AT-cut quartz resonator depends on the thickness of the quartz substrate.
This quartz resonator is placed and sealed in a package provided with a required support structure to form one piezoelectric device. Further, a quartz oscillator is formed by inserting the quartz resonator in an oscillation circuit loop constructed using chip parts or the like on a printed board. While the AT-cut quartz resonator is small in the amount of the change in the resonance frequency with a change in temperature as compared with quartz resonators of other cutting angles as referred to above, it is known in the art that the AT-cut quartz resonator shows a cubic-like temperature-frequency characteristic with a point of inflection at about 27.degree. C., for example, as depicted in FIG. 5.
But the temperature-frequency characteristic varies with the angle .theta. for cutting out the quartz substrate from quartz crystal. That is, the temperature-frequency characteristic of the AT-cut quartz resonator becomes a function of the cutting angle .theta., forming the cubic curve having an inflection point at 27.degree. C.
FIG. 6 is a graph showing temperature-frequency characteristics of ordinary quartz resonators using three kinds of quartz substrates of slightly different cutting angles. For example, in Japan specifications about a reference frequency source of a pager (beeper) as consumer-oriented communication equipment require that a frequency deviation in a temperature range of -10.degree. C. to 50.degree. C. be held .+-.2 ppm. Assume, for instance, that the curve A in FIG. 6 is representative of the frequency deviation which meets the above mentioned specs. In this instance, the specs ought to be met by a quartz resonator using a quartz substrate cut out at an angle that provides the temperature characteristic corresponding to the curve A.
However, even if an attempt

REFERENCES:
patent: 4418299 (1983-11-01), Momosaki
patent: 4468582 (1984-08-01), Fujiwara et al.
patent: 5376861 (1994-12-01), Nakamura et al.

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